Document
Piloted Evaluation of Slodernized Limited Authority Control Laws in the NASA-Ames Vertical Motion Simulator (VhlS) Chris L,. Blanken Vi nect Cahasrabudhe, Edgar Melkers and Alexander Faynberg Sikorsky Aircraft Corporation Army/NA,SA Rotorcraft Division Aerofl ightdynariics Directorate (.AMRDEC) Stratford, CT U.S. Army Aviation and Missile Command Moffett Field. CA Abstract The UH-60 BLACK HAWK was designed in the 1970s, when the US Army primarily operated during the day in good visual conditions. Subsequently, the introduction of night-vision goggles increased the BLACK HAWK'S mission effectiveness, but the accident rate also increased. The increased accident rate is strongly tied to increased pilot workload as a result of a degradation in visual cues. Over twenty years of resetarch in helicopter flight control and handling qualities has shown that these degraded handling qualities can be reco\.ered by modifying the response type of the helicopter in low speed flight. Sikorsky Aircraft Corporation initiatelj a project under the National Rotorcraft Technology Center (NRTC) to develop modern flight control laws while utilizing the existing partial- authority Stability Augmentation System (SAS) of the BLACK HAWK. This effort resulted in a set of Modernized Control Laws (MCLAWS) that incorporate rate command and attitude command response types. Sikorsky and the US Army Aeroflightdynamics Directorate (AFDD) conducted a piloted simulation on the NASA-Ames Vertical h4otion Simulator, to assess potential handling qualities and to reduce the risk of subsequent implementation and flight test of these modern control laws on AFDD's EHdOL helicopter. The sitnuladon showed that Attitude Command Attitude Hold control laws in pitch and roll improve handling qualities in the low speed flight regime.
These improvements are consistent across a range of mission task elements and for both good and degraded visual environments. The MCLAWS perform better than the baseline UHdOA control laws in the presence of wind and turbulence. Finally, while the improved handling qualities in the pitch and roll axjs allow the pilot to pay more attention to the vertical axis and hence altitude performance also improves, it is clear from pilot comments and altitude excursions that the addition of an Altitude Hold function would further reduce workload and improve overall handling qualities of the aircraft.
loop stability functions may need to be added as the Introduction UCE degrades: attitude, direction. height, and Over twenty years of research in helicopter flight position hold.
control and handling qualities has shown that as the pilot's visual environment degrades, there is a The UH-60 BLACK HAWK is the US Army's corresponding degradation in handling qualities for utility-class helicopter. The UH-60A was designed near-Earth tasks. Degraded handling qualities imply in the 1970s, when the Army primarily operated in the day in good visual conditions. Subsequently. the reduced task performance and increased pilot workload, which contribute to reduced mission introduction of night-vision goggles increased the effectiveness and increased accident rates. The same BLACK HAWK mission effectiveness, but the research has also shown that these degraded handling accident rate also increased [Ref 21. This increase is qualities can be recovered by increasing the stability strongly tied to increasej pilot workload as a result of of the helicopter, i.e., by changing the control The a degradation in visual cues from the goggles.
response type to a higher rank of stabilization. These basic control response of the flight control system has results and concepts have been incorporated into the not been upgraded frori the original rate-command US Army's Aeronautical Design Standard - 33 response type. Operating rate-command response (ADS-33). Handling Qualities Requirements for types at night (UCE>2) results in degraded handling Military Rotorcraft [Ref. I ] through the Usable Cue qualities and contributes to increased accident rates.
Eni:ironment (UCE) concept. As the UCE Improving the flight control system to help reduce deteriorates from clear day (UCE=I), to a starlit night accident rates has been recopnized by the US Army (VCE=2), to a moonless-overcast night (UCE=3), the Safety Center as a high priority toward reducing helicopter control response must be improved from a accident rates. A rec:nt Safety Center accident rate command, to an attitude command, to a investigation study states that the number one translational rate command response type, material fix toward reducing Army aviation accidents 'especrivel y, in ordcr to maintain satisfactory is to improve the howr and low speed handling handling qualities. In addition, the following outer- qualities. [Ref. 3J ' Presented at the i?\mcrican Helicopter Society j Y i h Annual Forum, Phoenix, AZ. Xlay f4. 2003. Copyright 0 2003 h!' the American Helicopter Society International. Inc. All rights reserved.
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UH-60X aircraft. The pitch-SAS is essentially a rate n i feedback system that augments the damping of the d) Rzcently the US Army has entered in:o a bare airframe dynamics.
recapitalization program to extend the -:r;.ice life of il ; 3 I the BLACK HAWK for decades to come (UH-60R.I).
