Air cushion landing gear applications study

: .m NASA ContractorReport C R 1 5 9002

' ( _ &S A -CR-159002) AIR CUSRIO N LAHD I NG G E AR R79-260 4 5 APPLIC&TI O qS STUD Y Rep o rt, J a n. - _ a r . 1 979 - : (Textron Bell Aer os pa c e C o . , P -u f fa l o , N . 7 .)

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_'' M R CUSHION LANDING GEAR _

APP L ICATIONS STUDY _

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- ._ T.D . EARL : : - :: , BELL AER O SPACE TEXTRON i!

BUFFALO, NY 14240 - .. _ ,EPORT NO . D7 6 0 5 -92 7 002 " _ APRIL 1979 ' _ "! CONTRA C T NAS 1- 15 202 i II . _ - ¢ f i '

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_ Ham p ton , Virginia 23665 __ A C 8 04 827 - 39 6 6 ',i /

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" AIR CUSHION LANDING GEAR ; APPLICATIONS STUDY _: !" T. D. EARL _ ' BE L L AEROSPACE TEXTRON i BUFFALO , NY 1 42 4 0 !

REPORT NO. D7 6 0 S -927002 APRIL 1979 C ONTRA C TNAS 1 15 202

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National A e rona u tics and S p ac e Administration , , Langley Re s ear c h Center

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Ham p ton, Virginia 23665 AC8 0 4 827-3966 t C O NTENTS FORE W OR D .......................................................... vii , _ ACKNOWLEDGEME N T .................................................. vii SUMMARY ............................................................ viii LIST OF A CRONYMS / ABBREVIATIONS .................................... ix Ge neral .............................................................. I ACLG Background.. ..................................................... 1 i ! O pera t ing Principles .................................................... 1 " Advantages ............................................................ 3 " _ ' Objectives and Study Scope 4 N e w A C LG Configura t ion 6 '_ • o.......... . ........ . • . • . ° • . • • * ** , ° . . ° . • , . , , o . ° SE L E C TE D APP L ICATIO N S .............................................. 1 0 "_ M edium Amphibi ou s Tra n sp ort ( MA T) ....................................... 34 _i , _ Large Mul ti- M issi on Amp h ibian (L M / A ) ...................................... 39 _ : _ Off-Runway Tac t ical Fig h ter (OT JT ) ............... '......................... 45 _ : _, Remotely Piloted Vehicle (RPV / Y .......................................... 48 '_ Ov e rvi e w ..... _ . / ........................................................ 5 4 Di sc us si on of ffurre nt Tec h nology Base ...................................... 5 7 m ' ./ REFERENCES 72 H, _ ' 111 ILL U STRATI O NS __ , Figur e Page 5 Inh er en t Kneelin g Fe at u r e of A i r c r af t wi t h ACLG ......................... 5 . e 8 (b) Fro nt a l V i ew Co mp a ri s on .......................................... 9 0 1 8 E qu il ib ri um Lo w - Speed T ax i C o nd i tio ns in St ro n g C ro ssw. i nd ............... 2 1 2 2 L A T E c o n o m i c C o mpa r is o ns ......................................... 2 5 2 3 S hort H au l Amp hi b i an ( 3-V i e w) ' 27 25 T -34-100 By-Pass Flo w C h ara c t e ristics ................................. 2 9 2 8 M edi u m Am p h ibi ous T r a nsport 3 -View ................................. 3 4 29 ( a ) C F6 - 50 St a n da r d En gi ne Cro ss Se c t io n 35 ... o • , • ° • • o , • • , • I , ° _ • i • ° o • • , , • ° I • 2 9(b) C F 6 - 5 0 E n g in e S h owing Propos e d M o dific at ion f o r A CLG Fan B le ed ......... 3 5 ': 3 0 Siz e C o m pa r iso n of YC -; 4 wit h Medi um An l p h ibious T ransport ACLG Concept. 36 " 31 V ari a tio n of Rang e Fac t or (T h rust Hors e po we r p e r Pound of F u e l) w i th A l t i tu d e ......................... 2 ; 7 : ,o.ll ° ,e,.,_,,o,,_,ol Je,°o m !

3 2 Es t i m at e d R a ng e - P a ylo a d Compa ri son of MAT wi th Y C -1 4 ................. 3 8 34 L arg e M u lti -M issi on A m p hi b i an (L M A) ................................. 4 0 • _ t 35 T ypic a l L MA Cr os s S e c ' t i o n " 4 0 ] 36 LM A / 759 - 182A Compar i son ......................................... 4 1 38 Productivity Compar i son ..................... , ..................... 44 i 4 0 OTF A rtist ' s Concep t ............................................... 4 6 !

i v ILL USTRAT ION S ( C O NT) Figur e Page " _ I 41 OTF Rang e and Enduranc e ......................................... 4 7 " 43 J i ndivik 3 -Vi e w ................................................. 4 9 44 Jindivik A C LG Syst e m " 4 9 . 46 Pr e l imi nary Conc e ptual D e s i gn o f W IG ................................ 5 1 ] 47 ASNA P An a lysis Corr e lation to Me asured Loads .......................... 5 9 ', 48 ACLS Fl u t te r Ana l y s is I d e ali za ti on .................................... 6 0 4 9 Air Lubricat i on T e s t R e sults ........................................ 6 2 TABLES Num ber Pag e I V E s t imat e d GAA Cha r a c t eri sti c s ............................................. 1 7 V GAA Weig h t B re akd o wn ................................................... 1 8 V ! G A A Ai / C u sh i o n G ear Cos t ................................................. 2 1 .

X I SHA and Bo e ing 737 - 100 Landing G e ar Costs ................................... 3 3 XV Comparison of P e rfo r man ce Charact e risti c s of the LMA D e sign with Two X XV X C- 8A P a rt i al H i story .......................................... • ........... 6 5 XX I X Alternativ e AC L G T echn o l o gy D evel o pment T im e tab le ........................... 7 0 vi { FOREWORD _ _' This document pres e nts the resul t s of the Bell Aerospace Textron studies of Air Cushion _ : La nding Gear Applications. These studi e s w ere p erf o rme d f or th e Nation al A e ronauti c s and Spac e Administrat i on Langley Research Center under C ontrac t NAS 1 5 2 0 2 . L TC J . C. V augha n I I I wa s th e NASA Technic al Rep re s e n t ative. The report was writ t en by Mr. T.D. Earl and assisting in the . t e chni c al work w ere : M e ssrsJ. D ale y (d e sign), C .E. Sat t erl ee (aircraft perfo rm anc e ), C.E. Tilyou (w e ights), and J.D. W i ts i l ( ai r c ra f t c ostin g ) ; Mr . H .K. Ow e ns assis te d with th e survey.

ACKNOWLEDGEMENT For t h e perfo rm ance of the study, opinions were sought from k e y organizations suc h as air- frame manufactu re rs, civil op e ra t ors and governmental agencies, both in v e rbal discussion and from comm e nts on a pr e liminary bri e f tha t was p re pared and circula t ed. Many valuabl e comme nts a nd cri ti cisms we re re ceiv e d, contribu ti ng gr e atly to the report, and are gr atefully acknowledged.

_ Th e author wishes part i cul a r l y to t h a nk a l l t hose i n d i viduals w h o provided e n gineeri n g .i comments, including r e p re s e nta t ives of the Boeing Airplan e Company, McDonnel Douglas Aircraft Company, Lock he ed G e orgia Co m pany, Roc k w e ll I n t e rn a t ional (C-olumbus), Nort h rop Co rp oration, ' _ B ee ch Ai rcraf t Co rp ora t ion, Cessna Ai rcraft Company, Piper Aircraft Corpora t ion, Hus t ler Gulf- tory), Na t ional Aerona u tics and Spac e A d m i n is t ra ti o n ( O.A. S .T ., A m e s and L e w i s Research Cen t e rs ) and t he Univ ers ity of Kansas (D e part me nt of Aerospace Engineering).

st re a m (Sava nn ah), U.S . Navy ( NA SC, N ADC , N S R DC), U .S. A ir Forc e (Flight Dynam i cs Labora- !

t O SUMMARY ._ " I n thi s s tudy , a s e ri e s of ai rc raft ai r c u s h ion landing g e a r a pplicati o ns w er e c o nsidered in ord e r t o det e rmi ne t he m o st attractiv e , and to analyz e pot en tial b e n e fit .

T h e met h od followed consist e d of asse m b l ing a long list from w h i c h preli m inary s e lections i • w ere made. Selected conc e pt designs were prepared and used in a survey to obtain informed opinion . _ ' w h ic h then modified t h e preliminary selections. T h e resulting final s e lections were t h en analyz e d and a preli m ina r y b ri ef circulated to about 60 organizations for comments. T h e analyses w ere modi- . i fled i n a cc ordance wi t h comm ents on t h e bri e f and the res u lts are present e d in t h is r e p o rt , i In t h e report, a s h ort backgrou n d of ACLG d e velop me nt test e xperience is first given , 1 foU o we d b y a n ex p l anation o f the ACL G e mb o di m e n t co n sidered. T he adv ant ag e s o f A C LG are .'

. b r i e fly st a t ed un d er the he adi ngs: Toler anc e of Co nd it i o ns (whi c h i n clu d e s c ro ss win d) , Tri p hibiou s !

Weight / Drag Savings, Safety and C omfor t , ln c ,e a se d Payload, Basing Flex i b i l i t y , Groun d L e v el Par ki ng an d Loa d Di st r i b u tion.

Eight fi nal selections were made consisting of a general aviation amphibian (GAA), li g ht ' am p h i b i ou s t rans p ort ( L AT), s hort haul a m p h i b ia n (SHA) , medi um amp h i b i o us tr ansp o rt (M AT ) , !

large m u lti - m is sion amphib i an ( LM A) , of f r unwa y t a ctic a l fi gh t er ( O T F ) , r emo t el y pi lo t e d vehicle i ' ( RPV ) a n d wing in gr o un d effec t wi t h A CL G ( WIG ) . i T he fi rst fi ve are t rans port s an d are a famil y o f d es igns em p lo y in g a ne w i n t eg rat ed A CL G a i rcraf t c o nfig u ra t ion . Thi s i s p o ss ible because in t hi s work A CL G .h as been co ns i de re d a s in c or- porated into the d esign f r om t ile st ar t an d not a s a re tr ofit . Th is ha s p e r mitte d a lower we i ght a n d cost approach to the A CLG, and should overcome a number of problems which hampered the XC-SA development program.

, _ T he ad vant a ges o f t his configuration partl y arise fr o m in c re a sed cu s hion area and wi der ¢ t r ack, wh ic h are comp a re d with previ o , , s d esi g ns and first displa y e d in t he GAA d esi g n. Weight , and c ost o f the A CLG a r e an al y zed.

': Ben e fit is iden t ified with e ffects on econom y and s afet y . O p e r at i ng co s t co m p ar iso n s we r e ', m ade lor t he GAA, L A T , M AT and LM A, a n d safe t y is discu s s ed re la t ive t o th e GA A and SHA.

'_ Significant eco n omy can result from provi s ion o f efficient triphibious capability (without weight drag penalty). Also an important contribution of ACLG to econo m y is to facilitate longer takeoff, p articularly overwater - le a din g to increased aircraft p ayload / gross weight. The p rincipal c ontri- butions of A CLG to safety would be improved crosswind landi n g and the g round accident tolerance re s ulting f ro m i t s of f -runw ay ca p ab i li ty . , c A su mm ary o f th e A CL G t e chno lo g y s ta t u s i s given. E le ven i t ems a r e discussed a nd fo u r ot " them are identified as near-term development priorities. These tour are tr u nk material life un_. . r study) and development, cushion braking d e velopment, t runk flt , tter suppressio n ( currentl y '= flight effects. Two scenario timetables of possible system development are suggested embracing ° t he el ev en it e ms di s cus s ed an d r e l ate d t o t he kinds o f ai r cr a ft p ostu l ated.

It is c oncluded that the dominant feature of.A C LG is the'provision of a superior amphibiou s / tri p hibious capability. Other desirable features such as crosswind landing, soft ground pertbrmance o r im p roved ground-accident tolerance art ' unlikely to lead to it s adoption. T hus the most attractive nea r - t erm use is a s re p lacement for exis t ing amphibian s . Th is lea ds to th e c o n c lu sio n that the l a r g est VI I !

mar ket m ay b e out sid e th e U nited St a t es. T he A CL G cou ld in trod u ce a ne w e co n om ic al wa t er / la n d _ , +

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basin g opt i o n . This opportu n i t y c a n be see n through the sp e ctru m of de s igns prese n ted a n d is par ti c ul ar ly attrac tiv e f or g e n er a l av i at i o n a nd a ls o f or ver y lar ge a ircra f t. ' _ g It is al so co n c l uded th a t wha te v e r cla ss of a ir c ra f t is th e m os t attra c tiv e end o bj ec tiv e , i n i t i a l tec h n olog y a dv ancement w i i l be most c o st-e ff ect iv e a t t h e s mallest m ean i n gf u l s i ze. Hence,

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; sma l l s ize tru n k de v e lopm ent i s r ec o m m e nd e d , w it h p a r a ll el mod e l te st s and op e ratio nal stu d ie s of " l a rge a ir c r aft . ] + L I ST O F AC R O NYM S / A BBREV IA T IONS A / C Ai r c r a ft A CL Ai r C u shi on Landin g / : ACLG Air Cus h ion Landing G ear ] ACV Ai r C u shion V e hic le t+ A I C Ac q u isition Inves t me nt Cost _ _ . :.

A LF- 502 L y coming Eng i ne D e sign at ion _ " AMS T Adva n c e d Medi um ST O L Tr an sp o rt i ASNAP A xisy mm etri c S ea l Non-Line a r An a lysi s P i ogram _' AS W An ti- Su b ma r i ne Wa r f are ATA Ai r T r anspo rt Associa t ion A V-8B USMC Ai rp l ane Des ign ation '_ r BHP B rake H or s e Powe r + [ C F - 6-50 G e neral El ectric Engine De s i g n a t io n s [ G E C F- 6- 50 4 CLAS S C a rgo Logi stic s A irl i f t S y s t em S tu d y !

CT OL Co n ve nt io n al T a k e -Off an d Lan d in g DLF Distributed Load Freighter F AA F e dera l Aviation Admini s trati o n F A R F ederal Ai rwo rthiness Re q uir e ment s ] FEBA For w a r d E d g e o f Batt l e A r e a F L A P F lut t e r L a t e r al Anal y si s P rogra m !

FR G F ederal Re p u b lic of Ge r m a ny _i GAA G e ne r al Avi a tion Am p hibian G E G ene ral Elect ri c / GW Gross Weigh t I CAC I nitial C rui s e Alt i tude Cap ab i li ty " IO, T-IO Ly c o m i n g E ngine D es ig na tio ns L / D L ift / Dr a g L A-4 Lake Ai rcra ft De s i g nati o n +_ _, LMA L a rg eMulti -M iss io n Am p hib i a n L A T Lig h t Am p hibi o us Tr ans p or t ;!

M AC Milit ary A i rl ift Co mmand , _ M ARS Mid Air Re tr ie v a l Sy s t e m MAT Med ium A m p hib i a n Tr a nspor t. I NA SA Nati o nal Ae r on a u ti cs & Spa ce Ad m i ni stra tion i i O T F O ff -R unway Tact i c a l Fi g h t e r i : ix i PT-6 . Pr a tt& Whitne y Canad a EngineDesign a tion ! i R O I Ret u r n o n In v e s tme nt RPV Remotely Piloted Ve h icle [ _ S E S S u rfac e Ef fe ct Ship SHA Sh ort H au l A mp h i b i an SLS Se a Level St a tic _ " S R-N5 Briti s hHovercr a f tAC V De s ig nat io n S T O L S hortT a ke- O f fan d L an di n g ; T F -34, T-3 4. G ener a l Electr i c Engine D es i gn at io ns TO F L T a ke-OffField Length U S AF U n i t ed S tat e s A i r F o r ce _ UK United Kingdo m i : USSR U n ion of Soviet Sociali s t Rep u blic s : VTOL Vert ica lT a ke- O ff a nd La n ding V / S TO L Ver tica l / Sh ort Ta ke - Of f a nd La nd ing WIG Wi ng I n G ro u nd Ef fect XC-8 A De si gn ati o n f or de H a v i ll an dBuf fal o w i th A C LG _ , ; YC-1 4 U SA F Ai rpl a neDes i g nat ion _ .

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" 7 p b _sm _ X , _ i '_ e f INTRODUCTION _ G e neral This document presents results of a study of Air Cushion Landing Gear (ACLC) application _: " to selected aircraft types.

/ The study concentrates on a part i cular integrated A CLG design approach, maximizing poten- tial benefit. A family of designs is presented , ranging from a small, single piston-en g ined general avia ti on air c raft up to a very large freighter and including a lightweight fi gh ter concept as well as ' ot he rs.

AC LG Backgro u nd A i r Cu s h io n Landi n g G e ar was fi rst fi tted to a n 1 1 3 4 kg ( 25 0 0 lb ) Lak e L A-4 li gh t a m p hib ia n.

Th e fi r s t ai r c u s hi o n takeo ff and l a n d ing w e re m ade o n Augu st 4, 1 9 67 , b y Bel l A e r ospace T extro n.

S ub s e q uen tly, a co n sid e ra b;z eff ort was s po ns or e d b y t h e U S A F a n d C anadi an Gov e r nmen t - t he si m ilar re tr ofi t o f a me di um ca : g o t r ansport - t h e 1 8, 59? k g (41 , 0 00 l b ) de H avilland Be ¢¢-_ o , F i f ty - s e v e n ai r cu s h i o n tak eoff s or l an di n gs were m ade i n t h is n ow co m p l et e d pro gr a m. C m t,_u rre n t l y, i n a s m aller e ffo rt , t he U S AF dev e lop e d a n a ir c u s h ion ta ke o ff a n d la n di ng re cove ry syste m for d r o n es , w hi c h was fi tt e d to t he 1 4 52 k g (3 , 2 00 I b ) Au stralia n J in divi k , a n d gr o un d tested .

The s e ai rc r a f t a re seen ridi ng t h eir r e sp e ctiv e ai r c u s h io n s i n Fi g u r e 1.

= Operati n g Principl e s The fun ction o f the ai r c u s h ion ge ar is to r e place w h eel g e ar , hu ll, fl oats an d s k is - or t he i r co mb i n atio r s - with a s ingl e , li gh tw e i gh t, pow e red , r etracta b le ai r cu s h io n g ear .

The air c u shio n is a la rge poc ke t of air b e n eat h t h e ai r c r a f t , co n tai n ed b y a fle xi b le m ate r ial cushion "t runk " and kep t a t t h e sli ght press u re nee d e d t o s u ppor t t he aircraf t b . ' a con t inuous air- flow escaping at the bottom near the ground.

The fl exible _ runk, w h en in fl ated, is like half o f a distorted inner tube or dou gh n u t, sliced across its axis and f a stened to the bottom of the ai rcraft. In fl a t ion for takeoff or landing is accom- plished by en gi n e fan bleed or a separate on-board f an . The fan pressure k eeps the t ru nk in fl ated and - also maintains an airflow th rough nozzles at the bottom near t h e .ground. N o ot h er f eed is needed to !

press u rize t h e air cus hi on, a nd keep the trunk just o ff the gr ound , supporting the aircraft nearly f riction f ree. Residual ground friction depends on t h e amount of airflo w , t h e sur f ace roug h ness and _, the longitudinal trim.

l When not in us e , eith e r in flight or on the ground, th e trunk i s retracted. In the pri m a ry vers i on it is elastic, being made of a fabric rein f orced ru bber material , and s imply shri n ks to fi t snugly _, on th e surface when the airflow is stop p ed, like pneu m a ! ic de-icing" boots on a wing or tail leading e t ude .

When t he aircraft reaches a t akeoff o _ l anding att i tude an d the fron t of th e trunk rises , making a v e nt, full cushion p re ssu re cannot be re t ai_ . - t . If wi _g ! ift i s not enough to c arry the re ma ining ai r- "---- ......... _ lF _ P" _ - _ _ : .I _"_ -- - _ . --_

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JINDIVIK Figur e ]. Th e d e Havi l land- B u f falo , LA-4 and Jindiv ik on Air Cushion c ra f t weigh t, s om e of i t wil l be s u ppo r t ed b y th e tr un k, w h ich will flatten again st th e grou n d, form - ,1 in g a rear f oo t_dnt at the p r essure inside the trunk, ab o ut twice t h e no rma l cush i on pressure, but s ti l l ve r y lo w. Be ca use t he noz zl es are at t he b o tt o m, air e scapes i n t o the f oo tprint f o rm i n g a l ubr i - q c at i ng fil m, so th at t h e r e is st ill ve r y l ow gr o u n d friction i n t ak e off r ot ation and l anding t o uchd o wn. - In l a ndin g , v *,rtical imp a ct _ne rgy i s ab so rb e d b y increa se d pr ess ure in th e cu s hion c a vity a s the '_ ' t r _ , nk is squas he d and b y the tr unk f ootprin t s pr ea d in g . Th is o ccur s in water la n d i ng a l so , p r o vi d i ng l o a d al lev i a tion • T h e a v ai lable s t r ok e i s t h e ha r d s_ructu re c lear a nce. Ex p ulsion of air fr om the cus h io n an d t runk t hro ughout the s t r o k e pr ov i des vert i cal d ampi n g. _i T h e l ub ri ca ti o n effect c a n be, b y d e s i gn , p artly e l im ina ted by o n u tting the r.o zz le s loca lly , to t •_, c re ate b r a ki ng, and fi tting wea r r e sis tant ( re p laceable) p ad s a t t he s e p laces. If c ushi o n pr e ss ur e and air ga p are maintained, there will b e no braking. T o brak e in the primary version, the bottom of the " t ru nk is distorted a t t h e p a ds b y i nt e rn a l ac t ua tor s, t o d el ibe - at e ly v e n t t he cushion an d caus e p a d c on tact a n d gro und f r i ct i on . T h e p ad s ar e at e a ch side , f o r d iff er enti a l a ctio n, a nd far eno u g h l o t- w a r d n o t t o in te rf e r e with th e r e ar foot p rint.

R EP R ODUCI B ILITY O F TI-I 1 _ ORIGINAI_PA_ , _g IS PO_)R Th e s e op e r a ting prin c ipl e s of the a ir c ushion and brakes a r e i l lustrated in Figur e 2.

" ' " '_ " '_ ' _' _ ; _ ; ' $ R O LL O UT - C USH I ON BORNE A I R IN P R E SSUR IZ ED - - _ = _ ' AIR C USH I ON C AVIT' _ . . ' " " _ _ 1 _ BRAK I NG- BRAKE CO NTA C T I NG GHOUND I Figure 2 . ACLG Operating Principles Advanta g es In s u mmary, the advantages c l aim e d for the air c ushio n h m ding gear are as follows: T olerance of Conditions - It makes for an easier takecff and landing maneuver (i.e. , is forgiving ) and relaxes the airqeld requirement - any surface softaess is acceptable. It also accepts crat bed ground- roll in takeoff at_d landin g - thus crosswmd tolerance is unlimited.

Tr ip hibious Wei g ht / Dra g S a vin g s - It permits triphibious takeoff and hmding (land , water , snow , ;is seen in the L A -4 photo g raphs, Figure 3 ) , without th e weight / drag penalties of c onventional landing g ear combinations.

Safety and C o mfort - It provides a higher takeoff and landing accident toleran c e and has low vulner- ability to damage , leading to improved safety compared with wheelgear. The element of dauge r in incidents such as landing short, veering-off or overrunni r _ g the paved runway may bc largely aw_idcd Emer g ency landing in fields or water ditchin g is possible without damage. ' l'he conventional scaplaae hazard of flotsam dama g e to floats or hulls, is avoided.

ACLG also introduces a new soft touch-down (and take o ff ) which is Colnfortable and , _hould be highl y a c c ep t ,'. bl, to p as s engers.

Figure 3 . LA-4 O p er a ti ng O v er Lan d , Wa t er an d Snow Inc re a se d Payload - The relaxe d surface req u irement (especially water ) allows the A C LG air p lan e _o be designed for lon g er takeoff and landing, resulting in improved payload / gross-weight and economy.

; Basin g Flex ibi l i t y - T he m u lt i -surface capabili ty inc r eases o p eration a l vers a til i ty, a l lowing ( for one example) taking off from snow or runway for a destination land in g on water or (for another, commonly a characteristic of amphibians ) taxi from a water landing to a ground parking ramp. T his permits a baking fl exibility for both commercial and mili t ary operations worldwide (Figure 4). Snow covered or bomb damaged runways become less of an obstacle i n military opera t ions.

Gr ou nd Lev e l P arkin g - Because of tile inherent kneeling characteristic of the air cushion, the aircraft : can be desig n ed to se tt le o n t o s hallow parki n g s kids whe n shu t down. This will usually permit easier , : loading, for example, permitting the cargo deck of a large freighter to be at truck bed height as in , Figur e 5. I Loa d Dis tri bu ti on - The A C L.Gcan diffuse ground loads into the aircraft structure Particularly lbr , " very l a rge a ircr a ft ( t w o o r mo r e times the 747) ; this will s ave weight and avoid a requirement for special runways. Extended high-speed taxi and takeoff maneuvers ca n be tolerated in an equilibrium condi- tion in co n trast to the limited tr a nsie n t I oa dings requir ed on c o _:, , mti o nal tir e s.

._ . Objec t ives and Study Scope N A S A 's objectives were to pick the most attractiv e applications , q u, ' mtitativ e ly ,;how their advantages, and identify technical barriers to their development in order to guide future t e chnology support. T he urgency and timing of needs were important so that the direction and pace of research and technology could be better defined. i _ , 4 The study methodology started w i th ident i fying 19 possible aerospace applica t ions f or ACLG .

A preli m inary selection of 7 m o re w o m isin g applica t ion s was then made and a brie fi ng prepared.

Vis i ts were then made to 16 organizations ( 10 governmen t , 5 aircraft manufac t urers, and one airline) whe re this initial br i efing wa s given, followed by in - depth discu ss io n a nd s o m e follow - on conv ersa tions, _ , B as ed o n the s e vi s it s , 6 o f t he i n iti a l s el ec t i o ns were b etter defi ne d, ot l e was subs t an ti a ll y m od i fi e d, a n d o ne w as a dded . The fi na l 8 s ele c tio ns t h en un der w e n t a preli m i na r y c o nc e p t ana l ysis. A p reli m - i nary fi r .d i n g s b r ief was th en p r epare d an d m a iled to 60 k ey org an i za tio ns ( 5 A rm y , 6 N a v y, 1 0 A ir F orce , 2 DoD, 4 N ASA , 5 D O T , 4 un iv ers itie s. 7 l arge a irf r am e manu f actu r ers , 5 fig h t er a ;r c r a f t - . ma nu f a c ture r s , 3 dro n e man uf a ct urers , a nd 6 other a ero s pace co m p an i es). C o m me nts w er e r e c e i ve d ; from 24 of t he se or ga ni za tio ns a nd further s tudy w a s conduc t ed i n re s pon s e to t he com ments.

Th e fi na l e ig ht app l ica tio ns a re n e w de s i gns c o ns id e ri n g AC L G from t h e sta rt , n ot as a r e tro fi t.

