Document
NASA-TR-111925
AIAA-95-3457
Ground-to-Flight Handling
Qualities Comparisons for a
High Performance Airplane
Jay M. Brandon, Louis J. Glaab,
Philip W. Brown, & Michael
R. Phillips
NASA Langley Research Center
Hampton, VA 23681-0001
Atmospheric Flight Mechanics Conference
August 7-9, 1995/Baltimore, Maryland
For permission to copy or republish, contact the American Institute of Aeronautics and Astronautics
370 L'Enfant Promenade, S.W., Washington, D.C. 20024
GROUND-TO-FLIGHT HANDLING QUALITIES COMPARISONS FOR A HIGH PERFORMANCE AIRPLANE Brandon, Jay, M., Glaab*, Louis, J., Brown, Philip, W, and Phillips, Michael, R.
NASA Langley Research Center Hampton, VA 23681 *Lockheed Engineering and Sciences Company Hampton, VA 0 pitch angle, deg ABSTRACT roll angle, deg abbreviations A flight test program was conducted in conjunction height above ground, ft with a ground-based piloted simulation study to enable a AGL course deviation indicator comparison of handling qualities ratings for a variety of CDI flight control system maneuvers between flight and simulation of a modem FCS global positioning system high performance airplane. Specific objectives included GPS handling qualities an evaluation of pilot-induced oscillation (PIt) HQ handling qualities rating tendencies and a determination of maneuver types which HQR heads-up display result in either good or poor ground-to-flight pilot HUD instrument landing system handling qualities ratings. ILS KCAS calibrated airspeed, kt mR milliradian A General Dynamics F-16XL aircraft was used for the NlVl nautical mile flight evaluations, and the NASA Langley Differential PIt pilot-induced oscillation Maneuvering Simulator was employed for the ground TACAN tactical air navigation set based evaluations. Two NASA research pilots evaluated both the airplane and simulator characteristics using tasks developed in the simulator. Simulator and flight INTRODUCTION tests were all conducted within approximately a one month time frame.
Flight simulation is increasingly being relied upon in the design of new aircraft or modifications to existing Maneuvers included numerous fine tracking evaluations airplanes due to the high cost of flight test. The at various angles of attack, load factors and speed requirements for effective simulation capabilities and the ranges, gross acquisitions involving longitudinal and uses of simulation have increased rapidly due to the lateral maneuvering, roll angle captures, and an ILS task reduction of funds available for prototyping and the with a sidestep to landing. Overall results showed increased complexity of modem airplane flight generally good correlation between ground and flight for systems I. Historically, piloted simulations have been PIt tendencies and general handling qualities used very effectively in systems studies, identifying comments. Differences in pilot technique used in control system problems in gain scheduling, rate simulator evaluations and effects of airplane limiting, or other control law implementation errors 2.
accelerations and motions are illustrated.
Actual prediction of flight handling qualities (HQ) using ground-based simulation studies, however, has NOMENCLATURE been less successful. Issues contributing to frequent poor correlation between ground-based and flight g normalized acceleration p roll rate, deg/sec handling qualities include psychological, physical, and 1 b roll rate acceleration, deg/sec 2 physiological factors 3. Many rules of thumb have been q pitch rate, deg/sec arrived at, usually discounting simulation HQ results r yaw rate, deg/sec because experience has shown that the airplane has ot angle of attack, deg usually been easier to fly than the simulator. Another This paper is declared a work of the U.S. Government and is not subject to copyright protection in the United States.
area inwhich simulation has notbeen reliable isthe
originally implemented for specific flight test envelope
prediction ofpilot-induced oscillation (PIt)
expansion reasons.
characteristics inflight.
The longitudinal flight control laws provide a g-
Inorder torelyonsimulation inthe design and
command system with the landing gear up and at ct's
evaluation ofnew airplane configurations, the strengths
below approximately 19 ° in the normal mode, and and limitations ofthe tools need tobeunderstood.
below et = 10° in the reduced et mode. For ot's > 19 °,
Many challenges are present when using ground based
(or l0 ° in reduced ct mode), the pitch command is a
simulation toevaluate flighthandling qualities. Pilots
blend of normal acceleration and angle of attack. With
generally aremore attentive toworkload than task
the landing gear down, the flight control laws transition
performance when using HQevaluation scales 4. This
to a pitch rate command system which blends angle of implies that the perception of the HQ is strongly related attack in above _ = l0 °. The lateral flight control laws to visual or motion cues which help or hinder the pilot provide a roll rate command system. The roll rate in performing the task - regardless of the actual airplane command limit is reduced at airspeeds below 250 response characteristics 5. In fact, most measures used to KCAS, u < 15 °, normal acceleration > 6 g's, or with predict longitudinal HQ and PIt characteristics involve the landing gear extended. The flight control system of pitch rate, pitch rate acceleration, or load factor the airplane is summarized in reference 8.
response 6'7which may be very difficult to present to a pilot in ground-based simulation. The present study DESCRIPTION OF SIMULATOR provides direct correlation of fixed-base ground The simulation studies were conducted in the NASA- simulation with flight results using the same 2 pilots, Langley Differential Maneuvering Simulator, which is a and the same maneuvers in both flight and simulation fixed base 40-foot diameter dome cockpit simulator _.
evaluations. The flight and simulation tests were Inflatable seat cushions were employed for g-cueing, conducted concurrently to obtain the best possible however no other motion cueing devices were used.
correlation between simulation and flight. The data The cockpit was fitted with an actual F-16 sidestick obtained included pilot comments and ratings as well as controller. The primary flight instruments were the time history information of control inputs, aircraft heads-up display (HUD) which was configured to states and other parameters obtained from the instrumented aircraft. represent the F-16XL display, and an angle of attack tape, similar to that in the airplane. The simulation math model was originally developed by General DESCRIPTION OF AIRCRAFT Dynamics from wind tunnel data and was subsequently The airplane utilized in this investigation was a General updated from flight test results. Before these simulation Dynamics F-16XL-1 (Figure l). This airplane is a tests were flown, a validation study of the simulator derivative of the F-16 made by extending the fuselage, was undertaken and time history responses of the removing the horizontal tails, and incorporating a simulation were judged to be very representative of the highly swept cranked delta wing and is one of two F- airplane. The simulation math model was a full 16XL's built. F-16XL-1 is a single-place airplane, and envelope representation of the airplane including angle F-16XL-2 was built as a two-place airplane. The test of attack, sideslip, Mach and altitude effects on the airplane was highly instrumented for aerodynamic and aerodynamic characteristics.
stability and control flight tests, and included air data, The simulation used a computer generated visual global positioning system (GPS) data, Euler angles, imagery system for nearly 360 ° field of view. The angular rates, linear accelerations, control surface target aircraft used for the tracking and gross acquisition positions, and control input force measurements evaluation tasks was displayed on the dome by a recorded in flight and telemetered to the ground station.
separate projector system.
