Aircraft Accident Brief Ntsb/aab-02/01 (Pb2002-910401): Egypt Air Flight 990, Boeing 767-366er, Su-Gap - National Transportation Safety Board Page 140
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160 of test autopilot disconnects was performed during cruise on a flight from Cairo to
Rome. As was expected, the data recording these disconnects showed no
significant movement of the elevator between autopilot and manual operation at
the moment the autopilot disconnected. This is in contrast to the data for the
EgyptAir 990 airplane where there ware downward elevator deflections when the
autopilot was disengaged.
4.
(Page 9, footnote 22) This footnote is devoted to asserting that during the dive
as reproduced on the simulator, the airplane’s controls could be worked without difficulty. The
NTSB notes, however, that the zero g loads recorded on the FDR could not be duplicated in the
simulator. This is typical of the NTSB’s approach in other areas -- identify a potential problem
and then totally ignore it.
The inability to simulate zero g may be critical in any evaluation of the potential
recoverability of the airplane; yet, the NTSB suggests that identifying the problem is all that it
must do. The issue is important where, as here, the control column force needed to recover the
airplane is much higher than normal and must be sustained by the crew for longer than normal.
Under zero g conditions, it may be difficult, if not impossible, for an unrestrained crewmember
to exert sufficient force on the controls to affect the same recovery demonstrated in the
simulator. Consequently, no conclusions as to probable cause should be based on the purported
recoverability of the airplane.
5.
(Page 15, footnote 32) The routing of the cable in Figure 1a appears to be the
opposite of the routing described in the footnote.
6.
(Page 21-22) The NTSB mischaracterizes the report of the EgyptAir Captain on
the outbound flight to Los Angeles regarding the operation of the autopilot. The important fact
is not that the autopilot could not be reengaged, but rather why Captain Arram disconnected the
autopilot in the first place. With respect to that question, Captain Arram reported that he
observed movement in the control column, as if the autopilot was “hunting.” Because of the
abnormal movement in the control column, he disengaged the autopilot. It is entirely possible
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