"This h as pe rmitted a n i n tegr a ted co nfi g u r at ion whic h i s a low-we i g h t, lo w -co s t a ppro a c h an d sh o u ld : a lso over c ome a nu mber of p roble ms whi c h ha m pe re d t h e XC - 8A d e v e lo p m en t p rogr am.

: N e w ACL G Co n figu ra t i o n Th is new typical configuration is shown by the general aviation design illustrated i n F ig u re 6 .

I t i s c har ac t e riz ed b y a low w ing with a h ig h ly ta pered in bo ar d section h av in g a wi d e o va l cushi on flus h-mo u nted be n ea t h it , on a c urve d u nder - sur fac e , pl u s a high - moun t e d en g ine. L . q l, . ., . H • ¢ ." } I Q J i , _ t . Fi g u re 6. G e ne r a l A vi a t i o n De s ig n "i} " _ '7 Th e gen e ral avia ti on d e sign was th e fi rst of th e eight applications studi e d. It is a utility type a i rcraft w i th provisio n for eight seats including p i lot, to be powered by a i_i sto n e n g i ne dr i v i ng a pusher prop, with rudder in the slipstream for cushionborne yaw con t rol. _ g . " From this basic con fi guration, a family of ACLG aircraf t designs has been evolved. Ea c h is subsequen t ly discussed.

The probl e ms e ncount ere d in the Buffalo program are tabulat e d in Tabl e I. Com m ents in th e 4 I tabl e in dicat e why th e in t e grat e d configu ra tion will hop e fully e liminat e the s e probl e ms. In addi ti on to th eir avoidance, this in tegrat e d concept provides a greater planform area, which improves cushion _I " p e rfor m an ce . Air gap and cushion p e rform ance equal to th e LA- 4 is pr e dicted for th e general avia ti on _ aircraft, using l e ss hors e power, d e spit e a 5 0% gr e at e r gr oss weight. Planfo rm s ar e compa re d in the ] diagram of Figur e 7. Figur e 8(a) is a larg e scal e d e tail sp e cifically to show th e chang e in strain r e sulting from unde rwing mounting. Th e XC-8A and GAA r e la ti ve radial strain is ill us trat e d by th e cross section. .

Additionally t he di a gram bene at h ill us t ra ted th e effect of superimpo sing peripher a l strain w hi ch is also ] reduc e d in the improv e d d e sign. - t _

i

Figure 8(b) mak e s th e com p arison sho w i n g a fro n tal view . In Fig u r e 7 and 8(b), the XC-8A is _ shown at 2 / 5 scal e w hi ch most clos e ly approximat e s th e r e lativ e airplan e d ime nsions an d w eig ht.

TABLE I _ ' PROBLEMSENCOUNTERED I N THE DE HAVILLAND - BUFFALC PROGRAM _ Probl e m Comm e nt "_ Engine ing e sti o n of grassand snow Did not occur on L A -4 amphibian. Engi n e l oc atio n ty p ical of amphib,an is n ee d e d. ] C ushionbome trunk vibration Should not occu r with stiff e r trunk geometry, wi t hout straight s id e s o r o J shion flow trim port s . . _] Cushionborn e pitch / heave ground Analysis shows a stiffer trunk geometry than XC-8A may . _ resonance( " Porpoising " ) be required. This is provid e d by und e rwing mounting. : _ Roll wallow Outer wing support is ade q ua t e. Wid e cushion track is better .

In - flight flagellation C an be avoided by curved undersurfaceand tauter retracted trunk .

Trunk fatigue Excessive strain result e d in short life. Ov e rall strain will be halved by u nderwing mountin _ Trunk structural failur e Rigo r ous analysisprograms a r e now available. This is not a continuing probl e m .

Exc ess iv e syst e mw e ight Major penalti e s were du e to th e e xternal duplic ate d a uxiliary po we r s y s t _ n _a nd the con st r a ints of r e trofit.

Excessiv e trunk r e plac e ment tim e N e w d e signwill a llow for rapid ch a ngeover.

.'' i !:

i ' i

t ' J _ Cushion Areas I J X C-SA I " _ , _ ' :'

t "

XC-SABuffalo : LA-4 2 / 5 Scale Full Scale GAA Cushion Area m2 (f t2 ) 4.09 (44) '3.53 (38) 22.3 (240) 7.15 (77) Perimeter m fi t ) 9.75 (3 2 ) 7.92 (26) 19.81 (65) 10.67 (35) Pressure Pa(Ib / ft 2) 2729 (57) 325 6 (68) 8187 (171) 2250 (47) Figure 7. Air C us h ion Planfor m Comparison _ )) EXRrquS _ ;: ( _ ch GeometricRatio _ Princip a l Stretch 1.87 Infla t ed 2.43 Direc t ion (87%) Defta t ed (143%) Only f_ - Shape _ - Sha pe 2 -Wa y _ U i st Con s idering .

retch ed Equal; _ reato EqualArea to S tre t ch _ Ele m ent _ Fin a lShape _ l e ment / Final Shape

* xN I @ 1

, GAA XC - 8A '; _ Figu re 8(a). Cro = Section Co m parison and Stretc h Diagram XC-SA Buffalo LA-4 2 1 5 Scala Full Scale GAA i Span m (ft) 11.6 (38) 11.7 (38.4) 29.3 (96) 11.0 (36.2) _ , q a x Track m (ft) 1.12 (3.6 6) 1.15 (3.78) 2.88 (9.45) 2.47 (8.1) • Ma x Trunk ; Radius cm (in.) 27.9 (11) 2 5 .4 (10) 63.5 (2 5 ) 38.1 (15) _ : Minimum Ground Clearancecm (in.) 20.3 (8) 34.5 (13.6) 86.4 (34) 35.6 (14) . - ', : , Figure 8(b). Froni al View Comparison

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i' :'_ " 9 SELE C TED APPLICATIONS j _ Fiv e of th e e i ght a pp l ica t io ns s t u di e d a r e t ran spor ts. E a c h w as selec t e d to be co mparable to an existing cr curre n tly proj ec t e d c onventio n al la n di n g g e ar air c raft of t he s ame c la s s , wh e ther a m- phibio us or no t , and to b e s u f fic i e ntly r e pr e s en tativ e of ot he r aircraft i n its c at e gory to show th e A C LG - - adva n tages. Th e tra n sp o r t appl i c a tio n s c onsi de re d , i n c lu d ing t he fi v e p r o m isi ng o ne s s e l e ct e d f or st u dy, ar e listed in Table 11. Pr e limi n ary desig n c o n c ept 3 -view drawi n gs, ill u stratio n s , a n d weight , • d r ag, p e r f orma n ce and c ost e st im at e s wer e ma de f or e ac h o f t h e fi v e c h os e n. T he d e s ig n w ei g h t and _ " ot he r diff e ren ce s bet wee n t he co mparable aircra f t and t he ACLG air c ra ft w ere analyzed for the e c onomic and ot he r e ff e cts resu l ting from t he u s e of ACLG . T he fi v e ar e s how n , a l l at t h e same s c al e i n F igur e 9 .

The o ther a ppli c atio n s c on side r ed, inclu d i ng t h e th r ee ch o sen a re li st e d i n T a ble I I I.

_ reli mi n ar y desi g n dra wi n gs a nd esti ma te s o f th e th ree se le ct ed are a lso sh o wn. T h e sam e = config u ration- driv e rs for i n t e g ra t in g t he a ir cus h ion produce a fi gh ter design resem b lin g th e tr ans- port s . A s imilar RPV wa s considered, how e ver, the e xisting Ji ndiv i k d e sign a de qu a tel y displa ys th e prin cipa l ad va ntage s of thi s app l i c ation, the r efo r e no new de s i g n was developed. The wing in ground effe c t (W IG) amphibian is an ACLG version of a new c o n c e pt.

E ac h d esign is pr e s ented se p ar ate l y in th e follow i ng p ag e s , with a p re lim i nary anal y si s o f b e nefits and c omments on market po te ntial.

TABL E 11 { T RANS P ORT APP L ICATI O NS , Selected Promising Proje ct ed L e ssPromising ,.: ACLG Application s G rossWeight k9 (Ib) Applications Considered 'i : 1. General Aviatior 1633 (3 , 60 0 ) 1 . L a r,d-BasedGeneral Avia t ion i Amphibian (GAA) 2. Agricul t ural Aircraft I A 2. Light Amphibious 5 7 00 (12 , 50 0 ) 3. Executive Trans p ort Transport (LAT) 4. Land-Based Commuter 3. Short-Haul Amphibian 47 , 628 (105 , 000) 5 . Land only pass e ngershort-haul, for (SHA) low d e nsity areas 4 . M e dium A m phibiou s 158 , 759 (350,000) 6 , Medium Range Passenger Transpor t (MAT) T r ansport " 7. STOL Transport 5. Multi.Mission 551 , 120 (1 , 215 , 000) 8. Tanker Air c raft Amphibian (LMA) 9. Lo n g Haul Pa ss enge r Transport 10. Supers o nic Transport It

;|

- ) : • 1105.000Ib) : SHA 47 , 628 kg " _ MAT 158,759 kg (350 , 000 Ib) i z_" 1 " .... "1 • t .i !

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)' _ \ _ LMA 551.120 kg ] LAT 5,670 kg \ _ GAA 1 , 633 kg ¢ _ 112,5001b1 _ 13 , 600Ib) 0 F ee t 6 0 ,I , , ' ' I 0 Scale- Meters 15 Figur e 9. Tran sport Applicatio n s I I . o _...................... .... _ " : "O T A B L E 11 1 F I GHT ER, R P V A ND WIG A PPLI CAT I ON S ,S e l ected Promising Projected Less Promising ACLGApplications Gross Weight kg (Ib) Appl ica t ions Con s idered ._, 6. Sma l l , Off-Runway 6,3E0 (14,000) 1 1. Figh t er Bomb s r Tactical Fighter 1 2. Fighter Interceptor (OTF) 1 3. VTOLAircraft 14. Carrier Based Aircraft 7. Remotely Piloted 1 , 452 (3 , 20 0 ) 1 5. SmalI RPV Vehicle (RPV) 1 6. Supersonic R P V 8. Wing in Ground 2 7 ,216 (6 0 , 0 00 ) 17 . L ighter ThanAir " Effect(WIG) 18. Helicopter 1 9. Space Shuttle APPLICATIO N DE S CRIPTI O NS AND A NAL Y SIS O F B E NEFITS • Though of generally similar configurat i on, t h e family of transport desi g ns h ave different fea - tures and advantages.

General Aviation Amphi b ian (GAA ) The GAA is attractive particularly because of its efficient tripbibious performance, tolerance of crosswind and safety aspects.

Descrip t ion - The twin - boom pus h er is chosen for cushionborne control (slipstream rudder), engin e lo cation (protection from water d amage to engine or pr o peller), and because it pr o vides a safe pro - pe l ler location in ground handling.

: The uns u pe r cha r ged 298 kw ( 400 hp) IO 720 L y co, n ing eng i ne provide s 56 kw (75 hp) to t he ai r c ushi o n f o r o pe r ation o n the g round wi t h all p o we r reve r ting to propulsion for a high crusi n g speed " a t a ltitud e .

The air cushion fan is powered by a hydraulic transmission from the propulsion engi n e which allows constant speed fan operatio n from ground idle to full power. After takeoff the fan is switched off and the extra power to the propeller provides a high climb rate ( 579 m / rain, 1900 ft / min ) . The fan ai r i s taken fr o m t he engine c o mpartment and the air cushi on fan also d o ubles as engi n e cooling fa n, i avoid i ng a typical difficulty of cylinder head tempe r ature contro l hi tax i , c o mmon i_ pusher i n stalia - !

ti o n s. T he resultin g warmin g o f trunk air i s beneficial in c o ld weather. 1 The ela st ic t runk re t rac t s onto the lowe r fu s elage and inne r wing immedia t ely af t er the fan is , s t o p p ed. O n l a n d, the ai r c r aft p a r ks on runners beneath the keel beams. T hese also accep t eme rg ency dead stic k lan d ings. This is ti_ o ught to be acceptable for this class o f aircraft. Emergency means f or t t emp o rar y r e-infla t i o n c o uld als o be c o nsidere d . Over water , wl i en shut down , the ai r craft fl o ats. The inne r wing an d fuselage a r e built as a wa t e r- t i ght bu o yancy uni t , shaped for stable floata t i o n whe n _ m oore d . Cush i on bra k ing is acc o mplished by mechanical ac t uat6rs w hich d i st o .r t t he trunk and vent t he air c us hion. Ha rd wea r in g r ubber e l ements arc provided.

The illust r ati o ns Figures 10 , I I and 12 , respec t ively , show t he air cushion in fla t ed with g ro t m d p a ds v isi b l e, floating in t he wa t er c on f i gu r ed as an ambulance , and res t ing on snow eonqgured as a ._ ] " 3 J ?

L . _. "

.f _

- * Figu re 12. Ge n e ral Aviation D e sign as L igh t Freighter , Park ed on S now lig h t freighter. Figure 13 is a 3 - view showing ground / water li n es cushionborne, parked and floating.

Figur e 14 is an in b oard profile showing engine and fan positions. The fan feeds the trunk through a ! : : singl e entry duct and the air is distribut e d by th e inflated trunk which is, in effe c t, it.self a large du c t.

Analysis - The estimated G A A characteristics are c ompared with oth e r aircraft in Table IV. One of the air c raft is the Cessna i 85 Skywagon which is offered by Cessna in an amphi b ious version as well as a lan d plane. Comparison of the Skywagon land plane figures with the Skywagon amphi b ian shows the - p e nalt i e s i n per f or ma nce a n d lo ad - ca rry in g typic a l of t h e a m p h ib i ou s float pla n e . T h e e m p ty w e ig h t ?

. diff e ren ce i s 254 k g (5 6 0 l b). T h e A C L G we i g ht b reakd ow n i s g i v en in T abl e V. For c o mparison purposes, the A CLG wei g ht sh o uld b e increased by 11.4 k g (25 lb) for the increm e nt in en g i ne weight needed for a new hydraulic power takeoff pad (includ e d in the e n g ine w e ight) and th e fuel for air cushion taxi, takeoff and landing (estimat e d at 4.5 k g , 10lb). Then , tocompare with th e above 254 kg (560 lb) figure, the appropriate wheel g ear w e i g ht of 69.9 kg ( 154 lb) is subtracted from th e resulting A CLG total of 99 k g (219 lb),.giving a difference of 2 9.5 k g (65 ib). Sinc e all of the engine power is used in climb and , cruise, the wei g ht incr e m e nt as s ociated with the air cushion power can not strictly b e ch arged t o t h e ai r cu s hi o n. B u t, i t c an be arg u edt ha t a 24 2 kw (325 h p) su perch ar ged engi ne co uld b e us e d in a wheel e d version o f th e sam e air c raft , givin g th e same p ow e r as th e 29 8 kw (400 h p ) unsu pe rch a r ge d e n g in e at 6000 ft and th e refor e similar tak e off and cruis e p erformanc e ( but not climb). Such an en g in e (L y comin g TIO-540 ) ,,' , ) uld w e i g h 20 k g (46 lb) less , makin g th e triphibious A CLG increment • :- 5 0 . 3 k g ( ! I 1 lb ) in c o mpar i s o n with the 254 k g (56 0 I b ) o f tile c o nventi o na l amph i bi o us float plane.

. . ". , Referr i ng again t o Table IV f o r the land plane / amphibian c o mparis o n,full-range payload i s : '. h a lved a nd m aximum s p eed cut b y ov er 3 2 km / h r ( 20 m p h ). The A CL G airplane t o p s p eed is i g r ea t e r than the S ky wag o n land p lane and cl i mb r ate i s nearl y d ou ble. The p erf o rm a nce penalties of 14 , : o:

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REPRODUCIBILITY OFpooRTllI_ _ i ORIGINA L PAGE IS _,_

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Floating Line !

- _ -- Parked Gro d nd Line ] 4 ' "__ " - ....... " _ . . .e lk -_% - Static Cushionborne Cushionbornex .Water Line _ Ground Line ' _ Part View, Showing Ground Lines - 3.05 m 110 f Figur e 1 3 . GAA 3 - V iew th e h ullborne c onvention a l a m ph i b ianare refl e cted by t h e figures for th e ot he r a ir c r aft sh own, a nd a re s im i l a r t o t he flo atpla ne.

The ACLG a ircraf t cost i s es ti m at ed to be less t h an the am p hibious flo at p lane b u t mor e t ha n th e fi xe d g e a r l a n d p l a ne. T h e e stim a te d A C LGcos t b r ea k d own is givenin Tabl e VI, b a s ed on 1977 doll a rs, a n d a p ro d uc t ion of 3 000 for nonrecurrin g costs. T h e air cus h ion c om p onen t s a re b a s ed on de ta il s y n thet i c es t im ate s, usin g known te c h niqu e s. No ta bl y the t runk s h ee t , w hi c h is a fl a t l a bbe r -ny lon l a m i n a t e is not a d om i n a nt e le m e nt. H owev e rit s r e p l ace ment ( a l so th e b ra ke ] : ele m e n ts ) at r e g u la r i n t e rv a l smu st b e expected , s i m il arl y to ti r e s.

The n eed i or a wide ba s ef o r t h e a ir cu shio n , t h e u t ilit y mi ss io n s espe c i all y, a nd th e p a ylo ad capa b ilitys u ggested a w ide bod y (1 52 c m , 60 i n.) a cc om m o d at i n g threea br easti n thr e e r o w s, the spa c ebei n g sim i lar t o a r eg u l ar au t om obi le s ta t i on w a g on wi t h a s e at p i t c h of 96. 5 cm ( 3 8 i n.) A cab i n c o mparis o n i s sh o wn i n Fi gu r e 1 5 . C om pa r ed w it h a fl o a t p l ane amph i b i an , t he AC L Ga ir- p l anei s a c l ea n d e si _ . a,w ith g oo d c ru isi n g e ffi ci ency, which l ead s t o lo wer p er - mi le c o s ts as w e ll a s t . ' grea te rpay l oad . Costs per a ircraftmile a n d pe r ton m i le a r e comp a redi n graph s,F igur e 16. T h e ca l - , • ' c ul at io ns s h ow low c ost p e r ai rcraft m ile d u e to hig h b lo c k s pe e d . I n ca l cu l at i n g c os t p er t o n -mile , , i p a y l oad was d e ter m inedfrom ava i l abl euse f u l lo ad,wit ho u t reg ard t o s e at capacity . Th e G AA de s ign : , pr ov ides f oreig ht seats i nclu di n g pi lo t, com paredt o's even f or the Ce ss n a 1 85 . Be ca use th ey were c onsideredpri m arilyas ut ili t y air c raft,t h e emp t y weightsfor t hese ai r c raftincl u de o n ly t he p ilo t 's seat. The estim at ed incrementalwe i g h t for t he G AA a s a p as sengeraircraftis 49 kg (110 lb).

/ , J , , < . ._ Pitch Propeller Rudder Lycoming 400 HP I0 720 Engine _ / _ artzell Contr o llable = Variable Displ a ce m ent _ Hyd r aulic P um p J Air-Cushion / Engine-Cooling Fan Hydraulic Motor Inflated Trunk Fig ure 14. GAA InboardProfile " Th e crosswi n d to l e r an c e of AC I.G i s an i m port ant b enef it for gene ral avi at io n whe r e pi l ot pr o fi c ien cy is l e s s and the haza r ds thea . fo r e mo:e severe. The A C LG aircraft la n ds c - ab b e d so that i wing - low la n din g or l a s t -s e co n d hea d i n g cor re c tio n is n ot ne c es s ar y . Th i s wil l g re atl y ease la nd i n g man e uver diffi c ul ty .

k l | t i A i r str i p p re p a ratio n f or the GAA w ill be s i gnili c a ntly e a s i e r t han f or n orm all y- t ir e d li g h t a ir- I c r af t, b e c aus e o f t i l e so f t f oo tp r int . S o f t or wet sp o ts on a g r ass s tr i p pr e se n t no p r o b lem , Y e a r- " roun d lan d i a g on t h e tu n dra can b e acc o mplished with o ut su r fa c e damage - t hi s ha s been established fo r ACVs in tests Ar m y Regions by t co ndu c t e d the U . S , C old Re s ear c h and Engin ee ring Laboratory , [ (R e f. 1) - w hi c h are equ all y appli c able to th e G AA.

i ' i n addi t ion, th e ai r cush io n lan d ing o n unev e n grass st r i p s is n-t o re co m fo r table t l:an wheele d ia q di n g, sinc e the trunk will not tran s mit small shocks comparable to succ e ssi v e wheel impacts. T he soft landing characteristic is equally pleasant in water landings where water slapping impacts a re c orres p ondingly in s u lated from th e aircraft its e lf b y the air cu s hion. Based on A C V experienc e , thick b otto m p l ati ng s h o ul d no t be i l ecessary , a voi d in g t he a sso ciat e d we i ght inc r eme n t . Th is is in ad di ti o n "_ to t h e a ll evi at ion o f i mp ac t a ccel e r at io n lo a ds b y t h e de fle ctio n of th e t ru n k. Quit e sma l l h ove r cr a f t ( SR-NS) hav e be e n o pe rat e d in t _ll g al e c o n ditio n s in the En g lish Channel in corr e s p ondin g ly rough s ea , an d the y h av e thin , 1. 0 mm (0 .04 in . ) a l umin u m bo t to m s kin s . I T he ACLG is at it s w ors t o n a roc k s tr e w n o r sha rp -g-a v el s u r face. I t is p ro bable tha t la r ge so ft wheel s will p e rform equally well and last "longer in these circumstances, though incurring a we i ght a n d d r a g penal t y.

1 6 . , • _ ; -p - _ ¢3 , * " T A B L E IV EST I MATED GAA CHARA C ' I ' ER I STICS C,J_ o m a r yUni t s C es sna 185 H ull Am ph ibian s ..

Land- Lake Tr ident GAA Plan e Amphibian B u c ca n eer T ri gull Gross W e ight (Ib) 3 , 600 3 , 350 3 , 265 2 , 600 3 , 800 " EmptyW e ight (Ib) 2 , 004 1 , 5 7 5 2,135 1 , 555 2,500 UsefulLoad (Ib) 1 , 5 _ 6 1 , 7 7 5 1 , 1 3 0 1, 0 45 1 ,300 i, l st a lledBHP (hp) c 00 300 300 200 320 " i opS p eeda t Se a Leve: (mph) 220 1 7 8 156 146 1 68 Se a L e velR a teof Climb (ft / mln) 1, 9 00 1 , 010 9 7 9 1,200 1 , 260 TakeoffDistance t o 50 fe e t Land (fl) 1,550 1,365 1,2 7 5 1,142 1,050 , _ : : Water (ft) 1,650 1,430 1, 7 80 1 , 400 S now fi t) 1 , 550 "_ / Land in gD i sta nce From50 feet '_ La n d (ft) 'J , 50 0 1 , 400 1 , 240 7 7 5* 1 , 300 " '_ Water (ft) 1 , 270 1,48 0 970* 1 , 20 0 'i_ Snow (ft) 1 , 950 Max Range (miles) 930 1 , 0 7 5 9 1 0 825 9 7 6 With Paylo a d (Ib) 1 , 050 1 , 289 644 715 660 ' ; Duration (hr) 5.7 8 . 3 9.0 ( ) ( ) Price 19 77 $ 65 , 000 38 , 650 80 , 000 45 , 000 100 , 000 S.I . Unit s Ce.na 185 H ull Am 3 hibian s Land. La k e Trident GAA Pla n e A m phibian Bu cc an ee r Trigull I Gros s W ei ght (kg) 1,633 1 , 520 1,481 1,17 9 1 , 7 24 EmptyWeight (kg) 909 714 968 705 1 , 1 34 i U s e f ul Load (kg) 7 _ 4 80b 513 4 7 4 590 I nsta l l e d P ower (kw) 298 224 224 149 239 Top Speed a t SeaL e vel (km / hr) 354 286 251 23 5 270 I S eaLev e lRat e of Climb (m / min) 5 7 9 308 296 366 384 ! Tak e off D i st an ce to 15m . i Land (m) 472 416 38 9 34 8 320 '!

Wat e r (m) 503 436 543 427 " Snow ( m ) 472 : La ndi ng Dista nce f r om 1 5 m Land (m) 457 427 378 236 386 _ Wat e r ( m ) 3 8 7 451 296 366 : Snow ( m ) 59 4 • Max Range (km) 1 , 496 1 , 730 1 , 464 1 , 327 1 , 5 7 0 WithPayload (kg) _ 76 58 5 292 324 299 _ , , Duration ( h r) 6.7 8 .3 9.0 ( ) ( ) Price 1977 $ 6 8 ,000 38 , 65 0 80 , 000 45,000 1 50 ,000 1 7 y 'L , • - , , g : T A BL E V . :, G AA W E I G HT B RE AK DO WN kg fib) kg fib) _ _, PowerPlant 376 . 1 (832) Engine 282 (624) " .

Propeller 39.4 (87) M o unting,etc. 54 _ . (121) Structure 347.6 (768) Wing 159 (351) Fuselage 122 (270) Booms 27 . 2 (60) Horizontal Tail 22.2 (49 VerticalTail 17.2 (38) Landing Gear 83.2 (184) Trunk 14.7 (32.5) BrakeSkids - Actuators 9.1 (20.0) Fan 14.5 (32.0) _ " : Hydr Motor 9.5 _ 21.0) Hydr Pump 12.0 (26.5) Hydr System 7 .7 (1 7 .0) Hydr Fluid 5.2 (11.5) - In s truments 2.3 (5. 0 ) Ducting 2.3 (5.0) Controls 1 . 4 (3.0) Trunk Atta c h m en t 4.5 (10 . 0) Equipment 99.5 (220) ControlSystem 28 . 1 (62) Fu e lSystem 23.5 (52) : Hydraulics i.4 (3) Ele c trics 26.2 (58) Heating andVentilation 13 . 1 (29) OneSeat 7 . 2 (16) E mptyWeight 907 (2004) UsefulLoad 723 (1 5 96) Gross Weight 1630 (3600) The ACLG a ircr a ft w ill b e e a sier to control i ll over w ater ta xi t h a n t he typic a l fl oa t plane be cause of t he lo w -speed o (' the lar g e w av e -dr ag p e ak wh ic h is c h arac t eristic of t h e c us h io n. Th is a llo w s e noug h t h ru s t to be used wit h out a cc e l e rating to e nabl e a dequat e ste ering f rom t he r u dder i n _ . t h e prop wa sh . M od e l t e st r e s u lt s comp a ring h ull dr a g with a n a ir cus h ion dr a g ov e r w at e r ar e shown i n Fi g ur e 17, i llustrating t he point. No te th at t he p ea k air c us h io n dra g is l e ss than t h a t o f t he h ull .

-t (4ft 1.in.) i _., .-- _ _ _ _ ! £' 1 [ I 1 _ Fm , = 0 .33 m --0.38 i _ ' i (13 in.) (15-1 / 2 in.) 0,79 m

i _L i_;I ;; I_

1 . 1 3 m Cessna S k ywagon (31 in.)

