Document
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Advisory ~ {,, , .t
U.S. Department of Transportation
Circular
Federal Aviation Administration Date: 6/20/85 AC No: 21-22 Subject: INJURY CRITERIA FOR HUMAN Change: Initiated by: AWS-120/ EXPOSURE 'IO IMPP.CT AAM-100 1. PURI:osE. This ~visory circular describes a range of impact trauma \ltlich may Ee used to establish bases for acceptance levels or ~rformance criteria in the ev-aluation of occupant survivability dlaracteristics in civil aircraft.
2. REL1il'ED FEDERAL AVIM'ION REGULlfi'IONS (FAR) SECTIONS. Sections 23.561, 23.785, 25.561, 25.563, 25.785, 25.soi, 25.803, 27.561, 27.785, 27.801, 29.561, 29.563, 29.785, 29.801, and 29.803.
3. REL1il'ED READING MATERIAL.
a. Aircraft Crash Survival Design Guide; (Volumes I-V); Simula, Inc.; USARrL-TR-79-22(A-E); l980; Applied Technology Laboratory, U.S. Army lesearch and Technology Laboratories (AVRAOCOM), Fort Eustis, Virginia 23604.
b. Bioastronautics Data Book; NASA SP-3006; 1973; National Aeronautics and Space Jlrlministration (NA,qA), washington, o.c. 20546.
c. Human Tolerance to I act Conditions as Related to Motor Vehicle Desi n; SAE J885; Apri ; Society o lutanotive Engineers (SAE), warrendale, Pennsylvania 15096.
d. Whole Bod Tolerance to I act with La Belt-Only Restraint; Laananen, D.H; TI- ; May ; Simu a, Inc., Tempe, Arizona 5282.
e. Human E~sure to I1eact with Two Point (La lt) and Three Point {La lt and Dia onal sfiouier Belt) Restraints stems; candler, R.F.; GO',t.rjy, R.V.; Memoran um No. AAC-119-83-7; August 31, 1983; Protection and Survival Laboratory, Civil .Aeranedical Institute, Mike tvbnroney Aeronautical Center, Federal Aviation Administration, Oklahoma City, Oklahoma 73125.
f. Human Survival in Aircraft Emergencies~ Yost, C.A.; 03.tes, R.W.; January 1969; National Aeronautics and Space Administration, washington, o.c.
20546.
g. Proceedings of the Stapp Car Crash Conference; (published annually since 1966 by the SAE under various SP numbers); Society of .Automotive Engineers, Warrendale, Pennsylvania 15096.
AC 21-22 6/20/85 h. I!!fulse Analysis of Aitplane Crash Data with Consideration Given to Human .Tolerance; Huey D. carden (NASA Iangley); SAE 830748; Ppril 1983; Society or iliitorrotive Engineers, warrendale, Pennsylvania 15096.
Note: Initial inquiries for any reading material in this p:3.ragraph may be d irect.ed to the address in the applicable subparagraph.
4. BACKGFOUND. The scientific study of human exposure to impact began during World War II when ejection seats were developed for high-speed aircraft. '!he work of Geertz and Ruff in Gennany developed l:::asic criteria \<Klich are still in use today for evaluating seat and restraint i;.erformance. After the war, the work was expanded by Stapp and other scientists \\Orking primarily for the U.S.A.
military services. Eiband provided a concise sUIT111ary of this early w:,rk. '!he concern for autorrobile crash safety \'tlich developed during the 1950's and 1960's resulted in a great expansion of studies to increase impact injury protection offered to a civil p::>pulation. G.Jidelines for the application of these studies' findings to Army helicopters is found in the Aircraft Crash Survival Design Guide; and for autorrobiles, in various Society of .Automotive Engineers ck>cuments arrl in the Federal Motor Vehicle Safety Standards. The developnents can also be followed in the Proceedings of the Stapp car Crash C.Onferences, p.1blished annually by the Society of rutorrotive Engineers since 1966.