Control effectors are elevons and ailerons at the wing trailing edge, and a rudder. Leading edge flaps are also TEST TECHNIQUES used which are scheduled with angle of attack and Mach number. The flight control system is very similar to Evaluation test maneuvers were selected using the the F-16A, with a limited displacement force stick simulator. Tasks were selected which involved high controller. The flight control system imposes an angle gain piloting tasks in order to evaluate the flight of attack limit of approximately 30 ° in normal mode, or characteristics in the longitudinal and lateral axis over a 20 ° in a special reduced angle-of-attack mode which was wide range of flight conditions. Additionally, PIt characteristics were evaluated by specifying close tolerances required forthe tracking and capture tasks representative data from one pilot will be presented. All selected. Pilotcomments were obtained in flight and at of the maneuvers (except the ILS) were initiated at an the post flight debrief following a question guidelines altitude of 15,000 ft. Table 3 lists a summary of pilot card which was developed during initial simulator ratings for each maneuver discussed.
evaluations. In addition to general comments on items such as adequacy of rates, initial response GROSS ACQUISITION characteristics, predictability of response, undesirable Two types of gross acquisition tasks were evaluated. A motions/coupling, etc., the pilots gave handling quality purely longitudinal acquisition and a multi-axis ratings (HQR) based on the Cooper-Harper scale H in acquisition. These maneuvers were set up at various accordance with the criteria established for each of the speeds and separation distances to evaluate the airplane maneuvers. Additionally, each of the maneuvers was characteristics across a range of g-loading, pitch rate, assessed with a PIO scale rating from the scale shown and acquisition geometry dynamics. Specific in table 1.
longitudinal gross acquisition examples will be Several maneuvers were selected from the STEMS discussed using maneuvers 2.1 and 2.4 from table 2.
maneuver set H and modified to be applicable in the The maneuver required 3 acquisitions of the target, each lower angle of attack range at which these tests were followed by reducing 0 to the horizon. Maneuver 2.1 conducted (below 30°). All of the target tasks and was initiated at approximately 150 KCAS and et = 15 °.
initial setups were developed in the simulator and then The target was co-speed and ahead and above by 6000 were used in both the simulation and flight evaluations.
and 5000 ft., respectively. The maneuver resulted in a The primary flight instrument used in the evaluations large amount of time on the angle-of-attack limiter of was the HUD. For tracking and gross acquisition tasks, 30 ° during the capture. Maneuver 2.4 was initiated at the HUD displayed a reticle which was depressed 3 ° an airspeed of approximately 240 KCAS and o_= 7.5 °.
below the aircraft reference line. The reticle had inner The target was ahead and above by 6000 and 2000 ft., and outer rings of 50 mR and 100 mR diameters, respectively. The maneuver maximum angle-of-attack respectively. The target aircraft which was available for was approximately 20 ° .
the flight evaluations was a Northrop T-38A. The Pilot HQR ratings for maneuver 2.1 show a discrepancy target T-38A was equipped with a GPS receiver to allow between the two pilots. Pilot A evaluated the post-flight analysis of the relative positions of the two simulation better than flight, whereas pilot B evaluated airplanes. Because of antenna placement on both the F- the simulator worse. Pilot A comments were that in 16XL and T-38A, GPS data was unavailable for most of flight there was large amplitude PIO, particularly on the the maneuvering flight conditions which involved second pull to the target. In the simulator, comments substantial bank angles. Air-to-air TACAN and visual were that after some learning, he could arrive on target references were used to setup initial conditions for the with only one overshoot, but that the target had a evaluation tasks in flight. Because of the dissimilar tendency to "bounce" out of the reticle. Figure 2 shows performance capabilities of the two aircraft, some of the a comparison of the maneuver between simulation and tracking tasks involved special setups which were flight. Flight data is shown for 2 captures, and developed in the simulator and subsequently worked simulation data is shown for 1 capture. Figure 2 shows well in flight. A list of the maneuvers evaluated and the angle-off the nose during the gross acquisition for their associated rating criteria is shown in table 2.
pilot A. The data show an initial overshoot of the Selected data from these tests will be shown.
target airplane during the captures in both simulation Two NASA research pilots conducted the flight and and flight, however the flight results show more simulator evaluations. Flight and simulation tests were oscillations while trying to keep the target in the conducted concurrently to provide the most valid reticle. The second capture (flight) shows a divergent comparisons possible between simulation and flight.
PIO with overshoots and undershoots getting progressively larger. The control input time histories, RESULTS AND DISCUSSION (figure 2), give some insight into the differences Correlation of handling qualities ratings, pilot between the simulation and flight maneuvers. As pilot comments and analysis of flight and simulated time comments indicated, in the simulator, the pilot was able histories of selected maneuvers will be presented in the to "learn" the task after several practice attempts and paper for the following tasks: gross acquisition, steady developed a procedure to accomplish it. This involved a tracking, roll angle captures, and the ILS landing large (full-scale) initial input then a release of the stick approach. Where significant differences existed between at an appropriate lead angle. After some time to see pilots, data will be shown for both pilots; otherwise,
where theairplane settled out,the pilotagain began
that it was similar to the airplane. A constant
making corrective inputs tokeep the target inthe
amplitude PIO developed when attempting to do
desired location. Inflight, thepilotdidnothave the
aggressive captures. If the maneuver was performed less
opportunity torepeatably flythe exact same task over
aggressively, then the target could be captured with one and over todevelop a"canned" technique. Asaresult, or two overshoots. Successful captures required
thepilotwas constantly inthe control loop with
substantial lead in taking out the control input.
