Aircraft Accident Brief Ntsb/aab-02/01 (Pb2002-910401): Egypt Air Flight 990, Boeing 767-366er, Su-Gap - National Transportation Safety Board Page 46

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3.0
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
8
ELEVATOR & STAB TRAILING EDGE UP
6
4
2
Left Elevator
Right Elevator
Stabilizer (Units)
0
-2
-4
ELEVATOR & STAB TRAILING EDGE DOWN
-6
01:49:40
01:49:45
01:49:50
01:49:55
01:50:00
01:50:05
01:50:10
01:50:15
01:50:20
01:50:25
01:50:30
01:50:35
01:50:40
ACK ASR-9 Time, HH:MM:SS EST
Figure 4. Graphs depicting the accident airplane’s normal load factor response to
elevator and stabilizer movement.
Potential Causes for Elevator Movements During the Accident Sequence
Investigators used Boeing’s six-degree-of-freedom, full-flight engineering
simulator (which incorporated, to the maximum extent possible, the flight characteristics
of the 767) to evaluate whether the accident airplane’s recorded pitch motions were
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consistent with the elevator position movements recorded on the FDR.
The results
showed that the elevator movements required to make the simulator duplicate the pitch
motions and flightpath recorded on the FDR were consistent with the elevator movements
recorded by the FDR throughout the recorded data, even during the time that the data
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The simulator data are based on wind tunnel tests and updated with available flight test data. The
maximum Mach number for which the simulator is programmed (Mach 0.91) corresponds to the airplane’s
never-exceed airspeed. The maximum speed calculated for the accident airplane during the accident
sequence was Mach 0.99 at 0150:23. To evaluate the performance of the airplane at Mach numbers greater
than 0.91, the simulator’s database was adjusted to reflect extrapolations, based on 777 wind tunnel tests.
(The 767 and 777 have aerodynamically similar horizontal stabilizers and elevators.)
NTSB/AAB-02/01

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