(3 ft 8-1 /2 in . )

t

{ _ I - _ - F -- o . _ m

t (4 ft 6 in.)

t _

,-- 0 , 51 m _ '1.52 m -m 120in.) ACLG A mphibian (5 ft) Fi gure 1 5 . C ompara t iveA cc ommodation Cost C o stsperAircr a ft Mile :$ / km $ 1 mi Cost Cost s p er Payload $ / 1"onne-k m S / ton- m ile Ton-mile " i 3- Depreciation , Insu r ance Mainte na nce Fueland Oil 2 / - Cessna-185 _ Cessna-185 2 - / (Am ph ibi a n ) " / ; r ._ s _ -185 i _ 1 " n : : ACLG Amph lb " _ ' Cessna-18 _ 1- T _ _ / (Land Plane) : S. Miles S . Mil e s 0 i _ i i i i i * I I l i i i * I I I I I I I T I I I 1 ' I 0 200 400 600 800 1.000 1,200. O 2 00 4 00 6 00 8 00 1000 1200

il ,oo ,o .oo ,oo , oo o oo.oo

•' BlockDlsti _ c e,Kilometers BlockDistanc e , Kilo m eters !

iII Figur e 16. OperatingCost Compariso n s _1 19 ..... _ . ,= _l i apW , i m_ lam w a m ," Drag "_ ; k g Ib .1 20 0 ; " 500- 2400 Ib Gross Weigh t _= -1000 400- i Measured Data 7 %

D ata C o rre c t j ; ;r

I/ "'--

100 - . 200 L i ft in 10 kt Headwind Cushion Drag Velocity ft / sec 5 10 1 5 20 25 30 35 40 45 50 0 I I I I I I I I I J I I ! I I 10 20 30 40 50 Veloc ity km / hr Fi g u re 1 7 . 1 / 4 Sc a le LA -4 M od el O verw a te r D r a g Da t a ( F u ll Scal e V a lue s ) Cu sh ionborn e c o n tr ol ov e r hind i s si m i l ar to ov e r wa t e r . In c ro s s w i n d taxi. co n s i d eri n g s te ady un a ccel erat ed mo t ion , ti le ai r c r af t is headed i t,t o t he r ela t ive wind , r equi r ing a c r ab a ng l e. Tend e nc y t o d r if t off t he in te nded tr ack downwind is co rr ec t ed b y chauge of heading in ti le upwind di r ec t ion a nd vic e- v er sa . The si t ua t ion i s illu str a te d b y t he diag r am of Figu r e 1 8 . 1, 1 t hes e ci r cum st ance s , wi t h l i tt le o r no sideslip, t he r e i s li tt le o r l ie t endenc y fo r ti le ai r c r af t t o r ol l . ht ea r l y t es t s , p re cise tr acking wa s accompli s h e d b y a skilled pilo t e ven i n str ong c ro sswi n d s , i n ta keoff, whe r e a la r ge ma r gin of t h r us t ov er d r ag e xis t s , ti le te ndenc y of t h e a ccele r a t ing fo r ce t o push t ile a i r c r af t upwind o ff ti le in t ended tr ack i s compensa t ed b y heading ou t of wind mo r e nearly a l ong ti le tr ack , a s t h r us t is inc r e a sed. In downwind t axi , u s e of b ra k e ma y be n e ces sary . ( ' o r ne r ing is a ccompli s hed b y yawi n g i n ti le de s i r ed d ir ec t ion and d r iving ar ound in a sl i pping tt t r n.

Though c l ea r l y cushionbo r n¢ opera t ion i s diffe r en t t o whe e i bor n e , t his does no t seem t o de- tr ac t f r om t he fa vor able e f fec t s o n l andin g safe ty, be li eved to be a s u bs t an t ial beqefit of ti le genera l aviati o n A C L G ap plic atio n . M a n y acciden t ., , are caus e d s i mply by uns kill f u l l and i ng i n d iMcu lt ci r- i cums t a n ces. T h o ugh a m or e t o l e r an t la nd i n g g ea r w i l l d o not hin g t o red uce ti le h a z ar d o f ni id- a ir co ll ision , which is so d r ama t ic a p r oblem t oda y , neve rt h el e ss ti le high fa t ali t y r a t e in ti l t : p r iva t e sec t o r ( ci t ed on one ba s is a s 4 00 t i m es t ha t of ti le comme r cia l - see U.S. News and Wo rl d R e po rt fo r Oc t. 9, 197 8) mus t be p r i nc ipally due t o ot he r ca uses tl l an mid -a i r c ol l i si o n .

Th e (; AA a ir c r af t is pro jec t ed fo r a var i e ty o f uses w orl dwide , itlcludi n g t radi t iona l "bush" , air taxi, private-owner recreational and businc: i s , utility freight for farm and industrial use . etc.

_ " " T he ma r ke t p o t e n t ia l f o r t ile GA A can be a s sessed f ro m .t he exi s t i ng p o pu l a t i o n a n d pr oduc tio n rates of con:parative light aircraft. Numbers for tile United States aqd Canadaonly arc given in tile following table - Table VII. Notably, the introduction of a new q -passenger amphibian ( (;rumman 71 I ) is in tile concep t ual design pllase, and the O-place Tri g ull is e n tering production. ( Aviatio n Week Dec. 4, 1978.)

', 20 "_.

= ,, !

i ------ 1 Relative_ _ 35 k m / hr (19 kt) _ , "

W n y r--Wn

I 1 _ ThrustIT) I -' I Wi n dd ue to _ ' _ _ " 10 km / hr (5.5 kt) -.-% / ! 1 ,r o -- s..

Ground .. . Ground _ " Drag " (D) _ Track Track F( I_ _ T sin _ = Y Atti t ude , and : T cos _ / = O VelocityVectors For c es J Figur e 18. Equilibrium Low-Speed Taxi Conditio ns in St r ong Cros s W ind

i •

TAB[ F Vl I GAA AIR C USI-. ,N GEAR C OST

]

j Trunk Sheet 1 , 200 Attachments andplugs 1 , 260 Brakes 750 Fan andMountin9 2 , 70 0 PowerDriv e 5,500 ] IncreasedEn gineCost 1 .50 0 ,

.!

TABLE VII GAA M ARKET POTENTIAL 1977 Regima tign !

• ": ' S inglePi s ton J Total S a l e l 1976 Float Plan e s Engine ' Aircraft I th r ou g h197 6 AnnualRate Ski Plane s A m phibi a n s LandPl a ce s 1, (All Type = U,S, 2 , 00 0 430 163 , 353 ' i Ce z ma Skywagon I 12,072 1,417 Canada 3,232 356 N / A LakeLA-4 723 90 ' Totals 5 , 232 786 Footnot e : (Datafrom J a ne' s "Allthe World ' sAircraft " a n dthe ATA " Aviation Fact an d Figures " ) Lig h t A m phibi o us Tr a nsport (L A T) Descriptio a - T he example design is in the Twin Otter / Bee ch 99 / S w earing e n Metro C lass of aircraft , r estricted t o 5 6 7 0 kg ( 1 2,5 0 0 lb ), and a ma ximum o f 1 9 seats t o re main in the FAA sm a ll- a ircr aft , n o - c a bi h - c r ew cate gori es. It m ee t s the r equ ir e m en t s f or a c o mmu t e r a ir p l ane o u tl ined by A ll egheny A irli nes i n R e f e r ei , ce 2. A 134 2 kw ( 1 8 0 0 hp) T w i n -P ack PT 6 tu r b o p ro p drivi ng a sin gl e 3 . 05 m ( 1 0 It) p rop e ll e r i s used i n a s imil a r c o n f i g u r a tio n to t he GAA excep t t ha t a g ea r ed d riv e to t he fan w o u l d be use d . T w i n- e n gi n e r e li abi lit y i s p rovid e d by ti le T w i n -P ack e ng i ne: tile e n gi ne i s i n w i de use i n the B e ll -Au g usta H e li c o p t e r . T h i s app ro ach to tw i n - en gi ne r e li ab ili ty i s al s o b ein g a do pted i n th e new Le a r A ri a 2 1 00. I n t he AC L G example, it o v e r c o mes t i l e difficu lt y of moun t in g t wo , en gi n e-driv en p ro pe ll e r s and r eta i ns t he r u dd e r - i n - p ro p-wash c o ncep t f or cushi o nb or ne c o nt rol . T he d es ig n i s a ! .5:1 sca l e - up o f the GAA excep t t ha t t he cab i n i s s lig ht l y w i den ed (2.54 m ( 1 00 i n. ) ). T he floor t o cei li n g he ig h t i s 1 .9 m (6 f t 3 i n.). Access by a for wa r d doo r disp l aces tw o s e ats but w i th f o u r a br eas t and liv e row s p lu s a ce n te r sea t in the back r o w , 1 8 sea t s c ould be p ro v id e d , at a seat p it ch o f 0.9 1 m (3 6 i n. ) . A na rro w a i s l e i s sa ti sfac to ry, s i nce the r e a r e o nly t h r ee ro ws to c ro ss. Th e des i gn i s ill us tr a ted i n F ig u r e 1 9. A c ab i n c om pa r is o n i s sh ow n i n F ig u r e 20 an d F ig u r e 2 1 i s a 3 -vi e w .

Figur e 1 9 . LA T Design !

(32 in.)-. _ 0.39m " (15 ¼ in.)

0.81 m ..., 1.61 m .,. Twin Otter (5 ft 3 ¼ in.

0.38 m.

_ - _ ------ _ -(20 in.)

(15 in.)

I " . " 1.4m - _ 1 0.51 m Beechcraft99 | (4 ft 7 in.)

: _} . ,.07m (4 __ ! .9 "" m _ (36n __ _ [ __ , i

_ o _o ' _ .. L _ ,, _ I .... ; I - H i I-Ill

r(14 in.) _ .3 •----(8 ft 2 in.)----- _ 2.49 m I . AT Design Figu r e 20. Comparativ e Accommodations • Ii _ 17.3 m (56.7 ft) - " I I1_ 1S.9§m 52.3ft) I I- I '" !

i li . ) < _

Fi gu R 21. Ught Amphibious Transport 3-V ie w ' 2 3 4 " ; _ -- -- ....... _ ................... _- 'r _ r -- ! - g T A BLE V III n_ C O M PA R IS O N OF C HAR AC TE R IS TICS (Cu s tomary Units) i Sw ea ringen LAT Twin O tter B e ech 99 Metro g ' • Gross Weight (Ib) 12 , 500 12,500 10,900 12,500 " No. of Pa s sengers 18 18 / 19 15 19 / 20 Wing Span (ft) 53 65 45.9 46.25 Overall Length (ft) 52 . 33 51 . 7 44.6 59 . 4 Wing Loading (Ib / sq ft) 36 31 39 4 5 .0 " Max. Cruise Sp eed (mph) 277 210(185)" 280 294 Max. Rate - of - Climb (f t / m in) 2,500 1 , 600(1,250)* 2,090 2,400 at Sea Level Takeoff Ground Run (f t ) 1 , 500 860 1,660 _ 2,100 I n stalled BHP (hp) 1,800 1,304 1,360 1,880 Cost and Production Approx. 1977 Price " " $1 . 000 , 000 $748 , 000 $846 , 000 $'942 , 000 Nu m ber Produced - 555 164 33 1977 Production - 48 20 (SI Units) Swearin g en LAT Twin O tt er Beech 99 Met r o GrossWeight (kg) 5,700 5,700 4,944 5 , 700 Wing Span ( m ' ) 16 , 2 19 . 8 14,0 14,1 Overall Length (m) 16 . 0 15 , 8 13 , 6 18 , 1 Wing Loading (kg / m 2 ) 176 151 120 220 Max. C ruise Speed (k m / hr) 446 338(298)" 451 473 Max . Rate.of-Climb (m / min) 762 487(381 )* 637 732 at Sea Level : Takeoff Ground Run (m) 457 262 50 6 _ _ 640 : In s talled Power (kw) 1,342 973 1 , 015 1,401 ( * Float Plane Vers ion 1 : : 24 , ,, r_ . T Range P a yload Twin Ott e r D i rect Op e rating C ost !

325 km / hr(202 mph) / 100 % LF I Standard WheelGear i - p 3.0 i Twin Ott e r /

• i _ - , _ /- _ ,o, , _ .,r / _ i_

| 2000 _ _ 274 km / hr / / - ACLG Aircraft !

_ , _L 0 00 / __ _ j/ . / 442 km / hr 2 fl kg - Ib / (170m1 _ ) _ __ FTWo _ t

oo c 1

• 1000 - 2000 "_ S / T on - M. e Statute Miles

I .o

200 40o t 00 o 8 00 1 000 0 I _l I I| ' , , ' ! .

0 500 1 0 00 1500 R a nge - Kilomete _ StatuteMiles 5 00 100 0 0 l i l I l i l i l t 0 500 ' w 1000 1500 Block " Distance - Kilo m eters _ , Productivity With Uniform FareAs s u m ption-60% L oad Factor FareAssu m ption 2 O O % Return / 40 , 5 Annum on Airplane 2O Profit : First Co st100 _ LA _ _ TTwin Otter 300 Pass C entsMilePer ' 30 _ ' _ ___ _ StatuteMiles

_. .., , , = o, . , , , _ l, l ,OpO l O

1 Block Distance Lo._s Kilomete rs 0 , , , , 10 00

o, , . o 5 00 , o _ 1_

T w in Otter J I FloatPl a ne d ' Bl oc k Distance - Kilometers •100 l ', • ; ( t F isur e 22. LAT EconomicComparisons 25 ; A n al y si s - P ri nc i p al c har a c te r is tic s o f t h e L AT a r e com p ar ed in T a bl e VIII with th e Twi n Otte r, B e e c h 99 and Sw e aring e n M e tro. At a power loading of 3.17 kg (7 lb) / p e r hp, LAT cruisin g speed of 442 km / h r ( 2 7 5 mp h) i s fore cast . R ang e -pa ylo ad, d i re c t op e r a t i ng c o st b y the AT A meth o d, with coefficients adjusted to 1 9 78 dollar v alues, and producti v it y are graphically compared i n Figure 22, also assumin g the fare structur e shown and using an indirect cost equal to 1.6 times direct operatin g c ost. Again a comparison between amphibian and land p lane is available, s ince the Twin Otter is sold in both versions. As with the Cessna 185 , the land p lane is a fixed g e ar de s ign. T he L AT (trunk retracted ) is predicted to hav e lower, clean fight dra g , contributing to the higher top speed and better air miles p er pound of fuel.

The quantitative e c onomic advantage of the LAT ov e r the equivalent land plane in terms of dir ec t o p erating cost and produ c tivity is due to the overall airplan e configuration based upon the use of the A C LG. A key characteristic of this dominant feature is the extension / retraction reliabil- it y of the elastic trunk compared to mechanical methods. The aircraft's performance advantage o v er the conventional amphibian is easily seen.

Improved crosswind landing capability is an important feature for this clas s of air c raft also.

In this connection N A SA has recently conducted a wheeled c ros s wind landin g g ear test series on a T win Otter, substantially improving the airplane's capabilit y in this respect. Se v e r al con fi gurations w er e t ri e d . T k e o ne pr e fer r ed b y pi lot s was t ile f r ee l y cast o r i ng wheel g ear which app ro ximates m o st c los e ly t o t i le A C L G c a s e (Ref. 3). P ros p ect s for the actu a l introduction of crosswind gear via c as to rin g w h eel s a re te m pered b y t h e a ss oci at ed a dd i t io nal co m ple xit y and wei g ht / dra g in cre m e nts. I ' Th e strong e st LAT advantage is versatility of operation, payload-access b y water, etc., sugg e sti n g u se in de v el op ing a r eas of tile w o rld.

For agsessment of market potential, production and cost data on the above three aircraft :i are als o g i v en in T able VIII .

S h ort Haul A m p h ibia n (SHA) J D e s cription - A s h ort h aul amph i bia n was also s t u d ie d . Th i s i s pro j ecte d as a s h or t r a nge ( 1850 km , :: 10 0 0 nm i ) lar ge c a p a cit y a ircraft with ACL G. I t is vi s u al iz e d as c omp mib le to, or derived f r o m th e ; Boeing 7 3 7 , h avi n g th e sa m e spa n a n d so m e what si m i lar wi n g b u t with a big fu s e la g e ( e i g ht a brea s t j sea tin g) a n d hi g h b y-pass t ur b ofan s ( th ree T -34 ) loc at e d s uit a bl y f or amp hibi o u s ope r at i o n. I t i s a 1 !.75 : i s ca l e-up o f the L AT . Fi g ure 2 3 is a 3 -v i ew o f the des ig n. P ri nc i pal character i stics o f tiffs design a r e co m pa re d wi th Boei n g 7 3 7 in T abl e I X. i I I C u sh ion a i r s up ply i s by fan b l e e d IYo m t wo o f the engi n e s. Th e fan air wo uld be du c t e d il forward al o n g the b ot t o m s ec t io n of the re a r fus el a ge t o a s i ng le a ir e ntr y po rt t o th e el as ti c tr unk.

I T h e f an bl ee d provides a l o w w eig ht ai r cu s h ion p o w er s y s te m , w i th a ll po we r re v er tin g to .

] propul s io n i mm e d i ately a f ter ta keo ff, an d a v a i labl e f o r c l im b -out a n d c r uise. Th e air c ushi on require- m e n t lb r c o ns t an t pr essu re and flow i n t ak eo ff and l and i n g i s m et by us i n g t h e e xc e ss p re ss ure a v a i l- a bl e fr o m the prop u l s io n engi n e fa n at ta k eo ff p o we r t o p ump a ddi t io n a l fl o w fr om ou t_ide, m i n i - ; m izing t an flo w bl eed a n d th ru st d r a i n ; w hi l e in l a nding suff i c i e n t p ress ure i s st il l a v aila b l e fro m the fan wit h th e e n gi nes ne ar flig h t - idl e , w i t h a gr eat er pr o porti on o f the fan air div e r t ed s o t hat the wh ole a ir cush ion fl o w i s bl ed dir ec tl y fro m t he f an. (_ 'u sh io nb or n¢ c o nt rol i n t ax i w ou ld be a cc o m- pli shed b y us e o f d i ff er en ti a l tan b leed . T h e b l eed a rr an geme n t i s ill ust r at ed by th e en gine i nb o a rd profile , Fig u re 2 4 an d de sc ri b e d i n t he f ollo w i ng.

26 " Figure 23. Short Haul Amphibian (3-Vi e w) ; The air c u s hi on flow r eq ui remen t is first determined f o r t a keoff. I t i s b as e d on L A-4 and ] XC- 8 A test e x pe rien c e. A n effectiv e ai r g ap 50% g r ea t er than the LA-4 is selected, to permi t l o w d ra g t r a v e r se o f s u rfac es somewha t b eyo nd LA-4 capa bility. T hi s g iv e s a to t a l c u s hi o n ai r w e igh t , fl ow requ i re m ent of 7 4 kg / _e c ( 1 63 I b / sec ) . Onl y t he t wo s id e e n gi ne s wo uld b e u se d , th u s t he flo w i is 3 7 k g / sec (81 . $ l b / sec) / per eng i ne. T he jet pu m p is ass u med to in c r ease fl o w suc h t ha t th e mix e d _ ; strea m i s at the same mo m entum flu x as t he f an bl eed ( c o n se rv atively n e gl ecti n g t h e pot en tial for thru s t a u g ment a tion) which giv esa 1.62 p um p in g ratio, thu s th e bl ee d in tak e off is 23 kg / s ec (50.5 ; l b / sec.) ( 17% of ma x im um fan flow f or t h e two engines). T h e r e s ul ti ng t o t a l th ru s t drain is 8 % , as - I itl sum ing 7 0 % of th e t h r us t com e s from th e cold flow.

In l anding, th e fa n ou t p u t pressure m us t mai nt a in tr unk pressure , set t i n g a m in im um rp m .

] T he conditions a r e d escr ib ed i n Figure 25 whic h plots T-3 4 f an flow an d o u tput an d a l so t ot a l n e t thru s t a g a in s t f a n r p m. The fa n r p m n ee d e d is a p proximat e l y 4100 and, at thi s r p m, a flow of 77.2 k g / s e c ( 17 0 lb / s e c) i s avai l ab l e f ro m eac h e n gi n e. F o rt y - eig ht p e rc ent o f t h e fan fl ow wou ld t h e n b e bl e d o f f t o th e a ir c u s hi o n t o p r ov id e th e total f l o w r e quir e m e nt of 74 k g / sec (163 lb / s ec ) without p um p in g . T he ava il a bl e n e t thru s t o f ea ch o f th e tw o e n g in es with o ut th e bl e ed i s 13.79 kN (3100 lb).

b u t with th e bl ee d thi s w o uld be r e du ce d t o 4 kN "(900lb ) which i s a s at isf a c tor y minimum f o r final app r oac h. A ll thr o ttl es can b e u se d as u s u a l for g lid e p ath co ntr o l, in c r e as e of th ru st b e in g accom- i I _ ani e dby an automa t icb l eed d ecrease,preve n t i ngincreaseo f t run k pressu r e .

I

!

i TABLE IX , , - COMPARISON OF SHA DESIGN AND BOEING 737-100 Customary Units '_ S HA Boeing 737 - 100 , .

PassengerC a pacity 14 0 1 0 3 GrossWe i g ht ( I b) 1 0 5 , 000 1 0 5, 0 0 0 Span _ ft) 93 93 * Length ( f t) 94 94 FuselageDiameter / Width (ft) 1 7 .5 1 2 . 33 Operating Weight Empty (Ib) 59 , 900 ( 1 ) 58 , 000 _ ' , ' Eng i nes 3 x T . 34 2 x JT8D . . Engine Weight (Ib) 4 , 281 6 , 310 : Total Engine (SLS) Thrust (Ib) 2 7 , 80 0 * 28 , 000 Cruise Specific Consumption Ib / hr / Ib 0 . 6 7 0 . 79 S t a tic Thrust / Gross Weight 0 .2 65 0, 2 66 P ayload (Ib) 2 9, 7 00 21 , 800 '_ RangeW i th Fu ll Payload a n d A ll owances ( nm i) 1 ,000 2, 000 - r Wing Loading Ib / sq f t 9 7 .5 1 0 7 Crui s_ Lift / Drag r atio 1 4 1 6 _ * 25,95 0 a fte r cush i on bleed S l Units SHA Boeing 73 7- 10 0 PassengerCapacity 1 4 0 10 3 " st GrossWeight (kg) 4 7 ,628 4 7 ,628 Span (m) 28.3 28.3 Length ( m ) 2 8. 7 2 8 .7 FuselageDiameter /W idth (m) 5.33 3. 7 6 Oper a ting Weight Empty (kg) 27 , 170 ( 1 ) 26 , 3 0 9 Engines 3 x T . 34 2 x JT8D Engine Weight (kg) 1 ,942 2 , 862 Total Eng i ne (SLS) T h rust (kn) 1 24 1 ,245 Cru is e Specific Consumpt i on (k g / m / k g l 0.6 7 0 . 7 9 Static Thru s t / Gro s s Weight 0 . 265 0.266 P a yload (kg) 1 3 , 472 9 , 888 Rangewith Full P ayload and Allowances (k in ) 1 , 852 3 , 704 Wing Loading kg / sq .m 477 524 Crui s e Li f t / Drag ratio 1 4 16 (1) Th e abov e SHA oper a ti n g weight em p ty re f lects a f uselageweight approximately 2300 kg (5000 Ib l heavier than that of the 737 with off - letting reductions in landinggear a nd engine weight comp a red with that airpla.ne(See Table XII for landing gea r weight.)

Air Cu s hi°n Bleed AirfJ°w e m'l[ A nn u la r PJ e num _ _ _ Thrust Re v erser / L ow Sp e ed V a n es s ho wn i n _ " _ _ _ Y a w Co n tro _ ( Ba s ed o n

cF. Thru

I!

J

l _ _ T F 34 Engine (Modified t o • Relocate Accessories) Figur e 2 4. T-3 4 In bo ar d Pr o fi le Sh owin g Fan B leed an d F l o w A ugm e n ter Sc h e m e : Fan Weight ; Flow kg / s ec Ib / sec 150 Fan Pressure q Pax 10" 4 Ib / f t = 15 0 0 300 7 . 0 _ ; 6 . 0 Flow Total Net Pressure _ Thrust 100 " 5 .0 - kn Ib , 2 0 0 1000 - 10000 Total F a n 40 - , Flow Available Thrust 4. 0 " L 3 0 - 3.0 - 50- F a n Pressurp • 100 for ACLG ,500 ,5000 ACLG Net Thru' " 2.0 -- 20 _ _ • Flow Reqd No Bleed Accounted _ _ ' 1 .0- 10 - Land i ng Approach Thrust - with 48% Bleed .... = . _ N o Spoiling b0 - 0 0 0 0 2000 4000 600 0 8000 Fa n rpm i' / Fig u re 25 . T - 34- 100 B ypass Flow C ha racte ri st i cs L A na l ys i s - The advanta ges of A C LG in th is a p p li cation w o uld be t o i m pro v e t ak eo ff and la nd ing a t th e many t housand s of d e v e lopi n g small ai r po rt s and al s o t o p e rmi t t he d e v el opm e n t of al ter na t iv e down- to wn water fr o nt si t es as pic t ured in the artists impression (Figure 4).

Figure 26 is an illustration depicting a crosswind landing attitude, with the aircraft headed 15 to 20 de g rees off the runway centerline, appropriate to a 35-knot crosswind. In this application, where the airplane utilization is directed generally at tLe use of less well d e veloped airfields, a cross- wind gear again app e ars as a useful feature, possibly not enough to warrant development of castoring wheelgear for this class of aircraft , but a valuable plus for the ACLG. The following points are made: f Landin g s are currently not infrequently aborted because of crosswind.

The b e st runway alignment is often not the longest available.

Approach aids are often only availabl e on the longest runway. In the developing system with smaller airports la gg ing in facilities, use of crosswind gear will show maximum ad - \ , van t age, enabling a single s t rip t o be used in an y wind condi t ion .

Roll-out distanco is decreased by h e ading into the relative wind a t touch down, and speed mar g in for rough air can be reduced. With stron g O0 ° crosswind, ground speed may be reduced 5 to 10% with resulting 10 to 15% reduction m roll-out $istance.

T _ _. t akeoff and landing at small airports can be improved in. two other ways by ACLG: Use of existing unpav e d or low bearing capacity overrun or allowing low cost runway ex- tension as unpaved surface or water.

- Shortening tak eo ff and landing field leng t h by tile use of "sucti o n braking" as d e scribe d in Reference 4. A reductio n of a t least 25% is feasible.

Improved economy would b e the res_,.l t of t h e high payload / gross weight r at i o r esul t ing from restricting the aircraft to short range, providing a larger passenger capacity and us i ng low specific consumption high-by-pass engines - providing the aircraft is suitably sized to available traffic on a sufficient number of routes. The example is intended to be futuristic (in common with : m o st o f t h o s e shown), i t represents a continuati o n of t h e trend to ward ever lar ge r fusela g e capa- _ ci t i e s on ever s malle r wings and is a design permi tt ing l e ng t hwise growth and increased gr o ss weight ! and ran g e. No problem is apparent in increasin g air cushion pressure w_ t hin r easo n . A g ross w e ight increase of 2 0% for example to 57,204 k g ( 126,000 lb) would increase cushion pressure to 11,158 Pa ( 2 33 lb / ft 2 ) , a nd m a ximum hump w av e-d ra g / w e igh t r atio from 0 . 162 to 0 . 195 , st ill g iv i n g a m a rgin i f o r t he tran s ient p eak dra g c o nditi o n.

