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2002 Biennial International Powered Lift Conference and Exhibit AIAA 2002-6016 5-7 November 2002, Williamsburg, Virginia EVALUATION OF FLYING QUALITIES AND GUIDANCE DISPLAYS FOR AN ADVANCED TILT-WING STOL TRANSPORT AIRCRAFT IN FINAL APPROACH AND LANDING Chad R. Frost James A. Franklin National Aeronautics and Space Administration Gordon H. Hardy Northrop Grumman Information Technology Ames Research Center Moffett Field, California Abstract While the overall objective of this simulation A piloted simulation was performed on the Vertical experiment was to determine handling qualities, Motion Simulator at NASA Ames Research Center to performance and flight control requirements for a evaluate flying qualities of a tilt-wing Short Take-Off variety of aircraft and control system configurations, and Landing (STOL) transport aircraft during final the data unique to the ATT design is proprietary to approach and landing. The experiment was conducted Boeing. This paper addresses the topic of what levels to assess the design’s handling qualities, and to evaluate of handling qualities and approach and landing the use of flightpath-centered guidance for the precision performance were attained from the still-evolving ATT approach and landing tasks required to perform STOL configuration.
operations in instrument meteorological conditions, STOL Transport Aircraft Concept turbulence, and wind. Pilots rated the handling The ATT configuration shown in Figure 1 features a qualities to be satisfactory for all operations evaluated tilt-wing, with a horizontal stabilizer of reduced size except those encountering extreme crosswinds and compared to conventional transport aircraft, and severe windshear; even in these difficult meteorological without a vertical tail. It is powered by four cross- conditions, adequate handling qualities were shafted turboprop engines driving eight-bladed maintained. The advanced flight control laws and propellers having variable collective and cyclic pitch.
guidance displays provided consistent performance and The wing planform includes forward sweep of the precision landings.
outboard wing sections, and large trailing edge flaps Introduction capable of very large deflection angles. The aircraft is The STOL aircraft configuration investigated in this sized to operate with payloads of up to 80,000 lb from experiment was the Advanced Theater Transport (ATT) an austere airfield of 750 – 1,500 ft in length. The concept developed by the Boeing Company-Phantom design STOL approach and landing speed is between 65 Works . Critical aspects of the design of this aircraft and 75 knots.
concern flying qualities and flight control requirements With the wing tilted at the approach configuration for a large transport aircraft to perform STOL and flaps fully deflected, the aircraft operates on the operations in demanding weather conditions. Existing backside of the power-required curve, exemplified by military and civil guidance for control system design is insufficient for these operations, particularly for a configuration with reduced static stability and advanced control augmentation. Most information that exists comes from STOL flight and simulation experience 30 or more years in the past that relates to aircraft configurations with conventional aerodynamic surfaces, mechanical controls, simple rate damper type stability 2,3 augmentation systems, and basic instrument displays .
Modern designs make use of highly augmented digital fly-by-wire controls and sophisticated displays, and the basic aerodynamic configurations tend to have relaxed static stability with minimal or no conventional tail Figure 1. Boeing Phantom Works Advanced Theater surfaces.
Transport American Institute of Aeronautics and Astronautics This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.
Commanded Control Pilot's the trend of decreasing flightpath angle with decreasing Acceleration Effectors Input airspeed at constant power. At constant pitch attitude, Response + + Control flightpath changes can be made with power without Σ Aircraft Regulator Σ Type Selector Command - - appreciably altering airspeed, which is a characteristic Estimated that is expected to reduce pilot workload in performing Acceleration Nonlinear Aerodynamic the landing approach. Airspeed is controlled through Propulsion Model attitude change, with a gradient on the order of 1.8 knots per degree of attitude. Powered-lift contributions Sensors are primarily a result of the large flap deflection, not of wing tilt. Wing tilt may thus be used to change the Figure 3. Control system structure.
Figure 2. Flight control system architecture attitude of the fuselage for a given flight condition without altering the basic aircraft performance.