The MCLAWS implement a two-mode control On May 2, 2001 the Army contracted with Sikorsky P' system. In the attitude mode the pitch and roll axes ai Aircraft Corporation to build four UH-60M have Attitude Command Attitude Hold (ACAH) type prototypes. The upgrades include not only new wide a: responses. while the yaw axis has Rate Command chord rotor blades, but also inclusion of two neu Direction Hold (RCDH) characteristics. The control digital flight control computers and associated 7 laws switch to a rate command mode if the helicopter n sensors. In the baseline plan, however, these velocities or attitudes exceed the limits shown in
prototypes will fly with flight control laws that are s
Table 1. As the name indicates, in the rate mode the C fundamentally similar to existing UH-60A flight control laws. Many years of research have been aircraft has a Rate Command (RC) response type. In performed: from documenting the UH-60 relative to order to switch back to ACAH mode from rate mode, more restrictive conditions must be met which are \ ADS-33 [Ref. 41, to developing and evaluating new control concepts [Refs. 5-81 that provide improved shown in Table 1. Note that in this study only the I inner loop S A S servos are used to implement I handling qualities while retaining the existing partial- MCLAWS. This simplifies the design and limits the I authority actuation system. In 2000, Sikorsky changes to the SAS computer - leaving the Flight initiated a project under the National Rotorcraft Path Stabilization (FPS) system untouched. It also Technology Center (NRTC) to develop modem flight control laws while still utilizing the existing partial- allows for a set of control laws that are not inherently dependent on whether or not the pilot has the trim authority Stability Augmentation System (SAS) of release switch depressed. This approach does not the BLACK HAWK. Sikorsky's NRTC effort preclude the integration of the outer loop trim servos resulted in a set of control laws that incorporate rate at a later stage to help re-center the SAS servos in the command and attitude command response types and Ion, - term.
have provisions for translational rate command response types.
When the system switches from attitude mode to rate To advance possible implementation of these modem mode the dashed paths in Figure 1 are gracefully control laws into the UHdOM, Sikorsky was invited removed, and the systems reverts back to a rate feedback architecture almost identical to the baseline by the US Army Aeroflightdynamics Directorate (AFDD) to participate in a piloted simulation on the UH-60A SAS control laws. Conversely, when the aircraft re-enters the attitude mode, these paths are NASA-Ames Vertical Motion Simulator (VMS).
The objectives of the VMS simulation were to assess brought back in gradually. The overall objective was to retain ACAH characteristics over a useful range of potential handling qualities improvements in simulated degraded visual environments and to aircraft velocities and attitudes without persistently reduce the risk of subsequent implementation and saturating the SAS.
flight test of these modem control laws on AFDD's EH-60L helicopter. This paper will describe The MCLAWS have a model following type architecture, where the pilot stick input is passed development of the modern control laws, the VMS based piloted simulation evaluation, and associated through a command model to generate desired 0- results. ideal rates and attitudes. These are compared to the actual rates and attitudes and the feedback reduces the difference between the two. There are a few key Modernized Control Laws differences from more conventional implementations This section describes the MCLAWS architecture, of the model following architecture. First, instead of the control modes, and the design and analysis techniques. In addition, results are presented from a just using a commanded attitude both rate and attitude commands are generated and used. Since the Sikorsky piloted simulation that was used as a basic aircraft responds like a rate command system, preliminary evaluation in preparation for the VMS experiment. using a commanded rate leads to some advantages.
Second, unlike a full authority system, the MCLAWS have to contend with a full authority mechanical path Basic striictitre that has ten times the authority of the flight control The basic structure of the Modernized Control Laws system. Finally, the current implementation uses a (MCLAWS) investigated in this study is shown in unity inverse plant model.
Figure 1. The figure shows the pitch axis structure only; the roll and yaw axes have a similar structure.
Linear Analysis Also shown for comparison is the structure of the current pitch axis control laws that are part of the The control laws were designed using nine and twenty-two state linear models of the UH-60 The Stability Augnentation System (SAS) on current nine state model represents only the rigid bod! Reconfizurable Cockpit Simulator shown in F i p e 3(a) while subsequent evaluations were carried out on dynamics. \\ hile the twenty-two state model adds the flap and lag dynamics and dynamic inflow. The SAS the Sikorsky Fixed-base simulator shown in Fisure and primary servos were modeled includin? rate and 3(b).
position limits. Also modeled were computational and filtering delays to account for implementation Figure 4 shows the results o f a n evaluation of the aspects of the control laws. MCLAWS as compared to the UH-60 control laws in the Sikorsky Fixed-base jimulator. This simulator has The control architecture, linear airframe and other a wide field-of-view and actual H-60 cyclic and collective sticks. The aircraft model used was a UH- models described above were implemented in a SIMULINK model and the linear' analysis was 60A Next-GenHel model at a heavy gross weight of 19.302 pounds. The intcmtion was to evaluate the carried out using standard MATLAB tools.