5 • IEFINITIONS • .
a. Human Tolerance. Whole bcx:ly human tolerance limits result from tests with voluntary fiuman subjects \!tho are exposed to increasingly severe impacts while being held by a specific seat and restraint system. 'lhe level of the impacts is increased until a subject feels that further tests w:,uld be unacceptable. Injury is seldom the endpoint for such tests, but \<Klen injury occurs it is often accidental and has always teen minor in nature. Tolerance limits fran such testing have limited general application for systems interxled to protect humans against serious injury or death for they represent a voluntarily accepted impact level and rot an impact level representative of serious injury or death.
b. InjuEY Criteria. Injury criteria describe the trauma limits of irrlividuaI human &xly oorrponents. 'lhese are rrore generally applicable to a variety of impact injury protection system designs. To provide data for protection a:3ainst serious injury or death, biological surrogates are used instead of human subjects in tests; however, correlation of data between the biological surrogates and living humans is difficult. Moreover, for evaluating the p:!rfonnance of a protection system, an anthroponorphic test device (ATD) may be used instead of a biological surrogate, and the 1Il'D is only a rudimentary representation of the human b:::rly. Impact injury criteria should be expressed in parameters \'tlich can be measured on an m'D.
c. Anth~rphic Test Device (KID). An KID is a durrmy used in place of a human for evauation of impact injury protection systems. While many dumny types have been manufactured, the only standardized oclult size 1fi'D generally available in the U.S.A. is the one described ~ 49 CFR 572. '!his device, carrronly called the Part 572 durrmy, provides only approximate correlations with Par 3 6/20/85 AC 21-22 humans, and considerable resources are being expended to develop better M'D's.
Impact injury criteria retermined using biological surrogates should be expressed in parameters \ttbich can be neasured on an l(I.10.
6 • DISCUSSION.
a. G:>als.
(1) The soal o~ this adviso:,X: circular is to provide guidance regarding useful human :impact injury 2fata :;.Jiich nay &; used to establish bases for acceptance levels or ~rformance criteria in the evaluation of occupant survivability characteristics in civil aircraft. The human·~ct in~ry data provided herein ~re neither·design criteria nor design·goal~~r itould be accepted that impact injury protection is a systems oonsideration with the human occupant as only one element in the system. Aircraft designs that absorb .impact energy, help oontrol the impact envirorunent, maintain a:lequate living space, provide egress pathways for rapid evacuation, and use fire resistant systems to provide a:lequate time for egress, oontribute nuch to occupant survivability.
The occupant protection system elements (such as occupant/seat restraints, equipnent, and furnishings) which are closest to an occupant, play a major role in injury protection. It is the proper interaction of all these and related elements t.bich should be a:ldressed to provide improvement in occupant i:rotection against injury.
( 2) The oal of an ct in · u rotection s stem should be to reduce the level of lllJury mso ar as p::,ss1 e; rom ata to ro 1fe threatening, to serious, to minor, to rone. The extent to \lhich progress can be made along that chain depends en many factors: {i) Personal characteristics {age, sex, i;:hysical oorrlition) of the occupant influence the ability to withstand the force of impact; ( ii) Restraint system resign retails g::>vern the placenent of lOcKis on the b::x:fy at locations and at levels ~ere loads can be nost readily taken; ( iii) Orientation of the impact vector relative to the occupant governs t.bich cx:f11?0nents of the b::x:fy are nost highly stressed; {iv) A seat, t.hich can provide distribution of load CNer the b::rly and absorption of energy, may reduce the stress in the b::rly; (v) If the occupant/seat restraint ches rot preclude secondary impact of an occupant with the interior of a passenger canpartment, then the ability of the cabin interior to distribute the impact load CNer the b::rly segnents and absorb energy influences the stress in the b::rly from secorrlary impact; and (vi) Finally, the characteristics of the :impact p.1lse, such as irrpact velocity and the "shape" of the time history of the acceleration (including duration, maximum levels, effective onset rate, etc.), influence the stress in the b::rly.
Par 5 AC 21-22 6/20/85 b. 'M1ole Body !!'Fact Tolerance.