control forces inboth directions resulting in oscillations
Figure 6 shows a comparison of pitch rates used during
relative tothetarget. Inthesecond capture, the pilot
maneuver 2.4 in the simulator and in flight for both entered adivergent PIO using fullaftcontrol forces.
pilots. Again, both pilots used considerably more
PilotBrated thesimulator worse than flight, and also
initial pitch rate in the simulation than in flight. For
rated the flight HQ much better than pilot A. It should
this maneuver, both pilots had excess control command be noted that pilot B conducted only one capture for this available, and the captures were occurring at maneuver in flight, compared to the two conducted by considerably lower u's (about 15 ° vs. 25 °) than for pilot A. Figure 3 shows the comparison of flight and maneuver 2.1. The improved agreement both between simulator performance of pilot B for maneuver 2.1. pilots and between flight and simulation for maneuver The angle-off nose data shows that both simulation and 2.4 compared to maneuver 2.1 could be related to the flight exhibited oscillations in the capture dynamics increased sensible cues presented to the pilot. At the resulting in slight excursions out of the desired capture higher airspeed of maneuver 2.4, pitch rate, acceleration, criteria. Pilot comments were very similar for both and load factor all increased. This allowed more tactile flight and simulation tasks. During evaluations in the feedback in flight. In the simulator, the increased pitch simulator and in flight, pilot B commented that the rate allowed better control through increased visual pitch rate was slow and that the configuration had PIO feedback due to the higher pitch rates, which resulted in tendencies.
better relationships between flight and simulator pilot inputs. Additionally, neither pilot saturated the stick One tendency seen in common to both pilots between command in flight or in the simulator.
simulation and flight was that in the simulation, both pilots had a tendency to use larger pitch inputs early in Multi-axis gross acquisitions were conducted to include the maneuvers. This resulted in significantly larger effects of lateral maneuvering. The maneuver placed the maximum pitch rates in the simulation as shown in target abeam and flying away from the F-16XL at a 90 ° figure 4. Pilot A used 80% higher maximum pitch rate heading difference at 160 KCAS. In general, lateral- for the first capture in the simulator compared to flight, directional HQR's for both flight and simulation were while pilot B used 225% higher maximum pitch rate.
very similar. Longitudinal ratings were not as The much larger pitch rates used in the simulation by consistent between flight and simulation as seen in the pilot B certainly could be a factor for the decreased HQ previous maneuver task. Relatively large variability ratings in the simulation relative to flight. Absence of between the pilots for a given maneuver was also seen.
tactile cues are probably a primary cause for the Figure 7 compares lateral stick force and roll angle time difference in pilot technique between simulation and histories between simulation and flight for maneuver flight for this maneuver. At these low speeds, the pitch 6.2 for pilot A. As can be seen, very similar roll rate is low, providing poor visual feedback in the angles and rates, and control activity were achieved for simulator, which combined with the lack of g or pitch both flight and simulation. A similar comparison was rate acceleration cues result in poor correlation between made with the longitudinal stick force and load factor in simulation and flight.
figure 8. As can be seen, the simulator was flown with considerably more stick input magnitude resulting in At higher speeds, the agreement both between pilots and higher load factors. Focusing on the first capture (at between simulation and flight improved. Figure 5 time = 18-28 sec), the lateral control inputs and shows a comparison of maneuver 2.4 in the simulator associated roll rates were similar between simulation and in flight for pilot A. Both simulation and flight and flight. The longitudinal characteristics of the data show very oscillatory behavior during the capture.
were very different during the capture as shown in figure Control forces for both simulation and flight have a 9. The simulator task resulted in large amplitude similar frequency and are indicative of a high pilot oscillatory control inputs and load factor response.
workload. Pilot comments for flight were that there Flight results show smaller amplitude control inputs was usually one overshoot (time history data show and associated load factor responses. These differences more) and that it was PIO prone. In the simulator, the may be attributable to the g-cues in flight allowing for comments were that the response was oscillatory and smoother aircraft control. Pilot comments for the characteristics obtained by pilot B look very similar to
simulation indicated that it was difficult toseparate
the simulation and flight results from pilot A, however
longitudinal and lateral problems, butthat there were
several overshoots, and very bad PIO (although noPIO due to learning, reduced stimulus or some other factor, rating was assigned). Flight comments were very pilot B approached the task differently in the simulator.
similar, however thepilotnoted that overshoots were
Tracking a target during reversals was also evaluated. In
primarily side-to-side overshoots inthe pull-up and roll
the simulator, the target reversed course after a heading
maneuver and chose toblame the lateral axis primarily
change of 30 ° for KCAS < 180, and after 60 ° at higher fortheovershoots.
speeds. In flight, the evaluation pilot called for reversals. General results were that both simulation and
PilotBflewthelateral portion ofmaneuver 6.2very
similarly between simulation and flight, as didpilotA. flight produced PIO tendencies at the higher speeds. As speed decreased, longitudinal handling qualities
Additionally, pilotBflewthelongitudinal part ofthe
improved for tracking. This is evident in the PIO scale
task very similarly between thesimulation and flightas
shown in figure 10.This resulted invery similar HQR ratings as shown in figure 13. Results obtained in this ratings between simulation and flight.Pilotcomments test show that the simulator tended to slightly over- indicated that pilotBdowngraded the flightlongitudinal predict PIO tendencies, especially at low speeds.
Another trend from this data is that PIO tendencies
HQrating from 4 to5 based onhisperception of
usually resulted in worse HQR's at high speeds in the
undesired slow pitch rate resulting inexcessive time to
simulator than in flight. Pilot comments for maneuver capture thetarget.
