Document
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NASA/TM- 1998-206562
Development and Testing of a High Stability
Engine Control (HISTEC) System
John S. Orme Dryden Flight Research Center Edwards, California John C. DeLaat NASA Lewis Research Center Cleveland, Ohio Robert D. Southwick and George W. Gallops United Technologies Corporation Pratt & Whitney West Palm Beach, Florida Paul M. Doane Boeing Phantom Works St. Louis, Missouri National Aeronautics and Space Administration Dryden Flight Research Center Edwards, California 93523-0273
July 1998
NOTICE
Use of trade names or names of manufacturers in this document does not constitute an official endorsement of such products or manufacturers, either expressed or implied, by the National Aeronautics and Space Administration.
Available from the following: NASA Center for AeroSpace Information (CASI) National Technical Information Service (NTIS) 7121 Standard Drive 5285 Port Royal Road Hanover, MD 21076-1320 Springfield, VA 22161-2171 (301) 621-0390 (703) 487-4650
DEVELOPMENT AND TESTING OF A HIGH STABILITY ENGINE
CONTROL (HISTEC) SYSTEM
John S. Orme* NASA Dryden Flight Research Center Edwards, California John C. DeLaat t NASA Lewis Research Center Cleveland, Ohio Robert D. Southwick _ and George W. Gallops § United Technologies Corporation Pratt & Whitney West Palm Beach, Florida Paul M. Doane _[ Boeing Phantom Works St. Louis, Missouri Nomenclature Abstract ACTIVE Flight tests were recently completed to demonstrate Advanced Control Technology for an inlet-distortion-tolerant engine control system. These Integrated Vehicles flight tests were part of NASA's High Stability Engine ADC airdata computer Control (HISTEC) program. The objective of the AOA HISTEC program was to design, develop, and flight angle of attack, deg demonstrate an advanced integrated engine control AOSS angle of sideslip, deg system that uses measurement-based, real-time BPW estimates of inlet airflow distortion to enhance engine Boeing Phantom Works, St. Louis, Missouri stability. With improved stability and tolerance of inlet airflow distortion, future engine designs may benefit CC central computer from a reduction in design stall-margin requirements and enhanced reliability, with a corresponding increase CST combined systems test in performance and decrease in fuel consumption. This DES distortion estimation system paper describes the HISTEC methodology, presents an DFRC aircraft test bed description (including HISTEC-specific Dryden Flight Research Center, modifications) and verification and validation ground Edwards, California tests. Additionally, flight test safety considerations, test EAIC electronic air inlet control computer plan and technique design and approach, and flight operations are addressed. Some illustrative results are EMC electromagnetic compatibility presented to demonstrate the type of analysis and results FCS flight control system produced from the flight test program.
acceleration of gravity g *Aerospace Engineer, AIAA member no. 102066-00.
HIDEC F-15 Highly Digital Electronic Engine tControl Systems Engineer, AIAA member.
Control _:Project Engineer.
§Technology Manager, ASME member.
HILS hardware-in-the-loop-simulation _[Engineering Manager.
Copyright © 1998 by the American Institute of Aeronautics and HISTEC High Stability Engine Control Astronautics, Inc. No copyright is asserted in the United States under ID inner diameter Title 17, U.S. Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Govern- IDEEC improved digital electronic engine control mental purposes. All other rights are reserved by the copyright owner.
American Institute of Aeronautics and Astronautics compromises were unavoidable. The F-15 Highly IFPC integrated flight and propulsion control Integrated Digital Electronic Engine Control (HIDEC) KCAS calibrated airspeed, kn program addressed these shortcomings in a series of flight test experiments to demonstrate the benefits of MUX Military Standard 1553 multiplex data bus integrated controls. Distortion effects on engine stability NC nozzle control computer were directly modeled onboard with airdata inputs to preprogrammed engine control schedules. The HIDEC- OD outer diameter unique engine control then determined whether PCM pulse code modulation excessive margins existed for the purposes of increasing performance. Indeed, HIDEC showed performance Psf pounds per square foot, lb/ft 2 improvements such as thrust increases, fuel PW Pratt & Whitney consumption reductions, and cooler turbine temperatures .2 SIT software integration test SMC stability management control law A new technique for estimating inlet distortion and its effects on engine stability has been developed as part of S/MTD Short Take-Off and Landing/Maneuver the NASA High Stability Engine Control (HISTEC) Technology Demonstrator program. 3 Distortion estimation is accomplished with a VMSC vehicle management system computer limited number of high-response static pressure measurements at the engine face and a frequency-based Introduction reduction algorithm. The algorithm, known as the distortion estimation system (DES), predicts the loss of Integrated propulsion controls technology has been engine stability margin as a result of inlet distortion. 3 successfully demonstrated on several previous flight test The DES relies on measurements that are more closely programs to provide propulsion system stability and correlated to distortion than the HIDEC model-based performance enhancements. Traditionally, it has been approach. An online stability audit technique, similar to the standard practice to design propulsion system that developed for HIDEC, was combined with the DES control schedules to accommodate worst-case stability to form the basis of a stability management control law conditions at all times, even though worst case (SMC). Unlike the HIDEC approach of up-matching the conditions were rarely encountered. Because there was engine for improved performance at low distortion no means of determining the variability of stability levels, the new SMC is designed to operate with margins in real-time, control schedules were not improved performance schedules closer to stall. For optimized for peak performance, but rather for high distortion levels, the SMC will down-match the maintaining an excess buffer of stability margin. This engine as required to maintain system stability. The worst-case stability margin buffer usually resulted in resulting reduction in design stall margin requirements reduced performance. Digital engine, inlet and flight can influence new engine design for improved control, and communications have allowed for improved performance or reduced weight, or both.