The block diagram in Figure 2 provides an overview Displays of the flight control system with its significant A head-up display (HUD) and a head-down primary elements. It includes (1) commands from the flight display (PFD) provided primary flight associated control response types introduced by the information, including aircraft attitude, flightpath angle, pilot through the inceptors, (2) a regulator that acts on airspeed, rate of change of airspeed, altitude, engine the response type commands and feedbacks from the power, wing tilt, flap angle, heading, sideslip, and aircraft’s sensors to produce commanded accelerations distance from the airfield. An example is shown for the necessary to achieve the pilot’s intended maneuver and head-up display in Figure 3 while the head-down to stabilize the aircraft against disturbances, (3) a primary flight display appears in Figure 4. Pursuit nonlinear aerodynamic/propulsion model that produces guidance symbology added to the display for precision estimates of the aircraft’s current accelerations, and (4) approaches is also shown in the two figures. Course the control selector that acts on the difference between and glideslope guidance were provided in the form of a the commanded and estimated accelerations to produce leader aircraft that followed the desired flight profile.
commands to the control effectors. The feedback of the Speed guidance was shown by the airspeed error tape aircraft’s estimated accelerations acts to cancel (or on the left wing of the flightpath symbol that displayed deaugment) the characteristics of the basic aircraft, the airspeed error from the desired airspeed. The leaving the aircraft to respond to the commanded guidance display was flightpath-centered and presented accelerations from the control response types and the pilot with a pursuit tracking task for following the regulator. Control effectors include aerodynamic 4 intended transition and approach to landing . The control surfaces and propulsion controls. The pilot’s task was to control the flightpath symbol to aerodynamic controls consist of wing tilt, ailerons, fast follow the leader using engine power and bank angle, acting flaps, and a horizontal stabilizer (used only for and to make airspeed corrections using pitch attitude.
pitch trim). Propulsive controls include propeller collective and cyclic pitch. Allocation of the control effectors depends on flight conditions and control Fuselage reference line effector inter-axis coupling.
Wind indicator Control augmentation for STOL operation consists of pitch, roll and yaw stability and command augmentation systems (SCAS) and a height damper for Leader aircraft flightpath response augmentation. Pilot inputs for pitch and roll control are made using a center stick. Pitch Airspeed rate caret control augmentation provides either rate Glideslope reference line command/attitude hold or attitude command/attitude hold response; response type is selectable by the pilot through a discrete switch on the center stick grip. Roll Airspeed error tape (shown slow) Flight path vector control augmentation provides rate command/attitude hold response. The pedals command sideslip.
Propeller thrust is controlled manually through the throttle levers. The height damper operates through propeller collective pitch and engine power to improve Figure 3. Head-up display configuration flightpath bandwidth in response to throttle lever inputs.
American Institute of Aeronautics and Astronautics The fuselage reference line, in combination with the pitch ladder, indicates the current pitch attitude of the aircraft. This symbol is fixed to the display surface and does not move. Seen in Figure 3, the fuselage reference line is centered laterally in the display and is six degrees above the display centerline.
An extended body centerline (or crab angle indicator line) consists of a line that descends vertically from the center of the fuselage reference line at low altitudes. From zero length above 100 feet altitude above ground level, the extended body centerline grows proportionally as altitude decreases to touchdown, where the bottom of the line is even with the top of the vertical tail of the flight path vector symbol. The extended body centerline provides the pilot a strong crab angle cue at touchdown.
Figure 4. Head-down primary flight display Conventional glideslope and localizer deviations are shown at the right and bottom of the display. They For the approach and landing task evaluated in this show deviations from desired trajectory during the study, the HUD was the primary display used and since initial approach, and deviations from the five degree the display formats are similar in concept, only the glideslope and localizer on final approach. They are HUD elements will be discussed. The flightpath symbol fixed to the display. The scaling of the glideslope is 12 was quickened to compensate for lags in aircraft feet per dot below 100 feet of altitude, 100 feet per dot response, while the airspeed rate caret was quickened to above 850 feet altitude, and varies linearly between 100 compensate for lags introduced by filtering to suppress and 850 feet. This glideslope scaling is equivalent to the effects of turbulence. The drive laws for these conventional instrument landing system (ILS) scaling symbols and a discussion of pursuit displays is between 100 and 850 feet of altitude. The localizer described in Ref. 4.