!

The short haul airplane concept envisages wid e spread use of less well developed airfields with shorter runways, with versatility to alternate with water landing sites or major airports. Safe t y aspects of t he ACLG loom large. Additionally, economic improvement can accrue due t o lower g ear wei g ht and cost on the one hand, and either reduced or more easily extended field length on the other.

,i Figure 26. Short Haul Amphibian (SHA) T he AC L G appears to offer an overall safety advantage. T he air cushion tr.lnk is not st:bject to catastrophic del]ation if punctured, the power source is duplicated and in the event of double engine failure the belly landing configuration is acceptable. The typical desig, ..,,n not have under- slung equipment such as engines. Single engine failure does not affect the cushion operation since the required flow will be made up by taking a larger bleed from the goot, engine. The vanes will automatically and immediately adjust to mai,ltain trunk pressure. A separate signal , indicating engine failure, would be used to set the vanes to the flight condition on the faile , ! engine, preven t ing backflow. The hazard of partial wheelgear extension is avoided. An increment of safety results from t he c r osswind capability discuss e d p r evious ly a nd safe emergency h mdings on _at er ar e possible. _ L Retractable wheelgear reliability is questionably satisfactory. Table X, extracted from Reference 5, shows all non-fatal incidents reported in scheduled operations lor the year 1973. !

Accidents resulting fr _m wheelgear failure from whatever prime cause whi_.il would apparently either not have happened or been better tolerated by an A( ' L(; equipped aircraft are marked with a n a st erisk. Twen ty of t he thi rt y - on e, s ta r r ed ha pp ened to d i fferent aircraft types. The A C LG will add i an increment of safety to overrunnir g or running off t tle runway mctdents, and to ditching, forced landing, tire burst, and bogging dow,l. All these predi_.aments are recorded in T able X.

r*• I r T A BLE X , NON-FATAL I N CIDENTS NON-FATAL INCIDENTg I I I I RI In l '1"_1 " Inl m l N Occ m m M Date C _ rde r Akcraft Loc a tl l m P h ase .(: k rc m m M im c cm C l e w P _ Ca w P a w J a n 19 T r o n e -Nuaonlir a DC.3 (PK- E HC) P o n t la n a k _ -- S -- L Burnt ou t o n cr as h landing J a n 1O Brlll s n M idland Vi s coun t (G-AZLR) Birmin g ham _ _ | L P o _ t undercarri a ge col la psed o n l a n d ing.

Airways Po o itlonlng flight Jan l g Execut i v e Tron ed od Le a r J e t 2 3 (F-BSTP) Nimc y _ _ ? T L Unde r carri a ge d e stroyed - Jan 24 BEA V a ngu a rd (G.APEB) Ta t , ellde -- -- g -- T IO D am ag ed st a rboard wing tip during t r ainin g t a ke-off J a n24 Ethio p i a n Ai r l i nes B.70T Lagoe -- -- | 104 L "Damaged poe win g a nd ur , derca rrio ge.

D _ e rled •It J a n 30 SAS DC.g (LN-ftLM) O$1o, F o r nob u _ -- 4 2 11 T IO O ve r r a n a fter ab a nd o ned l ab e -o ff • - J an 31 Ae r ovia s N a c l on o leo B .707 (HK-t4 1 0) M a drid w _ 10 72 L N o oe leg off • k J we r luse la t N d am a g ed on d e C(. Io m bil touchdowP * F e b S K i t-A i r Twin Otter (OH-KOA) Oulu, Fin la n d 2 t . 3 IS L Unsu( . C e aofL ; , force-landin g on f r ozen l ake ' _ * F o b 1S K a n a f Air Services islander (4X-AYT) Bee rs heb a _ -- ? ? ER S t ar b o ard p r opeq o r dhdnle gra la d m fl ig ht Fob 17 KLM DCo8 C a ro _ _ ? 1 3 7 ER Engine fire. Retu r nOd I , ) C t ;ro F e b t 8 Nor l h C o y Airw a ys I J lan d e r (NBTIJA) S a n Juan -- -- ' _ L Serious d a m a oe?

Feb 19 S EA - T r ld¢nl (G-AVFF) London -- -- ? 64 ER S oct i on of flap d a lKh e h,1 _ t Feb 7 1 BEA BAC O n e -Elev e n Te nsl d e -- -- g -- L Landed wheele up (G-AVMX) Fe b 21 TWA B. '/ 47 L - s Vegas -- _ ? Climb Emergenc y landing after eno _ .o fi re M a r 5 S p enl a x Conv a ir 9 _ 0 N a nt e s -- _ l m ER Mid-m r coll isi on with E C- B II (EC-BJC) Mn r 17 S ab ena C a r o velle " _ L a nd'0 E nd 1 3 ? ER " [ Alr m lo a . C era v e lia look a voidin g a ct i on S W o r ld Ai rwa ys PC-8 f ? E R M at 15 Lines A a r oposl al HS.7 4 8(YV-C-AMC) M a icluati a ? ? Exten si ve d a ma ge • Ve, ezo la na _ Apt 3 B E A T r id e n t (G-ARPU. Paris, Orly _ _ 6 t t2 L Nus e wheel failed t o l ock-down A p t 4 B rl s t owHohc o pters S -61N(G-AZNE ; North S ea _ _ 2 ? L O u t o f cont r ol landing on d r lllmg r0 o DIt , :he ¢_ -](-A p t 7 Spa n ie l PC-? Lisbon I 111 E ft Engine fai l u r e . U / C f a iled o n S a n ding A pt 8 Ph o e n i l Airways B. '/ O? (HS-IEG) " q l Avlv _ _ ? L Landed with engine on fi re 4(- Apr 17 Iraqi Airways V n lco unt (YI-ACL) Mosul -- _ ? L Under c a rflage colll p led -]( - Ap t 22 Brlt 0 sh West I n_ " sn 8.707 (gYBTO C ) Toronto | 4 8 L No s ewheel tailed to l o w er A p r 25 Ae rnm e r C-M (HI-2OI) Pu M a C a ule d O -- -- 4 -- T e a E n g in e f a ilur e. Ditched M a y 4 M ac ei r Charie r Islander (VH-MK'|) P a pua -- -- ? ER Pro p ollor d e tach e d M a y 7 P anA r '. B .74?,N751 P A} ) Lo nd on . Ho othr ow -- -- ; I J _ 14 G _ ) _ round cOlii ai On Aer Lin0ua B.737 (El-AS3) 2 M a y 10 Thai Alrhnel D C-8 (HS- 13U) K atm an d u -- "2 tO 100 L One ; d ta li t y on g r c,und Ma y 11 Oan tas 8 ,747 (VH-EBB) Sydney ? _ T / O M u ltiple bird Inoelhon K - M n_ 19 DaD-Air Co m et (G - APY C ) M e ss i ah _ -- ? 1 t O " L Nos e wheel fa i r ed to lower M _ ,' : , a Pak l s la n In t lrn'h F.27 (AP-AUW) R I sslew a l a ? ? L A i r cra ft de s t roye d • _ . _ un e 7 Ae r o l0 n ea s Tea V i scount (HK.1061) E l F ld o r a do ? ? L Wheell up la n da n g & - June g Brit is h Midland Vi s co un t (G- S APS) E ast M _ d i and s _ _ 4 S8 L Noeewheel colla p sed on lan d in g J un _ 13 Maya Isla n der (VP-H B X) Bel i ze ? L He av y la n dmO. C o l l ao s ed . mai n U I C J u ne 16 A i r FranCe B.707 (F-SH S X) Bu e nos A i re s -- 4 ? 60 L En g ine fell off a nd fi f e b r oke o u t o n lendin g * J u ne 20 Ov er se a l N at ional DC-g (N863 F ) Bangor, M ai ne 33 ? T / O Tyre blow st arted hydr a u ;iC f, r o - _ June 21 BOAC B.747 New York. Kennedy ? 153 L Overran e n d of wet r u n w a y : June 24 Lo f lle l de r DC-8 New York, Kennedy M g 110 L H e lvy Iond u n o. One engi n e de t ache d • X -J u ly 3 lad(st, Airlines Clravell e (VT-DPO) Bo m bay -- -- ? L Noeaie g collapsed & fire b r oke o u l foilow 0 n g h ea v y la n ding • X .J u ly 6 Ae r ovil l N a ci o nale s HS.748 (HK-1 4 C 6 ) Buc a r mm eye ? S 37 L Overran runw a y. Three killed o n ground d e Co l o m bi a July 11 El AI B.707 (4X-ATT) T e l Avlv _ -- ? 84 L Hydr a u lic fa il u re. Nose l eg colla p s e d July 17 Sale Conv l l r 600 (HB-IMM) T r o m¢ o 3 56 L Heavy lind*no J u ly 28 S a ae 8 HS.748 (XZ-SAB) Ac a pulc o 3 -- L Damag e d during tr a ini ng July g9 Air Bridge C a . i , J ra A rgosy (G-APRN) London, H d th r ow -- _ _ _ T I O Abandoned T t O with e ng i n e t i re •](- A u g 3 U r r a c a I . J e ra ld (HK-?fB) ? ? L Wh e el s -up I L ndl n o A u g 2 Geruda F.L)8(PK-GJT) S um at r a ? ? Severe da m ag e, C,rcu m stance s not re p ort e d • IF Aug 6 O ant sl B.707 (VH.EBN) Sydney ? T Igi Unde r c a r r ia g e col l n a l ed l ea ving a aron Aug 11 A* r F rance F,27 (F- B SUM) St r oebo u rg ? -- ? L Sched u led I t e, g ht fl ig ht A u g 1 '9 CSA Tu.10 4 (OK-MDE) N i colla -- I I I _ L D i v er sion l a n di ng lit e r e n-,n e trouble • X .Sept 4 Lufihsnl a 8.747 Delhi ? MO Toll B o gged down befo r e t a k e .off Sept . 5 Air Vi e , na t ' , B . Y g 7 (X' 4 -NJC) Bangkok 4 [ A T I O G a lley explo s ion S e a l fl Ca,,u , ,.a C.990 (N7878) Guam ? ? -- L C r ahaed on a , r po ¢ 1 A t r m ob v a • X.Sept 11 Swle| a lr DO.10 (HB-IHA) Z urich ? L U n de r c arn l g e f ade d to lock down Se pt 12 Lane X nng Al r llne _ DC-3 (XW-PKD) <o mp o t ? L S er ious d amage S e al g 3 A i r A l ger l e C ar ave l lo (7T-VA I ) . _ Ig l e r e -- -- ? L Se r ious Dam age •](- " )el S Ae r olln e s l T _ O Visc o un t (HK.1 0 58) El Gor a d o -- -- ? L R a n off runw ax ,. S u bstant ia l da m age Oct 6 T r i n e 8.707 (gO-FA X ) B ¢ . ,_ b a y ? -- T I O S tr uck wall g ad da m ag ed u n d e r c a .lege Mediterr anea n Airways Oct 6 Balka n- B u l g ari a n Tu.134 (L Z -TUA) Sofi, _ _ _ ? L Undercarria g e r ollepe e d Cot ?0 Mex i c a ns B.727 (X A -SEN) M a r a _ I n n 3 ? L L e n de_ a b or t at runway • X .Oct 28 Pie dm on t Airlines B.737 (NTSIN) Groan _ borg, N . C, "_ 3 4 g 0 L Overran r unway. H it embankment Ocl g 3 N ig e ri a Airw ays F- a T Ibldln _ I ? ? L Forced lending •IF Oct 25 Spnn [eli Air l ines Dc.e(NO14SE) Mi am i 1 _ :J L D itched In b a y s ho rt ol tuot • X - Nov t S Sesbolro World DC-I (N07 8 3R) London, f l es t h r ow -- -- ? " _ L Wheel lol l It Shannon. D , v e rte d • da m age d on lan d mg Nov 27 Delt a Ai r Li n es DC- g (N3323L) Chatta n oog a _ ? T ? L H it ILl a er ials. Ce u 0ht fir e 'l _ o v _ ? Eastern All Lines DC- g (NBM?E) Akron.Canton tS _ | 1 L Ove rr an runway and went down em bank m ent D ec 3 Air Unio n PC-3 (XW PHV) Phno m -P e nh ? ? - ? T I O N O d et a i l s. Ser io u s o ama gs " : Dec 1 _ F r ed glees Falcon : t O (LN.FO E ) Norwich 3 0 3 (J T O Mul tip le bird s tr ikes ; _' Oec 14 Loq ana lr S kyvsn (G-AWYE) London , Gatwlc k - ._ . -- 2 _ L P o rt un de rc sr r*a g e col la psed r _ Dec 15 Ai r Un i on CW-;q) (XW-PKK) Phno m .Penh ? ? ? L Po rt unde r c a r riag e c ol l a ps e d •N DeC 1 7 Ibsr ls DO-t0 (EC-CBN) B o st on Ill 14 t54 L Hi t runway li g h t s a nd burn t D e c t? Elli erh Ai r Lisle D C.O G r eanlboro, N.C. -- 1 06 T I O Tl ke -ol_ a ban d one d . S m al l fl t o De c 2 0 Luflhlnel B.?O?(D-ABCT) Delhi _ l g 11 M L Landed l h o _ l i _ Dec 23 C . ruzeiro d o Su l Clr a vel l e (PP-PDV) M a n ila -- t ? 6 0 L Ove r ra _ runway and ca u ght fire, _ • ke 0 e r *d: T I O, telle.,efl: ¢, I _'l*lllll climb. [IN,e ¢r e _ o: A S lI, eel)filch, _ i ifllll _ ll: O, avIN'eh N I ; *lr cldo _ ts which would proD a bly have been avoided or b aiter tolerat e d w i th ACt.G ;l REPrOD uc I B IL I T Y " "' - OF _ ORIGIN AL P AG _ I S P OOR Y f l The estimated air cushion l anding gear weight and cost for the SH A are compar e d with ' Boeing 737 f i gures i n Table XI. The air c us hion f' _ ,uresare bas e d on de t ail synthetic estimates.

! They inclu d e an incr e mental wei gh t an d cost for th e engine bleed modi fi cation for ACLG. A parallel economic comparison between t he Boeing 737 an d the SHA design has not been made be- i cause a l ar ge part of the economic advantage would be due to the use of modem hi gh by-pass ! e ngin e s , which coming into us e on shorter haul aircraft such a s the Bo e ing 7 5 7, f o r exampl e ,

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will prob a bly mak e th e 737 gradually obsol e te in an y cas e . The co m parative e ngin e w e ight an d i speci fi c fu e l consum pti ons ar e given in Table IX. As e xampled, the integrat e d A C LG c o ncept d e - p e nd s on bl ee d f rom a high by-pass e n gine (t he air cushi on being a high-flow, low-pr e ssure typ e of i d e vic e ) for a low weight pow e r supply, an d, although th e bl ee d syst e m wei gh t is charg e able to th e ! air cushion, it ca n b e ar gued that the e ngin e s are siz e d for c l imb and cruis e , th e ACLG pow e r dr ai n r es ult in g in a long e r t ak e off gr o und roll, acceptable becau se o f t h e r e laxed surface requir e m e nts.

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! TABLE XI • SHA AND BOEING 7 3 7-1 O0 LANDIN G GEAR C OSTS !

] SHA Boeing 737-100 ¢ Gea r W e ight kg,(Ib) 1,54 4 (3 , 4 00)" 1,989(4 , 382) GearCost ($) (1974$) 21 7 , 000 322,000 "includes thedelta foren g ine fanbleed an d a fuelallo w_ ance forcmhionbome operation.

T h e reduction in landing fi e ld l e ngth which could be achiev e d by the c us hion braking m e thod outlined in Reference 6 is shown by the diagra m , Figure 27. Its use could permi t e lim ination of engine thrust rev e rs e rsper se.

t : F Wheelgear orACLGwithRegular Br a king / O Runw a r

/ / --ACLG withSu c tion Braking ! : Y /

Height- / / / T---- C or r e sponding FAR 2 5 Meten'(Feet) / / / _ Wet Field Le n gths Requir ed 15. 2 4 (SO)' _ j _ _ CLGwi t h _ i 0 d _ -- _"_ I _ : z 21 1_ rak;ng _ Wheelgear orRegular ACLG - . ; Feet • _ 0 I000 2000 3000 4000 5000 6000 a a I I I I I | I I I I u _i O 50O 1000 1500 2000 :! Meters " l Landing D i stances . , _ Figur e 27. Landing Profile Comparison Mark e t pot e ntial for such an aircraft cannot b e realistically assessed at this tim e . B e cause th e application is sl an ted towards us e of landing surfac e s of gr e at variety and low cost, it m ay be on e of th e most attractive; but, in common wit h th e larg e r aircraft studied, t he re is no possibility SHA d e v e lopm e nt would b e und e rtak e n until A C LGt e chnology is furth e r advanc e d. Syst e m re - liability and potential lif e m ust first b e e stabfi she d by e xt e nsiv e operation at smaller scale.

e Me dium Amphibious Transport (MAT) De s cription -T h i s sho w s t h e pote n ti a l o f an ACLG ai rcraft as a m i h t a ry / c omm er c i al freig h te r de- sig n ed to acco m modate side by s ide 8 x 1 0 ft cro s s s ec ti on con ta iner s i n tw o i d e s a s sh o w n in t h e 3-view, F ig u r e 28. t Characteristics Aircra_: Wing Area 2 2 8 sq m • (245 6 s q ft) M a x GrossWt 158 , 900 k g - ( 3 _ 0,000 Ib) Eft Aspect Ra t io - 7.98 C us hion Power - 2 CF6-5 Engines at ,.

51 , 000 Ib St a tic T h rust ea Air Cushion: " - " _ " Maximum Cushion Pressure 1 3 ,500 Pa - (282 psf) --- - '1 -- " l r - .... -ir _ . I Cushion Area 115.3 m m - (1241.6 , _ 1 f t ) , L .... - _ b _ .--:------ -_c ,' fI ' _ I • '" _ erimeter 37.9 m - (124.34 ft) , ., , ..... .] [ ' ' Figu r e 28. Me d i u m Amphib i ous Tr ansp or t 3 -Vi ew it i s essen ti a l ly a 4 : i sca l e - up o f the GAA. T he des ig n fol l ows a s i m il a r app ro ach to pa r k i n g o n l an d o r fl o a t i n g o n w a t e r . The a ir c r af t i s p ow e r ed by two , GE CF6 - 50E en gi ne_ m odi fie d t o bleed s o m e o f the b y - p as s t an ai r t o su pp l y t he air cushi on , similarly to the SII A .

Th e kn e eling featur e inherent to the air cushion permits parking with the fuselage bottom nearl y at ground le v el. T his brings th e floor d own to tru c k bed height for loading beneath the tail as shown in Fi g ure 5 a n d Fi g ure 28 (1.32 m) ( 4.33 ft).

:. T h e C F6- 5 0 is p, , rticularl y adaptabl e to the b y - p ass t an bleed sch e me becaus e the space be- - twee n t h e inn e r wall of the by -p ass flow d u c t and t h e core engine is largely empty, the accessori e s b e in g h o u se d in the lbrward duct structure a n d dri v en by a quill shaf t a s shown in the standard e n g ine cro ss s ec tion, Fi g ur e 29(a). T h e modification w o uld be to bring the i n ner wall in as cl o s e to th e cor e eng in e as practicabl e and surround the fan flow duct with an annalar collector and je t pum p a s s h o w n i n Fi gu re 29 ( b ). T he estimated add i ti on al weight o f the A ( ' L( ; bleed i n clu d in g a ll du cti ng o " ° Four-stag e Low Pnm m m T u _i m Annul a r Combustor Gear box Figure 2 _ ( a). C F 6 - 5 0 StandardEngin eC rossS e c tion Air Bleed Vanes: LandingPosition Takeoff Position Control Vane Air Cushion Ai r Renum [ Relocated Fa n Exit v "1 Relocated Mixing ThrustR e verser Annulus FlightP os ition Fig ur e 29(b). CF 6 - 5 0 Engin e Showin g Propos e dModificationfo r ACLGFa n Bl ee d RI ': PRODUC1BILITYOF THI_ c "r'_ ' P _ AL P A GE I S P O _R O onthe engine'sid e of the interfa c e is 386 kg (8 5 0 Ib), which is 10 % of t he engine weight. Probably _' the percentage increase in engine cost would be less than I0%because the alteration consists largely of sheet metal work.

Cushionborne yaw control in taxi would be ac co m plished by differential o perati o n of the outboard sector o f the thrust r e verser. M o dificat i o n t o i m prove respon se , ratew o uld possi bl y b e requir e d. T h e engine fa i lure ca se i s si m i l ar t o t h at of t h e SH A. T il e bleed c ont rol wo ul d res pon d t o the p ressu re drop res u lting fro m t h e stopped or sp o o l in g -down fan by incre a s i n g t h e b l eed pro p or - tion o n t il e l i ve engine.

Analysis - The M A T de s ign co n ce pt i s si mi lar i n s i ze to the YC-I 4 , with wider f u selage and greater w i ng area, b u t u sing t il e sa m e engines . A si z e c o m par i son wit h ti l e Y C-14 i s s h ow n as F i g u re 3 0.

Four to one s cale-up from the GAA ( s i m ply assuming weigh t varies as span cu b ed) indicates a gros s weight of 104,32 8 kg ( 2 3 0,000 lb). Th e m axi m u m CTOL gross weight of ti l e YC-1 4 i s 107 ,5 03 k g (237,000 lb). i --'-'I t '- .......

_ , ',_0 .......... Jt . . J i l z I | i F ig u re 3 0. S i z e C o m parison of YC- ! 4 w ith Med iu m A m p hibiou s T r an s port ACL G Co nce pt A t 23 0,000 Ib , t h e MAT t hil s t o t a_kea dva n t a g e o f the i n c r ea s ed takeo f f a c celeration d i stanc , !

re lative to w h eelgear w h ic h it s h o u ld be pt : , r m itt e d t o use be c a u s e t h e a ir cu s h io n m a ke s t h e lo nger " distance so mu ch easi e r to prov i d e, e sp eci a l ly o ver 'wa t e r , and w h ic h w i l l in c r ea s e pr o d ucti v i ty . W i th t he A CLG , ST O L i s not an obj ec tiv e . A m_x i mum gr o ss weigh t o f 15 8 ,76 0 kg ( 35 0, 000 l b) w as t he r e - I bre ch os en. At t hi s weight , tl: e mom e n t ary l ow - spee d 18 . 5 km / h r ( 1 0 k t ) wave d r ag peak o ver water i s a bo u t 2 / 3 o f t he available e ngin e th r u st a nd e m ergen c y fl o ata t i o n i s a lso s ati s fa c t ory . T h e e s t im ated 3t , " L" i " ,¢ a m f K , m .,...,_ ........... _ = - --_ -I-_ _.

Altitude _ ,. , m ft 10 , 000 - _ _ , Ma ch 0.7 0. 81 i _ .

- 30 , 000 Typical Data • Ba se don T - 34 c -2o , ooo , 5 , 000 - ¢ ' --10 , 000 I Statute m i le s _ r 5 00 1 00 0 _' I " I • I SL , I , ,I v I , ,I , I , , I , , , , , 0 500 1000 1500 V / c - km Figure 3 1. Variation of Rang e Fac t or ( ' rhrust Hors e pow e r p e r P o und of Fuel) with Altitude wat e rlin e s fl oat in g cush i o n born e a n d ai r c u sh i o n of f a re s ho w n in F ig ure 28 . F l o a t ing cush i o n -off "_ in t h e wat e r at full gross w e ight will not b e a n ormal op e ratio n . W in g loadi n g is 69 3 kg / sq, m (142 lb / - , sq. ft), tak e off a c c e l e r a tion distance to rotation sp e ed is 2286 m (7 5 00 ft), c limb m ini m a are satis- f actory and i n itial cr u is e altitud e (at M = 0 .7 5 ) is approxi m at e ly 9 , 449 m ( 3 1 , 00 0 ft). E ngi ne s p eci f ic _ .

consumption per thrust horsepow e r (c / V ) vari e s only slightly with altitude at constant Ma c h num ber so t h at l o w e r cruis e altitud e is not disadvantag e ous. Figu re 3 1 plots typical lb / th ru st hors e po we r / hr ve rs us altitude at t w o values of M ac h n um b e r. T h e A C L G we i g h t i ncl u ding t he i n cre m ental power p l ant w e ig ht f or f an a i r b leed i s e sti m a ted t o b e 4 54 k g (1 000 lb ) le ss t han the Y C - 1 4 g e a r.

Th e grap h s in F igur e s 32 and 3 3 co m par e rang e -pay l oad a n d op er a t i n g cos t ( u si n g A T A meth od) of t he MAT and YC-I 4. Typical cur re nt air fr e ig h t rates for larg e s h ip me nts (908 kg , 2000 lb or gre at e r)ar e a l soshown. P r oductivity, ex pr e ss e d asa specificwor k capacityin ton - m il esp e r a nnum p e r dol lar o f airp l an e firs t cost, is a l so compar e d. T h is can b e mu lti p l i ed b y profit ma rg in t o o b tai n an ' , R OI fig ur e . T he cost of t he MAT was arriv ed at b y ra ti oing e m pty w e ig ht s.

This co m parison principall y shows the advantag e in ra ng e - payload cons e qu e nt on providin g a 1 t long fi e ld l e ngth, which th e AMST was d e sign e d to avoid. A wl 3 e e l e d air c raft d e sign e d for and pro- vid e d with th e sam e fi e ld l e ngth as th e MAT conc e pt , would r e cov e r most of th e diff e r e ntial shown.

What th e n n ee ds to b e d e t e rmin e d is th e e xt e nt to which th e r e quir e m e nt for STOL can b e c o m pro- 3 7 ?

e Gro ss Payload • kg Ib _ : • [ 200,000 75,000 ] -I / - MAT 158,900 kg (350 , 000 Ib) GW _ L ; L _ " 7500 f t Ground Roll 5 0 , 0o0 . 1. -- | YC - 14 107 , 598 kg - l ,. YC-14 _ (237,000 Ib) GW / 77096 - Kg 2 ft r n o

[_ -: _6_i _ roun d R o, I n m i

,1 0 2 000 13 000 4 0oo 60 2

0 f ' n " , , _ 0 2000 4000 6000 8000 100( ) 0 Block Distance - Kilometers ....

F i g u re 3 2 . E stim ated Ra n ge - Pa yl oad C o m Parison of MA T wit h YC - 14 : Operating Cost Cornparison $ / Tonne-k m S / Ton-Mile / nTK , / Ad i usted Rate ATA Method .... __ _ 0 _ / Ind i rect Cost = 1.6 x D.O.C. Included r _ .U _, A 85% Load Factor 3 Crew i _ _ ¢ \ STOL Fue13 7_ Gal 050 I I v _ --YC-14 .