( 1) ConsiderirlQ the many factors influencing the ability of a system to protect against impact injury, any sirrple statement of tolerance should be heavily corx:Utioned. Eibaoo, in 1959, atterrpted to compile a sUllll\ary of the knowledge existing at that time relative to human tolerance to impact and a ttenpted to present it in a sinple form. He chose to represent each test result as a i;x:>int on a log-log plot of acceleration vs. duration. The value of acceleration (or deceleration) chosen for this p:,int was the maximum acceleration neasured in the test, and the duration was the duration of that maximum acceleration. This approach was effective at that time because nost of the test data was ootained for ejection seat tests, \<'.here the acceleration J;X.llse was roughly trapezoidal in shape, and oould be fairly represented l:7j duration aoo magnitude of the maximum acceleration~ however, if the J;X.1lse shape deviates significantly fran a trapezoidal or 9:Juare shape, t.11is method becanes ineffective. For exarrple, the triangular J;X.1lse shape often recanmended as representative of aircraft crash deceleration \','OUld rot even appear on a log-log plot since the .r;:eak deceleration has ro duration. Also, a deceleration pulse with a superimposed short duration spike \'.Ould be characterized t¥ the anplitude aoo duration of the .r;:eak occeleration of the spike, and all other characteristics, such as velocity change or energy, would be ignored. Indeed, such a pulse w:>uld appear to be ro different than a pulse com:EX)sed only of the spike.
format, . but wi 11 ~'l'"".'.""~~~~~!"':'""~a~me--:-,~.--re~ce~n~tl'"'l""y---u~s~~---:~e--:-Army----in evaluating energy absorbing seat .r;:erformance. This method rreasures, and plots, the duration of all acceleration levels \<Vhich appear in the acceleration J;X.!lse of the test. Thus the test is represented as a curve, rather than just a single point on the log-log plot. A series of tests will appear as a family of curves, am the tangent to those curves represents an envelope of the maximum acceleration and duration of maximum acceleration to \<Vhich a human ...as exposed in the test series. 'While this provides a nore L11iversal ireans of including a variety of p.ilse shapes, it cannot oonsider all of the factors previously mentioned. Also, since it retains the log-log tolerance format originally proposed l:7j Eiband, it suffers fran the same p::>ssible misinterpretation that any test or crash, W'lich can be plotted within the tolerance curve, is tolerable without regard to velocity change.
( 3) The volunta e ure areas of Fi ures 1 throu h 4 represent the acceleration levels an rations 1c ve en to erat volunteer human subjects using the restraint ooncept indicated. The areas titled "low probability of life threatening injury" in Figures 2 and 4 represent accidental exposure of humans \<Vhich resulted in reversible injuries.
c. IpPact Injury Criteria. Of rrore importance for evaluating the performance of impact injury protection systems are rreasurements \'.hich can be made during testing. Historically, measurements of acceleration have been used as impact injury criteria, but these neasurements have only been rrede popular by the ready availability of accelerometers rather than the significance Par 6 100-.---------------------,r------------------- 0-, N
-
Tolerance to -Gx Impact
-
2 Point Restraint \J1 Headward i•Gzi Direction of Acceleralive Fo,ce Back to Chest Vertical (Slernumward) Headward - Eyeballs-down (•Gxl Ta11ward - Eyeballs-up Tran1v.,..
Lateral A1ght - Eyeballs-left La.teral Left - Eyeballs-nght Back to Chest - Eyeballs-in Chest to Back - Eyeballs-out O') 20 lateral Lett Chest to Back Note: (Sp1neward) t·Gyi The accelerative force on i·G,) the body acts tn the same C: d1rect1on as the arrows Ta,lward l·Gz) +J co ~ Q) Q) () Q) Voluntary Exposure .03 .1 .2 .3 .5 .6 .7 .8 .91.0 .01 .02 .04 .05 .4 \J1
Duration, seconds N
~ I N N Figure 1 100--r------------------r----------------- Tolerance to +Gz Impact N 2 Point Restraint .....