control laws at a higher gross weight that was more The linear design and analysis of the ACAH mode representative of the weights of current and future H- were driven by ADS-33E bandwidtwphase delay 60 variants. The mission task elements (MTEs) requirements and the more general time domain evaluated were a subset of those described in ADS- requirements for a "sood" attitude response. Broken 33E and the performan,:e limits imposed on the loop stability requirements [Ref. 91 were also evaluations were those for the utility configuration.
imposed. An example of the linear analysis carried Three pilots carried out the evaluations although due out is shown in Figure 2. The left half of Figure 2 to time constraints on14 one pilot evaluated the shows the ADS-33E small amplitude Accel./Decel. MTE. The figure shows the pilot bandwidthlphase-delay pitch and roll axes evaluation ratings as measured on the Cooper-Harper scale (on for an intermediate design. The right half of the this scale numerically lower ratings correspond to figure shows the gain and phase margins for the pitch better pilot opinion). As tie Figure shows, across all and roll axes. the MTE's evaluated the MCLAWS earned better pilot ratings on the Cooper-Harper handling qualities rating (HQR) scale [Ref. IO], with a maximum The rate mode was designed to be similar to the existing UH-60A rate feedback system. Considerable improvement of 2.3 points and an average effort was spent in making the transition between the improvement of 1.1 points.
attitude and rate modes seamless and transparent to the pilot. This included adjustments to the switching VMS and Test description The next phase of the assesment was carried out on conditions in Table 1 and the addition of faders and transient free switches. the NASA-Ames Vertical )Motion Simulator (VMS).
The VMS environment includes large-amplitude Once the linear design had been completed, a limited motion and the ability to simulate both day and amount of numerical optimization was carried out degraded visual environments. Handling quality using MATLAB optimization tools. This was done evaluations of five MTEs from ADS-33 were by making selected control system gains variables of performed with the baseline UH-60A control laws and the MCLAWS in a simulated day environment the optimization problem and imposing the above design specifications while minimizing actuator and a Degraded Visual Environment (DVE). In activity. The final gains obtained from this process addition, the baseline and :he modem control laws formed the starting point for implementation of were assessed in the presence of wind and turbulence.
MCLAWS in a nonlinear simulation model and This section describes the sLmulation facility, matrix subsequent piloted simulation evaluation.
of configurations, and the conduct of test.
Sample results j+orn recorzjiigurable and fixed-base Descriptiorz of the Facilih, The control laws developed using the linear analysis The NASA-Ames large-amplitude motion flight tools were implemented in the Sikorsky Next-GenHel simulator is shown in Figure 5. The VMS real-time model of the UH-60. This was done using an mathematical model of the UH-60.4 is based upon automated pictures-to-code framework developed at the generalized, modularized programs that make up Sikorsky, which allowed for a short cycle time the Sikorsky General Helicopter Flight Dynamics between control law changes and piloted simulation Simulation (GenHel) [Ref. 1 11. Off-axis corrections evaluation. to the model, also termed iierodynamic phase lap, were implemented to correct the low speed off-axis Once the control laws had been successfully response [Ref. 111. The overall helicopter weight was implemented i n the nonlinear Next-GenHel model. set to 16.525 pounds.
the simulation was hosted on two separate facilities.
Preliminary engineering and piloted evaluations of The crew station. or cochpit cab. has ; 1 single pilot the control laws were carried out on the Sikorsky ceat mounted in the center of the cab and four-trnaze Reference 14. Table 3 shows the matrix of theat preheiitation " w i n d o w s " to provide outside imagery Figure 6. The cockpit cab was recently modified configurations.
[Ref. 131 into a UH-60A configured cockpit to support the Joint Shipboard Helicopter Integration Cotidiict of the Test Process (JSHIP). The cockpit visual display r:. >.stem Participating in the test were five experienced rOt3r1 consisted of an array of five flat panel screens with
wing experimental test pilots representing the cs
each screen abutted against the others : n a 230-degree Army. NASA, and Sikorsky. The pilots were allo\red horizontal by 70-degree vertical senxircle. It was some time to practice each of the maneuvers to masked to represent the pilot's field of view from the acquainted with the aircraft's response and with thc BLACK HAWK'S right seat. The visual imagery simulator visual cues. The MTEs were first evaluated was carefully tailored t:> contain adequate macro- in the day scene to allow maneuver training 2nd texture (i.e.. large objects and lines on the ground) for course cueing familiarization under good lighting the determination of the rotorcraft position and conditions. All evaluation runs were carried out \\it11 heading with reasonable precision. The baseline the motion system operational. For evaluation i n a stick-to-visual delay was about 70 msec including a DVE, the out-the-window view was severel!; IO-msec math model cycle time. A seat shaker pro- degraded and the pilots used NVGs to carry out the vided vibration cueing to the pilot, with frequency maneuvers. The simulator has more travel in one and amplitude programmed as functions of airspeed, horizontal axis as compared to the other and the cab collective position, and lateral acceleration.