• -- _ _ r - Current Freight Tariff _ . _ n CTOL _ / (20O0,bor more) , 0.50 U l UL _ • / _ YC . 1 4 . -, - " -- --.---J Co sts l 1000 2000 ,t000 n , m l 40 0 0 5000 0 I I I I I I I | i I 1 2000 4000 6000 8000 10,000 Block Distance- Kilo m eters Productivity Potential Tonne-kilo m eters Ton-Mile s / Annum / $ Annum / $Airplane Airplane Cost 2 - MAT Cost 5 0 _ -_ As su m ed Cost $ 1 7 .5m 6 _ " f_ YC14 _ Cot J **" " _ - . " ...... _. s s are Proportioned ; t 1000 200 : 3000 n' mi 4000 ' 50001 / 2 000 4000 6000 8000 10 , 00 0 Block Distance • Kilometers - Figu r e3 3 . Cost Comparisons raised by t he ACLG capability for all s urfa c e la n ding . The ru n way dis t ance ( a s opposed t o the over- water distance or other clear space) which t he ACLG aircraf t is entitled t o use should al so be greater j than for Wheelgear , but a quantitative assessment is difficult. Survey of the underruns / overruns available at a s amp li ng of U.S. airports shows that a 2 0% landing distance h an dicap for wheel gear m ay not be unreasonable. At some places, regular use of such overrun m ay be unac ce ptable - for example for noise reasons - but at others, d is tance availab l e to the ACLG air c raft can be in creased at low cost co m pared to m aking similar provisions for wheeled aircraft. If generally applicable, such an in - " crement would have a large effect on overall economy.

Commer c ial market potential for thi s t ype aircr a f t is dependen t on a develop in g air ca rgo busine ss and could be large. Mi l i tary po t en t ial could also be large. I t appears to depend on t he increa s e in effec t iven e s s con s equen t on a ll sur f ace capabil it y, par t icul ar ly amp hi bious. Curre n tly (in th e li ght of co nventional amphibious landing gear) there i s no military r e q u ir eme nt f or seaplanes or amphibians.

The potential is far ter m due t o the technology development needed and becau se of presen t emphas is on possible AJ_i STproduction. I t would requ i re ac ce ptan ce of ACLG as a v i able al t erna- tiv e to ST O L.

/; La rge Multi-Mission Amphibian (LMA) D e scription - The large m u lti-mission amp h ibia n is ill u strated i n F ig u re 34. It is proje c ted as a very large c o mm er c ial / m ilit a ry freig h ter and h as been derived from a Boeing preliminary design call e d th e 7 5 9-182A whic h w as a co m pa ra tor in t h e study of distrib u t e d load fr e ig h ters (DLF) of R e f e r e nc e 8.

Th e approach taken was to m odify t h e given 7 5 9 -1 8 2A desig n minimally , for an A C L G in- stallation similar in c oncept to the AC L G family of transport desig n s. The wide body (with greater fus e lag e li ft) s ugg e st e d contain e rs b e ca rri e d at h w _ '.rts hi ps. This p e rmits sid e -door loading, w h ich is li gh t e r in w e ight. Alt ern ativ e ly if compatibility with gr ound rail load in g is n ece ssa ry , five abreast c o u ld be carrie d i n a three-lobe st ruc ture. T h e do u ble-lobe c ross se c tion is s h ow n i n Figur e 35 . Eac h sid e is ca pabl e of accommodating a 3 .66 m x 3 . 66 m (12 ft x 12 ft) rectangle.

Alternative loads to freig h t c ontainers have not been considered in detail b u t m ilitary payloads or pa ss engers c o u ld evidently be ac c ommodated. T he highly-swept, t h i c k-secti' m i nn er-wing and also th e f u sel a ge li ft- con tr i b u t i on sho ul d have f a vo ra bl e e f fe c ts on t h e str uc t u re we i g ht. T h e conv e n t i onal !

co ncentration of pay l oa d i n th e c ent e r , pr o d ucin g w in g r oo t be n d ing, be com es a difficult pr obl e m at very l a rge size, and i s o ne reason for t h e DLF a pproa ch .

The 7 5 9- 1 8 2A 3-view is co m pared wit h th e L MA desi gn 3- v i e w in Fi g u re 36 . Both a i rc raft a re p owered b y CF6-50 en g ine s of approximate ty 23,014 k g (52,500 lb) SLS thrust each. Becau se t h e L M A i s d es i g n e d t o b e a m p h ib iou s, t h e e ngine s a re l o ca t ed two a b ov e t h e fu se la ge and tw o ' : mount e d off t h e fu se l age s i de above t h e a i r cu s hi o n tr unk. T he l att e r are al s o u s ed t o p ow er t h e air c u s hion as de scr ib ed an d s ho w n f o r t h e MAT. T h e LMA i s rega rd e d a s prin ci p a lly e mployin g l _.i'_ I wat e r for ta ke off an d la ndi ng b ut a l ways l oa din g a nd unloadin g - o n sho re a s s h ow n in Fi g u re 3 4.

" _ An a i rc ra ft t hi s s i z e , w i th a 2 .0 to 2.5 m ( 7 to 8 ft j de ep a ir c u s hion tru nk will h a v e n o di f ficul t y ! o n 0. 9 to 1 . 2 m ( 3 to 4 I t) wav e s. Gen era l l y , t he A C LG ai r craf t wi l l b e a ble t o u se r o u g he r w at e r i t h an t he s a m e s i z e d fl y i ng b o a t hu ll . R o u g h w ater m o d e l tests were c onduc t ed b y N A SA o n an ' X C - 8A m o del l a nding on re g ular 5 ft. full-scale wave s , reported in Refer e nce 7. Table XII i s taken " 39 : !t . , , . ° . ¢ - ._ , , o .

- _ . _ . t ,. - ."_; _ _'d_ll_ - _k . j.

k Figure 34. l.._ge Multi-Missi on A m pl_bia n ( L M A ) w ! . 7.07 ; n (23.2 ft) I - 15 . 06 m (49 . 4 ft) Fi g ure 35 . T ypi c al L MA Cross Section from Tabl e I I I of t il e relZ ' r e n c e , Peak wa ve drag oc c urs at approxima t e ly 2" k m / !u" ( 12 kno t s) a n d is equal to 45 % of t akeoff t hrust , de c aying rapidly above t h i s sp e ed.

T he ai r c ushion distributes th e landing l o ad into the str u c ture in satisfactory fashion and at t he s c ale of t he LMA , is exp e c ted t o save ab o ut re,' ; of the s tru c t ur e weight c o mp ared will] wheel gear. Estimated weights are co rn .pared in Tab l e X II I The A C' L (; weight is lurll l ,, bt'o k ell down in Table X|V.' It is based o n XC-8A ex p erience, fa c toring to the large s c ale by IncaJ r , of the C t ) lnl'_ara- tire data also shown. The low c u shion pressure of th e LMA is notable. Ilic LMA is approximately a 3:1 scale tip from t he XC-8A B u ffalo, based on sig n ificant tlin l cnsiolls, therefore, a cushion p res- sure t h ree r imes greater would be expected. But, dttc to the large area cushion of the / ,MA the .... : ._ _ .,..., _ .,.,. !_ . _ ,p, , p , . _ , _ -- _ z, _ ,., _ , _ _ " ! .

76 m i _ : .

_ t - _1! ( 249 m I L 'L i.

• ii4 4 _, ' 4 ' b_ J i_! 4 ._ J " i

1 - - • I_i L t I

_ l _ "_- • 16.2 m (49.4 ft)-' P ' I_ --- I _" 12.3 m (37.5 ft, _ 3 .

_ 2 2 F i gure36. LMA / 759 - 182AComparison !

R _ D U CIBI L rI _ O FTi _

OR IGI NAL PAGE IS POOR TABLE X II 1 / 1 0 SCA LE C - 8 M O DEL WA TER L A ND I N G TESTS, SI MULA TED5 F T WAV ES _ Full Scale V ertical Maximum Ve rt i ca l Sink R a te Ac c eleration a t q l , m / N o ft / N ¢ g Units

!

4.1 13.6 4.24 3.8 12 . 3 _ i . 72 3 . 5 11.I 2.62 , _ 3 . 5 11.I 3.00 , :I ' " v i • ° e TABLE XIII ,,_ L H _ , / 75 9"18 2A WEIGH T BREAKDOWN Boeing 759-182A LMA \ Wei g ht - k 9 (Ib) % GW Wei g ht - kll (Ib) % GW Stru c ture Tota l 133 , 221 (293, 7 00) 139 , 675 (307 , 928) ILand i n g G e ar) ({56,8B0)) 5.5 ((41,278)) 3.4 Propulsi o n 17,835 (39,320) 17,635 (39 , 320) Fixed Equipment 2 1,638 (47,700) 24,310 (53,595) Pai n t end Optio n s 2,395 (5,280) 2 ,51 7 (5 , 550) Empty Weight 175,088 ( 35 6,000) 184,33 9 (406,393) Gro s sPayload 194,774 (4 29 , 400) 243 , 468 (536,750) Z e ro Fuel We i ght 369,863 ( £ ' 5,400) 78 . 8 427,807 (943,143) 7 7 .6 " J Maximum GW 46 9, 623 (1 , 035 . 330) 551 , 120 (1 , 215,000) - , I TABLE X I V LMA A C LG WEIGHT BREAKDO W N Summa ry kg lib) Elastic Trunk 10,024 (22,100) : Cushion BrakeSystem 3 , 039 (6 , 700) Parking Skids 2,756 (6 , 075) (0 . 5% WG) Trunk Attachment 1,929 ( 4, 253) CF6-50 Modificat i on 975 (2 , 150) " (12.5 % WE) 1 8,723 (4 ! , 278) Comparative Data i XC-8A LMA : Trunk Outer R a dius R 1max m (in.) 0.64 (25) 3.05 (120) "i I runk PressurePT, Pa (Psf) 16 , 375 (342) 23 , 46 1 (49 0 ) ; Cushion PressurePC , Pa (P sf ) 8 , 140 (170) 11 , 7 31 (245) l Tru n k Mat e rial Tension , I !

J N / m (Ib / in . ) 10 ,6 83 (61) 71 , 452 (408) ' Air Cushion Perimeter , m (ft) 19.8 (65) 7 5 . 9 (249) Wave Drag / Gro ss Weight Dw / W 0 .2 1 8 0 . 0 71 Displac em ent , m ( f t) 0 .82 (2.7) 1 . 1 9 (3.9) Cu s hion Length , m (ft) 8.5 (28) 4 0 .4 ( 1 32 . 5) fa ctor is only i . 44 and the re s ulting di s pl a ce me nt (in s t a tic over wa ter hover ) i s or.l y one third of ti le max i m u m tr u nk de p t h . A dd i tio na l l y, t h e p e a k overw at er w a ve dr a g i s o n ly 7% of t h e gro s s w ei g h t . The trunk p re s s u re is s i mil a rly low, c o mpa tibl e with CF6 - 50 fa n bl e ed an d th e res u l t i n g m at eri a l t e ns io n is well withi r cu rre n t te chn ology: n u m ero us e l as ti c ma teri a l sam ple s of v a r y ing s tre n gth ti p t o at le as t six tim e _,th i s v a l u e were ma de b y Bell in supp or t of t he XC - 8A p rogr a m an d p rov i de t h e b as i s f or a c o n fide n t t r un k w e i ght e st im a te .

A n a l ys i s - The 75 9 -1 8 2 A d esi gn a lre a dy c apita l iz e s on t i l e ec o n o mi c a d v an t a ge s of lo n g ta keoff : u sing a field length of n early 3 6 58 m (I 2 , 00 0 f t ) f or a very h ig h (41 % ) pay lo ad fra ct io n at a m oder a t e r an g e of 6 , 667 k m (3 600 n. m il es ) . I t has a s t a tic t hr us t / wei ght o f o n ly 0.202 a nd the , -I L

• spRO . £00R

! C B .b ,r y OF

ver y l o w power s ys tem we i ght f r action o f on ly about 3 .3 % . Th e l ong ta ke off a d v an ta g e i s ev id e nt _, from th e val ue s in Tabl e XV, comparing the 759 - 182A with t h e LMA and also with the 747 - 200F.

Part of t he advantage in pa y load / gross w e ight for both th e 759 - 182A and th e LMA is due to redu c ed ._ s t r u c ture wei gh t a ss um p ti o ns co ns eque n t on t e c hn o l og y development anticipated b efor e 1995, t w h ich is the earlies t date envisa g ed for such air c raft. The increased payload / gross weight fr_.ction is accompanied by a reducing static thrust to weight ratio as well as an increased field length. This will result in a lower initial cruise altitude capa b ility (ICAC) but is not significant as far as cruise efficiency is concerned .

TABLE XV COMPARISON OF PERFORMANCE CHARACTERISTICS OF THE LMA I DESIGN WITH TWO BOEING AIRCRAFT Customary Units _ Boe i ng 747.200F Boeing 759-182A LMA GrossWeight (Ib) 820,000 1, 0 35,3 0 0 1 , 215 , 0 0 0 • SLS Thrust (lb) 210,000 209,200 210,000 T / W 0.256 0.202 0.173 TOF L (f t ) . 10,250 11,900 15,600 : Wing Loading (Ib / ft 2 ) 1 49 122 133 GrossPalyoad ( I b) 260 , 000 429, 4 00 536,000 _ .

PI. / GW 0.32 0.41 0.44 r _ Cruise L / D 18.1 21.58 20.4 Range (nmi) 3,200 3 , 600 3 , 600 ,, I S.I. Unit s Boeing 747 . 200F Boeing 759 - 182A LMA GrossWeight (kg) 371,952 469 , 612 551,1 1 4 SLS T h rust (N) 9 3 4 , 080 9 3 0 , 5 2 6 934 , 080 T / W 0 . 2 56 0.202 0 . 173 TOFL (m) 3 , 124 3,6 2 7 4 , 755 Wing Loading (kg / m2) 728 596 649 GrossPayload (kg) 117 , 935 194,776 243 , 130 PL / GW 0 . 3 2 0.41 0.44 Cruise L / D 18.1 21 . 58 20 , 4 Range(km) 5,926 6,667 6 , 667 T h e inc r eased tak eo ff field l e n gth o f the LMA will be most readily obtainable over water , _ t hus the LMA o pera t i o n is c o nceiv e d a s principally using a s t retch of sheltered wa t e r for takeoff and landing, but transiti o ning t o sh o re f o r loading / unloading. T he increased TOFL resulting fr o m reduced thrust / weight permits 17.5% increase of gross weight compared with the 759-182A and .

results in a pa ylo a d fracti o n o f 44%, acc o mm o datin g 40 instead of 32 6078 kg (13 , 400 p o und) 2.44 x 2. 44 x 6.1 m (8 x 8 x 20 ft) c o ntainers, with structure weight and drag consideration for the increased fuselage ca p acit y and th e substitution of ACL gear for wheelgear. '_ The waterfront basing made p ossible by the ACLG would permit operation of such a large aircraft without the same domino effect on facilities eousequent on mtroducing a new land plane of the same size. The recent NAS A Cargo Logistics Airlift System Study ( Reference 9 ) establi s hed that present runways, taxiwa y s, parking spaces, etc., at major airports are sized to accept th e 747 or smaller aircraft. Notwithstanding this, the low footprint pressure of the A C LG aircraft and the t i , e , t " T w ide a re a o v er w hich t ile l o ad is sprea 'l may p e rmit operati o n into fields cu r rently unable t o acc e pt , , .

even the 747. Tile basing options req u ire more detailed study than was feasible for the present report.

T he effect of the i n creased payload fraction on economy and productivity is to increase the R OI po t e ntial f ro r,1 12% f o r t his v ersi o il o f B o ei n g's advanced dedicated freighter, to 17% for the _: ACLG-LMA. LMA operating c o sts have been determined in parallel fashion for comparison with those presented for the 759-182 A . T he direct operating cost comparison is shown i n Figure 37. " T h e fu e l price used was that as s umed for the 75 9 -182A analysis and is con s idered lo w at this time b u t dlangi n g it will hardly a ffect tile comp a rison. A.I . C. represents profit or re'urn on the airplane inv e stment, in F igure 37, cost is shown including A.I.C. as a fixed profit p e rcentage. In Figure 38, the e l e me n ts of op e rating cost are broken down and the o, ffect of a reduced operating cost on ' pr o fitability at equal tar i ff rate is displayed. Figures 37 and 38 show only direct operating cost. _ Indirect cost must b e added. This m a y alter the comparison gre a tly, since it is possible that con- C e n ts / Gross Ton - Mile 15 - Operating Cost= DOC + AIC 1976 Dollars 85% LoadFactor,FuelPrice37 C e nt s / Gal l on / : 10- B o e i ng Reference /s Conf i gura t ion 759-182A "- _/ d _ s S

5-

ACLGMult i-mi s si onAmphibian AIC 12 % ROI n mi 2000 4000 6 000 R 000 10,000 0 I I ! I I I , I I I , 1 I " I 1 5,000 10. 0 00 15 , 000 20 , 000 Block D is t a nce. K i lome t e rs Fig u re 37 . O p er a ti n g C o s t C om p ari s on C e nts / Gross Ton-Mi l e _ ' _ indirectCostN e glec t e r, , ' , : _ 10 - 1 9 76 Doll a rs,3600 nm, R a n g_ ,85 % L o ad Fac t or . Fuel37 Cen t s / Gallon ; _ : , _ AIC EqualT a riff 12%ROI _ _ .. 17%ROI _ - . t-- ' IC 12 % ROI Revenue _ _ = __= _ _ ; . _ . k 'X :' X ' X _ 'X J _ _. - __ -_ _. _ _ "-D e pr e ci a tion " _ -- I _ %C ' _ \%] ....... k \ \ X\ N __ , _ -Insurance Cost I _. 0 ' -- . L\ -, \\- , a _ - _ - ! 1 75 9 . 182A ACLG - LMA t . Maintenance Fi g ure 38. Pro d uct iv ity C o mparis o n [ ' I' .

I i r . .

siderable new facilities may have t o be charged against these large airplanes, which indeed may have to carry their whole b, x den. Such facilities may be greatly different a,d possibly much lower in cos t for t he LMA operating over wa t er t han for the comparable land plane whe t her of _onven t ional _.

: de s ign (i . e . , the 75 9 -182A) o r fl y ing w ing distributed load fieighters. _: • Off-Runway Tacti ca l Fig h t e r (OTF) . Des c ri pt ion A ligh t weigh t , s ubsonic (M = 0.9) design w as cho s en fo r t his example t o minimize : _ techn o l o g y r isks . I ts maj o r role w o ul d be gr o u n d at ta ck or p ri m ary je t t rainer . Primary a rmamen t ; consists of one Oerlikon 30 m m machine gun with 625 rounds ammunition.

In order to provide good low altitude duration and enough range to patrol over significant segments of a 900 km (560 mi.) front, a high bypass turbofan Lycoming (ALF 502) is selected as : th e pow e r pl an t w hich p erm its use of t he same typ e o f li g htwei g ht b ypa s s-f an bl e e d system d e - i s crib e d f or t he S HA, e t c. A simi la r lo w -speed cushionbome yaw control method, consisting of a t r , fan t hrust r e ve r ser / deflector, func t ionally split on t he cent e rline and operated differen t ially could i be used .

The design is outlined by , he 3-view Figure 39 and principal characteristics in T able X V I ._. , and is illus t ra t ed b y t he artist's concep t of Figure 40. The 3-view shows t he gu t and engine in " , ... ; _ " _ si lh o u ett e . A no t h ' r ad va nt age of th e AC LG w hich i s e sp eciall y u s ef ul in t hi s a pp lica t io n, i s i ts .: internal v olume ec o n o m y. With no nosewheel or main gear to h o use, the installation of this large gun is m uch easier, e : OFtlCINAL PAGE IS POOR m_ . | , _1 I_ 9.14m {30.0ft)., =,1 i • • m ' _ I 17ft 9 in.)

I_ 10 . 85m (35It 7 in . ) _ I ? !

Figure 39. Off-Run w ay Ta c tical Fighte r , 45 : f l T A BLE X V I OT F DESIGN PRINCIP A L CH A R A CTERISTICS Gross Weight 6,350 kg (! 4,000 Ib) Engines 1 Lycomin g ALF 502 ' _ Stratic T / W 0.55 (withou t Bleed) t Cu s hion Area 10.9 m 2 (117 sq . ft) Cushion Pressure 5 , 746 Pa (120 Ib / sC l . fi t ) Cushion Perimeter 12.1 m (39.7 ft) W;ng Ar ea 15.8 m 2 (170 sq. ft) : Wing Loading 400 kg / m 2 (82 Ib / _ l . f t ) Cushion Airflow 25.9 kg / sec (57 Ib / s e c) i T f r _ _ . • 'm l h jI k -

•

e ' Fi gu r e 40 . OTF A r t i st's Conc e pt • Ana l y si s - It i s ge n erall y co nc eded t hat a CTOL a ircraft will be ligh t er i n weight an d le s s co st ly th an a V / S T O L ai r c r a f t d es ig n ed t o p er f orm the sam e m i ss io n. T he O TF w ill p ermit th e C T O L m ode of o p eratio n wi th out t h e ass o c i a ted r equ ire m e n t s for a prep a red air s trip, an d i s th us an a lt e r nat ive t o V / S T O L, an d s ho u ld b e c omp a red wi th a V / S T O L a ir c r a f t suc h as t he A V- S B from th e p erfor m a nc e viewpoi n t .

Comp a riso n o f t he OTF wi t h th e AV- 8 B (H a rrier) i s i n v a lid bec a use th e OTF is n ot d e sign e d to carry th e sam e payload.* Ra n ge , e nduranc e and speed e n velop e figures calculat e d for th ,: OTF _, ar e plo t ted i n Fi g ur e s 41 a n d 4 2. W e i g ht a nd perfor ma nce su m mari es ar e g iv en in T a b le s XV II an d ' XVIII. The_e are a numb e r ofj e t - trainer / hght atta c k aircraft on the market worldwide, indica t ing _' int e n s e i nte r es t in t h is si z e a n d t y pe o f a i rcr aft i n t ernat io n ally. T abl e XIX co m pares p rin c i p a l ch a r a c' e ri s ti cs o f tho se i n th e sa me c l ass as th e O TF d e s i gn.

* Th e N a v y i s co n d u c t i ng a clo se a ir s up p ort AC L G co n c e pt d esi gn s tu dy, c a rryi n g a comp a rabl e p a y- load t _ th e A V- S B f or c om paris o n w ith VT OL , R FP No . N2 269 -7 8 -R - 03 8 3 .

-'i 4 6 ' 1 : t : GW- 6350 kg (14,000 Ib) No ExternalFuel / , Allowance + 10 % Resm've A lt itude Altitude : m ft m ft 12000 ,-40,0O0 12000. 1- 40,000 , _ i_ 8000 30 _ 00 0 O0 : , / , : _ : ooo / : ooo .;

_ I -' °. °°° I ,,. - ,, " °°° }, o. _

SL L_ r _ = __ = _ SL • | t ! i O 1000 2000 3000 4000 0 1 2 3 4 • . Ra n ge - Ki;omelmrs E n dura n ce-I'k Figure41. OTF Range a n d Enduranc e Alt i tude m ft

-F" / /

: = / I

" °°° ' i -, o ooo ' I

l ' / K.o,, /

0 2OO 4O0 600 8O0 Speed , k m / h r F i g ur e 42. OTF Spe ed E nve l ope -I T A BLE X V I I " _ OTF WEI GH T SU MM A R Y , K G ( L B ) Structure (including ACLG 487 Ib ) 1,588 (3,501) Powe r P l ant 756 (1 , 667) Systems 1,110 (2 , 447) Emp : y We i ght 3 , 454 (7,615) Armament 1 , 030 (2,270) Crew 98 (215) FuelendOil 1,769 (3,900) Gro. We i ght 6,351 (14,000) @ In c orpor a tio n o f ACL G into thi s t ype of low- c ost , light - weig h t gr o und att ac k air c raft woul d provide a co ns ider a ble incre as e i n b as ing fle x ibilit y a dding s ig nifi c an tly to it s oper a tion a l , _ utilit y.

T AB LE X VIII OTF PERFORMANCE AT 6 , 351 KG (14,000 LB) GW t (NO EXTERNAL F U EL) Ma ximum r angew i th _ llowance s ] MaximumEndu r ance, hr 4.25 +10%r e serv e fuel , k m (nmi) ] 2 , 971 ( 1 ,604) SL Rateof Cli m b , m / ra in (ft / m in) 2 . 011 (6 , 600l Cruise Ceili ng , m li t ) 112,497 (41,000) | ; Cr ui se Speed . km / nr (kt) I 963 (520) T a keoffgroundrun , m (ft) I 777 (2, 5 50) Takeoffto 50 ft , m (ft) I 1 . 1 28 (3,700) . TA B LE XIX LI G HT TRA I NER / S TRIKE AIRCRA F T Designation Alpha-Jet MB-339 A.37B 105 G Hawk Manufacturer Da s sault / Dornier Aermacchi Cessna Saab HawkerSiddeley (Fr a nce / F RG) (Italy) (US) (Sweden) (UK) Gross Weigh t , kg (Ib) 7 , 250 (15 . 983) 5 , 895 (13 . 000) 6 . 3 50 (14 , 000) 6 . 500 (14 , 330) 7 , 755 (17 . 097) PowerPlan t Larz ac 04-05 Viper 632-43 GE J85-1?-A " , _ EJ85 - 1 7 - B Adour 151 (Two) (One) (Two) _ Two) (One) M a xThrustkN (Ib) 26.48 (5 , 952) 17 . 79 (4 , 000) 25 . 4 (5700) 25 . 4 (5,700) 23.75 (5 . 340) (Total) Max Speed k m / hr (kt) 1 , 000 (540) _ 98 (485, _ 816 (440) 970 (523) 997 (538) NumberOrdered / 438 100 564 1 9 0 + 226 : Bu i lt R e mot e ly Pilot e d Vehicle (RPV) Desc ription - T h e a dv a nt a g es of A CL G for t a k e off a nd for recover y of a n RPV h a ve b e en st u d i ed i n d e tail i n the Air Force 's Ji nd ivik retro fi t progr am. The a ir c ushi o n wi l l provi d e a sa f e recov e ry mode at muc h lo w er c os t t ha n t he Mid Air Retri ee al Syst e m (MARS) c u rrently empl : _ y e d , u sing h elicopters .

T h e application to t he Ji n divik is s h o wn in the 3-vie w and illustr, o. tion - Figures 43 and 44.

A simple po w ering sd l e m e w a s d e veloped u sin g e ngine bl e ed air to drive a small t u rbine fan . Direc- tional control cus h ion b orn e w a s ac h ieved _ y a prop u lsiv e j e t defl e ctor u sing . Coanda effect opera t ing on a section of th e jet stream , a sys t e m requiring no m oving parts i n t he h ot gas sec t ion .

For t h e basic landing syste m , an in e las t ic t r u nk was u sed , f u rled w i th in a tig h t s h eat h as _... s h o w n in Figure 44 . For landing, t h e trunk inflates from w i th in and spread s t h e s h ea th a ut o m ati- c ally. T h i s is t h e basic system. To a dd a takeoff c ap a bility , a secondary dropa w ay t ru nk w as used, seen on t h e gro u nd also in Figure 44. T h is is releas e d a s soon as p ossib l e after t akeoff and recovered.

Dama g e t o t h e trunk by dropping _t is unlikely beca u se of its flexible m a terial construction s o t h at very h ig h percen t a ge r e us e is probabl e • L .; 4 8 ,; I °

49 i

P r i nc i pal c h a r act e r is t i c s a re sh o wn i n Ta bl e XX .