5.1 (150 KCAS) in the simulator were that moderate inputs tended to excite pitch PIO, but the PIO could be suppressed with increased pilot workload. Though TRA CKING workload was elevated to avoid oscillations, desired Fine tracking tasks were conducted to evaluate the performance could be achieved. In flight, comments characteristics of the airplane at various speeds, angle of indicated occasional PIO or "bobbles" following attack and g-loading conditions. Rating criteria were corrective inputs, but otherwise solid desired selected to excite PIO tendencies if any existed.
performance. At higher speeds, maneuver 5.5, Tracking tasks included tracking steady targets and simulator HQR's were significantly worse than flight reversing targets. Each of the maneuvers were flown ratings, however the pilot comments were very similar.
with a separation distance of approximately 1000 ft.
Both pilots' comments in the simulator included continuous PIO, sawing through the CG of the target, During the steady tracking evaluations, both pilots and target bouncing out of reticle. In flight comments consistently rated the lateral handling qualities of both were that there was continual moderate PIO.
flight and simulation as meeting desired criteria (HQR Comparison of data between simulator and flight for ratings 3 or 4). Both pilots also rated the airplane as maneuver 5.5 (figure 14) show increased amplitude of having longitudinal PIO tendencies, with PIO scale longitudinal inputs in the simulator, but the inputs ratings of 2 or 3 across the speed and g range tested. In were at a similar frequency as observed in flight.
the simulator, pilot A also rated PIO characteristics the Although angle-off data is not available from flight due same as flight, however pilot B rated all conditions at to GPS limitations previously discussed, simulator 350 KCAS or above as having no PIO tendencies (PIO results in figure 15 show continuous oscillations during scale = 1). A detailed look at the pilot comments and the tracking, but even while reversing course, the target data however, reveal that oscillations were occurring in remained within the 50 mR reticle.
all conditions, but at the higher speeds, pilot B did not identify the oscillations as PIO.
ROLL ANGLE CAPTURES Typical data for steady tracking at 200 KCAS (maneuver 3.4) is shown in figures 11 and 12. Data for CAPTURES l-g: pilot A shows continuous oscillations in load factor and Aircraft bank angle (_) captures were conducted to stick force in figure 11. The data show nearly identical evaluate lateral handling qualities and control of the magnitudes and frequency of both load factor and stick aircraft at four different angles of attack, which were input for both simulation and flight. Figure 12 shows produced by varying maneuver speed and are listed in the results for pilot B for the same maneuver. This data table 2. The maneuver was initiated while wings were reveal much higher frequency and amplitude results of level and at constant speed and altitude. Bank angles longitudinal stick inputs and load factor response during were captured in a sequence of-60 (left bank), 60 (right flight compared to simulation. The flight bank), and 0 degrees. The three sub-phases of the maneuver arereferred toasmaneuver entry, rollback, slower airspeeds (KCAS = 100 and 130), pilots
and rollout.Maneuver 1.4 could notbeaccomplished
downgraded the maneuver by increasing the resulting
atconstant airspeed due tolarge amounts ofnose down
HQR 2 to 3 units as a result of less than acceptable roll
control being generated bythe control system as a
rate available. This level of HQR degradation was response torollrate and was onlyattempted byone of common for both simulation and flight. The HQR thepilots in flight.
values presented in table 3 were results obtained without consideration of the roll rate available criteria.
Analysis ofthe resulting data forboth simulated and
actual flightshowed desired performance forallbank
angle captures attempted. Additionally, pilotinputs, CAPTURES elevated-g:
and aircraft performance were similar forboth simulated
Elevated-g 0-captures were conducted to evaluate lateral and actual flightresults. Figure 16shows bank angle, handling qualities and control in conjunction with a
rollrate, rollrate acceleration, and pilots lateral stick
longitudinal task of maintaining constant normal g-
input formaneuver 1.2 and isrepresentative ofallother
loading. Different combinations of aircraft speed and g-
l-g 0 captures forboth pilots.From thisfigure the
loading were employed to evaluate aircraft handling
similarities between flightand simulator results are
qualities for an angle of attack range from 7 up to 18
obvious. Anevaluation ofmaximum rollrate and
degrees, and are listed in table 2. The maneuver was
maximum rollrate acceleration forthe three sub-phases
initiated from left-wing-down turning flight at constant
ofthe maneuver was performed and results forflightare
speed and slightly varying altitude. Pilots adjusted
plotted against results obtained foranidentical
longitudinal stick force to obtain the specified initial g- maneuver sub-phase from simulation infigure 17.
loading at 0=-60 (left bank) degrees. Bank angles were
Lines representing values which are equal to, -I-20% and
captured in a sequence of 60 (right bank), and -60 + 40% of simulator results are included in figure 17 as a degrees. The two sub-phases of the maneuver are guide to interpret the comparison. From this figure it referred to as maneuver roll back, and roll out.
can be seen that a majority of points fell below the line Analysis of the resulting data for both simulated and where flight results were equal to simulator results for actual flight showed desired lateral performance for all maximum roll rate and roll rate acceleration. Table 4 bank angle captures attempted. Additionally, pilot presents a distribution of maximum roll rate and roll inputs, and aircraft performance were similar for both rate acceleration values in flight relative to simulation simulated and actual flight results. Figure 18 shows maximum values.
data from maneuver 8.3 and is representative of all of From this table it can be seen that generally pilots used the elevated-g _ captures flown. From figure 18a, the less roll rate and roll rate acceleration in flight than in similarities between flight and simulator results are simulation. This result can be attributed to the lack of obvious for lateral performance. Similarities also exist motion cues in the fixed-base simulation which are, of for longitudinal performance (figure 18b), however the course, present in flight. However, motion cues are pilots did not obtain desired accuracy for most of the usually assumed to affect roll rate acceleration, which maneuver, and even experienced some short excursions the pilot feels, not roll rate which the pilot sees. The beyond adequate limits. The relatively poor above table and associated figure show much more longitudinal performance was partially due to the significant reductions for flight results in roll rate than inadequacy of the HUD display for this task.
roll rate acceleration, which is an unexpected result.