Aural was rotated to take advantage of this depending 011 cueing was provided to the pilot by cab-mounted the maneuver being evaluated. Initial trainin2 speakers. The aural model, driven by aircraft sessions were provided prior to at least three data parameters, provided main rotor noise, tail rotor collection records for each maneuver. A structured noise, engine and transmission noise. Standard pilot questionnaire was used to elicit pilot comments helicopter instruments and BLACK HAWK grips and a HQR was provided. Aircraft flight dynamic were installed in the cockpit Figure 7 . The cockpit and control response parameters and task instruments were displayed on two Cathode Ray performance data were recorded for display and l;t~cr Tubes (CRTs) mounted on a panel directly in front of analysis. Monitors in the VMS control room the pilot seat. The orientation of the instruments was provided quick and easy assessment of pilot-task the same as the actual aircraft and they were performance relative to the A D S - 3 3 desired and compatible with night vision devices. The VMS adequate standards Figure 10. This information W:IS control loading system (McFadden Systems) is relayed to the evaluation pilot in the cockpit L o digitally programmed to provide realistic force-feel confirm of his perception of task performance based cues for the cyclic, pedal, and collective controls.
on course cueing. Evaluation sessions were limited The overall VMS motion system capabilities are to one hour to mitigate fatigue effects.
listed in Table 2.
Results Matri.r of Configurations The results below are presented in terms of HQRb The matrix of configurations included the baseline and summary task data for each of the MTEs. Also.
UHdOA flight control laws, the modem control laws, SAS actuator saturation data and task time histor) five ADS-33 MTEs, and variations in ambient data are presented for illustration.
conditions to include day and night, and calm or with windslturbulence. The five ADS-33 MTEs included Overview of HQRs Hover, Vertical Maneuver, Pirouette, Lateral Figure 1 1 and Figure 12 summarize the average Reposition, and Departure/Abort. Reference 1 HQRs for good and degraded visual condition> provides a detailed description of these MTEs along respectively for both the baseline UH-60A coiiti.01 with the desired and adequate performance standards.
laws and the MCLAWS. Figure 11 shows the averas The VMS course cueing for these MTEs was HQRs from up to three pilots across five difl'ercnc carefully matched to the flight test set-up (Figure 8) ADS-33 maneuvers. The patterened bars corresporld used in Reference 3. In this way, some comparison to baseline UH-60A CLAWS while the dark barb could be inferred between the actual flight test results represent MCLAWS. For day ( W E ) conditions.
and the UH-60A simulated day conditions on the there was a consistent improvement in the H Q R j VMS. Ambient conditions for pilot evaluation of across maneuvers and pilots as a result of usillr these five MTEs were varied from the day conditions MCLAWS instead of the baseline UH-60A cL,\bb's.
to night. In the night scene, the pilot's vision was It is clear that for each of the five rnaneuvsih aided by wearing night vision goggles (NVGs) evaluated, there w a s between a 0.5 and 2.5 Poi''' (Figure 9 ) . In addition, some MTEs were evaluated in improvement due to the MCLAWS. A\,eragelf oic" the presence of wind and turbulence. Details of all maneuiers the improvement was slight]? mor' these wind and turbulence models are reported in than 1.0 point.
for file out of the six comparisons. The RMS For DV-E. on the other hand, several of the debiations in longit ~ d i n a l and lateral position, mancu\.crs were too difficult to complete with altitude, and heading were less in three out of four adequate performance levels with either control cases with the MCLA'NS compared to the UH-60'4.
system. Pilot comments indicate that this was Looking at the maximum excursions, the lateral because of the degraded visual eni3ronment being position, altitude, and heading were within desired unrealistically degraded and the task cues blending performance standards for nearly all evaluations.
into the background. The result was a series of high However. maximum excursions in longitudinal HQRs with no ability to distinguish one control position ranged from desired, to adequate. to not adequate for both control laws. The problem in systcm from the other. Pilot debriefs indicated that operations in such conditions are unlikely. A UCE controlling the longitudinal axis was a main factor toward degrading the I-IQR. As the figure shows, determination was not performed. For other maneuvers however, at least one of the pilots was only two MCLAWs cases are within adequate time (5 able to distinguish differences. with the MCLAWS 8 sec); all the rest are outside of adequate.
always being superior to the baseline CLAWS.
Fizure 12 shows the DVE ratings only for those Figure 15 shows the performance trends for the Vertical maneuver in GVE. There are some maneuvers where cueing appeared to distinguish bctween desired and adequate standards. All pilot interesting differences between pilots for this MTE.
ratins pairs (i.e. ratings for baseline CLAWS and For Pilot 2, all the RMS deviations in longitudinal and lateral position, and heading were less with the MCLAWS) that were numerically high and equal have been eliminated. The resulting average ratings MCLAWS compared tcl the UH-60A evaluations.