I Headward N 50 i+Gz) Direction of N Accelerative Force Back to Chest Ve<tical (Sternumward) Headward - Eyeballs-down (+Gx) Ta11ward - Eyeballs-up Transverse Lateral Right - Eyeballs-left Lateral Left - Eyeballs-r,ght Back to Chest - Eyeballs-in Chest to Back - Eyeballs-out 20 Note: Lateral Left Chest to Back (Spmew ard) The accelerallve force on (·Gyi ~ i·Gxl ,hebodyacts,n,h•••m• Sustained C d1reclion as the arrows Ta1lward i·Gzi :..:; ~ Q) Q)
u
Q) Voluntary Exposure 1 -+--------'----....._-----11...-----11...----'---JL.-..-'---'--+------....i....---,...__---'-----L.-....L-....J.-.J.,_&......,.f .02 .03 .002 .003 .004 .006 .008 .01 .04 .05 .1 ·.001
Duration, seconds
°' N
-
(X)
-
Figure 2 V, 100-r-------------------,----------------- 0\ N
-
Tolerance to -Gy Impact (X)
-
2 Point Restraint VI Headward (+Gz) Dlrec:llon of Accele<alive Force Headward - Eyeballs-down Tailward - Eyeballs-up T rans'H'f'H La1erat Right - Eyeballs-ktft Lateral Left - Eyeballs-right Back to Chest - Eyeballs-in Chest 10 Back - Eyeballs-out o, 20 Lateral Left Chest to Back (Spineward) 1-Gy) The accelerative lorce on 1-G,) the bOdy acts m the same C direction as the arrows Ta,lward l·Gz) :.:; ~ Q) Q)
u
Q) Voluntary Exposure 1 -+-------..i,_ ___ ..,__ _ __. __ ,...___.,_....._ ........ _._-+ _____ __.I.A- ___ ...._ _ __..___,.___. _ _.___.__._ ......
.04 .05 .1 .01 .02 .03 .2 .3 .4 .5 .6 .7 .8 .91.0
Duration, seconds
N ......
I N N Figure 3 100-,------------------,---------------- Tolerance to -Gx Impact 3 Point Restraint Headward (+Gzi Direction of Accelerative Fmce HeadWard Eyeballs·down Tailwttrd - Eyeo.alls~up TrlMY- Lateral R,ght - Eyellalls-left Lateral Left - Eyeball!Hight Back lo Chest Eyeballs-in Chest to Back EyeballS·OUI Later-al Left N ....
Ch .. t to Back 0) 20 (·Gyi (Spmeward) The accelerati\le 10,ce on (·G,l the body acts. in the same ...
direction as lhe arrows Tallward C: (·Gzl Sustained
~
Q)
-
Q) Voluntary Exposure (.)
Q) Cl 1 -+-------"'----"'---"'--_...__..__.....__....._.....-+--------'----"'---.-.L.---'--..L.---1---1.-1.--I .1 .5 .6 .7 .8 .9 1.0 .02 .03 .04 .05 .2 .3 .4 .01
Duration, seconds
0\ N
-
-
\J1 Figure 4 AC 21-22 6/20/85 of acceleration as a factor in injury. In short duration a::ocelerations, such as occur in impacts (less than 0.02 seconds, for exarrple), the injury limit is tx>dy structural, and this limit w::.>Uld be expressed better in terms of stress or strain. In any e\l'ent, it should be understocrl that there are oo universally accepted handbcx:>k values for impact injury criteria in the sense that there are handbcx:>k values for the properties of materials used in the construction of aircraft. Injury is a progressive occurrence, and the rate of p['ogression varies with a number of factors \'bich have oot yet been o:xrpletely understcx:>d.