scaling is 75 feet per dot below 100 feet of altitude, 300 To use the displays for lateral and vertical flight feet per dot above 850 feet altitude, and varies linearly path control down to decision height, the pilot places between 100 and 850 feet, and is more sensitive than the flight path vector on the leader, causing the actual conventional ILS scaling.
flight path to converge exponentially on the desired The glidepath reference line is a dashed line with a trajectory. The scaling on the leader (driven by scaled gap in the center and is shown displayed five degees glideslope and localizer errors) was set to give an below the horizon line for the final approach in Figure exponential convergence time constant of 15 seconds at 3. The glidepath reference line slides left and right with altitudes above 1000 feet, varying linearly to a five the flight path vector symbol so that the flight path second time constant at altitudes below 100 feet.
vector symbol is always centered in the gap.
Below decision height, the pilot uses the airspeed error tape and the airspeed rate caret to control airspeed.
Simulator Facility The scaling on the airspeed error tape and airspeed rate The experiment was conducted on the Vertical caret were chosen to give approximately a 10 second Motion Simulator (Figure 5) at NASA Ames Research exponential convergence to the desired speed if the Center. The simulator provides six degree-of-freedom caret is placed opposite to the tape with the same motion that permits large excursions in the vertical and magnitude as the airspeed error; thus if the tape is two either the longitudinal or lateral axes, depending on cab degrees below the wing, indicating the airspeed is low, mounting orientation. Bandwidths of acceleration in all the pilot would pitch down to place the caret two axes, including pitch, roll, and yaw, encompass the degrees above the wing, to accelerate to the desired bandwidths of motion sensing that are expected to be of airspeed.
primary importance to the pilot in approach and landing In addition to these symbols, sideslip was presented tasks. The cockpit was oriented with its lateral axis as a flag on the vertical tail of the flight path symbol.
along the largest horizontal dimension of the motion Deflection to the right indicates a right sideslip and system in order to exploit the motion system authority calls for right rudder to correct to zero sideslip.
for lateral maneuvers.
Equivalent airspeed is digitally presented at the lower left of the flight path symbol with digital barometric altitude to the lower right. Radar altitude is shown directly below the flight path symbol.
American Institute of Aeronautics and Astronautics pilot-induced oscillation (PIO) rating scales were obtained during the experiment.
Pilots’ evaluations were obtained for a range of control response type characteristics and levels of dynamic augmentation. Nominal and off-nominal approach conditions and go around, including visual and instrument meteorological conditions along with varying winds and turbulence were used to expose the aircraft to a broad range of anticipated operating environments.
Seven evaluation tasks were selected for the simulation program, encompassing the approach and landing phases of vertical offset, lateral offset, slalom, deceleration, and 30-knot crosswind tasks, and an aborted approach with go-around. The first three tasks were conducted in visual meteorological conditions (VMC), while the last four tasks were flown in instrument meteorological conditions (IMC). Pilots Figure 5. Vertical motion simulator were instructed to fly the tasks to landing, although the conditions were difficult enough that in an operational An interior view of the cockpit is shown in Figure 6.
environment, many of the approaches would have The evaluation pilot occupied the left seat with a test resulted in go-arounds.
engineer/observer in the right seat. A six-window, Most of the landing tasks were initiated in a five computer-generated imaging (CGI) system provided the degree descent at an equivalent airspeed in the range of external view. A dirt strip STOL runway having 65-75 knots, with a wing tilt suitable for approach and dimensions of 90- by 750 ft was located among trees in flaps fully deflected. For these tasks, the attitude otherwise open terrain. Six panel-mounted displays and command/attitude hold pitch response type was the head-up display presented flight information to the selected. The aircraft was nominally positioned on pilot and observer. The panel displays included (left to glideslope and localizer at 800 ft altitude above the right) a task/pilot performance display, primary flight runway at a distance of 1.5 nmi from the runway display, and navigation display and were replicated threshold, as shown in Figure 7a. The nominal identically at each seat. The HUD was superimposed touchdown point on the runway was located 50 feet on the forward-facing windows of the CGI.
from the threshold, and the corresponding visual aim point was marked with an X further down the runway.