For Pilot 1, only the RMS deviations in longitudinal are shown i n the figure. It can be seen that the MCLAWS configuration was rated between 1.0 and position were less with MCLAWS whereas, the lateral position and heading deviations were less with 1.5 points better than the baseline and that the average improvement across maneuvers was a little the UH-60A. Looking at the maximum longitudinal more than one point. and lateral position excursions, evaluations included a mixture of desired and adequate performance with Finally shown in Figure 13 are the HQRs for only one falling to not adequate. Six of nine cases different wind levels. The patterned group of bars with excursions into adequate were with the UH- correspond to the baseline UH-GOA control laws with 60A. Maximum heading excursions were nearly all the first pattern corresponding to evaluation without within desired tolerances for both MCLAWS and any winds and the checked pattern for evaluation in UH-60A evaluations.
light winds. The shaded bars are for the MCLAWS with the shading corresponding to different levels of The performance summary for the Pirouette MTE is wind and turbulence (black is no winds, dark gray is shown in Figure 16. The t h e subplot shows both the with winds, and light gray is with winds and time to complete the circle and time to stabilize to a turbulence) with MCLAWS. It is immediately hover at the end of the maneuver. Both apparent from the figure that the MCLAWS configurations were roughly equivalent. The RMS performed well in rejecting the disturbances and did deviations show a mixturt of less deviation with not show significant degradation as a result of the either MCLAWS or UH-t10A depending upon the wind and turbulence. Note that in all MCLAWS task parameter and pilot. The maximum radial cases, the HQRs in the presence of winds and excursion was within desired tolerance for nearly all turbulence were still better than the HQRs for the evaluations. However, altitude excursions for two- baseline CLAWS without winds and turbulence. thirds of all evaluations were within the adequate range. Improving the height axis response with the Peiforntarrce analysis of G V E rims addition of Altitude Hold could be beneficial.
In order to further understand handling qualities For two-thirds of the etaluarions, the heading improbements offered by MCLAWS, task excursion data show Izrger deviations with perl'ormance data were analyzed for both general MCLAWS. It should be noted that a MCLAWS- trends and to provide specific examples of to-GenHel implementation error was discovered ILnprovement. This subsection presents some of after the VMS simulation which caused the thcse trends for the GVE runs.
MCLAWS heading hold tc nzork well for small deviations, but saturate for larger ones.
Figure 13 shows the performance summary data for h e Precision Hover maneuver for both the baseline Figure 17 shows the performance trends for the [IH-60A control laws and the MCLAWS for two Lateral Reposition MTE. The times to complete the Pilots. Although the times to achieve a stabilized maneuver were shorter for the MCLAWS for every were rather long for both control laws. the comparison a i t h LIH-60'4 e x n ihrough the times X'ICLAWS e\.aluations were completed in less time performance summary data for the Vertical LITE \%ere all similar in duration. For 13--out--of-- I Y in the DVE is shown in Figure 20. All the cases. the RMS deviations for longitudinal position.
evaluations werz completed within desired times nith altitudz, and heading \yere less with hICLAWS all of the MCLAWS cases being slightly better than compared to UH-60% Maximum exccrsions for the UH-60A cases. With the exception of a couple of altitude and heading were nearly all within desired comparisons, the &\Is deviations in position and performance standards for both MCLAWS and UH- heading were substantially less with b.ICL,A&s 60A. Longitudinal excursions wer: nearly all within compared to UH-60A. In general, maximurn desired for Pilot 2 for both control laws. Although excursions in longitudinal and lateral position were Pilot 1 had mainly adequate performance for all within desired performance standards with longitudinal excursions for both control laws, the MCLAWS whereas the UH-60A cases were in the MCLAWS evaluations were always significantly adequate range. All of the maximum heading better.
excursions were within desired performance for both sets of control laws.
The Normal Depart-Abort MTE performance summary is shown in Figure 18. For this MTE. all MCLAWs cases were completed within desired Actiiutor satiiratiori times whereas only 2 of 7 runs with UH-60A were One of the primary concerns when designing control within desired. One UH-60A time was outside of laws for a partial authority system is actuator adequate. Smaller RMS deviations in lateral position.
saturation. In the current implementation of the altitude, and heading are about equally split between MCLAWS actuator saturation is addressed directly the control law comparisons. For comparisons where by switching from an ACAH response system to a large differences in RMS exist, the MCLAWS RC system before actuator saturation occurs.
deviations were always smaller compared to the UH- However, this switching needs to be balanced with 604. Maximum altitude and heading excursions for the need to maintain ACAH characteristics over a the two control laws were all within desired useful range of aircraft velocities and attitudes. As a performance and roughly the same. Lateral result at the extreme edges of the ACAH envelope excursions were generally less with the MCLAWS some saturation is expected to occur. Figure 21 compared to UH-60A.
shows the percentage of time for which the pitch and roll axis actuator authority was saturated. when Pe formnnce analysis of DVE rims performing different MTEs.