Also, inpact injury criteria are oot design criteria in the sense that they can be used during the design of an aircraft in the same manner as the p['operties of materials are used. Instead, such injury criteria should be viewed as test measurements \'bich can be used to determine if an impact p['Otection system is 1 ikely to have achieved eome level of success. If a minimlDl\ level of protection has been established by regulatory teqUirerrents, as has been generated either by the rulemaking process for the autarotive industry or by military specifications for defense suppliers, then the criteria and rrethods of denonstrating CXJtPliance with those criteria are defined. In the absence of such a definitive p['ocess, the responsibility for the selection of injury criteria p!rtinent to a particular cl>J?lication and for the developnent of appropriate test i;rocedures to demonstrate that the injury criteria have been net falls on the manufacturer of the system. To assist in this effort, the following subparagraphs sunmarize sane of the nore important concepts for injury criteria \tbich may, depending on · the application, be of irrp:>rtance in the develop:nent of :impact injury protection systems for civil aircraft. Other roncepts, as well as argurrents :tbr and against nost of the roncepts presented here, can be found in the literature.
( 1) Head I~U!¼. Injuries to the head can be fractures or concussions. 1.lie ne an1sm of injury depends on the energy of the impact, the rotational and translational novement of the head relative to the txxly, the characteristics of the impacted surface (area, shape, and load distribution properties, for exarrple), and the site and direction of the load (force) vector relative to the head. 'Ihe wayne State University concussion Tolerance Curve (\'EUCTC), prcposed by Lissner, et al., in 1960, forms the basis for nost current head injury criteria. Gadd devised a weighted impulse criterion to define a Severity Index (GSI) to represent the vouc.rc, &> that a GSI less than 1000 represented the limit for skull fracture from localized impacts cgainst a harq surface, and a GSI less than 1500 represented a roncussion injury limit for distributed or oon-contact blows to the head. An alternate representation of the \'EUCTC, suggested by Versace, led to the Head Injury Criterion (HIC) specified in Federal foobtor Vehicle Safety Standard (FMVSS) No. 208. '!be HIC requires a measurement in g's of the resultant acceleration at the center of mass of the head to be inserted into the following ~ation: (t HIC -t ) a (t) dt
< 1000 ·
[
2 1 t -t 2 1 max t 1 where a(t) is the tirre history of the acceleration at the center of mass of the Par 6 ·Ac 21-22 6/20/85 head measured with a system having a frequency response of 1000 Hz, t1 and t 2 are the initial and final times (seconds) during a p.ilse interval, and a value of 1000 is the limit for ~ad injury. Although usually rot specified in the criterion, this limit is rrost useful with p.ilse intervals rot greater than 0.05 seconds.
( 2) Chest· I~7;1· Upper torso injuries include l:x:>th skeletal and soft tissue injury mec isms. Neathery suggested that chest deflection showed gcxxl correlation with blunt frontal impacts and recxmnended a sternal deflection 1 imit of 75 nm for representing severe, ronlife threatening, chest injury for a 45 year old mid-sized male. 'llle primary problem with a deflection measurement is in making a single measurement which is descriptive of the canplex thorax behavior l.llder all oonditions of inpact. The same pc-oblem exists with a single acceleration measurement, such as used in limits which state " ••• shall mt exceed 60 g's except for intervals \\hose cumulative duration is rot rrore than 3 milliseconds," and is cx,npouooed by the difficulty of oorrelating an acceleration rreasurement with injury. Eppinger suggested an alternate, easily measured criteria, shoulder t:elt load, as a means of predicting thoracic fractures in cadaver tests (with consideration of cadaver \\eight and cge at death). He suggested that a 5.8 to 6. 7 kilo newtons (kN) upper torso diagonal belt force would produce the minimum average rumber of fractures in the autarobile fatality p::>pulation in a 13.4 meters/secooo (m/s) frontal crash with a particular belt restraint system. 'Ibis approach is c::oooitioned by the understanding that belt loads are also strongly influenced by b:!lt geonetry, a factor mt represented in the analysis.
( 3) Abdaninal Injuq. The clinical literature provides extensive documentation ol ai'e serious, ife threatening injuries \\hich can result from blunt abdominal trauma; however, the research accarplished to date to define atx:lominal injury criteria has been limited, and ro practical criteria have evolved. 'lllus, considering the p:,tential severity of abdominal loading, the only suitable recomrendation is to avoid applying loads to the abdooen. In particular, a safety belt should be designed&> that it <bes mt slip from the pelvis to the abdanen.