An evaluation of maximum roll rate and maximum roll Pilot remarks and handling quality ratings were similar rate acceleration for the two sub-phases of the maneuver for both simulator and flight. However, there was some was performed. Figure 19 presents results for flight perception by the pilots that adequate performance was plotted against results obtained for an identical not being achieved especially in the simulator. As maneuver sub-phase from simulation. Lines mentioned above, desired performance was achieved for representing values which are equal to, + 20%, and + all bank angle captures both in flight and in the 40% of simulator results are included in figure 19 as a simulator. Pilot remarks indicated that lateral sideforce guide to interpret the comparison. From this figure it cues combined with outside visual cues made it much can be seen that a majority of points fell below the line easier to evaluate roll characteristics such as roll rate and where flight results were equal to simulator results for damping, and to feel roll rate non-linearities. Pilots maximum roll rate and roll rate acceleration. Table 5 also commented that technique was important and that summarizes the percentage of points in each plot the limited displacement force stick made it difficult to region.
determine maximum control inputs. For the two system of the aircraft which placed the aircraft a distance
From table 5thesame trends seen inthe1-g _-captures
of two nautical miles, as measured along the intercept
areevident - that generally pilots used less rollrate and
course, from the localizer intercept point. When this
rollrate acceleration inflightthan insimulation. A
maneuver was performed using the ground-based
totalof87%ofthemaneuver sub-phases performed in
simulator, initialization of the maneuver was at the
flightemployed less rollrate than the identical
waypoint. Once at the waypoint, the aircraft was flown
maneuver sub-phase performed insimulation as
on a 30 ° lateral intercept of the Iocalizer course. At compared to63% forrollrate acceleration.
approximately 8 NM from the runway threshold an Pilot remarks and handling quality ratings were similar intercept of the localizer was performed with the aircraft at 2,000 ft. AGL. Intercept of the glideslope occurred at
forboth flightand ground based simulation. As
about 6 NM from runway threshold. This was the first
mentioned above, desired lateral performance was
sub-phase of the maneuver and is referred to as
achieved forallbank angle captures both inflightand in
localizer/glideslope intercept. The second sub-phase
simulation. Pilots remarked thatconcentrating on
required the pilot to track the localizer/glideslope course.
maintaining g-forces, through theuse ofthe HUD g
The final sub-phase of the maneuver was the sidestep to presentation, oraheads-down angle ofattack gauge, landing, which was initiated at an altitude of 300 ft.
heavily detracted from the bank angle capture
AGL. The entire approach was flown without the use
performance. Relying onbody forces togauge normal
of a flight director, which increased pilot workload
acceleration also didnotyield adequate results for
compared to normal ILS approaches in this airplane.
maintaining desired oreven adequate performance levels.
Rollrate non-linearities caused byangle ofsideslip Analysis of the resulting data showed similar performance of the maneuver from both flight and
build-up during the maneuver were observed inground
ground-based simulation. Pilots had little difficulty
based simulation and flight.Lateral sideforce cues
with the localizer/glideslope intercept sub-phase of the
combined withoutside visual cues made itmuch easier
ILS maneuver with regards to aircraft position.
toevaluate rollcharacteristics such as rollrate and
However, less than adequate performance of airspeed
damping, and tofeelrollrate non-linearities. Pilots
management was noticed for all ILS intercepts
also commented that thesimulator "felt"likethe
performed. Pilots tended to focus attention on accurate airplane without the neck-snapping acceleration cues.
management of trajectory performance rather than on
Asaresult they were less likely touse sudden stick
precise airspeed control. This could be due to the low
inputs in flight, which isalso confirmed through
number of ILS maneuvers performed and minimal speed
analysis oftheavailable data. The HQR values
cues afforded to the pilot by the FCS and sidestick presented intable 3were results obtained based on controller. Desired performance (other than airspeed) was achieved during the intercept with only minor lateral performance alone.
excursions, which were well within the desired range, before stabilization on the localizer/glideslope course in
From table 3it can beseen thatpilotBgenerally rated
flight. In addition, similar bank and pitch angles and
flightone HQR unitbetter than the same maneuver
stick force activity were apparent between simulation performed inground-based simulation. Otherwise and flight.
identical HQR results were obtained forallelevated-g
Desired trajectory performance was accomplished during captures.
the localizer/glideslope tracking portion of the ILS maneuver. Results were very similar between flight and ILS Sidestep Approach to Landing simulation, except the speed used in the simulator tended to be up to 20 kts. less than used in flight.
An ILS task was evaluated to determine the correlation value of a maneuver which involved tight tolerances on The final sub-phase of the ILS maneuver was the aircraft flight path control and a large lateral sidestep to landing, which was specified to begin at an repositioning of the aircraft in close proximity to the altitude of 300 feet AGL. Figure 22 presents aircraft ground. There were three sub-phases of the ILS distance from runway centerline, bank angle, and lateral maneuver, which are presented in figure 20. As can be stick force as a function of distance from runway seen in this figure a simulated localizer/glideslope threshold. Figure 23 presents aircraft altitude, angle of approach was established with an offset of 840 feet from attack, pitch attitude, and longitudinal stick force. The the runway centerline. Adiagram presenting important specified touchdown point was located approximately elements of the HUD ILS guidance used by the pilots is 1,049 feet down the runway and on the centerline. As shown in figure 21.
can be seen in figure 22 and 23, pilot workload increased dramatically as pilot progressed through the The maneuver began in flight with the pilot flying the sidestep maneuver. Initially pilot activity was mainly aircraft to a waypoint using the inertial navigation
anincrease inlateral commands. However, as the pilots
began rolling outofthe second part ofthe sidestep
CONCLUDING REMARKS
maneuver, pitch activity increased rapidly forflightand
A flight test validation of several handling qualities
was notas pronounced intheground-based simulation
tasks has been conducted on a high performance airplane
data as canbeseen infigure 23.Pilots tended tonotbe
with a highly swept wing to compare with results from
as aggressive toacquire the designated touchdown point
a fixed-base dome simulator. These results give
in ground-based simulation ascan beseen bythe more
guidance to which classes of evaluation maneuvers are
gradual flareinthe altitude results. Neither ground-
based simulation orflightresults produced desired, or likely to give comparable results in the simulator, and
even adequate results fortouchdown distances. Flight
what differences one may expect when evaluating an
results were much closer tothe desired touchdown point
airplane using piloted simulation prior to flight, or in
than forground-based simulation withand average of
the design stage. Specific results are as follows:
540 ft.short ofthespecified touchdown point forflight
I. Task learning in the simulator can result in better
as compared with2,203 ft.passed the desired touchdown
point forground-based simulation. Although very few
handling qualities ratings in simulator than in flight.