integrated propulsion control techniques to recapture some of that lost performance. 1 For example, with The overall goal of the HISTEC program is to define shared digital information, real-time stability margin the requirements for, design, develop, and demonstrate identification may be used with adaptive control in flight an advanced high stability engine control techniques to optimize propulsion system performance, system that uses real-time estimation of distortion to or conversely, improve the robustness of the controller enhance engine stability. The HISTEC program consists in response to instabilities.
of three phases: Phase I - Algorithm Development, Phase II - System Development, and Phase III - Engine High levels of inlet airflow distortion can lead to Test/Flight Demonstration. The flight test demonstration propulsion system instabilities such as engine stall or of the HISTEC distortion-tolerant control system was surge. On the F-15 that has variable geometry inlets, an conducted at the NASA Dryden Flight Research Center inlet control is designed about the airflow demands of (DFRC), Edwards, California during the summer the engine. Meanwhile, a separate engine control is months of 1997 on the F-15 ACTIVE (Advanced designed to accommodate the worst levels of distortion Control Technology for Integrated Vehicles) research with sufficient stability margin to ensure stall-free aircraft. Specific flight test objectives were to calibrate engine operation. But because the subsystems were not and verify the DES and stability accommodation. 4 designed to communicate in flight, performance American Institute of Aeronautics and Astronautics
documents the preparation and execution of the
A low-cost, minimal-impact-to-schedule philosophy
HISTEC flighttest, including aircraft modifications and
wasadopted for implementing HISTEC systems with
the F-15ACTIVEvehicle. Aircraftmodifications to verifications ofthose changes, flighttest planand devel- accommodate theHISTEC systems primarily involved opment of flighttesttechniques, safety considerations,
andflightoperations. Useof trade names or names of
the right-hand engine,integration of a research
manufacturers in thisdocument does notconstitute an
computer, and a new instrumentation system. To
official endorsement ofsuch products ormanufacturers, minimize theimpact ofadding anew research computer,
either expressed orimplied, bythe National Aeronautics
theHISTEC research computer was integrated withthe
and Space Administration.
existingaircraftavionicsby replacing an existing
ACTIVE research computer. Thisapproach eliminated
HISTEC Algorithm Description
the needfor anyflight controlsoftware changes to
ACTIVE. Toaccommodate theadditional sensors and
The distortion-tolerant control approach developed
measurement recording requirements for HISTEC, a
for HISTEC is illustrated in Figure 1. The approach uses new instrumentation system was added totheaircraft.
a distortion-sensing concept developed by PW and a practical design implementation for estimating in-flight
TheHISTEC program is managed by NASALewis
Research Center, Cleveland, Ohio. The prime contractor distortion. The DES is integrated with advanced stability management control laws designed for the
fortheprogram is Pratt & Whitney (PW), a division of
F100-PW-229 improved digital electronic engine United Technologies, WestPalm Beach,Florida.
control (IDEEC). High-response pressure measurements
NASA's Dryden FlightResearch Center managed flight
at the engine face are used as inputs to the DES. For the testingactivities.BoeingPhantom Works(BPW), (formerly McDonnell Douglas) St. Louis,Missouri, HISTEC flight test, the DES computer calculates real- time inlet distortion characteristics from fan inlet
assisted in theintegration oftheHISTEC systems onto
theaircraft. TheU.S.Air Force provided theairframe, pressure measurements. The DES then determines corresponding engine stall line sensitivities for the
engine, andrelated systems. Flighttestshaveaug-
sensed distortion. The DES also uses data from the
mented existing databases forinletdistortion data, vali-
dated thedistortion estimation method, andconfirmed aircraft flight control system to predict high angle of attack (AOA) and angle of sideslip (AOSS) conditions.
theabilityof theHISTEC distortion-tolerant control to
accommodate time-varying distortion. 5 This paper This look-ahead capability allows the HISTEC Engine face F100-PW-229 pressure sensors Actuator commands Flight control data
I
commands Stability management control (SMC) • Distortion estimates v • Onboard stability audit Trim I II Distortion estimation system (DES) • Engine sensitivities • Stall margin control laws 980385 Figure 1. HISTEC approach.
American Institute of Aeronautics and Astronautics ,' _'j,:'_'_'7_ , ACTIVE's highly integrated flight and propulsion
controller to anticipate and accommodate for high
control (IFPC) system. These computers are linked
distortion conditions in a timelyfashion. Theprimary
using the MIL-STD-1553 multiplex data bus (MUX).
outputs of theDESarecommands to theIDEEC that
trimthe fanand compressor operating lines.
The ACTIVE propulsion system consists of two Toimplement HISTEC, advanced control lawswere F100-PW-229 engines, each of which is equipped with a addedto the IDEECfor managing the fan and PW axisymmetric thrust vectoring nozzle. An engine compressor transient operating lines. An onboard real- mounted IDEEC and avionics bay-mounted nozzle timestability audit ofalldestabilizing factors forthefan control computer (NC) provide closed-loop control of andcompressor was added totheengine controller. The each respective component. However, the nozzle capability for improving enginestabilityunderall vectoring system was depowered and never engaged
conditions, includinghigh levelsof distortion, is
during any HISTEC flight mission.
achieved by including measurement-based distortion
The F100-PW-229 is the most recent production
effects in theonboard stability audit, andoperating the
model in the F100 series of engines. It is an augmented engine withstability management control laws.