( 4) ~ ~nj_ury.
( i) Early studies by Patrick, et al., used enbalmed cadavers with head, chest, and knees striking lightly padded load cells during sled tests.
They concluded that a load of 6.2 kN represented a oonservative value for overall injury threshold for the patella-femur-pelvis c::onplex. tJbre recent studies by Melvin, et al., using unembalmed cadavers and an impactor with 25 mm of energy absorbing padding, indicated a threshold of fracture of 13.3 kN, with a threshold impactor rromentum of 180-220 Ns recessary to cause fracture. The current limit specified in EMVSS 208 is 10 kN which is suggested as being appropriate criteria in aircraft. 'lllese studies concerned impacts \\hich \\ere essentially in line with the femur.
(ii) Concentrated loading of the p:itella by impactors having circular or ring shapes less than 16 rrm in diarreter demonstrated failures as low as 2.5 kN, with i;:atella damage varying dramatically with impact velocity.
Par 6 AC 21-22 6/20/85 (iii) Transverse loading of the lower leg was reported by Young to result in tibia fracture at force levels from 4.45 to 6.67 kN. Kramer, et al., .....
found a 50 percent fracture limit of the lower leg to lie between 3.3 and 4 .4 kN, depending en the dianeter of the impacting cylinder.
(5) Spinal Injury.
( i) Damage to the vertebral oolumn, particularly to the q:>per lumbar and lower thoracic segments, occurs frequently W1ere severe .impact force is directed P3rallel to the spine. Stech and Payne nodeled this impact as a single lurrped-mass, damped-spring system, assuming that the total body mass which acts en the vertebrae to cause injury can be represented by ::ne rigid mass. 'lhe nodel is used to predict the rraximum deformation and the associated force of the spring (representing the vertebral oolumn) for an input acceleration-time history rooasured en the structural seat p:3n of an ejection seat. 'lhe injury criterion which results is called the Dynamic Response Index (DRI). DRI limits for uniaxial spinal carpression fractures of military aircrew have been suggested as follows: DRI = 18.0 :inplies less than 5 percent risk of injury DRI = 20.4 irrplies less than 20 percent risk of injury DRI = 23.0 implies greater than 50 percent risk of injury While the DRI has been successfully used for several military programs, these programs have also used well designed restraint systems to avoid bending looos on the spinal oolumn "'1ich are mt always p:,ssible in civil systems. M:>reover, , few civil aircraft seats have well defined structural seat :p3ns en W1ich respresentative accelerations can be rreasured. In an attempt to OV'ercane these problems, Olandler oonducted tests using a rrodified Part 572 M'D with a load cell inserted into the pelvis at the base of the rubber "lumbar" cylinder of the durrmy. He found that, under a variety of test oorrlitions with a military type seat, a pelvic oompression load of 6.7 kN correlated with a DRI of 19, irrlicating a low to noderate risk of injury. Since loads from the restraint system which would cause spinal oorrpression ~uld nost likely be reflected in an increased pelvic load, this rreasurerrent rray have nore general application and is suggested for use in aircraft.
( ii) Models which are, in effect, limited to ene injury indicator for spinal oolumn injury cannot predict the oomplex stress distribution "'1ich exists in this oomplex structure. Several nore oophisticated nodels have been suggested, but there is oo general oonsensus of nore representative injury criteria. In any e'ilent, the rreasureroonts "'1ich can be made during a test will probably limit any proposed criteria to axial and shear loads and rroments and torque in practice.
d. Restraint Effectiveness arrl Other Criteria. There are several other criteria for effective protection against impact injury \<\hich cannot be defined by numerical limits. Pmong the nore important of these are: Par 6 11 AC 21-22 6/20/85 (1) Restraint systems should re designed to encourage frequent and proper use by occupants. Restraints \\hich are corrplex, uncanfortable, or l.B1duly restrictive to rormal cperational functions of the occupant are unlikely to be successful.