ILStask evaluations were conducted, they doreveal
2. Pilot input magnitudes, especially in pitch, tend to
trends. Pilots were capable ofcontrolling touchdown
be much greater in the simulator than in flight -
rate better inflight, in spite oflanding before the
particularly at lower airspeeds - probably due to reduced
specified touchdown point, and averaged approximately
2.5ft/sec as compared with3.4ft/sec forsimulation. feedback cues. At slow speeds, pitch rate is slow, so visual feedback in the simulator is weak.
Pilotratings fortheIocalizer/glideslope intercept and
3. Lateral inputs are similar across the speed range.
tracking sub-phases ofthe maneuver were almost
The relatively high roll rates provide good visual cues
identical inflightand simulation. Comments indicated
in the simulator and show that for lateral control, visual
the maneuver was notdifficult toperform and generally
cues are probably more important than acceleration
attained desired performance both inflightand in
cues.
ground-based simulation. HQR ratings of3were
generally assigned byboth pilots forthe twoinitial
4. When the simulation is flown with initial inputs
sub-phases ofthe ILSmaneuver forlateral and
similar to flight, much better agreement between flight longitudinal tasks. PilotArated the lateral part of and simulation HQR's result. This indicates that pilot
localizer/glideslope tracking a4due tocontinual S-
approach can have a large impact on simulator-to-flight correlation.
turning across the desired course. The sidestep sub-
phase ofthe ILSmaneuver received aHQR of7byboth
5. Pilot induced oscillations were observed both in the
pilots forground-based simulation and from pilotAin
simulator and in flight, and were more pronounced in
flight. Pilot Brated thesidestep maneuver inflighta
the simulator at slow speeds during the fine tracking
HQR of4,butbegan the maneuver higher than the
tasks.
specified 300 ft.AGL.Comments cited theneed togo
below thepreviously tracked glideslope flightpath to 6. The ILS sidestep maneuver was valuable for touchdown atthespecified point asasignificant evaluating a high gain task. Good correlation between problem. The touchdown point was specified tobe flight and simulation is evidence that the motion cues adjacent towhere the glideslope intersected the ground.
are not a primary factor in assessing handling qualities for this task. The touchdown task was not suitable to
PilotBcommented that thesidestep maneuver should
have been started at400 to500AGL instead of300
be used in the simulation for flight correlation.
feet.Thispilotaborted hisfirstflightattempt ofthe
Future plans include a more thorough review and sidestep maneuver, which was initiated at300 ft.AGL, analysis of the flight and simulation data. A piloted
atanaltitude ofapproximately 40ft.AGL. Both pilots
simulation study with motion should be conducted to commented that lack ofclear peripheral visual cues, evaluate the postulated importance of pitch rate
inherent tothedome simulator visual system, impaired
acceleration and/or g-cues on low-speed gross
theability tojudge theheight above the runway and
acquisition tasks. Finally, although this study included
made precision landing impossible. Nocomments were
too few pilot samples to give definitive answers, it has
made regarding the lackofmotion cues forground-based
shown that simulation-to-flight comparisons can be simulation asalimiting factor.
very good, but are highly dependent on pilot technique and therefore may vary from pilot to pilot.
REFERENCES Numerical Description 1. Borowski, R. A.: Piloted Simulation Effectiveness Ratin_, No tendency for pilot to induce Development Applications and Limitations.
undesirable motions.
AGARD CP-513, February 1992.
2. Keller, K. L., Janzen, D. B., and Asay, A. A.: Undesirable motions tend to occur Utility of Ground Simulation in Flight Control when pilot initiates abrupt maneuvers Problem Identification, Solution Development and or attempts tight control. These Verification. AGARD CP-513, February 1992.
motions can be prevented or eliminated 3. Reynolds, P. A., and Gawron, V. J.: When In- by pilot technique.
Flight Simulation is Necessary. AIAA-90-3130- CP.
Undesirable motions easily induced 4. Lindsey, S. W.: Prediction of Longitudinal Pilot when pilot initiates abrupt maneuvers Induced Oscillations Using the Optimal Control or attempts tight control. These Model. AFIT Thesis, December 1989. motions can be prevented or eliminated but only at sacrifice to task 5. Mitchell, D. G., Hoh, R. H., Atencio, A. Jr., and performance or through considerable Key, D. L.: The Use of Ground Based Simulation pilot attention and effort.
for Handling Qualities Research: A New Assessment. AGARD CP-513, February 1992.
Oscillations tend to develop when pilot 6. Gibson, J. C.: Handling Qualities for Unstable initiates abrupt maneuvers or attempts Combat Aircraft. ICAS-86-5.3.4, September, tight control. Pilot must reduce gain 1986.
or abandon task to recover.
7. Military specification, Flying Qualities of Piloted Airplanes. MIL-F-8785C, 1980.
Divergent oscillations tend to develop 8. Ogburn, M. E., Nguyen, L. T., and Brown, P. W.: when pilot initiates abrupt maneuvers or attempts tight control. Pilot must Simulation Study of a Cranked-Arrow-Wing open loop by releasing or freezing the Fighter Configuration at High Angles of Attack.
stick.
NASA TM-85800, November, 1984.
9. Ashworth, B. R., and Kahlbaum, W. M., Jr.: Disturbance or normal pilot control Description and Performance of the Langley may cause divergent oscillations.
Differential Maneuvering Simulator. NASA TND- Pilot must open control loop by 7304, 1973.
releasin_ or freezing; the stick.
10. Cooper, G. E., and Harper, R. P., Jr.: The Use of Pilot Rating in the Evaluation of Aircraft Handling Table 1. PIO rating scale Qualities. NASA TN D-5153, 1969.
11. Wilson, Riley, and Citurs: Aircraft Maneuvers for the Evaluation of Flying Qualities and Agility.
WL-TR-93-3082. August, 1993.