The leader aircraft guidance symbology was used down to decision height, below which pilots aligned the glideslope reference line on the HUD with the visual aim point, using the flight path symbol to accomplish the landing.
As Figure 7b and Figure 7c illustrate, the offset approaches were initiated with the aircraft displaced either 45 ft above the glideslope or 300 ft laterally from the localizer. In these cases the approach was flown with this offset until the pilot was commanded by the experimenter to maneuver to correct for the offset error.
This correction was called for at an altitude of 200 ft above the runway for the vertical offset, or at 250 ft for Figure 6. Simulator cockpit the lateral offset, at which point the pilot acquired the glideslope or localizer and continued with the landing.
No-flare landings were performed at the target Evaluation Tasks and Procedures touchdown point and approach airspeed. These offset Four pilots, two from NASA and two from Boeing, tasks were flown both with the height damper turned were the subjects of this experiment. All pilots had off and with it turned on, which nearly halved the time previous STOL aircraft experience. Pilot comments constant of the flight path response.
and pilot ratings using the Cooper-Harper rating and American Institute of Aeronautics and Astronautics Visual aim point o o 5 5 (marked with X on runway) 800 ft 1.5 nm 1.5 nm 50 ft (a) Nominal approach o Nominal touchdown location 800 ft 200 ft 1.5 nm o 5 (d) Slalom approach 845 ft 200 ft 1.5 nm (b) Vertical Offset approach 100 kts 69 kts o 1000 ft 3.0 nm (e) Decelerating approach 300 ft Figure 7. Plan and Profile Views of Approach Tasks o 800 ft 250 ft 1.5 nm (c) Lateral Offset approach The slalom maneuver shown in Figure 7d was approaches and go-around approaches were initiated at performed while descending on the glideslope by the nominal altitude and range. All of these approaches maneuvering laterally, on command of the were carried to the landing; go-arounds were initiated experimenter, between lines extended from tree rows on experimenter command at 50 ft radar altitude, in the paralleling the runway, then correcting back to the landing configuration and with a target pitch attitude localizer and completing the landing. The decelerating and climb out airspeed selected for maximum climb approach was initiated in level flight at 1000 ft above capability while maintaining runway heading.
the runway at a distance of 3 nm from the threshold on The offset approaches and the slalom task were a 45-degree intercept path to the extended runway carried out in VMC with light turbulence (3 ft/sec rms).
centerline at an airspeed of 100 knots. The pitch The decelerating approach and approaches in wind response type was set to rate command/attitude hold at shear were conducted in IMC consisting of a ceiling of the start of the approach. The pilot task was to turn to 200 ft and a visual range of 3000 ft in fog. For acquire the localizer, command wing tilt to the crosswind approaches, weather minimums consisted of approach configuration, decelerate to the final approach a ceiling of 300 ft and a visual range of 6000 ft.
speed, acquire the glideslope, select the attitude Crosswind and wind shear approaches and landings command/attitude hold pitch response, and proceed on were made in moderate turbulence (5 ft/sec rms), while the final approach to landing. This approach profile is the deceleration task took place in light turbulence (3 shown in Figure 7e. Crosswind and wind shear ft/sec rms). Discrete longitudinal, lateral, and vertical American Institute of Aeronautics and Astronautics gusts were introduced for all approach configurations to One pilot rated the 30-knot crosswind landing further complicate the pilot’s task. The wind shear task inadequate (HQR 8) for both longitudinal and lateral- included a horizontal decreasing headwind and a directional tasks, based on his impression that downdraft representative of a thunderstorm situated controllability was in question. This rating represented about 4000 feet prior to the runway threshold. Wind the pilot’s first exposure to the crosswind landing task; shear approaches were initiated in a steady headwind of considering that his subsequent ratings were HQR 6, 20 knots, which decayed to zero at a rate of 1 knot/sec. the HQR 8 rating is likely too severe. One pilot also rated the longitudinal landing portion of the windshear task as inadequate (HQR 9). This rating reflected a Results The averaged handling qualities ratings (HQRs) for near loss-of-control situation following large flightpath all pilots and all configurations versus task, for the and airspeed perturbations close in to the runway. In an longitudinal and lateral/directional axes, respectively, operational situation, a go-around would have been are presented in Figure 8 and Figure 9. The approach initiated.