(2) Restraints should fit the size range of occupants that are likely to use the system. Misfit restraint systems can cause injury1 for example, a diagonal belt \\hich bears against the side of the head can pro:note neck injury if vertical impact takes place: a diagonal belt \\'hich passes belCM the center of mass of the upper torso-head-neck CX)Tfl)lex may allow the torso to rotate oot of the restraint and increase the p:>tential of either impact with the aircraft interior or injury fran spinal column torque, etc.
( 3) Restraints should apply loads to the body areas 110st able to withstand the loads (i.e., ~lvis or shoulders), and should rot rrove from those areas during the impact.
(4) Seats and·restraints should distribute their load OV'er a maximum body contact area to reduce concentrated load en the body.
(5) Seat and restraint ststems should provide as nuch miform load
distribution to the b:rly as p:>ss16 e to limit relative displacement of the body
segments.
( 6) Elasticity of elements in the restraint and seat allows body motion and can increase impact severity. For example, long lengths of restraint webbing stretch rrore than.short webbing lengths and allow ITOre occupant notion.
e. Accepted Injury Criteria. The follCMing docwnents oontain injury criteria and test procedures which have been accepted by user groups and have served as guidance for establishing similar criteria for civil aircraft crash injury protection systems: (1) Federal Motor Vehicle Safety Standard No. 201, <xcupant protection in interior impact (49 CFR 571.201), contains criteria for head impact with instrument panels and seat backs.
(2) Federal Motor Vehicle Safet Standard No. 202, Head restraints (49 CFR 571.202, contains criteria r oo restraints intended to reduce neck injury in rear-end oollisions, and may be applicable to rear facing seat, hea1 rest design in aircraft.
( 3) Federal Motor Vehicle Safety Standard No. 203, Impact protection for the driver from the steering control system (49 CFR 571.203), contains criteria to minimize d1est, neck, and facial injuries resulting from impact with the steering control.
(4) Federal Motor Vehicle Safety Standard No. 208, <xcupant crash protection (49 CFR 571.208), contains criteria for the ti;ad, thorax, and upper legs to minimize injury in an aut0110bile crash.
Par 6 6/20/85 AC 21-22 - (5) Milita';)' seecification 58095(AV), General Specification for Crashworthy, N:'>n-EJect1on, Aircrew Seat System (MIL-S-58095(AV)), oontains specifications for limiting spinal injury created by \\hole l:x:xiy vertical acceleration.
f. sussested NlUllerical Values for Aircraft Use. The following subparagraphs summarize the impact injury data that are suggested herein for use in assessing the :i;:erformance of impact injury protection systems in civil aircraft, and these data are rot to te considered as regulatory criteria. It is rot intended that all of the suggested :i;:erformance criteria should te used in every case to assess each :impact injury protection system. When regulatory requirements are established, specific performance criteria will te defined within the rule. In such cases, the regulatory criteria take precedenc ~ wer anything presented in this advisory circular. In the absence of a definitive regulatory requirement though, a manufacturer should select appropriate :i;:erformance criteria, develop ai:propriate test procedures for the :i;articular c:lf)plication, and derronstrate that the selected :i;:erfotmance criteria have teen rret.
( 1) Whole t>ody !!!J2.a:ct tolerance ( i) (2-p:::>int restraint) Figure 1 - Gx ( ii) (2-p:::>int restraint) Figure 2 + Gz ( iii) (2-p:::>int restraint) Figure 3 - Gy ( iv} (3-p:::>int restraint) Figure 4 - Gx (2) Head injury - HIC < 1000 (t2-t1 < 0.05 secorrls} (3) Chest injury - Diagonal shoulder belt load - 7.8 kN (1750 lbs.} (4) Abdaninal injury - No quantitative data suggested.
(5) Leg inju!l' (i) In line with femur - 10 kN (2250 lbs.} (ii) Patella (ooncentrated load) - 2.5 kN (560 lbs.} (iii) Transverse (lower leg) - 4.45 kN (1000 lbs.} (6) Spinal injury - Pelvic oorrpression load - 6.7 kN (1500 lbs.)
. <JJ,?~
eph A. Pontecorvo puty Director of Airworthiness Par 6