Angle of attack
Angle of sideslip
1.8
1.6
1.4
EPR
1.2
1.0
.8
Right
Left
Cente r
Figure 47. Time history of response to right throttle step inputs, MD-11 FDS, 205 kn, altitude = 7500 ft, gear and .aps up, dampers off, 35 in. lateral CG offset.
0 10 20 30 40 Time, sec
970392
240
Track angle, 220 deg
200
Measured
Command
1
Angular rates, 0 deg/sec
–1
Roll rate Pitch rate Yaw rate
1.5
1.3
EPR
1.1
.9 1500 1550 1600 1650 1700 Time, sec
Right
Cen ter Left
970393
Figure 48. MD-11 FDS with left engine idle, lateral CG offset 31 in. right, gear and .aps up, PCA lateral track mode active, 15,000 ft, GW = 380,000 lb.
Bank angle feedback gain = 1.0 Bank angle feedback gain = 0.5
Altitude, ft
Airspeed, kn
Flightpath, deg
Angular rates, deg/sec
Track angle, deg
Bank angle, deg
EPR
16 15 200
190 2
0
–2
2
–2
240
0
200
160 10 0
– 10
1.6
1.4
1.2
1.0
.8 1700
1800 1900 2000 2100
Time, sec 970394
time permitted, they would then have .own to Edwards and landed on the lakebed. If not, they would have made another ILS approach and pulled the power to idle during the .are. All of this was done without any training, and indicates that PCA system operation is so suf.ciently straightforward that extensive training is not required. The demonstration also showed that the .are logic that worked for Flaps 28 would need more tuning to operate at other conditions.
FUTURE APPLICATION OF A PCA SYSTEM
Based on the success of the MD-11 PCA system tests, previous F-15 PCA .ight tests, and B-747 and C-17 simulator tests, a PCA system appears to provide an acceptable backup .ight control system capable of safe landings independent of hydraulic power. The addition of a slow electric actuator for trimming the stabilizer would allow the crew to select the trim speed, thereby eliminating the need to plan and use CG and weight control for controlling trim speed. Of course, annunciation, display, and engagement issues would have to be re.ned over what was done in this concept demonstration .ight test.
CONCLUSIONS
A concept demonstration propulsion-controlled aircraft (PCA) system using closed-loop thrust for control has been designed, developed, and .ight tested on an MD-11 airplane. The system was implemented with software changes to existing .ight and engine control computers, and uses the autopilot knobs on the glareshield .ight control panel for pilot inputs.
1.
Flight tests totaling 25 hr have shown that a PCA system can successfully provide control adequate for up-and-away .ight and for runway landings without the use of normal .ight control surfaces.
2.
Pitch PCA control using the wing engines was excellent primarily because of the location of the wing engines well below the vertical center of gravity. Approximately 8 to 10 sec was required to achieve a .ightpath command. In smooth air, .ightpath was held to within less than 0.5° of the pilot’s command; in light-to-moderate turbulence, .ightpath was held within 1° of that commanded.
3.
Lateral PCA control was stable and adequate for up-and-away .ight. In smooth air, track angle was held to within 0.5° of the pilot’s command. A 5° track command took 15 sec to achieve. On approach, lateral control was sluggish and required some pilot compensation.
4.
In smooth air, a new pilot could make a successful PCA approach on a .rst try. In turbulence, three or four approaches were needed before a new pilot was able to effectively adapt to the sluggish lateral control and maintain runway alignment.
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