Flight 252, first ILS-coupled landing
Flight 256 demonstration ILS-coupled landing
Flight 252, 3 engine dynamic mode, ILS-coupled approach to 50 ft
ILS glideslope transmitter Localizer deviation less than 0.1 deg
Flightpath angle, deg
Radar altitude, ft AGL 0
–1
–2
–3 800 600
400 200
Flare 2 sec
ILS gli deslope command command
Sef3 cond lare at 0 ft
First fl are at 130 ft
All 3 approaches
Figure 38. Overlay of three MD-11 PCA ILS-coupled .nal approaches. Flaps 28, gear down, light winds, no turbulence.
0 20 40 60 80 Time, sec
970621
Touchdown
Crosswind and
1000
750
Radar
altitude, 500
ft AGL
250
0
2
0 Flightpath angle, – 2 deg
–4
–6
170
Airspeed, 160 kn 150
244
242
Magnetic
heading, 240
deg
238
236
5
0
Bank
angle, – 5
deg
–
10
–
15
1.4
1.3
EPR 1.2
1.1
1.0
0
Figure 39. Time history of MD-11 .ight deck simulation ILS-coupled landing, severe turbulence, wind 270° at 15 kn, two-engine pitch mode, Flaps 28.
Honeywell also conducted an analysis to study the statistical probability of ILS-coupled PCA landing success. This analysis is normally used for autoland studies and certi.cation, and includes a full range of variables in weather, aircraft weight, and CG, including turbulence up to severe. Before the study, the problems of the overshoot on glideslope capture and the 2-sec lag in the transition from the glideslope to the .rst .are were corrected. Reference 13 gave results of 400 landings. Results of 100 landings are summarized in .gure 40. All 100 landings were at safe sink rates and bank angles; the touchdown dispersion data are seen to be very good. The ability of the ILS-coupled PCA system to make small thrust changes to correct a deviation immediately provided a major improvement in capability over PCA system pilot-in-the loop control as well as a signi.cant reduction in pilot workload.
Demonstration Flights
The PCA system was demonstrated to many pilots and observers (table 3), representing NASA, airlines,
U.S. Air Force, U.S. Navy, industry, and the Federal Aviation Agency. For each pilot, there was a brie.ng and simulator session. Once in the MD-11 test airplane, each pilot could observe the previous pilot’s demonstration. Then, each of the pilots .ew the pattern shown in .gure 32; most of the tests were .own at Edwards, but some were .own at Palmdale. On the downwind approach leg, they .rst .ew a few minutes of manual throttles-only control, then .ew with the PCA system using the FCP knobs. Usually, both FPA and V/S modes were used in pitch, and track angle (TRK) and bank angle modes were used for lateral control, but FPA and TRK were usually used on the approach. Figure 41 shows typical manual throttles-only .ight control. Even though starting from a trimmed condition in very smooth air, and having some recent simulator experience, pitch control was not good, with excursions of at least ± 3° . Bank angle was typically held within a few degrees, but the task was to hold heading, not to turn and establish a new heading. After PCA was engaged, all were impressed at the immediate improvement in control and the precision of PCA operation being very similar to a normal autopilot.
Flag location indicates touchdown point and height is sink rate
Turbulence from none to severe
Approach
7
6 3Sink 5rate, 4ft/sec 3
970623
Altitude, ft MSL
Airspeed, kn
Flightpath angle, deg
Magnetic heading, deg
Bank angle, deg
EPR
5300 5200 5100 5000 4900
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