Aircraft Accident Brief Ntsb/aab-02/01 (Pb2002-910401): Egypt Air Flight 990, Boeing 767-366er, Su-Gap - National Transportation Safety Board Page 148
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160 simulator results and Boeing’s calculated predictions. Without further study, it is not possible to
determine the margin of error. It is, however, clear that many of the NTSB’s factual assertions
are derived from faulty simulator tests.
23.
(Page 48) The assertion that “calculations” showed that there would initially be 6
degree nose-down elevator deflection is accurate, but misleading. As noted above, this number
was derived from Boeing calculations -- not from testing -- that could not be replicated on a real
airplane, thus raising a significant question as to their validity. The simulator was then
programmed to produce a 6 degree nose-down deflection as shown in NTSB figure 2. The clear
implication of the NTSB’s text and its charts is that the dual PCA jam testing produced certain
results that did not “match” the FDR. This is simply not the case because the test parameters
were nothing more than Boeing’s calculations. Consequently, none of the testing confirmed
Boeing’s calculations. Indeed, it was just the opposite as shown by the ground tests. Therefore,
the NTSB’s assertions that a dual PCA jam would produce a deflection of 6 degree nose-down
on the failed side and 4 degree nose-down on the non-failed side suggests a degree of precision
not warranted by any of the tests conducted during the investigation. The error built into the
simulator testing along with normal variations in airplane performance make it impossible to
conclude (with any reasonable scientific certainty) that Flight 990 was not affected by a dual
PCA jam.
24.
(Page 50) In an effort to convince the reader that the simulation results were
valid, the NTSB states (a) that the simulator reflected the flight characteristics “to the maximum
extent possible,” (b) that all flight conditions “were calculated correctly,” and (c) that the out-
the-window view replicated the visual cues during actual flight. Again, these statements are both
misleading and inaccurate. Even if the simulator reflected the EgyptAir 990 characteristics “to
the maximum extent possible,” the NTSB has omitted any discussion of the inaccuracies in the
modeling and whether those inaccuracies affected the test results. As noted previously, the
ECAA believes that there were sufficient inaccuracies in the data used in the simulator which,
when combined with the limitations of the simulator, produced inaccurate results. In particular,
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