29,000 lbf thrust class motor, featuring a three-stage fan Aircraft Description and ten-stage compressor, each driven by a two-stage turbine. An eleven-segment augmentor delivers smooth The aircraft used in the HISTEC program is a highly afterburner ignition and transient performance.
modified preproduction, two-seat F- 15B (fig. 2) referred to as the ACTIVE aircraft. This aircraft is controlled by The ACTIVE aircraft (fig. 2), like other F-15 aircraft, a quad-redundant, full authority digital fly-by-wire has two two-dimensional, three-ramp, external flight control system (FCS), coupled canards, a glass compression inlets which supply airflow to the engines.
cockpit similar to the F-15E cockpit, and sophisticated For supersonic operation, compression is accomplished onboard computers for evaluating advanced aircraft and through three oblique shocks and one terminal normal engine control algorithms. All mechanical linkages shock. The aircraft has two electronic air inlet between the control stick, rudder pedals, and control controllers to control the inlet variable geometry. The surfaces have been removed from the aircraft. The inlet control logic configures the inlet to achieve throttles control the engines digitially through the FCS, adequate performance while maintaining safe operating and no mechanical linkages exist between the throttles margins. An inlet delivers high performance when it and the engines. Ten major separate computers form provides for high pressure recovery at the engine face and low airflow spillage drag. The inlet controller maintains inlet stability margins by using schedules to avoid encountering inlet buzz and supercritical operation. Inlet buzz is primarily a high distortion phenomena that occurs at low airflows. Supercritical operation occurs when the oblique shocks terminate inside of the inlet lip, and the normal shock is ingested beyond the inlet throat. Additional information on this test vehicle and its vectoring nozzles can be found in references 6 and 7.
Aircraft Modifications for HISTEC Extensive modifications were made to the ACTIVE aircraft to accommodate the HISTEC system. The most Major modifications significant changes involved the fight-hand engine, a • Integrated flight/propulsion control system (IFPC) new instrumentation system, and a new research • Electronic air inlet controllers computer. The right-hand F100-PW-229 engine was • Canards fitted with a highly instrumented inlet case for flight • VMS research computer • F100-PW-229 engines with vectoring nozzles testing. A third instrumentation system was added to the • F-15E cockpit ACTIVE to measure and record the required 980386 parameters. A new research computer hosting the DES Figure 2. F- 15 ACTIVE test bed. algorithm required avionics integration.
American Instituteof Aeronautics and Astronautics (VMSC) and is required to emulate a portion of the Engine Modifications VMSC bus traffic. The DES receives airframe and The DES algorithm required only 6 high-response engine control inputs through the MUX. The message inlet static pressure inputs: 5 outer diameter (OD) wall traffic (i.e. size and number of messages) is set to be static sensors mounted circumferentially around the consistent with the existing aircraft flight test data inlet and the average of 5 inner diameter (ID) wall static communications architecture. A digital signal processor sensors. In addition to the HISTEC system static in the DES executed all of the distortion estimation pressures, separate instrumentation to measure algorithms that were programmed in the Ada software temperature and pressure were incorporated into an language. The DES hardware and software were engine inlet case. The instrumented inlet case is a designed to facilitate flight-line software updates to the Bill-of-Material F100-PW-229 inlet case, modified to DES constants and schedules.
install 35 strut leading-edge total pressure sensors, 7 strut leading-edge total temperature sensors, 9 OD and The main inputs to the DES computer are 6 inlet 5 ID high-response static pressure sensors. The strut pressures (5 OD wall static sensors and the average of leading-edge pressure sensors are located on 7 struts, the 5 ID wall static sensors); aircraft altitude and 5 sensors per strut, distributed radially by equal Mach number; and engine low rotor speed, high rotor flowpath area. These pressure sensors served as an speed, inlet temperature and airflow. Other airframe- independent reference for evaluating the DES. The total required inputs are used to support the VMSC emulation temperature sensors are located at approximately and an AOA/AOSS predictor algorithm supplied by midspan on the same inlet struts as the total pressure BPW. The outputs are (1) the distortion related trims to sensors. Static pressure taps are located between struts the fan and compressor stall pressure ratio and (2) the on the OD and ID inlet case shrouds. An inlet face average pressure.
aircraft-mounted electrical signal averaging circuit was Another algorithm predicted the aircraft's AOA and required to provide an average of the five I.D. signals to AOSS one-half second in the future. Inputs to this the DES computer.
predictor algorithm included AOA from the airdata Hardware modifications external to the engine were computer (ADC), pilot stick and pedal positions, and required to accommodate HISTEC inlet instrumentation aircraft lateral acceleration. This algorithm allowed the installation. Minor modifications to the engine externals DES to downmatch the engine prior to dynamic aircraft were made to prevent physical interference. Anti-ice maneuvering, allowing the engine control to provide the capability was removed to prevent high temperatures necessary stall margins to accommodate the anticipated from damaging the inlet strut flight test instrumentation.
high distortion flight conditions.
Removal of the engine anti-ice air supply manifold and Avionics Modifications and Integration valve, which is between the engine bleed air supply and inlet case, provided the necessary room for inlet sensor The IFPC avionics architecture of the ACTIVE test lead wire routing and termination.
bed was modified to integrate the DES into the avionics suite with minimal cost and schedule impact (fig. 3).
No hardware modifications were required for the IDEEC. The production engine control software was modified to incorporate the stability management features of HISTEC. This software was implemented Right Right within the existing engine control laws. The IDEEC FCS B software is designed to allow easy updates on the flight- line to engine control schedules and constants. I I Distortion Estimation System Computer E ; i Right IDEEC For HISTEC, an FI19 comprehensive engine i Left IDEEC diagnostic unit was used as the DES computer. This ili'_ii_iN_;%:: i computer was selected for its computational capability, availability, and flight-quality design. To reduce cost, the unit was aircraft mounted and required no "_C L_IC 980387 environmental conditioning. The DES computer is connected to the avionics MUX in place of the Figure 3. HISTEC Military Standard 1553 avionics bus modifications.