Longitudinal Results and landing portions of each task were rated separately.
Average HQR - Approach For the offset and slalom tasks, the final correction to Average HQR - Landing glideslope and localizer was considered part of the Std. Deviation - Approach landing, while for the IMC tasks, the landing was Std. Deviation - Landing considered to start at decision height.
Min - Max values Neither the vertical or lateral offset nor slalom tasks posed any challenge to the aircraft’s longitudinal flying qualities for the approach, and were rated satisfactory.
Significant degradations in flying qualities (1-2 HQRs) occurred in IMC, particularly in moderate turbulence, or during wind shear. Given that the turbulence and wind shear were of a moderate to severe magnitude, the Cooper-Harper Handling Qualities Rating flying qualities were considered adequate. Demands of the vertical offset correction prior to landing increased the workload for landing in comparison to the approach Lateral Offset 30-knot Windshear Vertical Offset Height Damper Height Damper Crosswind and led to degraded ratings, although with the height Off Off Slalom Vertical Offset damper turned on, the ratings were still within the Lateral Offset Decelerating Height Damper Approach Height Damper adequate range. The most dramatic difference between On On Task approach and landing HQRs, and the poorest average HQR overall, were generated by landings with the Figure 8. Longitudinal handling-quality ratings height damper disabled; the height damper directly Lateral-Directional Results influences flightpath bandwidth. Pilot comments noted Average HQR - Approach the poor flightpath predictability and sluggish response Average HQR - Landing Std. Deviation - Approach that led to handling qualities degradation.
Std. Deviation - Landing The small standard deviations of about 0.5 HQR for Min - Max values the approach portions of the offset tasks demonstrate insensitivity in pilot workload to the range of pitch control bandwidths and center-of-gravity locations explored in the Boeing-proprietary portion of the simulation.
The lateral offset and crosswind tasks placed the greatest demands on the pilot for lateral and directional control in the landing. Handling qualities for these two Cooper-Harper Handling Qualities Rating tasks were just adequate in contrast to less demanding straight in landings that were considered to be 1 Lateral Offset 30-knot Windshear Vertical Offset satisfactory.
Height Damper Crosswind Height Damper Off Off Coupling of the degraded flightpath response with Lateral Offset Decelerating Slalom Vertical Offset Height Damper the height damper off into the lateral-directional ratings Height Damper Approach On On can be observed in the lateral offset landing task. The Task increased workload required by the longitudinal control Figure 9. Lateral-directional handling-quality task influenced pilots’ ability to simultaneously control ratings lateral alignment with the runway.
American Institute of Aeronautics and Astronautics Maximum Deviation from Glideslope on Approach An insufficient number of HQRs were collected for the go-around task to present them for comparison.
Mean However, pilot comments indicated that the approach Std Deviation portion of the task was completely satisfactory.
Adequate Maintaining a positive climb rate after initiating the go- around proved difficult; precise control of pitch attitude Desired was required to increase airspeed while gaining altitude after application of full power. Pilots initially found the required technique of lowering the nose to initiate the go-around to be disconcerting. The go-arounds were -1 Glideslope Deviation (dots) flown in the approach configuration; no investigation of alternate control surface configurations was carried out.