The performance summary for the Pirouette and As the figure shows, for the lateral reposition the roll Lateral Reposition MTEs in DVE is shown in Figure axis actuator authority was saturated for 19. Similar to the GVE evaluations, the two times approximately 1520% of the time. Analysis of associated with the DVE Pirouette were all within the individual run data shows that most of the saturation desired tolerances and roughly the same between the occured at the start and the end of lateral maneuver.
two control laws. With the exception of an initial The saturation in the pitch axis happened primarily comparison, the RMS excursions in radial position during the terminal phase of the maneuver.
and altitude were significantly less for the MCLAWS cases compared to the UH-60A. RMS heading During the normal depadabort maneuver, the lateral deviations appear larger with MCLAWS, but this is axis showed almost no saturation, but there was up to attributed to the previously mentioned integration 30% saturation on some runs in the longitudinal axis.
error. Looking at the maximum excursion data, Most of this occured when transitioning out from trends that mimic the RMS results are seen. It should ACAH to RC during the forward acceleration phase be noted that nearly all of the altitude excursions of the maneuver and was not extensively commented were within the adequate performance standards.
upon by the pilots.
Once again this points to further improvement possible by addition of an altitude hold function.
Finally, during the precision hover maneuver there was minor saturation in the longitudinal axis but none The performance summary data for the Lateral in the lateral axis. The vertical and pirouette MTEs Reposition in DVE shows all times were adequate and about the same for both configurations. The RMS showed no pitch or roll axis saturation for any of the runs with the MCLAWS.
deviations for longitudinal position, altitude, and heading are all less with MCLAWS compared to UH- The general trends shown in Figure 21 compare 60A cases. Maximum altitude and heading favorably to the results in (Ref. 7). For the precision excursions were nearly all within the desired range for both the lCICLAWS and UH-60X cases. On the hover maneuver. the MCLAWS longitudinal saturation is senerally at a much lower level. For the other hand, maximum longitudinal excursions were lateral reposition and departlabort maneuvers. i t must nearly all in thz adequate range for both control laws.
be pointed out that the more asgressive ccout/attack versions of the performance requirements were u . orkload and improi e overall handling qualities imposed during the Ref. 7 evaluation and some of the aircraft.
allou~ance must be made for this.
Acknowledgements Ilbtstmrive examples Technical tasks described in this document include tasks supported with shared funding by the U.S.
In order to illustrate the improvements due to the rotorcraft industry iind government under the MCLAWS as compared to the baseline UHdOA RITANASA Cooper; tive Agreement No. NCC2- control laws, Figure 22 compares two individual 9019. Advanced Rotorcraft Technology, January 01, Precision Hover cases, one for each control system.
2001. The authors would also like to thank the pilots The top row of subplots shows cyclic stick movement who participated in different phases of the study and for 30 seconds after the pilot declares a hover contributed valuable comments and insight.
capture, while the bottom row shows the task performance in terms of lateral and longitudinal drift.
Re.feerences It is immediately apparent that for the MCLAWS run 1 . Anon., “Handling Qualities Requirements for the pilot was expending a smaller effort (as reflected Military Rotorcraft.” Aeronautical Design in stick movement) to obtain better position keeping Standard-33 (ADS-33E-PRF), US Army (as reflected in the small drift) when compared to the Aviation and Missile Command, March 21, case with the baseline UH-60A control laws.
2000.
Key, D.L., “Analysis of Army Helicopter Pilot Finally, shown in Figure 23 is a comparison of the 2.
lateral reposition MTE using the two control laws.
Error Mishap Data and the Implications for The top half shows the ground trace of typical runs Handling Qualities,” NASA TM-1999-208797, for each type as executed by Pilot 1 . The figure USAAMCOM AFDIYTR-99-A-006, September shows that the performance in terms of longitudinal 1999.
drift was much smaller with the MCLAWS. The pilot 3. Hicks, J.E., “Army P,viation Safety Investment activity as measured by lateral stick Power Spectral Strategy,” presented at American Helicopter Density (PSD) (calculated using CIFER, Ref. 15) was Society 58th Annual Forum, Montreal, Canada, also lower for the MLCAWS case than for the case June 11-13,2002.
with baseline UH-60A control laws.