TABLE XX ACLG J INDIVIK PR I N C I P AL CHARAC T ERIS T ICS GrossWe i ght , kg (Ib) 1,452 (3,200) Landing Weight , kg (Ib) 1 , 179 (2 , 600) Span (Overall) , m (ft) 6 . 93 (22.75) Air Cushion Area, m 2 . (ft2) 1 74 (18 . 7) Air Cushion Pressureat Landing Weight , Pa (Ib / sq ft) 6,703 (140} Air Cushion System Weight , kg (It)) 46.3 (102) J A naly s is- R P V r e co ve rycostsby ACLC w e r e stud i e dand co m paredwith th e mi d a i r retri e val syst e min Ref ere nc e i 0. A s u m m aryof th e r e sultsisgiv e nin the chart , Figur e 4 5 . In thisst ud y, th e application e xa m ple wast h e Ryan ! 47 - (3.

: Assumption s : 1000 Re c overies; 1 Recovery / Day Vehicle t ife = 20 Flights Installations and Modifications during Vehicle Manufacture *ACLS usedGrd Ba se d Landing Aids for Night and All Weather Operations MARS I'--!

_ _J ' P 8 i Amortization of 2 He lico pters (1.6 M) == I oe t' _. I I __ 0 I - l e Ii copt e r Operat i on a nd Ma i nt e nance c 6 Repair Vehicle Damage ACLS 4 (On 147 G Vehicles; _ MARS Chute s , ConservativeE st imates) ACLS ( N ew Vehicle Dedgned etc. not R e c ov e red F ; " _ Amo rt ization for ACl :] , , o,,1. . di ,, . A i d .

=1 o K .Veh i=le Mo d ,,r- , l , -,i,. , ion o, $20 K ACLS = i $1 M Landing Aids " ¢ _ _ 2 i_ $16 K Rudder / Control Mods 0 _ '$1 K A C L S , : Figure45. RPV R e cov e ryCosts Th e maneuvertol e ranceo f th e ACLG is particularlyimportant i n this a ppii c ation , including crosswind, e xtre me attitudesand ' impact damping , in addition, the s u ctionbrakingmethod can u s e f u lly b e appliedto stop th e vehicl e in a smalldistanc e . T he r e isan a cco m panyin g pot e ntial f or usingsteep - a pproach landingand rapiddec e lerationwith verticalaccelerationfa c tor s hi g h e rthan _"" '_ cou l d be accepted by a m anne d a i rcr a ft for RP V reco v ery i n smal l sp ac es , s u c h as t he d e c k s of non- a i r c ra f t sh ip s .

Th e m ar k et po tent i a l fo r t h e RPV a pplica ti o n is cons i d ere d f ar t e r m b ec aus e t h e fund a m ent al n ee d fo r t his type mili t a ry a i r c ra f t ha s n o t b e e n wid , : l y a cc epte d. The lif e cycle co st advan t ag e t h at \ == . . _,_ 5 0 | ACLG t echnology offers an a dva n ced RPV oper a tio na l sys te m w a s defined in the Boeing st udy of Ref e r e nce 11. _ '; t Wing In Ground Effect (WIG) Description - Win g in ground effect studies related e xclusiv e ly to ov e rwat e r operation hav e r e c en tl y b e e n co n d u cte d by th e Navy (R e f ere nc e 12) .

A principal advantag e of th e W IGco n c e pt is th e r e ali z ation o f v e ry high lift to drag ratio whil e cruising in gr o und e ff e ct. This m ay h e achi e v e d if th e h e i gh t abov e th e surfa ce is signi fi cantly less t h an t he wing span an d if end plates which project downwardly to the surfac e ar e us e d. This suggests a rec t angular air cushion with sidewalls could b e incorporated with the WIG.

A reduc e d r e quirement for propulsive t hr us t w i th resu l ting improv e ment in overall e fficiency _ _ [ ca n b e ac hi eved b eca use of th e WIG'shigh L / D i n ground effect, the long takeoff available over water _ and th e ACLG's ability to make safe emergency landings in an y clear ar e a. An explorato ry ty p e air- • ] craft with a singl e e ngine and installed t hr ust / weight ra t io of O.15 is, t herefore, projected to ill us trate this po s sibi l ity.

A prelim in ary con ce ptual de s i gn d raw i n g is s ho w n in Fig ur e 46 , with principal c h aracteri s tics _ in Table X X I. T hi s desi gn fea t ures a rect a ngular pl an for m wi t h se m i-ri n d r et r a c t able s idewall s an d I : i " _ 26 m ft " i R EP RO D U C_I[:_ / " OF THE ORI G INA L P_ (;}'_ IS P OOR } |(19.75 ft)[ (68.88ft) i F i g u re 46. Pr el i m in a ry Co n ceptual Design of WIG

I

:t 5 1 , t g TAB L E XXI WI G CH A RA C TERISTICS ", Characteristics Gross Weight 27,215kg(60,000Ib) Wing Area 97.5rn 2 (1 , 050sq . ft) Wing Span 26.2m (85.94ft) Len 0 th Overall 21.0m (68 . 88ft) Height Overall 4.2 m (13.67ft) Cushion Area= Sc 63 . 5m 2 (683 . 6 s q . ft) Cushion Pressure = P c 4,213Pa(88 Ib / ft2) Power Plant . - OneTF34 withFanBleed • hinged inflated flexible s e a ls fore a nd a ft . Air c u shion powering by fan bleed similar to previou s con- cepts is proposed.

An a lysis - The princip a l advantage of integr a ting ACLG in t o the WIG concept is to allow beaching or l a nd operation. A s e c o n d a dv an t a ge i s th a t the ACL G seal s and e n d plates can be n a tur al ly sh o c k ab s orbi n g , th e r e for e no lar ge s t ru ct u r e w e ig h t p en al ty i s n ee d e d to p rot e c t ag ains t rog ue w a v e im p ac t s d u ri n g ov e r wa t e r c r uise.

T he m a rk et p ot en ti a l for t he WI G app li ca tio n i s co ns i de r e d far te r m be c ause the fun d a m en t a l nee d for th i s ty pe of a ir c r a f t has n ot be en wid e l y acc e p t e d i n th .e U n it ed S t ates. A l m o s t t he en tir e w orl dw ide r esea r c h an d d e velo pmen t i n W IG a ir c r a ft i s bein g c o n d uc ted in t he Sovi e t U n i on. T h e A d m ir a l o f t i l e F le e t o f t he S ovi e t U n io n , S.G. G or shk ov , i s r ep or te d to ha v e in d i cate d tha t WI G v e hi c l e s will pl a y a s ig n ifi can t f u tur e r o l e i n v a rio us na v a l m i ss io ns, t o i nc l ude AS W , Re f e r ence 1 3.

S U RVEY AND E V ALUATION A s u rve y o f po te ntial ACL G u se wa s c o n du ct ed b y s o l i cit i n g tile v ie w s o f p l a nn ers, a i rfram e manufacturers, civil operators and g overnm, ": agencies on the subject. This was performed in two sta ges . Fi rs t, du r in g th e s ele c t io n o f t i le ca ndidat e de si g ns, d iscussi ons w ere h e ld w i th c erta in k ey or g anizations to g uide this selection. Then a preliminary brief was prepared and circulated to about 60 reci p ients requestin g comments. Numerous va l uable comments wer e re c eived and are addressed in this re p ort, both b y modifying the d e si g ns shown or am p lif y in g d e sign information, and by add- in g a techn o lo gy scenario and "conclusions based on th e responses. The author is greatly indebted for th e se comments as is a c knowled g ed els e where in the report.

" T h e ev al ua t ion fi n dings i nc l uded i n th e c ir culat ed bri e f w e r e ge n er a lly con cu rred wit h a nd le a d to t h e f ollowing co m ments on presen t market potential for ACLG tec h nology.

_"'" I. ACLG could provide t h e follo w i fi g benefits t o r u n w ay operations t ' rom present air- p orts: (1) ta keoff and l a nding sa f ety in case of landing s h or t , veering e l f , or le a ving th e end of th e run w ay ; (2) increased payload capabili ty fro m making a longer takeoff r u n from presently a vai lable ru nw ay exte n s ions , a n d po s s ibl y f r om re d uce d la ndi n g g ea r we ig ht als o ; (3) e asie r oper a - 52 1 IS l ---- • i , ) _rr) °A" - ti o n s fro m ice and s now c o ver ; ( 4 ) c a p ab i hty o f a very large ai r craf t ( on e mill ion po un ds or m ore) _ to opera t e on present ai r po r ts w i t h runways l im it e d t o 45 .7 m ( 1 50 f ee t) wide and t ax i ways i : li m it ed t o 22. 9 m (7 5 f eet) wi de . I t i s c onsid ere d doubtfu l t h a t th ese b e n e fit s wo u l d ju s t i f v th e - : t e ch n ol ogy in vest m e nt r e quir e d for an ACLG land transport air c r a ft .

2. Off-runwa y op e ration s from roads or c lear e d fi e ld s c ould b e n e fit from ACLG to s om e • exten t , but th e n ew t ec hn o l ogy invest m e nt ri sk m a y n ot b e warr ant ed in view o f o t he r m o r e c on- ' : _ v entio n al tec hn o lo gies s uch a s s oft , o v e r s ize d t i r e s or e x pa n dab l e ti r e s. S m all ai rcraf t ca n more , easily be fitt e d wit h la r ge ti r es th at give of f -r un way capabili t y • As l arger aircraf t si z es ar e c o n- • sider e d, t he ACLG tec h nology b ecomes more attractive.

" 3 . V ery l arge ai r c raf t ( o ne millio n p o unds or m ore) c an bene fit subs t an t ially fro m ACL G in t erms of we i ght sav in gs, ai rport availabili t y and airport cons tru c t ion costs. The de fi ciencies of ti r es o n pr e se n t day l arge a i rcraft are appa rent from r ece n t accide n ts. Alt h o u g h t h ese problems can be solved, t he basic inefficiency of suppor t i n g m uc h larger airc ra f t on t ires is recog n ized.

4. T he m o s t a tt rac t ive g eneral use for air cus hio n t echnology on aircraP , is for amphibious and t r i p h ibio u s a ir craf t . No land i ng gear is available t oday t ha t can provide an efficie nt way t o opera t e from land, wa t er, and snow. T h e r es u l t is ineff i c i e nt opera ti ons u sing h eavy and high drag comb in a ti ons of w h ee l ed gear, seapla n e h ulls o r flo a t s, a n d s n ow s k is. Because o f th e c o n straint s o n wh ee l gear si z e and w e igh t a ll e ffici e n t airc raft o perati on s a re c o nd u c t ed f r o m paved run wa ys . ,_ T h e n u mber of la nding si t es ava ila ble to an a ircr aft e qu i pped w ith A C L G is very l arge • T h is new c a pabili t y w oul d h ave an e normou s ef f ec t on cert ai n fu t u r e mi l i t ar y a n d c omm ercial o per a t io ns.

B a sed o n the a b ove , t h e s e t e nt a t ive co nc lusio ns a re d r a wrt r e gar d i ng p ot e nt i al cus to m e rs " fo r ACL G ai r craf t : I. Th e ACLG will fi nd its initial use in foreign countries more than th e U. S . Th e n u m- b e r of A CLG equi p ped aircraft that could be sold to foreign free world aircraft operators from 1990 on may exceed the ACLG aircraft sold in the U.S. by an order of ma g nitude. The growth of aviation worldwide is related to Gross National Product growth. The recent NASA C L ASS s tudy (R e f. 9) indicated, for example, that the ratio of all-cargo ton miles flown by 44 forei g n airlines to that flown b y U.S. international airlines should increase from 3.3 in 1977 to 6.2 in 1990. Th e worldwid e us e of A CLG is expected to b e even higher in developing countri e s and ar e as of the world with a less dev e lop e d airport system than the continental U.S. Interest in waterfront and similar off-runway operations with amphibious vehicles is more intense today in the USSR, Japan, G er man y , Un it ed Kin gd om , Fra n c e , and C a na da than it is in th e U.S. N e v e rth e le s s, a U.S. l e ad : _ r o l e in th e d eve l o pm e nt and manufactur e o f ACLG aircraft is consid e r e d to b e e asil y achi e vab le at ._ thi s tim e a nd al s o to b e in th e b est nat i onal i ntere s t.

2. T h e best n ear t e rm A C LG app lic a tion is consi de r e d t o b e for a gene r a l avi atio n a m p h i- bian . Su ch an ai r craft wo uld h ave wor l d wide sales potent i al for pr i va te , gov er nment, and entre- , ' , p r ene ur u ses. Less t e ch ni cal d e v e lo p m e nt i s n eeded for ge n e r a l av i a ti o n t ha n for an y o ther AC LG _ u s e on m anned air c r aft. Fu r th er m o r e , addi tio na l deve l op m en t a t smal l s c a l e is a ne c essa ry pre l imina ry / !

to an y s imilar l a r ge-s c ale app li cat i on .

.,I 3 . Th e U . S. M a rin e s ar e p o tent i a l c ustomers d u e t o t h ei r as so ciati on w i th wa t e rf ro nt . : , - . , and with o f f- r unway av i ation. A lig ht we ight , c lo se a i r s u ppo / t aircra f t i s c o n sid ere d a g oo d ) c a nd ida t e f or ear l y t e ch no l ogy de v e l op m e nt em p ha si's. A l arge worl d wi de m a r k e t e xis t s fo) 9 _wo - sea t trainer / ground att ac k fig ht er, equipped w it h one or t w o turbofan en gi nes. A s _ fig h ter t h e air- ,: 5 3 i_- b -' t _ . . _, _ . , " _" c ro ft would be eq ui pp e d wi t h o n e seat and a n a nt ita n k g un . R un way de ni al i s a serio us co n cern for m any A i r F orce s. T h e ACLG aircraf t could be oper a ted independently of paved su rf a ces . ' _ 4. T h e po t e nt ial u s e of ACL G for other U.S . military missions is s omew h at confused by presently defined roles and missions. Army aviation i considered t h e lowest priori t y application t due to t h eir current h elicopter concen t ration. Air Force fig h ter use is conside z ed long term be- cau se of t h e present production emp h asis on F-15, F-I 6, and A-I 0. Air Force tactical tr an sport use is considered quite attractive but far te rm be ca use of t h e present e m phasis on possible AMST production. Ai r Force strategic t ransport use is considered ve ry attractive but also far te rm , due to t h e tec h nology d e velopment needed and because of M AC's emp has is on t h e C-141 stretch, C-5 re- wing and eventually a ne w C-XX conventional aircraft design w h ic h must h ave strong appeal to t h e U.S. sc hed uled airlines ( wh o operate on assigned routes bet w een existing airports). T h e basic in- t eres t by t h e U.S. Air Force in using wa t e r fo r a r unway is recognized as v ery low and possibly it h as to b e a Navy mission.

T h e U.S. Navy Aviation, h o w ever, h as primari l y f ocused on operations of small aircraft from s h ips. As sl fi ps become s m aller, t h e interest h as m oved to V TOL aircraft. Land based naval aviation h as not been widely considered . Nev erth eless, it appears at t h is t ime t h at enlarging t h e Navy's role and mission to consider land based w aterfront airc r a ft operations of larger aircraft t h an can fi t on s h ips may b e as likely as expanding t h e Air Force ' s role and mission to use of w ater run- w ays and waterfront basing. In eit he r ca o e, a basic modifica t ion of today ' s accepted roles and missions w ould be requi r ed to accept a w eapon system w it h t h e basing versatility of t h e ACLG equipped i air c ra f t .

£- , , . The ACLG technology appears attractive for use.on two new military aircraft conc e pts - the advanced remotely piloted vehicle (RPV), and the wind in ground effect (WIG). The Jindivik technology p rogram demonstrated much of the low-cost, near-term ACLG technology with inelastic • trunk materials tbat could be used f or a large, tur b o j et-po w ered , land based RPV . T h e WI G equipped w it h ACLG wo uld gain a m p h i b ious advantages and m ay use ne w ACLG concepts based on SES " te chnolo gy an d p ossibl y i n e l a stic t ru n k mate ri als. Bo t h t he R P V a n d t he WIG us e s for AC LG a r e c on - s id e red lower priority.now because the fundamental mil!.ta:y need for these new aircraft has not yet be e n widely a c cepted.

Relative to the A C LG d e si g ns shown, the following opinion rating s are thought ap p ropriat e .

Fi, _t Level Interest - Iarge multi-mission amphibian Ge n eral Avi a tio n am p hibian S e con d Le v e l Int e r e st - O ff - runwa y tactical fi g hter t T h i r d L e v el - Me di um amp h i b i o us t r a nsp o r t : , TECH N O L OGY D EV E L OPMENT SC ENA R I O ; • ." Ove r vi e w The A C LG a ppli c a t io ns con s ide re d cove r ' r adic a lly diff ere n t ai r c ra f t t yp es a n d f a ll i nt o diff ere n t c at ego r i es defined by siz e , weigh t , wing loading, e t c . Ten c ate go r i es w ere est abli s h e d b y NASA fo r st udy a s s hown in T a ble XXll.

.L • _ 54 REPRODUCIBIL I TY OF TH E ._ ORIC r _' M PA N_ T_ p _ , _ TABLE XX I I ) CATEGORIES ESTABLISHED BY NASA FOR ST U DY Aircraft Descriptions ACLG Ca pabi'lity _ i ACLG A /C Gro s s W e ight Land Amphib. or C at e gory 1000 Ib Oth e r Only Triphibian 1 Wt _ 50 Wing Loading < _ 50 psf X 2 X 3 Wt _ 50 Wing Loading _ >50 psf X _ , 4 X :_

- !

! 5 50 _ Wt _ 250 Wing Loadin9 _ 50 psf X 6 X \!

! 7 250 < _ Wt Conventional Config . X - _- 8 X i £ I 9 r 0 < _ W t * Unconventional Config . X _ 10 X *(e.g . , spanloaders) _, In th e study , it h as bec o me clear t h at i n most cas e s e xc e p t , t he d e ns e aircraft e xampl e s of I fi g ht er and RPV , th e added a tt rac t ion of over wa t er capabili t y i s available t o a land only version, provid e d a suitabl e a ir cra f t con f iguration is chosen (no u n d e rwing en g i n e , e tc.). Suc h a c on figuration m ay be requ i red in any c _ e for a land only version t o avoid engine i nges ti on problems. T h e most a t trac ti ve ACLG appl i ca tio ns a _ e t hus all amphibious and even the fi g ht er, though n o t truly amphibious ( i t w i l l n ot flo at), can operat e over wat e r c u sh ion b o r n e .

A considerable ACLG t echnology base covering t he analy _ s of landing dynamics, s t ability and con t rol , and t r u nk s t ress strain and t he syn t hesis of a tru nk m aterial syst e m , and a braking system h as bee n b ui lt up s in ce th e i ntroduct i o n of t he c on ce p t i n 19 63, a n d it s r edu cti o n t o p rac ti c e in 1967. Bu t t o proceed t hroug h major engineering development programs, fur t her expansion of t h i s ba s e w ill be n eeded . In t he f o l lowin g disc u ssi on , de t ail i s give n t o the significa nt tech n ology items in t he curren t base and also the deficiencies recognized and problem areas foreseen. The de - v e lop m ent tim e tabl e s req u i r e d by NASA are t h e n projec t ed on the assumpt i on that initial us e will : i be for ACLG appl i cation w h ic h w i ll entail on l y prob le ms w h ic h ar e s t rai gh tforward in solutio n . Th e i tim e ta ble s a re generated from th e t w o alternative r e _ .d in ess dat e s of 1982 and 198 5 sp e ci fie d by l NASA for Cat e gori e s 1 and 2 aircraft ( l ess than 22,680 k g (5 0,000 l b) gross w e ight and l e ss than . ! 244 k g / m 2 ( 5 0 l b / sq ft) wing loading).

• I S i n ce i t was d e ter m in e d t h at t he t e ch n o l ogy r e quir e m e nts for providi n g a land only v e rsion _ ar e no t n ec e ssarily l e ss d e manding tha n thos e for an amp h ibia n , the t e n cat e gori e s h av e g e nerally j b ee n consid e r e d as fi ve pairs in dev e loping th e sc e narios.

i As an i n i tia l ov e rvi e w , th e fol l owi n g Table XXIII gi ve s a broad picture o f pr e v i o u s and pro - ' ! je ct e d technology d e v el opment, by i d e nt i fy i ng'significant " d e sign fi rs ts " . Th e e ight st ud y candi - ! dat e s ar e u s e d to e xampl e th e f u tur e , i !

i

] "; • " i ......... - _ -q ' r , TAB L E XXII!

A C LG A PP L I CA TION S _ ' • Aircraft ACL G Design Fir s ts ] _ A, LA - 4 1 , 1 34 k g (2500 pounds) First ACL G - concept feasibility proven (elongated doughnut planfor m , F easibility testing (1967-1968) with tail control in propeller wash) Singl *. reciproca t ing One way stretch trunk material auxiliary engine driving fan Pillow brakes Two-way stretch trunk material Suction braking B. XC-8A (Buffalo) 1 8 , 597 kg (41 , 000 pounds) Duplicate auxiliary engines , re q uiring trunk pr e ssurecontrol valv e s Advanceddevelopment testing ( 1 9 7 3- Replaceable trunk wear plugs 1974) _ Static floatation bladder parking Twin turboprop ;Twin beta prop control ; Twin auxiliary shaft turbines driving fans C . Jindivik Drone 1 , 45 2 kg (3 , 200 pounds) Drop away takeoff , and prepackagedlanding inelastic trunks ( i ntegral . Exploratory development testing pressurevessels) ( 1 9 7 5) ACLG air from main engine - air diverted directly for landing and via pneu- Single Turbojet matic driven fan for takeoff Main engine compressorbleed air Cushion vent for distributed braking (dual mod = ) Inward air injection at trunk ground tangent Jet exhaust yaw control m : 1 . General Aviation Amphibian (GAA) 1 , 633 kg (3,600 pounds) Ovoid planform under low wing , wide body. Wing-tip skidseliminated Business,private, civil government, Variable displacement hydraulic pump for ACLG power ' and military u s e worldwide Parking skids Single reciprocating Long life elastic trunk (400 hour s ) Main engine hydraulic transmission Quick change trunk mounting driving fan 2. L ight Amphibious Tra n sport : (LAT) 5 , 670 kg ( 1 2 , 500 pounds) Shaft drive of fan from f ree turbine main engine Business , military , and civil government usesworldwide Twin tur bo shaft 0 sin _ . _! e prop ( t win pack) Main enginesshaft drive fan 3. High Density, Short Ha u l Amphibian (SHA) 47,628 kg (105,000 pounds) None !

Carry passengers to downtown w a teP Use OTF design (presumed to precede this) for ACLG power source and for front sites in densely populated areas high forward speed elastic trunk design;uses c aled up GAA trunk planfor m - .

Three tur bo fa n s Main engine fan a i r (dual m od e ) ) , !" TABLE X X I II i 3' A C LG AP P LI C ATI O NS ( CO NT'D ) Aircraft ACLG Design Firm 4. Medium Amphibious Transport t ' (MAT) 155,759 kg (350,000 pounds) None- usescaled up SHA design i ! Carry military cargo or side by side i " 8x lOft containers ! Twin Turbof a n ' Main engine fan a ir (du a l mode) I : ' 5. Large Multi-Mission ii Amphibian ( L MA) ' ii 551 , 120 kg (1 , 2 1 5 , 000 pounds) None- use scaleup MAT planform design. No apparent weight limit for ACLG Military and civil cargo, U.S . Air Force technology.

strategicmissilecarrier , U.S . Navy . _ missionsworldwide Four turbofa ns Main engine fan air (dual mode) 6. Off Runway T a ctical Fighter (OTF) 6 , 350 kg (14,000 pounds) Integrated ACLG air supply by bleed from main engine fan. Air diver , : e d Antiarmor , 30mm , directly for landing and via ejector for takeoff ,_ ; Ground attack; also trainer High speed (su iJ ;onic) in flight retention of an elastic trunk : _ .

Single turbofan High takeoff and landing speedsand high energy absorption brake system _ ; Main engine fan air (dual mode) 7. Remotely Piloted Vehicle (RPV) : _ 1 , 452 kg (3,200 pounds) None - use basicJindivik design Air Force , Navy, and Civil government ,i i use- flying preprogra m med paths Single turbojet Main enginec¢ _m pre ss or bleed air , (dual mode) 8. Wing in Ground Effect • (WIG) 27 , 2 1 6 kg (60 , 000 pounds) (approx.) Adaption of SES planing sealsfore and aft to an amphibious takeoff and landing U . S . Navy antisubmarine warfare , systemwith shock absorbingside hulls. Elastic trunk material not required special military missions for side hulls or fore and aft planing _ eal s .

Tur bo fan Side hulls usedfor parking , braking , i a -f h ;Iht end plates , and op e n water power Main engine f an air (dual mode) off d;splacementstability.

Discussion of Curre nt T e c h nology Bas e v , F ? _ o D UCIBILI3 _ " " O F Tt t _ G e n e ral - Eig h t te c h nolo g y ite ms a r e first dis cuss e d: _)_,i G Ibl / kt_ p / k G _ I5 p O0 1 _ , - I 1. Trunk i ,, _ t e d s h ap e and load prediction, i ; 2. Trunk flutte r pre diction and suppre ssion, 3 . Aircraft landing dynamics analysis _ _ . 4. Cushionborn e stability and control analysis, 5 . Ai r lubrication e ff e ct, 6. C u shion pow e ring a n d s u rfac e p e rformanc e pr e diction, 7 . Cu sh ion po wer ing mec h anisms , , , - 8 . Low s p ee d groun d co n tr o l mecha ni sms.

T h e s e a re see n a s previou s AC L G pr o b lem a re as that h ave been or a re being a dequa t e l y e n o ugh a ddre s sed for ne ar. term e n g inee r i ng d e ve lo p m en ts t o p roceed . Th ey w i l l need fur the r de v el o p m en t fa r t erm f or ACLG to b e app lied to l a rg e r a ir c r aft.

A s eco nd gro up o f t hree i t e ms is t he n a l s o discuss ed . T h e follo w i n g ar e th e th ree t e chno lo gy ite ms id e nt if i ed as n e a r te r m de v e lo pm e nt n ee ds: 9. T_'unk material, 10. AC L G fli g ht effects, 1I. Braking.

Key aspects of these items fwhich have also been extensively addressed) are identified as crucial to n ea r - ter m en g ineerin g development and ha' , e tl , e most urg a nt need f o r techn o logy ex te nsi o n . De- tails of the eleven items are discussed as follows.

Tr u nk In fl ated Sha p e and L o ad s P redi c ti o n - P ri or to the XC-SA program no analytical me t hods were available for predicting inflated, three-dimensional shapes or analyzing mate ri al loads. Du ri ng that pro g ram semi- ri gorous methods were developed by Bell. These methods have show _ . xcellent a g reement with test data. A computer code A SNAP (Axis y mmetric Seal Non-linear A n, _ o is Pro- . gram) is n o w available. I t has t he f o ll o wing capab i li t ies: ; !. I t acc o mmod a tes a three-dimension a l t oroidal shap e .