-2 Figure 10 through Figure 14 illustrate the precision Lateral Offset 30-knot Windshear trajectory and speed control achieved through the use of Height Damper On Crosswind Lateral Offset Decelerating the flightpath-centered guidance displays. As seen in Height Damper Off Approach Figure 10, for most tasks pilots were able to stay on the Task glideslope quite well. The windshear encounter was designed to require more than the available power, Figure 10. Maximum deviation from glideslope hence the significant error for this task. Note that data Maximum Deviation from Localizer on Approach for the vertical offset and slalom tasks are not presented -- large glideslope errors are inherent to the offset task, Mean Std Deviation Adequate and glideslope data for the slalom task was not recorded, although no notable deviations were Desired observed. Figure 11 illustrates how accurately the localizer can be tracked, despite significant turbulence, gusts, and crosswinds. The localizer was not tracked on -1 the approach for the lateral offset and slalom tasks; Localizer Deviation (dots) therefore data for these tasks are not presented.
Vertical Offset 30-knot Windshear Figure 12 plots the indicated airspeed recorded at Height Damper On Crosswind touchdown for each of the tasks. Results were Vertical Offset Decelerating Height Damper Off Approach generally within the adequate range of ±6 knots from Task the nominal approach speed, and for tasks demanding less pilot concentration during the landing phase, results Figure 11. Maximum deviation from localizer within ±1 standard deviation fell within the desired range of ±3 knots from nominal. The crosswind results damper is very noticeable in the vertical offset task – reflect the difficulty of the multi-axis task in moderate with the height damper on, touchdowns were clustered turbulence, with a tendency to carry too much airspeed tightly around the nominal, while without the height into the landing. Similarly, the slalom task placed last- damper, the average touchdown was 25 feet long, and minute multi-axis demands on the pilots, as they were compares most closely with the windshear task. The required to make a large lateral correction to align with lateral offset task required much less throttle activity the runway, and the larger spread in airspeed is evident.
during the final approach, and this is reflected by Sink rate errors at touchdown are shown in Figure comparable results with the height damper on and off.
13. An increase in sink rate can be seen for the offset The multi-axis requirements of the slalom and tasks performed with the height damper turned off; the crosswind tasks during the final correction resulted in slower flight path response to throttle inputs prevented slightly long average touchdowns, but consistency was pilots from making fine corrections in the last moments generally good for both tasks. The outlying points in before touchdown. As with the airspeed results of the crosswind task resulted from directional control Figure 12, the demands of the crosswind task are saturation – the 30-knot crosswind was designed to be a evidenced by the increased variation of sink rate for the limiting task for cockpit (pedal) controls, and task.
demonstrated the thin margin of control available with Lateral and longitudinal touchdown dispersion from nearly full pedal displacement required to de-crab the the nominal touchdown point is plotted in Figure 14.
aircraft. In an actual operational situation, pilots would Lateral results for all tasks are excellent, with standard have chosen to abort the landing. Control effectors in deviations of only ± 2 to ± 5 feet about the runway this case were not necessarily the limiting factor. In the centerline. Longitudinal results show greater variation future, pedal command characteristics may be adjusted across tasks. The effect of turning off the height American Institute of Aeronautics and Astronautics Pilot 1 Touchdown Dispersion Results Pilot 2 Pilot 3 Pilot 4 Indicated Airspeed Deviation at Touchdown Mean Std Dev Mean n = 39 σ = +/- 13.33 +9 Vertical Offset, Height Damper On x Std Deviation σ = +/- 3.23 y Adequate +6 -50 n = 12 σ = +/- 25.38 x Vertical Offset, Height Damper Off σ = +/- 4.63 y Desired +3 -50 n = 102 0 50 σ = +/- 15.87 Lateral Offset, Height Damper On x σ = +/- 3.41 y Airspeed Error (kts) -3 n = 17 σ = +/- 9.18 Lateral Offset, Height Damper Off x σ = +/- 2.03 y -6 -50 n = 83 -9 σ = +/- 15.48 Lateral Offset 30-knot Windshear Vertical Offset x Slalom σ = +/- 3.01 Height Damper Height Damper Crosswind y Off Off 0 Lateral Offset Decelerating Slalom Vertical Offset Height Damper Approach Height Damper -50 On On n = 93 σ = +/- 19.20 x 30-knot Crosswind Task σ = +/- 5.02 y Figure 12. Indicated airspeed at touchdown Lateral Distance (ft), from Runway Centerline -50 n = 15 σ = +/- 11.47 x Decelerating Approach σ = +/- 2.48 y -50 n = 18 Sink Rate Error at Touchdown σ = +/- 30.53 x Windshear σ = +/- 3.81 y Mean -6 Std Deviation -50 -50 0 50 100 150 Nominal Touchdown Point -4 Longitudinal Distance (ft), from Runway Threshold (softer) Figure 14. Touchdown dispersion -2 to address such limitations. The short landings for the decel task are likely due to the higher-intensity longitudinal gusts (16.9 knots) employed for the task, which ramp in 2000 feet from the runway threshold.