4. Blanken, C.L., Cicolani, L., Sullivan, C.C., and Arterburn, D.L., “Evaliiation of ADS-33 Using a Conclusions UH-60A Black Hawk Helicopter,” presented at Sikorsky Aircraft Corporation developed modernized American Helicopter Society 56th Annual flight control laws that incorporate rate and attitude Forum, Virginia Beach, Virginia, May 2-4, 2000.
command response types, while utilizing the existing 5 . Mitchell, D.G., Aponso. B.L., Atencio, A., Key, partial authority SAS actuators of the BLACK D.L., and Hoh, R.H., “Increased Stabilization for HAWK helicopter. These control laws were UH-60A Black Hawk Night Operations,” evaluated in a VMS simulation effort, where the USAVSCOM TR-92-A-00’7, November 1992.
objectives were to assess potential handling qualities 6. Hoh, R.H., Mitchell, D.G., Baillie, S.W., and improvements in simulated degraded visual Morgan, J.M., “Flight 1.ivestigation of Limited environments and to reduce the risk of subsequent Authority Attitude Command Flight Control implementation and flight test of these modern System Architectures for Rotorcraft,” NASA CR control laws on AFDD’s EH-60L helicopter.
196707, US.4d4TCOh$ TF: 97-.4-008? July 1997.
The conclusions of this investigation are: 7. Whalley, M.S. Howitt, J., and Clift, S., (1) Attitude Command Attitude Hold control laws in “Optimization of Partial Authority Automatic pitch and roll improve handling qualities in the Flight Control Systems i‘or HoverLow Speed low speed flight regime. These improvements are Maneuvering in Degraded Visual consistent across a range of MTEs and for both Environments,” presented at American GVE and DVE.
Helicopter Society 55th Annual Forum, (2) The MCLAWS perform better than the baseline Washington D.C? May 1999.
UH-60A control laws in the presence of wind 8. Key, D.L. and Heffley, R.K., “Piloted and turbulence.
Simulation Investigation of Techniques to (3) The improved handling qualities in the pitch and Achieve Attitude Command Response with roll axis allow the pilot to pay more attention to Limited Authority Servo,’ NASA CR 2002- the vertical axis and hence altitude performance 2 1 139 1, USAAMCOM i\FDI)lTR-02-A-003, also improves. However, it is clear from pilot January 3002.
comments and altitude excursions, especially during the Pirouette MTE. that the addition of an Altitude Hold function would further reduce
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209-2 13, July, 2002.
13. Sweeney, C., and Nichloson, R., “Using Dynamic Interface Modeling and Simulation to Develop a Launch Recovery Flight Simulation for a UH-60A Black Hawk,” Interservice/Industry Training, Simulation and Education Conference, Orlando, Florida, November 200 1.
14. Lusardi, J.A., Blanken, C.L., and Tischler, M.B., “Piloted Evaluation of a UH-60 Mixer Equivalent Turbulence Simulation Model”, presented at American Helicopter Society 59th Annual Forum, Phoenix, AZ, May 2003.
15. Tischler, M.B. , Cauffman, M.G., “Frequency- Response Method for Rotorcraft System Identification: Flight Applications to BO- 105 Coupled RotorFuselage Dynamics,” Jocirnal of the American Helicopter Society, Vol. 37, No 3, P ~ S 3-17, July 1992.
i .
Figure 1: Architecture of MCLA'CVS compared to baseline UH-60A SAS Pitch Bandwith Pitch GainlPhase Margins 0 . 4
-
0 . 3
- 60
Y > P) m
s
5 0 . 2 -0 I 40 a l n VI
2 0.1 20
n n 0 v 0 10 20 0 2 4 GM[db] Bandwidth [radisec] Roll Bandwith Roll GainIPhase Margins 0.4
-
f 0 . 3
t - 60 Y OI > Q) m
s
z 0 . 2
I 40 P) n VI
2 0.1 20