2. It accepts non-linear large st : ain orthotropic material pr o perties.

3. It computes the no n -linear relationships between trunk shape, load and water surface load.

- . 4. I t p ro vides peripheral and vertica l loads inc l ud i ng a l so material strain effects on shape.

5 . It inclu d e s "water car ry " e f f ec t s .

T h is p ro g ram i s a d equat e for int erme d ia t e t e rm t r u nk d e sig n ( through C a t egory 4). E v en - tu a l impro v e ments are v i sual i ze d su c h as the d eve lo pment of exa c t bi - ax ial stra i n c al culati o n. Fig- ure 4 7 i s a n exam p le o f l o ad analysis corre l ation with test , usin g this pr og ram.

T ru nk Flutt e r P r ed i cti o n and S u p pres s i on - Also develo p ed by B e ll durin g the XC-8 A p ro g ram was the com p uter code FLAP. T his i s a mathema t ical model of a two-dimensional slice of t he ACLG tr u n k a pp r opri ately l o ad e d w i th a propor ti o n o f the ai r c r a f t we ig ht and free t o heave ( ve r tical ': ; m o t ion ). Co mp lete tru n k memb r ane dyn amics ar_ re p rese n ted. Th i s model successful ly predic t e d XC-8A a ir c r aft and tr u n k dy n a mic behav ior . Tr unk fl utter was a continuing problem in th e XC-8A i program and g round res o nance was also enc o untered. This o r o m p ted the de v elo p ment of the FLAP program b y B e ll. T h_ USA F is currently developin g a similar new p ro g ram with increased c a pability "- t h ro ugh a c ont ract wi t h Fos ter-Miller Ass o ciates.

58 _ I{_ , tiODU C I B ILI , r y OF q_I-I_ O1_I G Ilq b -L p A G _ I S ?0 0B Load OP Height = 0.069m (2.750 in . ) Load Kg Lb above Waterline0 Kg Lb 180 - .400 OPAngl e = 1.584 Degrees 9 0 - r 200 , _ 160 .

•360 Pc = Cushion Pre s sure - t " | Pb = BagPressure 80 1C.q ; ' / 140- -320 7 0-. _ - 280 ASNA ?

120 - (Pb / Pc= 1.25) _ 60- (Pb= 3352 Pa (70 PSF);Pb / Pc = 1 . 25)

. -24 0 \ / 1

2 _ 0 / ASNAP !

" 2 00 /

o 1 0 0

, oo ,o \

8 0- _ o 4 0- - = 160 / o 80 60- j 0 30- A - 120 4_ :> 60

4 o 8o 2 o- 4 0

20- . 40 Lb / Ft 2 1 0 -. 20 _ -- " L _ -- 10 20 30 40 50 60 70 80 O- I II I I I I I I I I i 0 I I I I I _ _ _ . L . -- . --I 0 1000 2000 3000 4000 0 1 . 5 3 4 . 5 6 7.5 9 10.5 12 BagPressure (Pb) - ;oa s c a l s GroundPl a neAngle (Deg) Fig u re 47 . ASNAP Anal ys i s Cor relati o n t o Measured L o ads 1 / 6-Scale SES T hree-Dimensional Bow Seal The FLA P program is illustrated by ti, _, d iagram - Figure 48. It has the following capabilities: 1. It accepts general non-linear material plastic and damping prop 'ies.

2. It incorporates fan characteristics and rigid body motion effects.

3. It includes surface contact effects (friction, etc.).

4. Georr, try variations such as strakes, i n ternal diaphragms concentrated masses, etc., can be analyzed.

The model aceurate!y predicts vibration modes and frequencies. Table XXIV is in dicative of it s p .redictive ca p ability. References 20 and 21 are a n alyses of XC-8A behavior made by using tb_s " p r o g , ; am.

I n thi s area re fi nement of c omputer code te c hniq u e together with evaluati_ . ._ of g eometri- c al a n d p re s s a re related s tabilit y boundarie s a n d relationship s i s s een as a near-term requirement whi c h m_. y be f u l fi lle d b y the c urrent USA F program. The extension of the methods to include the c omplete trunk rather th a n a two- d imensional slice is an eventu,tl technology goal. _ con- s id_rabl e effort will be require d to re a c h thi s go ,l; it i s p o s tulated a s being reached at the Category 6 sta ge (ai rc r a ft of o v er 22,6 8 0 kg (50,000 lb) weight and over 2,394 P a (50 lt_ / s q It)), A ir c r a f t Landin g Dyna mi cs A na ly si s - The abo v e analytical model s provide the e ss ential informatiu n for a n edu c ated d es ign of the trunk it s elf. Additional analy s e s of cu s hionborne and cushion-i v flated- a i rborne air c raft behavior are releva n t to the desigl t of the ACLG a s a sy s tem. Of primary importan " e I + , , Fuselage Rigid Body Motion ]; t m bient Y | F F _ A an : Trunk Element Elasticity Mas s Damping Poro s ity _ QT C Trunk : P T ' VT ' PT _ Distributud Flow . ? j Cu s hion " _ ,,q L , _ _ / i t . _ , _ . . ....-- - -- St r ake - P c' Vc Pc _ ' _" t _ _ ' ° ' _ miD, , QCA Ground Plane Membrane Surface Pressure Friction F igu re 4 8. A C LG F lutt er Analysis Id e ali z ati o n ! T ABI,E XXI V MA T H MODEL SIMULA TION S OF l / 4-A N D FU L L - S C ALE ACL G TRUNK FLU T T ER ; " Trun k Cu _lo n Fusible Ai r Gap I q ll w n u i M ll h : 1 / 4 o r P a lm # , rum- Pre = ure Prll surl Cl es rlnol Un der Trun k Oiphr i gm F lu tt lr Furl S es le No. Section Ri(psf) Pa (psf) cm(m.) ¢m5n.) ? ofTrunk ? Fluttw?

[ -

I Fwd . 3 , 9 1 )9 1 01.64) 1 , 569 (32.76) 24.0( 9 .75) 1.9 ( 0.75) No Yes Y es 2 Fwd I 3 .9 09181 . 64) 1,569 (32.76) 24 . 0(9 . 75) 1. 5I0 .TS) Y es N o No 1 1 4 3 Side i 2,9 88 (62.4) 1 , 465 (3 0. 6) 24.6(9 . 70) 1. 0 10.4) No Y k J N o_ ) Y m Scab 4 Si d e [ 3 .9 0 0 181. 64) 1 , 569 ( 3 2.76) 24 . 6(9 . 70) 1 .0 ( 0 .4) N o Yes Yes 5 Side [ 3 , 909181 . 64) 1,569 (32.76) 24 . 6(9.70) 1. 5 (0.6) Y es No No 6 Skis i 4.096($5.54) 1.560 (32 . 76) 24 . 619.7 0 ) 1.510.6) Y es N o N o XC- _ 7 Side 115 , _ ZZ 1320 . 0 ) 6 , 2241130. 0 ) 11 0. 5143.51 5.1 (2.0i h o Y es Yes Full 8 S, de il6 . 37 5 (34 2 .0) 6.9431145.0) 9 2 . 7( 3 6 , 5) 5 . 1 (2 .0 ) Yes N o No Sade 0 F wd 116,375 (342 . 0) 6 , 0 43(14 5 .0) $6`5 1 _ .0) 6.1( 2. 0) No Y es Y es 10 Fw d 1 16 , 37 5 (34 _ . 0 ) 6 , 9431146 . 0) 91.4(36. 0 1 5 . 1 12 . 01 Y es N o N o _ C _ One = d e univ .

are t he l anding impact energy ab s orpti on a nd da m ping ¢ l +ara c t e r is ti c . _ of the landing gear . T he_ c h aract e risti _. s h ave been ext e nsiv e ly r ese ar c i _ed an d t h e c urr en t =ethno l o gy ba st " in c lud e s _ veral c o m - puter codes w h ic h h a w : been corr e lat e d w it h variou s d yna m i c mo d e l drop I t , s is , and gi _ e r eh a b l e results. Hig h sink rate landint. ,_ we r e al s o a ccom pli shed in b ot h t he LA-4 ( 2 . 0 re ' see. _. 0 ft / s e . ' ) and XC-8A (2.6 m / see, 8.0 ft / sec) programs , v e r if ying e n e rgy absorption capability . T he I 2 ft / s ec impa c t velocity limit o f t h e XC-8A w as _¢ ri fie d i n model tests.

I .l One suc h computer code is t h e Bell A C LSDY program whi c h is a three-degree-of-freedom pi t c h -pla n e pr ogr am. T h e progr a m includes fa n pressur e / flo w c h arac t eristi c s as w ell as aerodynamic ri ft a nd pi t c h co ntrol mo m en t s . I npu t s of trunk sha p e , trunk a nd cus hi on pre s s ures a re provided " : from calculati o ns performed using ASNAP wh ic h are incorporated as a table look-up. Ou t puts in _ =_ in t hi s area t he U S AF is also pro c uring an ACLG la n ding dynamics pro gr am incorpo ra ted in terms of aircr a ft applied loads and attitud e s t h roug h t h e landing maneuv e r are obtained• ; t h e generalized EASY ai rplane dyna m ics computer code from th e Boeing Company , and NASA has • g e ner a ted a s imil a r progr am throug h a contr act w i th F oster-Miller Ass oci a te s (Refer e nce 14) .

These ana l y ti ca l tool s a re p ro bab ly m or e s o ph i s ti ca ted than the c o mpa r at ivel y s im p le me t h od s us ed i n t h e d es ig n o f cu rr en t g e n e r a tio n lig h t g en er a l a v ia tio n a ir c r af t an d cert ain l y appea r a de q u a te fo r C_t egory 1 an d 2 de s ig ns. Fu rt h e r near -t erm d ev e l o pmen t s a r e n o t a pparently ne ce ssa ry . , _ C ushionhorne S tability and C ontrol Analy s i s - An al y t ical m et h ods fo r veri ficat i o n of cus h ionborne s tability and cont r ol have also bee n developed. St a t ic s t ability and dampi n g is e st im a ted by s ligh t modi fi c ation of l a n d i n g dyn a mics pro grams a nd a comp u ter c ode for a nal ys i s of a ircr a f t c us h ion- borne be h avior in w ind s w as deve l oped by t h e de Havilland Company as a th ree-de gr ee-of-freedo m ya _ plane m od el. Again it is prob a ble t h at t h is type of an al ysis goes b eyond wh at is required for Category ! and 2 d . dopment. Ho w ever , complete visual simulator representation - as was accom- plis h ed b y th e U SAF in th e xC - gA program - is u n doub t edly a desirable t ool f or pilot t raining in ACLG c h a ra ct e ristic s , and would form pa rt of any major development progra m . T hi s latter i s not re g a rd e d as an A C L G tec h nology dev e lop m ent item.

Air Lubric a ti o n Eff e ct - Air lubri ca tion e f fect has been explore.d by s yste m atic s t a tic l a boratory t e sts and confirm e d by full-scal e t e sts in t he LA-4, Jindivik and xC -gA prog ra ms. The air lubri c ation effect du ri ng tak e off rotation and d uri ng taxi over concrete w ith the va ri ous center of gravity c e n t er of pr e ssu re offs e t distan ce s within th e airplan e longitudinal c e nt e r of gr avity rang e is an it e m to be clo se ly monitor e d in any n e w d e v e lopm e nt pro gr a m.

Th e labo ra to ry t e sts e stablish e d th e low frictio n , _' h aracteristic w h e n l a bri ca t e d vis- a -vis the case wh e n th e trunk i s pr es s e d to t he gr ound at trunk pres s ur e, for a series of mem b ra ne to gr o u nd cl e a ra nc e valu e s provid e d by stand-off w e ar plugs. Figur e 49 from R e f e r e n ce 1 5 , s u mm ariz es s om e k e y r e sults. W e ar pl u gs we r e tri e d on t he x C -gA pro gr a m, b u t t he ir futur e pot e ntial n ee ds furth e r conf i rmation.

Cushio , ' P otv e ring a n d Surfac e P e rfo rm ance Pr e diction - T he prediction of cushion fl ow r e quir e d to pro s " giv e n surfac e pe rfor m anc e for give n trunk and cushion press u re remai ns a n empiri c al pro- cess . ., t he p rese nt s tag e , n o analyti c al m et h od has prov e d possibl e: t he refore , t he pe rformance of th e LA-4 a w l th e xC -gA a re u s e d as th e guid e, e sp e cially t he form e r , w h ich w as op e rated on a vari e ty of surfac e s. C , e n e raily, it can b e assum e d that a given e ff e ctiv e air gap b e n e at h th e tr u nk is re lat e d to giv e n s urfac e [,e rfor m an ce . It has b ee n assu me d that larg e airplan e s do not r e q u ir e a gr e at e r air gap than s mall one s for t ra v e r s ing th e sam e s urfac e . On thi s bas is, th e po we r r e quir eme nt vari es 3 / 2 as cPc w he r e c i s t he cu s hio n p e rim e ter a nd Pc i s t h e cu sh ion pr es s u r e. Alt e rnativ e ly fl ow r eq uir e - m e nt for giv e n air gap is proportional to c x / Pc.

At t he pr ese nt tim e, t es ts hav e b ee n ins u ffici e nt _ o r e late the c u s h ion pow e r requir e d accu- ra t e l y to a s p e cific surfac e .

T he d e v e lopm e nt of op e rational type t e st e x p e ri e n ce is s ee n as an on-going t e chnology nee d ; h ow e ver, for C at e gori es I and 2 th e e x trapolation fro m the L A- 4 i s small . Reliable e sti m a te s can be mad e at this scal e .

6 1 Body - _ /-- Membrane ¢ ,J _ 0 . 4 r

\

c ' / - 0.006m10.25 in .)

0.2 [ / J -- 0 . 003m(0 . 125in . } " _ _ Io Plu - . \ \ . 0, 0 0 . 01 0.02 0 , 03 0. 04 0 . 05 JetArea / Footprint Area F i g u r e 4 9 . A ir Lu b r i c a t i on Te s t Res u lt s C u sh ion Power ins M ec ha n ism s - M e c h a nis ms for p ro v iding th e n e c essa r y a ir s up ply to the a i r cus hion at mi ni mum wei g ht an d c o st i s a te ch n ology a r ea a lso re qu iring f u rth e r de v e lop men t . T h e p rovi s ion of sepa r a t e aux ili ary po we r un it s as a dopt e d i n t h e L A - 4 a nd XC - 8A progr a m s is exp e ns iv e i n bot h co s t an d w ei g h t si nc e t hei r we ig ht mus t p ro p erly be cha rg e d t o t h e AC L G s u bsyste m . Ble e d from th e p rop u l s ion en gin e s i n s o m e for m as su gg es t e d i n t his report v i ll prov i d e a bette r m a tc h ed i n te gr a t e d sy s t em , in som e ca s es acce pt in g a p e n a lt y in i n cr eased t ake o ff gro und r un as an ap pro p r iate c orol' ar y to t he rel axe d ai rfi e kl s. rl ' a c e r e q u ire m e n t . W he r e ti le AC L G p o we r is i nte gr a ted wi t h propul s io, t t h e pro p r iet y of ch a rg i ng the ex tr a wei g h t o f t he de lt a AC L G p o we r to th e AC L G s y stt m (as was do ne in pre, : iou s a n a ly s e s w it h separa t e p o we r u ni ts ) i s q u es t i o nab l e. As d iscusse d ea rl ie r , the 1 ,6 33 kg (3 , 6 00 lb) GAA co nside r e d as a w h ee le d ai rcr aft w o ul d b e adeqha te[ y p o we r ed f ro: ta keo f f b y a 3 _ 5 HP engine . Howev e r, al tit u d e p cr f cr m ance wou ld d e ma n d a s u p e rc h ar ge d ( h e a vier th a n unsup e r - c h arged) e n gin e . For ACLG m at ch i n g, a larger , 400 H P , un s uperc h arged e ngi n e is us e d h av i n g ade - q u ate capa c ity for the same a l tit u d e perfor man ce .

A gain , i n t h e ca s e of t h e LMA, if field le n gt h is h eld to what i t w o u ld be w it hou t t h e ACLG bleed, by using largerengine s , a ltitude cruise perform a nce w ou ld n ot be impr o ved . A 7%larger tot a l ; propulsion power would be ne e ded a dding O . 1 59 _ to gross w e ;.ght .

The develop me nt re q u ire ment in t h ese ca s es is one of est a bli sh ing b y det a il a nalysis th a t exi s ting s tate-of- t he-art t e c h nologies can be appli e d . Hig h risk tec h nology developme n t does not ¢ a ppe a r t o be required, alth o ug h c e rt a inly t he du a l mode mech a nisms exampled here w il l req u ire de s ign and t est development t h roug h t h e no r mal engine e rin g cycle .

Lo w Speed Ground Control Mec ha ni s m s - Ability to accept a crabbed a t t itude and its crosswind advantages ha s b e en disc uss ed p reviou s ly . F or ad e qu a te man e uv e r a bility rapid a nd responsive control o f ya w a t titude is e ss e nti a l . S inc e t h e t o ta l mom e ntum reaction of t h e air cus h ion flo w is small and i t s us e d e prives the air cus h ion i t s e lf, it is probabl e th a t aircr a f t' s primary propul s io n m e ans , ra the r t i t an c ush ion flo w div e rsion, m us t b e used for lo w spe e d co nt rol belo w a e rody n a m ic control s p ee ds. In t axi. th is con t rol ma y be reinforced by differen t ial braking.

• _ The mec h anism c h osen f or low speed yaw c on trol w ill vary wit h th e airplane design. The _ , _ " LA _ h ad bot h differential brak i ng and t h e blown rudder commonly effec ti ve on small seaplanes.

_e X C-8 A p ri m a r i ly rel i e d on differential propel l er pi t c h ( fl - prop) . T h e J i ndiv ik in c orporated a Co a nda j e t e xha u st d e fl ector.

i Whe re engine fan bleed is us ed f or air c u s h ion , as suggested in t his report, an integr at ed

i

i sys t e m f o r ground con t ro l also appears app r op ria te and c a n be designed t o operate independent l y i of the t hrust, forward or reverse . This ty pe system w i ll require t ec h nology deve l opment which is i " t h erefore seen as impo rt ant for C a tego ri es 5 a nd above . ] • The fol l owi n g are t he t h ree near- t erm techno l o gy it ems not current l y be i ng add re ssed : ! Tru n k Materi a l - T h e p rinci pa l co m po n en t o f t he ai r c ushi o n i s the flexib l e t r u n k for w hi c h re- a , i tractio n i s t he fi r st req u irement . Retr a ction of a n ine la s t ic f le x ible t r unk wi th in me t al doo rs w as I at fi r s t ex t ens i vely consi d ered, a nd v ari ou s s cheme s have been pro p osed . Bell has con st ructed a sma ll- s c ale wor k in g m odel of a co mp le t ely i n t ern a l tr u n k w it hin m et a l d oo rs and demon st ra t e d i satisfactory d e p lo ym e n t (th o ugh n o t retrac t i on ) . This was f o l l o w e d by ful l -scal e con structi o n o f a l ar ge in el as t ic trunk s e cti o n a n d hinged retrac t ion doo r , d e sign e d f o r a C-130 ret ro fi t . T h e dis- _" advanta ge s i de nt i fi ed for s u ch sy stems a r e ex ce s s ive weig ht and p oo r e xt en s io n / re t r acti o n r e li ab i lity du e t o t he m ec han i ca l c o m p lexities in vo lv e d. _, A manual ly st o w e d in el astic r ecove ry trunk f o r R P V ' s whi c h av o ids thes e disad va ntag e s, _ ; h a s b e e n d eve lo pe d on the Jindi v ik b y the USAF (Fi g ure 44 ) . Th_s system is n o t r e tractab le in fli g ht and, t h e ref ore , is onl y us e d for landing. T o suppl e m e nt it with a takeoff capabili ty a sec ond- _ ary dropaway takeoff trunk is added. The disadvar.tage is the n e ed to recover the takeoff trunk _ and re-stow the landing trunk, a procedure which is unacceptable in commercial applications and " J also limits practicable size.

Be cau se o f t h e s e inelast ic tru n k di s a d vantages, th e maj o r ACLG t runk ma t eri a l deve l opme n t , _ effort has been devoted to elastic material, for external retraction. Through th e LA-4 and XC-8A -t Buffalo programs an entirely new, reinforced-rubber, high-stretch material system, having corn- .!

par a bl e stren g th / w e ight r ati o t o the b e st avai l abl e inelastic mat e ria' . s , has been developed. N o funda- m e ntal t e chnical barri er t o its furthe r dev e l o pm e nt and us e ov e r tl,_ full spectrum o f p o tentia l a i r- _!

• craf t applica t io n has be e n iden t ified. C omputa t ions of t runk weigh t -ughout t his repor t are , bas e d o n t hi s t ype o f mate r ial.

The m os t im po rt a nt u n k n o w n at the pre sen t s tage of de v el op m e nt is in- s er v ice trunk life.

_ Trunk lif e ma y b e limited by fatigue, environmental conditions, or abrasive wear.

Rel a tive t o f a ti g ue, u s e o f r ubb e r in a partially stretched condition increases rather than _ d e c r e as es its d y nami c f ati g u e lif e and r e duc e s its s e nsit i vi t y t o cut pr o pa g ati o n, etc. This is shown by Fi g ur e 5 0, tak ea fr o m R e f ere n ce 16 , w hi c h p r e s e nts t h e r e sults o f a t h o r o u g h s e ri e s o f fa t i g u e i t e s ts o n a t ypic a l s o ft r ub b L . c f or mulation. T w o c o ndi ti o n s ar e o f i n t e r e st i n th e A CL G appli c ati o n.

T h e first i s hi g h cyc l e fatigue du e t o rand o m s train v a riati o ns with th e t r unk inflat e d. Th e stra in t a rge t w ill be in t he o rd er o f 13 0 % in future desi g ns, as d i scussed in this report. With an additional ._ oscillator y 25% imposed to allow for flexing in operation, the fatigue life is 100 times greater when . main t ainin g t he 1 30 % str ain l e v el t han it w o u l d b e if the o sci ll a t ion w e r e app l i e d t o uns t r et ched _ ru bb er . Th e s e c on d co nditi on is th e low c y c l e fati g u e du e to repea ted inflati o n and d e flation f r o m an initial str e t c h c ondition r e tra c ted taut on the surface: for which the maintained strain ma y be 10% to 20%. T h e increm e ntal strain will be approximatel y 120% and fati g ue life will b e incr e as e d 3 t o 10 tim e s c ompar e d with c y clin g from a sla c k condition. Fi g ure 50 also shows the sh o rt fati g ue _. 63 !

tl I nm nl mr tll Strain Added in Osci l lation _' 2S % 1 00 , 000 A

ss

Kiloher t z / :

T o ,,,..,.° .i / !

- 100 0 100 200 300 400 500 600 700 Minimum Strain During Oscillation -g Fi g ure 50. RubberF a ti g u e : li fe to b e e x pec t e d if ti le r u h b e r is o pe r a te d c lo s e to i t s u lti ma t e stra i n l i m its. T he XC-8A tr u n k design required op er a ti o n a t st r ai n levels too close to u l timate limi t s. This le d t o cracks deve l oping i n th e surface skins with prog r essi v e de t erioration , excessive maintenan c e and sho r t life. For a per - sp c c t ive on XC-8A tru n k main t enance Ta b le XXV is included. Detail information o n man h our s expended i n particular maintenance ac t i v ities is not avai l abl e , so t he t able shows principal a c ti v i t i e s and da y s expended only. f r om a dail y record of a period whic h included the c h ange from fir s t to seco n d tr unk.

Relative t o enviro m nental tolerance it is widel y r ecog n ized that natural rubber is p r one to o x ida t io n a nd c r acki ng from o z one at t ack. However , sig n ificant advances have recentl y be e n made i n the protect i o n o f rubber. A new surface-pene t rating an t i -o zonan t called A g e Mas t er was used in th e L A - 4 and XC - SA p r ograms.. This was foun d t o be effecti v e, providing excellen t r e sul t s in ozon e chamber testin g an d in ac t ual tr unk applica t io n s: appare nt ly p r ovi d ing g oo d p r o t ectio n for at l east four y ears. Rela t iv e to o t i le r envi r onmen t al eff e cts such as exposu r e to cold t empera t ures , imme r- si on in sal t wa t e r , e tc., the b asic r ub b e r p r oper t ies are satisfac t ory.

The p r obabl e limi t a t ion on tr unk life is a b r a sive wea r . To r e tain flexi l _ilit y and higll s t rai n ch ara c t e r i st ic s , u se of a so f t r u bb e r carca ss is ind i cat ed , w hi ch w i ll no t i t se l f b e har d w ea r i n g.

Thoug_ l ittle w ea r will b e e x pe c t e d o n s o me su r fac e s , part i cula r l y w a te r and snow , a b r as i ve wear w ill b e enc o unt e d o n har d su r fa c e s be ca us e o f local impe r fec t i on s, d e spi t e t he air l u bri c ati o n d e - _ ' _ REPRODUCIBILITY OP T ItS O RIGI _ A L PAGE IS POOE _ TABLE XXV X C -8A PARTIAL HISTORY j_ 216 Day Workday Period Feb 13- Dec 31 1974 r" ' Days i ' l Tests 39 Aircraft Display 1 _ - , Adverse Weather 1 1 " _ Aircraft Maintenance • Airplane 5 APU 1 . _ Wheelgear 21 _ .

Pro p eller 20 Preflight 5 _ , ACLG Maintenance " i No. 1 Trunk 21 No. 2 Trunk 9 J - ASP-10 13 Parking Bladder Valves 11 Cushion Trim Valves 8 _ Cushion Brakes 5 , if Trunk Change and Configuration Mods 38 ; Instrumentation 8 .

scribed e a rli er, part i cularly i f sharploose m ate ri a l i s pres e n t. S usta ine doperationon thesesurfaces i s e ssential i f the AC LG a i rcraft i s to link with e x i st i ng fac i l i t ie s, particularlylow-qual i ty runways at minor airports. Th e L A -4 wasop e rat ed sparinglyo n su c hsu r fac e s and land e donceon soft sand without signi fi cantd e gradatio n of t h e very thin rubberskinof its trunk ( a pprox im ately 0 .2 5 ram , 0.0l in. stretc he d), p er mitt i n g som e caut i ousoptimismin re g ardto a ir lu b ricat i on pr ev e nt i n g wear.

H o we v e r , it s tot al ta x i distan c e w a s o nl y in the or der o f 30 mi l es . Al so , so m e pro gres s h as been _ _ mad e i n pr o t e cting t he tr u nk b y inc o rp o rating hard wearing ele men t s in th e g r o und t a ngen t r eg i on, , which was accomplished by using point-attach e d wear plugs in the XC-S A trunks (Referen ce 17).

However, XC-8A runway op e rations wer e very limited and such wear as was experienced w as probably mainl y th e r e sult of excessive nose-up t rim. T hese data are insufficient for any realistic lif e predictions to b e made. Therefore collection of syst e matic data on in-s e rvice w e ar and trunk lif e is see n as the primar y n ee d in th e d e v e lopment of ACLG trunk material. Acceptabl e trunk life is r e lat e d to trunk cost; high cost and lon g r e placem e nt time can prev e nt a s atisfactory main- tenanc e interval from b e ing acc e ptable.