Channel-B vehicle management system computer American Institute of Aeronautics and Astronautics standard flight research noseboom, separate from the The modification consisted of disconnecting Channel B of the VMSC from the aircraft MUX, and substituting ADC, provided another source of aircraft AOA and was the only measurement for AOSS.
the DES in its place. This swap allowed the IDEEC to communicate with the DES without incorporating any Special consideration was given to the criticality of flight control computer (FCS) software changes. The the instrumented inlet rake transducers. In past flight latter advantage provided significant cost savings and programs, pressure transducers have displayed minimized flight safety concerns.
sensitivity to the harsh operating temperature and vibration environment near engines. The severe Instrumentation environment where the HISTEC transducers were The ACTIVE aircraft incorporates a flexible located posed a threat to their longevity. Because of high-speed data acquisition system which transmits and their criticality to the success of the HISTEC records analog and digital parameters, and MIL-STD- experiment and the difficulty of replacing failed sensors, 1553 data bus. A new pulse code modulation (PCM) replacement criteria were defined and the sequence of system was added to the ACTIVE vehicle to testing was established to proceed from high transducer accommodate the large amount of additional criticality, low risk flight conditions to low criticality, instrumentation required to support HISTEC. On the high risk flight conditions. As will be described later, the new PCM system, 7 temperature and 54 high-response flight test was staged in two phases with the criticality for most of the inlet sensors relaxed during the second pressure measurements were added to analog instrumentation. Over 3700 parameters were recorded phase of flights. Additionally, supersonic testing, which onboard and simultaneously downlinked to the NASA provides the harshest transducer environment, was Dryden mission control center during the HISTEC accomplished only after most of the subsonic testing flights. Instrumentation included such categories of was completed.
parameters as: Ground Tests • Aircraft, engine, nozzle trims, commands, and effector feedbacks Verification and validation of the HISTEC system was required prior to flight for all hardware and software • Engine, nozzle, fuel flow and quantity information aircraft modifications. Avionics verification and • Pilot activity and flight conditions validation ranged from unit level testing of software and hardware, to hardware-in-the-loop tests, to aircraft • Aircraft attitude and states ground tests. Propulsion system validation testing • Airdata including aircraft AOA, altitude, and included structural integrity tests for the instrumented Mach number inlet case, sea level functional tests, and an uninstalled engine run. Finally, integrated system validation testing • Cockpit discretes and switches was accomplished with all systems installed on the • DES, IDEEC MUX traffic aircraft as it was to be configured for flight.
• Inlet rake instrumentation including DES sensors Avionics Verification and Validation Tests A description of the airdata system is worthwhile, As part of the HISTEC preflight checkout, the considering its importance to the DES algorithm. The software integration test (SIT) and hardware-in-the- aircraft is equipped with an airdata computer to execute loop-simulation (HILS) tests were performed on the computations and furnish parameters required to aircraft HISTEC avionics architecture. While these tests were systems and cockpit displays. The ADC receives inputs not required for flight safety, they were required for from a pitot-static system, AOA probes, and a total software validation. The integration tests were temperature probe. The ADC corrects these inputs for conducted at the BPW facilities in St. Louis.
sensor error as required. The pitot-static system The FCS/DES/VMSC/IDEEC interfaces were employs multiple pitot and static sources for verified in the SIT test. In this test, all the avionics boxes redundancy, including left- and right-side of the forward are integrated, just as they are in the aircraft. External fuselage and in each inlet duct. AOA probes are located inputs to the various boxes are emulated. Proper data on each side of the forward fuselage and measure local bus communication can then be verified between the AOA. A single probe located on the left forward boxes.
fuselage provides total temperature to the ADC. A American Institute of Aeronautics and Astronautics ") - ' i" _! "'i '_'i _ The proper operation of the AOA/AOSS prediction Inlet configurations included standard and complex screens to obtain undistorted flow patterns, as well as algorithm was verified in the HILS test. In this test, all the avionics units are connected, as in the SIT test, but radial and circumferential distortion patterns. Also, the circumferential screen was rotated through three the external inputs to the units are generated by a orientations in 120 ° increments.
manned simulation of the aircraft. The HILS test allows the aircraft to be flown throughout the envelope with all The objectives of the uninstalled test were avionics units functioning as they would on the aircraft.
successfully achieved. The inlet case and HISTEC The need for the HILS test was verified, when the first system performed as expected. Instrumentation failures entry found an error in the AOAJAOSS coding of the encountered during the uninstalled testing were DES. The second entry verified proper operation of the predominantly wiring related. All failures were algorithm. Had this error not been found in ground corrected prior to aircraft installation.
testing, it would have reduced the effectiveness of the flight test.
The most significant modification identified by uninstalled testing was the blending of the OD wall Uninstalled Engine Run on M-37 Stand static pressure ports to the inlet case surface. These were originally designed to protrude into the flowpath about The objectives of the uninstalled engine run were to: 0.250 in., in an attempt to escape the separated region (1) flight qualify the instrumented inlet case, (2) qualify downstream of the aircraft inlet seal. At high flow rates the HISTEC sensors, electronics and software, and (3) the position error caused by this configuration was too define the steady and dynamic performance of the large to be reliably corrected. After review, one of the HISTEC instrumentation. These objectives were ports was redesigned and installed to protrude just accomplished in approximately 11 hours of engine run 0.080in. The redesign was checked during the time with five inlet screen configurations.
uninstalled testing and demonstrated successful solution The HISTEC M-37 configuration, as shown in to the problem. Subsequently, all ports were ground to figure 4, consisted of the F100-PW-229 engine, engine 0.040 in. prior to aircraft installation.
mount, M-37 bell mouth, inlet ducts, and distortion Integrated System Validation Tests screen mount. Test control, data recording, and control monitoring were performed in a nearby control room.