a n 0 U 0 10 20 0 2 4 GM[db] Bandwidth [radisec] Figure 2: Linear analysis for ,\.ICLACVS pitch and roll axes Figure 3: (a) Sikorsky Reconfigurable cockpit simulator; (b) Sikorsky Fixed-base simulator P 1 OUH-GOA ___ WMCLAWS - " I p Level 2 Vertical Hover Pirouette Lat. Reposition AcceliDecel Figure 3: Average pilot HQRs from Fixed-base evaluation at Sikorsliy Figure 5: The NASA Ames VMS motion system Figure 6: VXIS JSHIP cockpit cab (a) Collective Stick (b) Cyclic Stick c 1 Hot er t,irget/t oarc' Figure 9: Aviator’s night vision goggles k igure 10: 13I.S task performance assessment display Hover Vertical Pirouette Lateral Depart-Abort Average Reposition Figure 11: Average Handling Qualities ratings in Good Visual Environment (GVE) lo-- I_ - 1 - - - 9 __._
OUH-GOA ---' I - - - -
0 h I I I _ X Hover Vertical PirouetIe Lateral Depart-Abort Averag D Reposition Figure 1 2 Average Handling Qualities ratings in Degraded Visual Environment (DVE) Hove: 'Vertical Pirouette Figure 13: .-I-. er:iee Bandling Qrmlities ratings in n.irrds Pilot I Pilot 1 1 2 3 1 2 3
- - 4
-
- v
E 4 r 7 n
L 3.5 3.5 E k 3 ui 2 . 5 2.5 r 2 1.5 1.5 = 1 a
5 0.5
0.5 - 1 0 1 2 3 L L 2 1.5 2 1 5 L 2 9 0) t ui l i
g 1 g 1
c n Z i
s 0.5
a 0 5
-
-
m rn -1 -1 1 2 3 1 2 3 1.2
-
c -
c
.I- -
.I- -
L 1 - L 1 E $ 0 . 8 v) 0 6 0.4
s
-
‘Z 0.2
-
=x 1 2 3 1 2 3
-
-
n 4 n 4 Q)
g 3 . 5
c 3.5
-
& 3 L 3 $ 2.5 $ 2.5 “ 2
g 2
4 2 a 1 . 5 1 5 cn cn .f 1 .f 1 U U
z 0.5
z 0 5
I o * o 1 2 3 1 2 3 Data R u n s Data R u n s Pi!ot I Riot 2 - DUH-BOA
T B I MCLAWS r
16 , 'D
z 12
s 12 u 10 0, 2 8 C 8 E 6 c - 4 1 2 3 1 2 3 4 4.5 4.5
- Y
-
-
L 4 L 4 2 3 . 5
e 3.5
L a 3 $ 3 uj uj o 2.5 0 2.5 Q Q v , 2 c n 2 1.5 s i 1.5 a : a ci c i l 0.5
5 0.5
J O J o 1 2 3 1 2 3 4
- -
2 . 5 L & * t uj d o 1.5 1.5 Q Q
g 1
a : * 0.5
- 0.5
m - I o 1 2 3 1 2 3 4 'Ei; 4 5 a , I ! 4 L 3.5 g 3 v, 2.5 z 2 1.5 a 1.5 .- S 0 1 5 1 0.5
3 0 5
= o = o 1 2 3 1 2 3 4 Data Runs Data Runs Pijot 2 Pilot 1 50 r I UH-GOA I ;ii 40
7 35
0 30
x 25
fn
- 20
i= 10 1 2 3 6 -
I 14.4
c -
z 5 -
2 9 7
t T / 7 0
1 2 3 1 2 3 2 . 5 r -
-
-
E L + 2 5.4
L 2 4 9
e 4 0
1 2 3 1 2 3 g ~ - 9 cn 13.3 a
g a
7 L 7 6 g 6 : 5 4 9 4 U 0 3 .-c 2 U I ’ = o 1 2 3 1 2 3 Data R u n s Data Runs Figure 16: Pirouette SITE performance summary data in GVE.
Pilot 1 Pilot 2 I n , m
- m
Y a 10 a 10 E F
-
c - 5 F 5 1 2 3 1 2 3 '= 20
c -
L al
u i al t-
uj c 10
!i?
u 5 u 5 d, d, C 1 0 - 1 0 1 2 3 1 2 3 - 4 L 7 8
-
- 3 . 5
2 3 2 . 5 H 2 l x a 1.5 U .- 2 1 c 0.5 1 2 3 1 2 3 1 2 3 1 2 3 Data Runs Data Runs Figure 17: Lateral reposition JITE performance summar> data ir GVE.
Pilot 1 Pilot I
oUH-60A , 35 r
MCLAWSI-
-
2 25 25
g 20 g 20
2 15 2 15 E 10
? 10
F i = 0 0 1 2 3 4 1 2 3 - 6 c
- -
L 5
e
a J 4 ui Q 3 cn I 2 U L m ’ -1 1 2 3 1 2 3 4
-
c -
‘z 40 L
e
cn cn I 0 : 20
5 20
a , -0 .- 2 10 c
a
1 2 3 1 2 3 4 1 2 3 1 2 3 4 Data Runs Data Runs Figure 13: Departure-Abort MTE performance summary data in GC’E.
A
- -
30 7-
h 25
-
v) v)
U = 20
U c 40
f 15
Y
-
E 20
F 5 i= 10 n 1 2 3 1 2 3 4
-
- c
- 6 L e 5 L m m 4 z 3 a - 0 2 3
-
.- = 1 Q 1 3 1 2 3 4
-
13.9 15.2 m 8 r 1 2 3 1 2 3 4 Data Runs Data Runs i : UH-GOA 81 MCLAWS 1 2 3 4 1 2 3 4 A I L
-
2 . 5 a u i 2 IZ 1.5 2 1 [r C: 0.5 Q -I 1 2 3 4
-
c n 3 al E 2.5 L- 2 2
z
: c n 1 K .- 0.5 a l I o 1 2 3 4 Data Runs Figure 30: Vertical AITE performance surnmarj data in DVE (Pilot 2).
i Figure 21 : Longitudinal and Lateral SAS authority saturation percentages for individual runs for different AITEs using AICLA\VS I Figure 23: Comparison of Lateral Reposition ;CITE by Pilot 1 using JICLAWS and baseiine UH-60.4 control laws