W i t h regard to cost, t h e materi al constr u c t io n s u sed t o f a b rica t e thi s ini t i al A C LG e l as t ic m a t er i al a re descr i bed i n References 1 7 and 18. The re i nforcing ma t eri a l used i s nylon ti re cord wh i ch a ppe a rs satis f actory for t h e f oresee a b l e fut u r e . T h e e la s : omer is a s im p l e ble nd of na tu ra l r u b b e r .

Some i m provements in rubber for mu lation c a n be expected near term . Both , raw materia l s a re low

t

cost an d h ave b ee n wide l y used i n t i re m a n ufa c tu re . Bec au se th e trunk w e i g ht i s co m p arabl e t o t i r e _] w e ight and be c a use the tr u nk is fabri c at e d a s a fiat s h ee t, it i s lo g i c al to e x pec t (a pri o ri) that . ' manufa c t u rin g t ec hniqu es d eve lopm e nt will allow the AC LG trunk to be quantity-produced at a lower cost t h a n t h e a i rc r af t tire se t . A t prese nt, m an uf act u ri n g m et h ods are in t h e i r infan cy ; th e XC -8 A cons t ructions we re very unsophist i cated, p rin cipally b y h and. T hi s , p l us design compl i ca ti ons accep t e d for prototypi n g i n order to m i nim i ze ope rat ion a l ri sk , res ul t in g in very high cos t s for th e th ree XC - 8A t trunk s h eets m ade . O n th e ot h er ha n d, a lo w-c os t fab ric ation tec h niq u e wa s reac h ed on t h e LA-4 .

Detail analyses of cost have been made at Bell and show that the high XC-8A trunk cost s were the re s ult of many detail cau s es. The co s ts used in ' , he application s t u die s have been ba s ed on im p roved i de s i gn a nd also on r ea s on ab le ne ar- te rm i mprov e m e nt o f m an ufa c . t uri ng te ch n i que . C o s t est im ate s ; a re ba s ed o n d eta il a n a lysi s main l y usin g current c o nstruc tio n ex p e ri ence. P r edic t ed c o s t ( 1 974 $) t i o f the fi n i s he d e la s t ic s h e et f o r t h e G AA i s $ 1,200 a n d for t h e S HA $ 45,000.

t b , Despi te t he re su lt s achi e ved wi t h e l as ti c ma t erial devel o pment, o nly a few varia t i o ns o f J basi c co nstruction p a ramet e rs ha ve been explored and it is unlikely that present c o nstructi o ns ev en a pp r o a c h op timum . M u c h r emains t o be d o ne relative t o basic se l ecti o n o f e l ast o _er c o m- i ] p o un d s , reinf orc in g co r d m a t e r ials , sizes , s p ac i ng , p lies, o r i enta t i o n, ad hesive s , p r o c e ssin g , etc . To ' t an extent, the material desi g n can be analyzed and a computer code is available for calculating ] co r d w rap / di a m e t e r / extension cha r act e ristics.

i In g e ne ra l , s ucces s ive lab o rat o ry experim e nt in p aral l el w it h full-scale op e r atio n a l e xp eri en ce is seen as a major A C LG te c hnology development need.

Fli g ht Effect s - Aer o dynamic characteristic effects of the inflated air cushion have been investigated through a number of wind tunnel tests and through flight tests of the LA-4 and XC-8A. Analytical methods for drag and pitching moment prediction are also available. Generally, for the configura- tions so far adopted, it has been found that the flight drag of the inflated air cushion is similar to that of extended wheels.

Unexpected problems can occur such as the snaking oscill.ation in yaw initially encountered on the XC-8A. This was due to an unsteady flow separation plienomenon. In this instance, the oscillating separation point was fixed by introducing a flow trip attached to the trunk. Such effects are not readily amenable to analysis, but can be shown up by wind tunnel testing. The inflated trunk ma y a ls o aff e ct the l o n g itu di nal o r directional st a bil i ty and in fl uence the m a ximu m lift. On th e XC- 8A , wind tunnel tests showed a small increase in direction' a tl and little effect on longitudinal stability or lift but this may be changed with a configuration of trunk extending beneath the i n ner wing.

Favorable lift effects'are p robable , but stall characteristics of a low wing with swept trailing edge may not be satisfactory, dep_ , nding on body configuration. Thus, it appears that wind tunnel tes t s of a t y pical con fi guration are a necessary preliminar y to Categ o ry 1 and 2 development, and will give valuable _nsi g ht into the probable characteristics of similar configurations a t larger scale.

B r aking - Brakin g is s e en as an essential feature of an y land-based or amphibious aircraft. It does not a p pear feasible to rely entirel y on reverse thrust or other deceleration means such as drag para- chutes, f o r ei ther c om merc i al o r m i litar y operat io ns.

q The pillow braking method adopted for the L A-4 and XC-SA program is effective and a c hiev e s the three functions: fi rst, that of v enting cushion su pp ort to ensure a g round contact load , se c ondl y , o f pro v idin g a skid at the ground interface a nd , thirdly of a llowin g differential braking.

The skid brake function differs i : undamentally from wh e el braking because the energy (heat) is absorbed at the ground interface rather than in a brake drum. This h'4s the adva n tage of dissipatin g pr ob a bl y mor e t ha n half o i" t he h e a t i n to t he gr o und whi l e t he rema in de r ( abs or bed into th e sk i d) • is n o t co n fi ne d a nd is rapi d ly co oled aft er o p e r at i on. Il o w ev e r , the u s e of a n e lastom er ic s k i d mate - rial wi ll limit th e max i m u m int e rface t e m p era t ure.to a mucll lower wlue than is currently a chi e vable in c onv ent ional wh ee l brak e s. Furth e r, in th e pillow brake scheme the con t act pressure is well abov e trunk pr es sure , whi c h results in concentra t ing the en e r_.v into s mall skid a reas with r e sulting higher interface tem p eratur e .

!

r T h is _i isadvantagewas overcome in t h e Jindivik program by spreading t h e braking over t h e w h ole tru n k f oo t p rint at th e r ear and re d uci n g i nter fa c e pre ss u r e t o t runk p re ss u re, wi th gr e a t l y ' _ reduced wear r ate. Thi s was nec e ssar y because of the high landing sp e ed and greatly increased ene r g y a bs orp t io n r e qu ire me nt p e r squa re foo t of c u s hio n p l an f o rm. , .

: In l arger, faste[ , aircr a ft the ene r g y absorp t ion r e quir e men t s will bec o m e much more demand - inc'. This is illustrated in Table X XVI which.lists energy absorption rate comparisons for se v eral of i t h e A C LG a ircraft stu d i e d. The p roblem is common to an y braking d evi c e ( includi n g _heel b r akes ) ' __ ' • and is d u e t o t he fac t tha t a i rplane kine t ic energ y at t ouchdown t ends t o vary as the fourth power : of sc a l e (w ei g ht v arying as t he cube an d s pee d as the sq u are root ) and a v aila b le co nt a ct a r ea t e nds , t o v ary at t he square of s c a le. T h i s p roblem appears a s a t echnic al barr i er t o high-energ y lan d- l a n d i n g w ith the L A4 / X C-8 A pi llow b rake syst em. It w o ul d not, ho w e v er, i m p act a p rimaril y water-landing : aircraft - for example the LMA as presented in this report which would only require braking at low ._ sp ee ds ov e rl an d . "_ ' TABLE XX VI CO M P A R A TIVE LANDING KINETIC ENERGY ABSORPTION PARAME T ERS • GAA MAT LMA OTF Landing Weight,kg (Ib) 1,630 (3600} 136 , 000 (300 , 000) 45 4 , 0 0 0 (1, 000 , 000) 6 , 3 5 0 (14 , 000) _, i Landing WingLoading 11 2.5 (23) 596 ( 1 22) 538 ( 110 ) 4 0 2 (82} kg / sqm (Ib / sqft) StallingSpeed,km / hr 111 (60) 226 (122) 215 (116) 204 (110) : (knots) Stopping Energy - Aircraft Weight 478 (160) 1,980 (660) 1,785 (596) 1,606 (536) Joules / kg(ft - lb / Ib) TotalStopping Heat _ / kg - calories / B t u _ 0 . 19 (0. 7 4) 64 (254) 193 (766) 2 . 43 (9 . 65)

1ooo " "

CushionArea,sq m (sqft) 6.68 ( 7 2) 11 5.5 ( 1 , 2 42) 46 1 (4 , 960) 1 0.9 ( 117 ) 1 / 2 Total Heat Cushion Area kg-cal / sq m (Btu / s q ft) 1 3.85 (5. 1 ) 2 77 (102) 2 1 0 ( 77 .3) 111 (41 Vari o u s m eth ods can b e s ugge s t ed for in cr e asi ng b ra ke ener g y a b s o rpti on: i a. Increased c o ntact ar e a, b. Al ter n a t ive h ig h t e m perat ur e interface mate r ials, i c. Wa t e r c o o l ing, . : d. Techniques for rejec t ing a greater propor ti o n of th e hea t d i rectly t o t he gro u nd.

This problem i s not thought to be s i gnif i can t in Categorie s 1 and 2 a nd wo u ld no t impac t '_ . t h e LAT f or exa m p l e i n Ca t ego ry 4. However , on the p dl o w b r akin g sc h e me s imi lar l y t o t he trunk, data ar e curr e ntl y in s uf fi ci e nt to enable reali s tic life projection and further d e velopment con c urr e nt with it is see n as a n ea r-t e rm requirement. For the OTF and for lar ge r aircraft, s i g ni- fic a nt a dditional d e velo p m en t i s requir e d, unless water basin g form s the main thru s t o f A CLG pr ogre ss.

6 7 , The i n t ro d u c t i o n of s uc t i o n braking, wi th a much gr eat er fea s i b l e s t o p p ing rate, ag g rava t e s t he e n er gy a bso rp tion pr oble m s. Su c tion b r aking is an attra ct iv e f eature f o r inclusio n i n th e ACL G : _ becau s e a lo W -weights y stem can be introduced easily, using the existing large area cushion cavi t y f o r suct io n and t he trunk to m o unt t he inte r face skid surfaces. Dec e lerati o ns o f 2 to 3 g can k pro bab l y b e achi eve d o n high f r i c ti o n dry ru n w ays. N or mal dr y d ece l e rati o n r a t es c o uld b e t , achie v ed on w e t or slipp e r y runways. T his f e ature provides an unequivocal advantage over whe e l gea r,wh i chis u n able to dup licat e t h i s pe r formance.

M e thods o f satisfactoril y combining the suction braking with high energy absorption skids have yet to be developed. The basic feasibility has been shown by LA-4 tests and some theoretical approaches are discussed in Reference 19. If treated as an emergency method for stopping on slippery surfaces , the energ y absorption requirements would not exceed those of the regular braking m e th o d. "_ Dev e lopment Ti m etab l e s Based on the foregoing dis c ussion, pa c ing technology development items can b e identified f or the a i r c r a f t examples stu d ie d in ea ch c a t eg ory . T able XXVl l su m marizes these projections.

From Table XXVII. technology development timetables h ave been developed using the NASA designated technology readiness dates for Category I of 1982 and 1985 and are shown in Tables XXVII! and XXIX, respectively.

T ABLE XXVli T I'. ' CHNOLOGY DEV E LOPMEN T RE Q UIREMEN T S Aircraft and Technol o gy Dev e lopm e nt Category Requirem e nts GAA Trunk and BrakeMat e r ial - L i fe 1, 2 Aerodynamic Char a cteristics Flutt e r - GroundR e sonan c e : I .. AT Inte gra te dP o w e r Sy st e m i , 2 SHA Trunk Material 5, 6 Cu s hionborne Stability andControl PowerC o rre l a t ion SuctionBr a king MAT Trunk M a t e rial 7 , 8 S tress Prediction Braking MMA None - Foli o , '. = tro m SHA and MAT 7 , 8 OTF ' Aerodynamic Chara c teristics 3 Inte g rated PowerSystem B r a kingMaterials and Methods RPV Inelastic Trunk Li f e 3 Aerodynamic Character is tics WIG GroundResonance 10 Landing Dynamics .

Aerodynamic Characteristics Power C orrel a tion . v

t

TABLE XXVI I I A CLG TECHNOLOGY DEVELOP M EN T TIMET A BLE " Year _ 19 79 2000 _, _ Trunk De s ign Tech n ology _ M a terial Infl a tedShape a nd LoadPrediction Trunk Flutter Prediction a nd t ACLG Aircraft Characteristics Analsysis Landing Dyn a mics ACLG FlightEffect s Air Lubrication and Rotation Cushionbome Stabilityand C o ntrol Cush i on Powering Performa n c e Pr ed i ct ion Cu s h ion Powering Mech a n is ms . _ Braking S ystems Development Materials a ndMe t hodsDeve l op m ent Suction Braking Feasible Example Aircraft Daz e s OverallCategory Techn o l og y ; Re a diness Dates The worl dwide ma r ket ne e d for t he s e 8 app l ica t ions w a s covered in a quali t a t ive m a n n er d ur- ing dis c ussions wi t h the key organizatio n s visited. The conc l usion arrived at is that t he application s c o u ld b e used i n app r oxima t el y t he t ime p h asing indicated b y the te c h nol og y deve l opment , with ,: t h e ex c epti o n of t h e RPV te chnol o gy which wi ll be r ead y l on g before th e ma r ket application s devel op . , i R EPRODUC E BI L 1T _ . OF T _ O RI G I 'h _ A , t >A_r ¢, r _ P qo r _ I v 4 "' TAB L E XXIX A L T ERN A TIV E A C L G T ECHNO L OGY D EVE L O P MENT TIMET AB LE , ,.

Year 19 79 200 0 Trunk DesignTechnology Material Inflat e d S h a pe a nd Load Pr ed iction Trunk Flutter Pr ed iction a nd Suppres s ionl ACLG Ai r craft C h ar a c t e ristics A n alsy si s Landi n g Dynamic s ACLG Flight Effects Air Lubricati o n and Rotation Cushionborne Stability and Con t rol Cu s hion Powering Performance Pr ed iction Cushion Powering Mechanisms Braking SystemsD e velopment Materials and Methods Development Suction Braking Feasible 7 xa mp le Aircraft Dates WIG • ReadinessD a tes _! Overall C ategor y Technology 9, _ 10 .

CONCL US I ONS A ND RECO M M EN D AT I ONS It i s genera ll y conclude d that tile d o minant feature o f A C LG is the prov i sion o f a su p e ri o r . am p h i b i ous / t ri phib io us capa b i l it y . Other des i rable fea t ures d i spla y ed i n this r ep o rt such as c r oss - , w i nd l and i ng , soft g r oun d p erfo r mance or imp rov ed gr o und - acc i d e nt tolerance , wh i le go od in t he m sel v es , a r e unlike ly to l ead to t he adopt i on of A C LG . Possible excepti o ns to t hi s conc h tsio n a r e t he f ig ht e r and R P V a ppl ica ti ons.

" I n these circum st ances t he m o s t a ttr ac t ive near -t e r m use is as rep l acemen t fo r exist ing amphibious aircraft. A large part of the population of these aircraft is employed in areas such as Canada and Alaska , where the economy is s t rong enough t o support them and the condi t ions re- " qu i re t he ir use.

' t

T he , _CLG aircraft will also be sufficiently competitive witla the land plane to greatly sti m ulate the market for amphibians , in, - iudi n g larger aircraft, particularly in countries with k_s L J d ev e lop ed ground trans p o r t a ti o n sys te m s . The present d e m and fo r am p hi b ians and fl o at gea r o n s mal l aircraf t i s re p o r te dl y i nc reasi ng at a gr eate r r at e tha n ge ne r a l aviat io n s a l es de spit e t he r ec o g - !

nize d p enalt i es i n p erfor m ance, we i gh t a n d co s t. ( Av i a ti o n Week, Dec. 11 , 1978, p 63).

T h e m ajo rit y of amphi b i o u s a i r c ra?t in use are s mall air cra ft. The l a r g est in p r o duct_ o r _.s the specialized Canadian CL-215 water bomber ( 19,731 kg (43,500 lb) and no very large ar_ , phibian has ev e r bee n built. Th e A CL G intr o d u ce s a new ec ono m i ca l wa t er / lan d basing opti o n that does • not se e m p ossible of ach i evement an y o t her w a y . Thi s op p ortun i t y can be s een thro u ghou t the ' sp ectrum of de si gn s p re s ente d an d i s parti c ularl y a t t ractive for v ery large aircraft. I t m ay e v en t uall y lead to the use of ACLG as a main s tream competitor to c on v entional wheel gear.

exception of high-energy absorption braking methods, but a number of areas where the technology is inadequate for any production embodiment have been identified. C hief among these is P . e xible i ] ' No fun da men t al t e chnic a l barriers t o A C L G d e velo p ment are foreseen, with the possible . trunk life definition which can only be achieved through extensive ground testing in an opt . rational t context. Con t inua t ion of t he elas t ic trunk approach is recommended, par t icularly because during _ the 14 y ears of desultor y A C LG development that h a s t aken place , no general - use v iable al t ernati v e to the elastic trunk a s a means of extension / retraction has been pr o posed. Second tier problems .I of m e mbrane s tabilit y ( retr a cte d an d inflate d ) and ae r o d yn a m i c effe c ts are te c hne::)gy area s re- quiting increased analytical depth and model test.

A Ex p a nsion of t he techn olo gy base i n the a b o ve a r e as is n ecess a ry to p ro v id e the i mp_ , t us t o z embark on any solidly founded enterprise projecting an aircraft dependent on A C LG. Previous i ex p erience an d current s tu d ies s how that the A C LG can o n l y p rov id e the _l' ansp o r t ef fi cienc y incre - ment necessary to it s ado p tion on one basis; first that it is the sole means of takeoff and ; anding, I and s " ondly t ha t it is incorpo r a t ed in the design from t he s t art and not as a retrofit , since only in t hi s wa y ca n t h e pro jec t e d bene fi ts in weigh t and r .ost be real i zed.

e :i Wh a t eve r cla ss o f ai rc raft is c o ns idered or selecte d a s the mo s t attractive en d -objective, the | initial technology advancement will be most cost-effective if accomplished at the smallest meaning- ful siz e. Small s ize trunk a n d brake d evelopment t e s ts on a suita o l y con fi gure d ground test v e hicle are therefore recommended using a scale appropriate to an available vehicle. In addition, analytical membrane dynamics technology should be advanced and the re s ulting capability used to aid the de- i sign a n d al s t to v a l ida te the beh av ior o f the small si ze tr u nk and m a ke p re d ict i on s fo r othe r de s ig n s.

The reconlmended tests will also provide validation for trunk weight and cost predicti o ns. They I will not provide data on the important second tier problem areas of in-flight membrane stability a nd g en eral t r u n k in-fl igh t a r e ody na mi c effe c t s . Win d tunne l te s t s of a generaq y representative con fi guration are , th e refor e , al s o recom m ended.

Concur re ntly furth e r d es ign and o p erational studies of thos e c onfig u rations id e nti fi ed as • m ost attr acti ve b y the p res e n t r e p ort s ho u l d b e co nduc te d , in order to broaden the basis for the above efforts.

',: 7 1 REFEREN C E S _ : .

1. Abele , G., A tw ood . D.M , and G ou l d, L . D., " Ef fe c t s o f S K - 5 Ai r Cu six ion Veh icl e Operations On O rg a n ic T e rr ains After Two and Thre e Years" . Cor p s o f E n gi n eer s, U . S. Arm y C o l d R e - glens Research and Engineering Laboratory, November 1974.

2. Jenkins, Robert A., "'The Allegheny Commuter Concept", NASA Symposium On Short Haul - S_nall Commun i ty Service, 9 November 1977.

-: 3 . f ' ish er , B . P, Sl e epe r , R.K . , and Stubbs, S.M . , "Summar y of N A Sa, Landing G e ar Res e arc h " , ' " NA2A Technical Memorandum TM 7807 9 , M arch 1978.

4. Earl , T .D., "ACLS For A Commercial T ransport" , S.A.E Paper 740452, May 197 4 .

5. Flight International , 17 Janu a ry 1974.

6. J o u r n a l Of A ircraft, "Suction Braking", V o lume 13, N o. 9, pp 658-661, Septemb e r 1976.

7. Thompson, William ( ' ., " L anding Performance of an Air Cushion Landing System installed on a 1 / 10th-scale Dynamic Model of the C-8 Buffalo Airplane", NASA Technical note T N D-7 2 95, September 1973.

8. Boein g Co mme r ci a l Airpl a ne Co., "Technical and Eco no mic Assessment of Sw e pt-Win g Span-Distributed Lo ad C oncepts for Civil and Military Air ( ' argo Transpo_'ts", NASA 3 " 3 ( C o ntract o r Rep ort N o . 145__9, Octo b er 1 97 7 9. Ca rg o L o g ist i c s A i r li f t Sys t ems S t udy, NASA L ang l ey Resea r ch Cente r 1 978.

10. R yken, J. M ., "A Study of Air ('u . _hi o n L an d in g Systems f or R eco v e r y o f U fimanne d A ir c r af t ", Rep or t N o . AFFD L -TR -7 2 - 8 7 , Be l l Ae ro spa c e Textron, J u l y 1 972.

, ! I. Inn o vative Airplane De s ign Study, T ask II. B o eing C o mpany for P .SD / XRL, Contract F3361_ ' "_ . -76-( -01 __, March 1977.

12. Krause . Fred II.. (;ailingt w l, Roger W., Rouseau, David G., and Kidwdl, George H., "The Current L evel of I)ower-Augmentcd-Ram Wi n g Technology", DT NSRDC 78 / 067 *!

froln AI A A paper 78 -7 5 2 . November IO '_ .

13. USAF i : orcign Technology l)ivision , "EKRANOP L AN T RENDS - - -ECC", DS T -13405- 432-78, 5 September. 1978 ISE('RliT).

1 4. Ca p t ain , K.M . Bog han i , A . B. and W o rmley . I ).N., " H e a ve -P i t ch-Roll / A na lysi s a n d T e s ting o f - b '* Air ( ' ush ion Landing Sy st ems , Re port N o. NAS ( ' R - 291 7, National Aerona u ti c s and Space Ad m ini st r a tion , F_ b 1978 .

15. Sa tt e ri ce , C. E., " 1975 I R &D R e port, A CL S S y stem s A na lysis. T a sk Ill . - F o o tprint Air L ub r icat io n", Rep or t No . 7 50 0 - ') 270 ( _ 7 . B e l l Ae r ospace T extr o n.

_ .4__ _............................. _ - - : t 16. Cadwell, S.M., Merrill, R.A., Sl o man, C.M., and Y o st, F.L., "Dynamic Fa t igue Life of ,_ Rubber", United States Rubber Co., Detroit, MI.

17. Earl, T .D., "Elasticall 7 Retracting ACLS Trunks", Canadian Aeronautics and Space Journal, l Volume 21, No. 5 May 1975.

18 . Earl, T. D., "CC-I 15 Design Development", Paper G iven a t First Conference o n _dvanced : Development Pr _grams fo" ACLS, Miami, Florida, December 1972.

19. Earl, T.D. , Stauffer, C.L. and Satterlee, C.E., "Tests of ' he Bell Aerospace LA-4 A CLS , Fitted' with Suction Braking and Predicti,_ns for Other Aircraft", Report No. AFFDL-TR- -: 75-135, Air Force Flight Dynamics Laboratory at Wright-Patterson, November 19 7 5. :" 20. Hughes, J. T ., "t-.,_' L S Trunk Flutter V e rification Analysis", ITM / XC- 8 A ACLS / 175 Bell Aerospace Textron , March 1976.

21. Earl , T.D and Hughes , J.T. , "Analysis of XC-8A Dynamic Heave / Pitch In:tabil'ity Problems" , : ITM / XC-8A ACLS / 177 Bell Aerospace Textron, August 1976 .... : REPRODUCIBILITY OF TIIE ORIGINA_ p&G_'] IS pO_, . i, f *, _ "- _ . R et o rt Ne. 12. C wD ve e _ ! A ccess i em lle . - .... • 3- R ec i p i e nt'$ C otcllo _ Ne. 1 C 'R 1 5 9 002 i t _- m J S, , b t_ a e T-_.-l lg -_ffIhi T e - ..........

q A ir Cus llio ll L a_l di n g G e a r . M a rc h 1 9 7 9 A pplic a tio n S t u di es " - i P, . f o. . . n g - 6.g *- .,o,. * .. C :_g-- , 7. a .a h e, ls) T. D esm o a d Earl s Pe, 4 o, min g O,go a , t ot i on Repo,t I _ 70 0 5 - 9270 0 2 S 9. °e e fo r m i n 90 e ge n lzot ic q _ _ Add re ss ' 10 . Wo r k Un i t No.

: B e ll A e r o spa ce T e x t r o n B o x I I I . Co n , e c* o, _ cm t No * d u ffa lo . N Y 1 42 40 . NA. S I - 1_ 33 . .0 __ _ 13. Type of R e_f t en d Pe ¢io d Cove e ed "._z S q ,,., _ m in ¢ A _ .cy _ , .n_ A d S , e,s Cont r act o r Rep o rt Nati o nal A er o na u tics and Space Administra t ion January i c ) 79 - M arch 1 9 70 i Washinl z t o n, IX ? 20546 : : h i S / o, , , .. n _ Zge-,Y c.J,- I r i S . S. , l _ l. _n_1_ . ' y _ ,, _ .......................

NASA T echnical Repre_ntative L t.-Coi. J.C. Va u : ',an 1 6 . Abst , oct A ser e s o l Ai r ( 'ushi o a L a_ldin g ( ; ea r Appl ic a tionr. _ as stu . !_ed a, :d p o le_:tial bene fi ts analysed in order t o identify th,.. h OSt attr a ctive of these. The selected appli- catio n s are new integrated d esigns ( not _clrotitsl and empi o : e modified dr- 2n ap p roach with improved characteristics and pcrt o _m a nce. T o a id the study, a survey • of potentia l users was made. A ppl icati o ns wer e eva l uate d in t i _e hght of commcnt_ r e c e i v ed. A te : hn o l ogy s c- nari o is develop.'d, wi ' h dis c ussmn of problem areas, c ur- rent reel- 4ogy level and future needs. Feasible de v elopment t!melalqes are suggcsled It : s c on t ' . ' d t h a t near- t erra de v elopmen! of sn:_ll-si z e A ' L G tru n k_, exploraho n of .,_ q '° d lt el'It .tS al_d brakin g are key lit . ill _ , I he m o _t . : t ra,'l'_ e al , ph c a tt ons arc am- .h,bious ,_,t i _ very large cars() air c raf t a_ ' d small ge n eral avtatton ha x in s the greatesl cntial.

17 . K ey Wor4s (S, letted by Autho, _ . _ . _ 1 18. D ittr : but,o _ Sto tem e n t ¢ ' _ L andin g -Gear I ' Air Cushi o n _ln cl assified - Unlimited _ ' i : ' U n c!assifi,:d Unclassified ' I "F or s .'. l e by t he Cl r a r t , l! h . u. e f or F . - d e r al ¢_c_e n lt l _ c a n d "let hn_ ( .d I n for m._ on. Kprmgl_ c hl. _. _ rg _ma 22 1_ . 1.

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