Just prior to the first HISTEC flight, a series of five Data recording equipment for the HISTEC installed engine ground tests were performed as a final instrumentation included three 16-channel recorders, check of the integrated system as it was configured for each recording at 6000 samples per second for each flight. The purpose of ground testing was to demonstrate channel. The control monitor could examine and record the test aircraft was airworthy and that the HISTEC any internal control variables.
system was ready for flight testing. After successfully completing these tests a functional check flight was accomplished to ensure all critical flight systems operated as expected and that aircraft handling qualities _- 1.5 x diameter were acceptable.
\ inlet duct /-- 1.5 x diameter _. Inlet bell \ // inlet duct Instrumentation Ground Test \ mouth and \ _Distortion // /-Instrumented \debris screen \ \screen / / engine inlet \//1_- \ \mount / / case The first integrated systems tests measured the accuracy and response of all the HISTEC pressure and temperature transducers by applying known pressures and temperatures and comparing the readings. The _- Pitot-static F100-PW-229 engine _ instrumentation test also evaluated the accuracy of the probes DES sensor outputs on the MUX and the DES ID transducer averaging circuit. During the test, all aircraft ata recorder HISTEC systems were electrically powered, including the ata recorder I DES un t IDEEC, but the engines were not running. The test Data recorder I DES IDEEC objectives were successfully met. All HISTEC monitor monitor transducers were accurate and working properly. The 980388 DES outputs on the MUX were nominal and the Figure 4. M-37 uninstalled testing configuration.
averaging circuit worked as expected.
American Institute of Aeronautics and Astronautics Functional Ground Test The CST was conducted with engmes on. Different engine power settings were tested to collect ground A functional ground test was then accomplished to static distortion patterns. The aircraft was required to be verify nominal aircraft systems and HISTEC specific tied down during the CST. The purpose of the CST was systems. The functional ground test was conducted in to find any discrepancies that the integrated systems the hangar with external electrical power, hydraulic tests may have failed to identify. The CST was power, and cooling air. Engine operation was not successfully accomplished and initial inlet data required during this test. The functional test objectives gathered.
of the included verifying the proper operation following: Flight Tests flight control initiated-built-in-test, The successful execution of a flight research program involves the careful integration and balancing of MUX communications, research objectives and safety considerations. Safety nominal operations of the VMSC, DES, IDEEC was always considered in the approach and design of the computers, HISTEC system and its implementation into the ACTIVE vehicle. A flight test plan that included specific • HISTEC-specific cockpit switches and displays, mission objectives was designed to accomplish the • proper engage and disengage states of the VMSC, overall objectives, and mission planning was reviewed DES, and IDEEC computers, before each flight operation. Test technique development determined the most efficient means of • system response to MUX and power failures, gathering flight research data without sacrificing data • functionality of DES pressure transducers, and quality or flight safety.
• the ability to engage the HISTEC system during Safety Considerations simulated flight conditions.
In the design of the HISTEC flight test, system safety were All of the functional ground test objectives was emphasized in the interest of aircraft safety. System successfully met.
safety was addressed by assessing the risk involved, implementing safety design features, verifying and Hangar Radiation Test validating the system, performing a safety hazard The next step in the integrated systems tests, the analysis, and flight operational procedures. Some of the hangar radiation test, involved verifying that aircraft major steps taken to mitigate risks included: (1) not telemetry was received and displayed in the control activating the ACTIVE vectoring nozzles during room and that the displays operated as expected. The HISTEC tests, (2) installing the HISTEC system on test required external electrical power and external only the right-hand engine while leaving the left-hand cooling air. In order to check out all of the displays it engine unmodified, and (3) not making any software or was necessary to have engines running. All test hardware changes to the aircraft flight control system.
As a side note, this approach resulted in substantial objectives were successfully met. HISTEC control room benefits to costs and scheduling.
displays and operation were nominal.
Electromagnetic Compatibility Test The HISTEC risk assessment relied on the history of similar programs flown on the F-15 HIDEC and As a result of the modifications to aircraft electrical ACTIVE. During the HIDEC program, F100-PW-1128 systems, a fourth integrated systems test was required, engines (of similar design to the F100-PW-229), were the electromagnetic compatibility (EMC) test. This test aggressively controlled to improve performance while was completed with engines running. The EMC reducing stability stall margins. 8 HISTEC benefited evaluation of the new HISTEC system with ACTIVE from the safety features and the proven safe track subsystems revealed no interference conditions.
record of the ACTIVE vehicle and flight test team.
ACTIVE, as a research test bed, has proven the Combined Systems Test flexibility to accommodate diverse experiments--such as an adaptive performance optimizing control, an A combined systems test (CST), the final integrated acoustics experiment, and vectoring nozzles--while systems test, was accomplished with the aircraft retaining uncompromising safety. Because the aircraft is configured exactly as it would be for flight and all capable of safe operation with a single engine, the risk procedures were followed as if preparing for a flight.
American Institute of Aeronautics and Astronautics of any HISTEC-related failure causinginjury or disengaged and without trim application. Later, after significant damage was greatly reduced.
reviewing test results and verifying algorithm operation, testing was accomplished with the system coupled.