MANEUVER Conditions DESIRED CRITERIA ADEQUATE CRITERIA 1-g _b Captures #_ KCAS a 2 sec steady at ea. bank 2 sec steady at ea. bank 1.1 200 10 ° angle (-+5°), desired time for angle, two overshoots, 1.2 150 15 ° maneuver, one overshoot adequate time 1.3 130 18 ° 1.4 100 25 ° Longitudinal gross __ KCAS A0 Aggressively acquire aim Aggressively acquire aim acquisition 2.1 150 40 o point within 50 mR with 1 point within 50 mR with 2 overshoot and within 2.2 200 40 ° overshoots and within 2.3 240 40 ° desired time adequate time 2.4 240 18 ° Steady tracking No PIO. Target within + 5 mR KCAS 2 g Pipper within + 5 mR 10% 3.1 350 7.5 o 2 of pipper 50% of task and of task and within ±25 mR 3.2 350 10 o 3 within +25 mR remainder of remainder of task task 3.3 470 10 o 5 3.4 200 15 ° 2 3.5 150 20 ° 1.5 Reversals _. KCAS a Target within ± 5 mR dia. Target within ± 5 mR dia.
tracking 5.1 150 16 ° pipper 50% of time, ± 25 mR pipper 10% of time, ± 25 remainder of task 5.2 180 13 ° mR remainder of task 5.3 200 15 ° 5.4 240 12 ° 5.5 300 9° Multi-axis gross Target within 50 mR dia. of #_ KCAS Target within 50 mR dia. of acquisition 6.1 200 30 ° pipper with no overshoot pipper with 1 overshoot and within a desirable time 6.2 240 30 ° and within an adequate 6.3 300 20 ° time 6.4 240 20 ° ILS intercept Altitude within + 5(I feet, Altitude ± 150 feet and before glideslope intercept, speed ± 10 kts. with two 7a and speed to within +5 kts. overshoots greater than with no overshoots of one one CDI dot or more dot or more.
Maintain localizer and ILS tracking Maintain localizer and glideslope CDI's to within glideslope CDI's to within 2 one dot, and airspeed to 7b dots and airspeed to ±10 kts within ± 5 kts Touchdown sink rate less ILS sidestep to # Touchdown sink rate less landing than 2.5 feet per second at than 5 feet per second at an 7c an angle of attack of + 1° of angle of attack of ± 2 ° of the the target value. Touchdown target value. Touchdown within + 20 feet laterally and within + 50 feet laterally ant + 60 feet longitudinally of + 100 feet longitudinally of specified touchdown point.
specified touchdown point.
Loaded e_ - # KCAS a g 2 sec steady at ea. bank 2 sec steady at ea. bank Captures 8.1 300 10 ° 2 angle (±5°), desired time for angle, two overshoots, 8.2 250 12 ° 2 maneuver, one overshoot, ± +4 ° ot (+ 0.4 g), adequate time 8.3 200 16 ° 2 2° ct (± 0.2 g) 8.4 200 13 ° 1.5 8.5 350 7 ° 2 Table 2. Rating criteria Task Sim lat HQR Fit lat HQR Pilot Sim Ion[ HQR Sim lon_ PIO Fit Ion_ H(_R Fit Ion_ PIO 1.1 A 4 6 B 4 3 1.2 A 5 4 B 5 4 1.3 A 4 B 6 5 2.1 --A 4 7 B 6 4 2.4 A 4 4 B 4 4 3.4 A 6 4 3 B 5 7 3 5.1 A 4 3 3 B 4 3 3 5.5 A 7 4 4 B 6 5 3 6.2 A 8 7 B 5 5 3 7a A 3 3 3 B 3 3 3 4 7b A 3 B 3 3 3 7c A 7 7 B 7 4 8.1 A B 8.2 A B 8.3 A B 8A A B A 8.5 B TABLE 3. Handling qualities ratings summary Roll rate Roll rate Flight maximum acceleration values (% of sim maximum values Roll rate Roll rate Flight maximum >140% acceleration 7% 0% values (% of sim 140% to 120% 7% 7% maximum values / 0 20% 120% to equal > 140% 5% 5% 33% 40% 5% 14% equal to 80% 140% to 120% 80% to 60% 47% 20% 5% 19% 120% to equal <60% 7% 13% 52% 43% equal to 80% 80% to 60% 33% 14% <60% 0% 5% Table 5. Distribution of maximum values obtained in flight relative to simulation for elevated-g _- Table 4. Distribution of maximum captures values obtained in flight relative to simulation for 1-g _-captures.
I o Simulation | D Flight | Angle-Off No_, _g
I mR
I I I Figure 1.- F-16XL -1 teat airplane Pull 32 lO Slick For_, Ib Ang_e-off -8 nose, dig -16 Push -32 0 cl 115 T , Figure 3.- Longitudinal gross acquielUon, maneuver 2,1, pilot B Pull 32 8; Lon_tudinsl St_Ck Force, Ib o -8 -16 -24 ! !
Pu4h -32
:0
5 15 Time, lec Figure 2.- Longitudinal gross acquisition, maneuver 2.1, pilot A.
PILOT A 2O Angle-OH No_e, deg q, deg/lalC -10 T 50mR -20 _L I I I -30 PILOT B Pull 32 2O q, deg/=ec Longii'gdinal 0 Stick Force, b -8 -16 -10 _J/ -20 -24 I I I Pu_ -32 5 10 15 -30 i i i Time, imc 5 10 15 Time, sec Figure 5.- Longitudinal gross acquisition, maneuver 2.4, pilot A.
Figure 4.- Pitch rate comparison, maneuver 2.1 PILOT A 100 o Simulation l = FIgt_t I is I -Fli_ I 20 1 L/_ I 0 Simulatio¢) I o,a_ 0 q, dog,'_c
2'
-50 ,iif- , I -100 i i i I RigM 20 PILOTB Lat_il S_k Force, It) 0 q, d_mc 0 -5 -5 -10 -10 -15 -15 -20 Le. -20 i I I I I -25 20 40 60 80 1O0 ! 110 I 0 Time, =ec 5 15 TLmm, =ec Figure 7.- Multi-axis gross acquisition, maneuver 6.2, pilot A.