Desired +2 Sink Rate Error (ft/sec) Landings for the windshear task tended to be long of the target landing point. This was the result of the large (firmer) Adequate power increase required during the shear encounter, +4 which then needed to be reduced quickly as the aircraft Lateral Offset 30-knot Windshear Vertical Offset exited the shear and approached the runway threshold.
Height Damper Crosswind Height Damper Off Off The average of the standard deviations of the Slalom Vertical Offset Lateral Offset Decelerating Height Damper Height Damper Approach longitudinal dispersion, exclusive of tasks performed On On with the height damper off and the windshear task, was Task ± 15.07 feet. This result compares very favorably with no-flare touchdown results for the NASA Quiet Short- Figure 13. Sink rate at touchdown haul Research Aircraft (QSRA), which achieved a American Institute of Aeronautics and Astronautics standard deviation of the longitudinal dispersions of ± 18 feet for more normal conditions than evaluated in Berthe, C. J., Chalk, C. R., and Sarrafian, S., “Pitch this study. Rate Flight Control Systems in the Flared Landing Task and Design Criteria Development.” NASA CR-172491, Conclusions October 1984.
Flying qualities of a tilt wing STOL transport during Stevens, V.C., Riddle, D.W., Martin, J.L., and Innis, final approach and landing have been evaluated in a R.C., “Powered-Lift STOL Arcraft Shipboard large-scale moving-base simulation. A range of control Operations; A Comparison of Simulation, Land-Based response type characteristics was investigated, and a and Sea Trial Results for the QSRA,” AIAA Paper 81- variety of approach conditions in visual and instrument 2480, 1981.
meteorological conditions, varying winds and turbulence were explored. Evaluations included vertical and lateral offset approaches, slalom maneuvers on the approach, and approaches in limiting crosswind and wind shear to assess the effects of more stressful conditions on flying qualities and susceptibility to pilot- induced oscillations. A decelerating approach from a mid-transition configuration and flight condition to final approach and landing was used to represent a STOL operational task. Flightpath-centered head-up and head-down displays were used, incorporating leader aircraft pursuit guidance symbology.
Assessments of these controls and displays were made by pilots from both NASA and Boeing.
The aircraft, control modes, and display combination produced satisfactory flying qualities for all operations except for those in extreme cross winds and in severe wind shear. This test was one of the first piloted simulations of the Boeing ATT concept. Thus, areas for improvement and refinement of the design are one of the valuable outcomes of this test. The need for flight path augmentation was demonstrated by the poorer performance results and HQRs recorded with the height damper turned off. The head-up display provided guidance cues that produced desired approach path tracking performance that yielded precision landing performance.
References Manley, D. J., and von Klein, W., “Design and Development of a Super-Short Takeoff and Landing Transport Aircraft”, Proceedings of the International Powered Lift Conference, Williamsburg, Virginia, November 5-7, 2002.
Innis, R. C., Holzhauser, C. A., and Quigley, H. C., “Airworthiness Considerations for STOL Aircraft.” NASA TN D-5594, 1970.
Gerken, G., “USAF Flying Qualities Requirements for a STOL Transport.” ASD-TR-78-13, 1979.
Hardy, G. H., "Pursuit Display Review and Extension to a Civil Tilt Rotor Flight Director," AIAA 2002-4925, August 2002.
Cooper, G. E. and Harper, R. P., Jr., “The Use of Pilot Rating in the Evaluation of Aircraft Handling Qualities.” NASA TN D-5153, April 1969.
American Institute of Aeronautics and Astronautics