Thesafety assessment of theHISTEC-instrumented
inletrakedesign wasbased upon structural analysis, Because the HISTEC was an incremental change to ground testing, and flighttestexperience withinletrakes the ACTIVE aircraft, the starting point for the HISTEC hazard analysis was the baseline ACTIVE hazard
of similar design. Flightclearance of the inletcase was
analysis. The incremental hazard analysis for HISTEC
gained fromuninstalled engine ground tests. During
revealed that all HISTEC-specific risks had been
flighttests, theinletcase was inspected after every flight
reduced to an acceptable level and that some of the
as a further safety precaution. Thereliability of the
ACTIVE risks relating to the vectoring system were not
instrumentation Was initiallyofsome concern given the
applicable.
harsh environment. However, these concerns were putto
restas nearly all theinstrumentation remained intact
Test Plan Design and Approach throughout theHISTEC flighttesting.
Overall flight test objectives were to demonstrate a
Therightengine IDEEC andDES required a safety
high stability engine control that could accurately
review. The hardware forboth theIDEEC andtheDES
estimate in-flight inlet distortion and its effects on stall
had beenpreviously flight qualified(as part of
margin loss, and to flight validate the SMC. A secondary
production programs) andthishardware is of sufficient
objective was to augment the inlet distortion database.
reliability foroperational aircraft, andthus byextension
Flight testing involved two phases to accomplish the
were acceptable for the ACTIVE aircraft. The software
primary objectives. Specific Phase I objectives were as for both of these computers was checked during the SIT follows: and HILS tests.
• Quantify inlet distortion at steady-state and Several system safety design features were transient flight conditions implemented for HISTEC. These included the • Correlate measured inlet distortion from total engage-disengage logic, input signal management, trim pressure measurements to DES pressure command limiting, and engine stall protection. The measurements engage-disengage procedures for HISTEC were • Define any DES software changes that may be borrowed from ACTIVE and were designed to prevent required for calibration and implement these before unintended trim application, to allow for engagement Phase 2 only by the pilot, and to allow the pilot to disengage the system at any time by several different means. Input • Demonstrate acceptable DES accuracy at selected signal management checked the validity of inputs before flight conditions.
processing any trim commands and if engaged could Specific Phase II objectives were as follows: cause the system to uncouple if any input failed. Trim command limiting by the HISTEC software included • Demonstrate accurate inlet distortion estimation at limits to allowable engine trims. For example, the steady-state and transient flight conditions software only allowed negative incremental trims to the engine pressure ratio, thereby increasing stability • Demonstrate functional engine trim capability to accommodate inlet distortion margins and decreasing the likelihood of an engine stall.
The reliability of the HISTEC software was • Demonstrate adequate AOA and AOSS prediction demonstrated in software integration tests and during and resulting engine trims.
portions of the integrated systems validation testing.
The first phase of flight test consisted of a baseline Well-established Dryden safety procedures were also algorithm checkout and refinement along with inlet followed during flight tests. An additional requirement distortion database collection. No engine trims were for HISTEC was that all test points be flown on the applied during this phase. Algorithm updates were made NASA ACTIVE piloted simulation prior to flight on the after analyzing Phase 1 flight data. The second phase of aircraft. This simulation requirement also proved testing was completed with the HISTEC system valuable in defining and practicing test techniques. The coupled, where DES-generated engine trims were flight test approach involved a buildup in risk where applied when requested, during periods of relatively initial testing was accomplished with the system higher inlet distortion. Target conditions ofAOA, AOSS, American Institute of Aeronautics and Astronautics • Basic operational fighter maneuvers (offensive, engine airflow, Mach number, and altitude were all defensive and neutral) required to be within specified tolerances.
• NASA-supplied aircraft maneuvers (maximum-g The flight test points shown in Figure 5 were designed windup turns, pushovers with sideslip) to evaluate HISTEC in both a research and an operational environment. Data were obtained during Test Technique Development steady aerodynamic conditions. These conditions consisted of: To achieve these target conditions, flight maneuver techniques were developed in the NASA ACTIVE • Stabilized points at various altitudes and Mach piloted simulator, as mentioned in the "Safety numbers, including supersonic Consideration" section. A range of maneuvers from the relatively benign maneuver of straight and level flight to • Combinations of constant AOA and AOSS limits.
the more aggressive Split-S maneuver to nearly 30°AOA were developed and flown. Maneuvers at The above aerodynamic conditions were held steady steady aerodynamic conditions and rapid AOA and during fixed engine power levels and during engine AOSS transients were accomplished at mostly subsonic transients.
Mach numbers. Because aircraft takeoffs provide the highest inlet distortion levels, data were also collected Transient flight conditions included: during takeoffs with the HISTEC system disengaged and then repeated with the system engaged.
• AOA sweeps (two rates) to aircraft limits at various flight conditions and engine power settings Control Room Monitoring • AOSS sweeps to aircraft limits at various flight Aircraft and HISTEC systems instrumentation was conditions and engine power settings monitored from the DFRC Mission Control Center • Combinations of AOA and AOSS sweeps to aircraft during flight test operations. Information was provided limits through a range of stripcharts and displays to ensure 60 x 10 3 100 200 300 400 i i i i i i i i i i i t i l ' '/ .... ......
50 ..... " ...... :- : ' ' ' ' ' pressure, psf ,° t ........
iiii I Dynamic Altitude, / Steady flight . =r .... i1- ....
0 AOA = AOSS = 0 20 ......
• Large AOA/AOSS Transient flight 10 ........
A AOA/AOSS sweep [] Maneuver transient 0 .2 .4 .6 .8 1.0 1.2 1.4 1.6 1.8 2.0 Mach number 980389 Figure 5. ACTIVE flight envelope overlaid with HISTEC test points.
