Aircraft Accident Brief Ntsb/aab-02/01 (Pb2002-910401): Egypt Air Flight 990, Boeing 767-366er, Su-Gap - National Transportation Safety Board Page 141
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160 that the RFO also observed unusual movement in the control column and, like Captain Arram
before him, decided to disconnect the autopilot.
7.
(Page 22) The NTSB states that all of the previous elevator movements on
autopilot disconnect -- which were “primarily in the trailing-edge-down (TED) direction” --
were consistent with “normal operation.” The ECAA is not aware of any Boeing supplied data
that shows a TED movement is expected consistently upon autopilot disconnect and has not been
shown any data or studies to confirm that movement of .88 degrees or less is “normal.”
8.
(Page 23) The discussion of Boeing 767 bellcrank anomalies minimizes the
critical safety aspects represented by these findings and is presented in such a way as to convince
the reader that these types of failures never happened on EgyptAir Flight 990. The report does
not point out that the Egyptian Team was responsible for the identification of the possibility of
bellcrank assembly failures due to rivet shears and PCA jams. The NTSB Systems investigation
refused to address these issues or to bring the safety deficiencies to the attention of the FAA.
The draft report does not discuss the cumulative findings that were developed which suggest that
there was a similar bellcrank/PCA failure associated with EgyptAir Flight 990.
The facts are that, as a result of the safety issues raised during the EgyptAir Flight 990
investigation, the FAA issued two Airworthiness Directives concerning the Boeing 767 bellcrank
assemblies. More than 152 bellcrank assembly rivets were found defective. Of this number, 52
had to be replaced before the airplanes were allowed to fly again. The FAA determined that the
approved Boeing inspection procedure for the rivets was inadequate. Boeing is evaluating
design changes, as the potential terminating action, of the system.
The sheared elevator bellcrank rivets on an AeroMexico Boeing 767 (a fact
acknowledged only in a footnote on page 23), along with the discovery of numerous defective
rivets as a result of the FAA’s August 2000 Emergency AD, are ample proof of unusual and
unexplained forces acting within the Boeing 767 elevator system. These anomalies may well be
related not only to the Flight 990 accident, but also to three other incidents involving the
improper functioning of the Boeing 767 elevator system.
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