Figure 6.- Pitch rate comparison, maneuver 2.4.
]4 Io Simulation | D Flight | Load Factor, Load Fact_, g g I I I I I I I I I I 0 I 0 18 20 22 24 26 28 30 Pu= 32 . Puit 32 24 24 16 16 Longiludlnal Longitudinal Sitcit Forco, Ib 0 SIi¢_ Force, It) -8 -8 -16 -16 -24 , -24 Pu_ -32 I I I I I Push "32 I I I I I I 0 20 40 60 80 100 18 20 22 24 26 28 30 Time, sac Time, soc Figure 8.- Longitudinal control, maneuver 6.2, pilot A.
Figure 9.- Longitudinal control during capture, maneuver 6.2, pilot A.
I o Simulation I 2.5 LosdFsclor, L_dFi¢_. 2 g g 1.5 -1 I I I I 1 I I I I Pull 32 Pal 20 Lo¢_JIt udi¢_lll SlickFoqce. Ib 0 Lonoitudirmi St_ Force, Io "8 "16 -24
/V
I I I I I Pu,h -32 I P=h "5 20 40 60 80 100 ll0 t J 15 2O Tirne, lK Tm_e. Bit Figure 10.- Multi-axis gross acquisition, maneuver 6.2, pilot B Figure 11.- Steady tracking, maneuver 3.4, pilot A PILOT A o Simulation | u Flight | 2,5 " :3 Load Factor, 2 g 1.5 I I I I I I I I I PILOT B PuN 15 LoP,gitudinal PrO RlUng Sl_ck Force, ID i Pu_-lO I I I 5 10 15 2o i 0 I I I I 1 O0 150 200 250 300 350 Time. =ec KCAS Figure 12.- Steady tracking, maneuver 3.4, pilot B.
Figure 13.- PIO ratings tor tracking reversals.
8O l e Simulation I a Flight I r'----"l desir_ performance m 80 .
4O _'g 0 ...... _._ o -40 -60 -20 _ -20 -80 -40 -6O -8O -40 -80 -120 I i I i I I !
Pull 20 • 50 -100 -150 L -200 -250 = i = = = = = = o Lateral 4 -5 Stick 0 Fo_, -4 Push -10 i -8 R_gh_16 _ __1128
,'o "o 3'o
o -12 Te_, r_ec Lift "16 I Figure 14.- Trmcklng reversal, maneuver 5.5, pilot B.
2 4 6 8 10 12 14 16 Time lec Figure 16.- l-g _ captures, maneuver 1.2, pilot B.
NoJe. dig _4_om 3 _R 0 I I I I I I 0 5 10 15 20 25 30 T_o, lec Figure 15.-Tracking _sults in simulator, maneuver 5.5, pilot B.
_ flightr_ults equad to aim. m_ults i o Simulation I i = F ght I _ de,red performance 8O 120 j 0, deg -20 p 4060 _, -40 (,_ht), degts_
°o I-"
-60 -80 0 l i i i i i de_c - _ :- 20 40 60 80 1O0 120 -40 p (igmulator}. deg/lec -80 -120 I I J 8O (",ohq, 2 _'_c -go -120 -160 -200 i i J i i i i 0 I I I I 40 80 120 160 200 240 (I.muillor). deg/s6c 2 Lateral 4 Stick Figure 17.- Summary of maximum roll rata and maximum roll rate acceleration for l-g ¢ capture maneuver during maneuver entry, roll F_:_e. 0 -4 beck, and roll out sub-phases.
-8 -12 Let -16 0 2 4 6 8 10 12 14 Time (_¢ond_) Figure 18a.- Elevated-g ¢ captures, maneuver 8.3, pilot A.
I o Simulation | m O Flight I _ dem¢lKI pedorrmlnce u flight m=uh _luli ,,4-20% et =Ira. mlun= | I adequate pedormlnco _ flight relmltl equal to lira. fll_ltl I m flight mlultl _lull +/40% of lira. rllultt | m 2O0 Load FlClOr, g (Bight), Ol_/Im¢ 100 I l l i i i l S//"/ 0 I I o 50 100 150 20O p {simulltoq), dlg/MC 503 • , _, / .....
11 ,.
Pull 32 L°n_nxl 8 F_co, 0 -8 ,oo : -16 -24 I I I I I I I o ....
_h -32 2 4 6 8 10 12 14 0 100 200 300 400 500 iime imc (szmu4ator), deg/lec 2 Figure 18b.- Elevated-g ¢ captures, maneuver 8.3, pilot A.
Figure 19.- Summary of maximum roll rate and roll rate acceleration for elevat_-O $ captures during roll back and roll out sul_l_s.
1049' extended runway centedine offset Iocallzer/gf_desJope approach paffl I_ 30 d_. l_alizer inlercept angle slmulateO gildes_ope I_'ansmlller I_ nm 4 nm approxlmatety 1.7 nm X=glidesfope Intercept at 2000 feet AGL at 6nm from runway threshold.
Figure 20.- Definition of ILS-offlet approach and maneuver sub-phazms.
2O • Simulation | _ Glideslope reference I 800 III Ri_lht I __ '+31 I.¢I 200 Diagram of ILS HUD guidance showing Diagram of ILS HUD g_dance important guidance e_ernents with indicabng no-error condltton.
hypol/mbcal errors.
Figure 21 .- Diagram of ILS HUD guidance employed for ILS maneuver.
i i i i i i i D_=. t_ 600 4 runway CL., f_t Pull 32 4OO 2O0 -200 i i I i i I i F_¢. 0 -8 -16 4O -24 Push -32 -12000 -10000 -8000 -6000 -4000 -2000 0 2000 2O oa_ from _m=hokl (hi Figure 23.- Sidestep to landing, Iongltudi_l plx'f_'_ance, pilot A.
c_$'g -20 -30 -40 ' I I I Right 16 _l.n¢ S_d_ Forco. 0 m Ib= -4 _ I"1 -8 -12 Left =16 I I I I I I I - 12000 - 10000 -8000 -6000 -4000 -2000 0 2000 D_.t,mc. fro_ mr_ (R.)
Figure 22.- Sidestep to landing, lateral performance, pilot A.