American Institute of Aeronautics and Astronautics safe operation and mission success. Extensive displays typical results are presented here. For a more thorough of real-time data including inlet instrumentation, review and discussion of flight data analysis, results and HISTEC IDEEC parameters, and parameters from the conclusions of the HISTEC sensors, algorithms, and control laws, see Southwick et al. in reference 8. The DES algorithm and computer status. These displays provided the rapid interpretation of critical data for the following figures and discussion were measurements. The control room displays supplied obtained at Mach 0.6, at an altitude of 20,000 ft, and at research engineers with the critical information needed an intermediate power setting.
to make decisions concerning the flight test progression.
Inlet Distortion Measurement and Estimation This capability for near real-time decision making resulted in productivity increases and greater testing Inlet face total pressure patterns were generated from efficiency. For example, flight measured AOA was the DES static pressure ports at the wall and compared monitored and compared with the desired target with those patterns more directly measured from the AOA conditions to determine whether the test point was 35 total pressure probes to qualitatively assess the acceptable or needed repeating. The AOA data quality accuracy of the inlet distortion estimation at steady and decision could be made within the same mission thus transient aerodynamic conditions. Figure 6 presents avoiding the possibility of having to wait for postflight data evaluation to mdetermine whether or not the test instantaneous total pressure contours taken from a data sample during an AOA sweep as viewed from the engine needed repeating. Another example of how the control looking forward. In general, the contour patterns room displays and procedures benefited the flight tests was shown in the ability to display (1) the DES trims showed excellent agreement between the total pressure and (2) the fan and compressor stall margins in the probes and DES static pressure ports. Circumferential SMC. This allowed a determination of whether or not distortion, as determined by the DES, matched very well the trims were being properly applied to the engine and with that measured with the total pressure probes. At whether or not repeat tests or software modifications this condition, the DES predicted only slightly higher would be required.
radial distortion than was measured. Generally the steady-state distortion intensities derived from the wall Flight Operations static ports are within 2 percent of those computed from the total pressure probes. The dynamic distortion Flight operations were typically conducted twice a intensities are generally within 5 percent.
day for up to 3 days a week. Preparation for a typical mission involved preflight aircraft checkout, including Stability Management Distortion Accommodation checkout of instrumentation systems and engine inlet case inspections. Inspections were necessary to verify During aircraft maneuvering, when sufficient inlet that no structural damage had occurred to the inlet case distortion was sensed by the DES, fan-operating line and that the instrumentation was ready for flight. Prior trim commands in terms of fan pressure ratio were sent to starting engines, and as part of the day-of-flight to the engine control and then applied by the IDEEC in aircraft checks, the instrumentation systems were turned terms of engine pressure ratio. Figure 7 shows aircraft on to obtain inlet pressure readings at ambient and system response from a data sample during an AOA conditions. Comparisons were made with the known sweep at an altitude of 20,000 ft and Mach 0.6 for an ambient conditions to track any transducer drift between intermediate power setting. In figure 7(a), the time flights. Once in flight, but prior to acquiring the first test history of AOA shows AOA rates generated during the conditions, and again just prior to completion of the maneuver reached about 4 ° per sec on the pull-up and flight, a data repeatability test was flown at the standard about minus 7 ° per sec on the recovery. A maximum conditions of Mach 0.6 at an altitude of 20,000 ft and AOA of 27.5 ° was reached. Engine pressure ratio, maximum nonaugmented power setting during figure 7(b), tracks the AOA as expected, and is wings-level cruise. This repeatability test verified that consistent for both increasing and decreasing AOA. The no significant transducer drift had occurred during HISTEC-controlled engine is down-matched as the flight.
stability debit begins to exceed the available stability Illustrative Results margin, and is removed when the debit decreases below the available margin. Fan pressure ratio trims from the To give an indication of the type of results that were DES cross-plotted with AOA in figure 8 show that the obtained from the flight test program, a sample of trims are nearly linear with AOA.
American Institute of Aeronautics and Astronautics Research total pressure sensors DES static pressure sensors Right-hand engine, aft looking forward Normalized total pressure .80 .85 .90 .95 1.00 1.05 1.10 980390 Figure 6. Comparison of DES-derived contours to measured contours of total pressure at the inlet face for Mach 0.6 at an altitude of 20,000 ft and 21 ° AOA and 0 ° AOSS.
Nominal engine HISTEC engine 30 , , 1 , t i i t i i i " --"l---i--- _---, ....
i i I i i u u t i u i i i i i I I I , , ,\, Engine Angle of ,_1_4___-__'____ _ attack, pressure i i i '1 • o i ratio deg
l-l-ii
l,Y aA _/ n a II--_r', Increasin.g.. : i i I ItVI I i .__.J___l_ __ J.___l ....
I I I I -i ...... i...... i--i ...... i......
i i i i i I i i 0 5 10 0 5 10 Time, sec Time, sec 980391 980392 (b) Engine pressure ratio time history.
(a) Angle of attack time history.
Figure 7. Flight test results, maneuver distortion accommodation.
American Institute of Aeronautics and Astronautics .12 i i , i i i ......... a .................... 4 .................... .t ..........
/ I I ......... -i .................... -t .................... -¢. ..........
i t i ......... '3 .................... l .................... "/ ..........
......... .J .................... a .................... .t ........
.......... 7 .................... 7 .................... 3 ......
.......... .J .................... a ..................... _ .....
t i • .10 Fan pressure ......... JI .................... 21 ............... t ..........
......... ...i .................... J. ........... J. ..........
ratio t I I trim I I I .09 ......... .1 .......................... .1 ..........
' I I ..... End of maneuver ....... . .......... 4 ..........
I _ II I , wJ l.J _. . • I .08 , _ _tart OTmaneuver , ......... n .I .................... _ T .............................. _-_ -[_ ........ r ........ Increasing inlet distortion .......... _ ..........
t I I .......... _ .................... 4 ..................... -+ ..........
t t t .07 0 10 20 30 Angle of attack, deg 980393 Figure 8. Fan pressure ratio trim as compared with angle of attack.
