5.
A PCA instrument landing system-coupled approach and landing capability was added, which allowed new pilots to make very good approaches on their .rst try. The instrument landing system-coupled approaches were successful in turbulence levels up to at least moderate.
6.
The PCA system was tested over a wide .ight envelope well beyond the design envelope and was found to perform somewhat better than predicted. Performance at 30,000 ft, at an aft center of gravity position, and at 360 kn was adequate, even though the design was developed for speeds from 150 to 200 kn at altitudes below 15,000 ft.
7.
The PCA system was tested with all three hydraulic systems depressurized and functioned normally during 25 min of .ight tests.
8.
In general, .ight-to-simulation comparisons were reasonably good. An exception was that although the trim speed change with loss of hydraulic pressure was predicted to be a 20 kn gain, it was found to be a 20 kn loss.
9.
A total of 16 demonstration pilots .ew the PCA system, and pilot comments were very favorable. All pilots adapted rapidly to the PCA system, and all made successful instrument-landing system-coupled approaches on the .rst try.
10.
Several ways are available to adjust the trim speed on the MD-11: reducing weight, moving the CG, extending the landing gear, and changing the throttle setting on the center engine. A more .exible way to control trim speed on a new aircraft design would be to incorporate an independent slow rate stabilizer trim capability.
11.
Digital electronic engine controllers provide accurate and repeatable thrust control that improves the performance of a PCA system.
12.
Wing-engine-out lateral control using only thrust and a lateral center-of-gravity offset from fuel transfer has been demonstrated in the .ight deck simulator (FDS), and appears promising for further development.
LESSONS LEARNED
Digital .ight control and engine control systems with digital data buses provide a powerful capability to add new control modes with only software changes.
PCA capability on a transport airplane was accurately predicted by a high-.delity simulation. This prediction was in contrast to the PCA system tested on the F-15 .ghter airplane, where the simulation required extensive modi.cation to duplicate .ight trends. The podded engines on a typical transport airplane are believed to be more easily modeled, in contrast to the dif.culty in modeling the characteristics of the typical highly integrated .ghter engine and inlet.
The .exibility designed into the .ight software was key in the successful PCA test. In particular, it was possible to improve the lateral response and to test the system far beyond its design envelope using this software .exibility.
PCA system .ight tests on the MD-11 were needed to validate the PCA concept. Before the .ight test, one knowledgeable company test pilot said that the airplane would never be landed under PCA system control. At the end of the demonstration .ights, this same pilot was advocating additional PCA landings.
Dryden Flight Research Center National Aeronautics and Space Administration Edwards, California, April 16, 1997
REFERENCES
1.
Burcham, Frank W., Jr., Trindel A. Maine, C. Gordon Fullerton, and Lannie Dean Webb, Development and Flight Evaluation of an Emergency Digital Flight Control System Using Only Engine Thrust on an F-15 Airplane, NASA TP-3627, Sept. 1996.
2.
Burcham, Frank W., Jr. and C. Gordon Fullerton, Controlling Crippled Aircraft—With Throttles, NASA TM-104238, Sept. 1991.
3.
Gilyard, Glenn B., Joseph L. Conley, Jeanette Le, and Frank W. Burcham, Jr., “A Simulation Evaluation of a Four-Engine Jet Transport Using Engine Thrust Modulation for Flightpath Control,” AIAA-91-2223, June 1991.
4. 中國航空網 www.k6050.com 航空翻譯 www.aviation.cn 本文鏈接地址：Development and Flight Test of an Emergency Flight Control System Using Only Engine Thrust on an MD-11 Transport Airplane(43)