3Southwick, Robert D., George W. Gallops, Louis J.
Concluding Remarks Larkin, and Kurt J. Sobanski, High Stability Engine The HISTEC distortion-tolerant control has been Control (HISTEC) Phase I: Algorithm Development, successfully demonstrated in flight on the F-15 ACTIVE vol. I, Final Report and Appendix A, NASA aircraft. All flight test objectives were successfully met CR-198399, Sept. 1995.
over the course of 10 flights and over 100 test points.
4DeLaat, J., R. Southwick, G. Gallops, and J. Orme, Approximately 65 gigabytes of high quality inlet The High Stability Engine Control (HISTEC) Program: distortion and DES algorithm data were collected. A Flight Demonstration Phase, AIAA-98-3756, July 1998.
maximum angle of attack of 29 ° and angle of sideslip of 5 ° were achieved, yielding increased levels of distortion.
5Southwick, R., G. Gallops, J. DeLaat, and J. Orme, A maximum Mach number of 1.6 was attained. During High Stability Engine Control (HISTEC) Flight Test the first phase of flight test, it was verified that inlet Results, AIAA 98-3757, July 1998.
distortion was accurately estimated by the DES in flight.
Only minor algorithm updates were required between 6Smolka, James W., Laurence A. Wallace, flight missions. During the second phase of testing, Major Gregory H. Johnson, Gerard S. Schkolnik, Curtis engine stability accommodation was demonstrated W. Burger, Timothy R. Conners, John S. Orme, Karla S.
when the stability management control applied stability- Shy, and C. Brent Wood, F-15 ACTIVE Flight Research enhancing trims during periods of high distortion levels.
Program, 1996 Report to the Aerospace Profession, Because of the preparation and up front test planning, 40th Symposium Proceedings, The Society of execution of the flight tests was extremely efficient Experimental Test Pilots, Sept. 1996, pp. 112-145.
and safe.
7Doane, P., R. Bursey, and G. Schkolnik, F-15 References ACTIVE: A Flexible Propulsion Integration Testbed, AIAA 94-3360, June 1994.
1Stewart, James F., Frank W. Burcham, and Donald H. Gatlin, Flight-Determined Benefits of Integrated 8An Electronic Workshop on the Performance Seeking Flight-Propulsion Control Systems, NASA TM-4393, Control and Propulsion Controlled Aircraft Results of June 1992.
the F-15 Highly Integrated Digital Electronic Control Flight Research Program, Proceedings of the Electronic 2Highly Integrated Digital Electronic Engine Control Workshop, compiled by Sheryll Goecke Powers, NASA Symposium, NASA CP-3024, February 1989.
TM-104278, Jan. 1995.
American Institute of Aeronautics and Astronautics i ¸¸ ._ • , . .
R E PO RT D OC U M E NTATIO N PAG E Form Approved
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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and RE _orts, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503, 1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORTTYPE AND DATES COVERED July 1998 Technical Memorandum 5. FUNDING NUMBERS 4.TITLE AND SUBTITLE Development and Testing of a High Stability Engine Control (HISTEC) System WU 529-20-04-00-33-00-MGT 6. AUTHOR(S) John S. Orme, John C. DeLaat, Robert D. Southwick, George W. Gallops, and Paul M. Doane 8. PERFORMING ORGANIZATION 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) REPORT NUMBER NASA Dryden Flight Research Center P.O. Box 273 H-2269 Edwards, California 93523-0273 10. SPONSORING/MONITORING 9.SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) AGENCY REPORT NUMBER National Aeronautics and Space Administration NASA/TM- 1998-206562 Washington, DC 20546-0001 11. SUPPLEMENTARY NOTES Presented at the 34th AIAA/ASME/SAE/ASEE Joint Propulsion Conference, Cleveland, Ohio, July 13-15, 1998. John Orme, NASA Dryden, Edwards, California; John DeLaat, NASA Lewis Research Center, Cleveland, Ohio; Robert Southwick and George Gallops, United Technologies Corporation, Pratt & Whitney, West Palm Beach, Florida; Paul Doane, Boeing Phantom Works, St. Louis, Missouri.
12a. DISTRIBUTION/AVAILABILITY STATEMENT 12b. DISTRIBUTION CODE Unclassified--Unlimited Subject Category 05, 07 13. ABSTRACT (Maximum 200 words) Flight tests were recently completed to demonstrate an inlet-distortion-tolerant engine control system. These flight tests were part of NASA's High Stability Engine Control (HISTEC) program. The objective of the HISTEC program was to design, develop, and flight demonstrate an advanced integrated engine control system that uses measurement-based, real-time estimates of inlet airflow distortion to enhance engine stability. With improved stability and tolerance of inlet airflow distortion, future engine designs may benefit from a reduction in design stall-margin requirements and enhanced reliability, with a corresponding increase in performance and decrease in fuel consumption. This paper describes the HISTEC methodology, presents an aircraft test bed description (including HISTEC-specific modifications) and verification and validation ground tests.
Additionally, flight test safety considerations, test plan and technique design and approach, and flight operations are addressed. Some illustrative results are presented to demonstrate the type of analysis and results produced from the flight test program.
14. SUBJECTTERMS 15. NUMBER OF PAGES Air data, Avionics, Controls, Engine control, Engine stability, F-15 ACTIVE, 16. PRICE CODE Flight research, Inlet distortion, Propulsion A03 17. SECURITY CLASSIFICATION 18. SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT OF REPORT OF THIS PAGE OF ABSTRACT Unclassified Unclassified Unclassified Unlimited NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89) Prescribed by ANSI Std. Z39-18 298-102