Aircraft Accident Brief Ntsb/aab-02/01 (Pb2002-910401): Egypt Air Flight 990, Boeing 767-366er, Su-Gap - National Transportation Safety Board Page 11
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160 5
Between 0149:57 and 0150:05, the relief first officer quietly repeated, “I rely on
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God,” seven additional times.
During this time, as a result of the nose-down elevator
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movement, the airplane’s load factor
decreased from about 1 to about 0.2 G.
Between
0150:04 and 0150:05 (about 10 to 11 seconds after the initial nose-down movement of the
elevators), the FDR recorded additional, slightly larger inboard aileron movements, and
the elevators started moving further in the nose-down direction. Immediately after the
FDR recorded the increased nose-down elevator movement, the CVR recorded the sounds
of the captain asking loudly (beginning at 0150:06), “What’s happening? What’s
happening?,” as he returned to the cockpit.
The airplane’s load factor decreased further as a result of the increased nose-down
elevator deflection, reaching negative G loads (about -0.2 G) between 0150:06
and 0150:07. During this time (and while the captain was still speaking [at 0150:07]), the
relief first officer stated for the tenth time, “I rely on God.” Additionally, the CVR
transcript indicated that beginning at 0150:07, the CVR recorded the “sound of numerous
thumps and clinks,” which continued for about 15 seconds.
According to the CVR and FDR data, at 0150:08, as the airplane exceeded its
maximum operating airspeed (0.86 Mach), a master warning alarm began to sound. (The
warning continued until the FDR and CVR stopped recording at 0150:36.64
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and 0150:38.47, respectively.)
Also at 0150:08, the relief first officer stated quietly for
the eleventh and final time, “I rely on God,” and the captain repeated his question,
“What’s happening?” At 0150:15, the captain again asked, “What’s happening, [relief first
officer’s first name]? What’s happening?” At this time, as the airplane was descending
through about 27,300 feet msl, the FDR recorded both elevator surfaces beginning to
move in the nose-up direction. Shortly thereafter, the airplane’s rate of descent began to
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decrease.
At 0150:21, about 6 seconds after the airplane’s rate of descent began to
decrease, the left and right elevator surfaces began to move in opposite directions; the left
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Throughout the FDR data for the accident airplane (including data recorded during uneventful
portions of the accident flight and during previous flights and ground operations), small (less than 1° )
differences between the left and right elevator surface positions were observed. The left and right elevator
surface movements were consistent (that is, moved in the same direction about the same time) where these
offsets were observed. According to Boeing, there are several factors that could result in differences between
the left and right elevator surfaces, including rigging of the elevator control system, tolerances within the
system’s temperature compensation rods, routing differences between the left and right elevator control
cables, friction distribution within the system, the accuracy of the sensors used to measure elevator position,
and differences in FDR sampling times for the left and right elevator parameters.
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Although earlier statements made by the relief first officer were recorded by the hot microphone at the
first officer’s position, the “I rely on God” statements were not, which was consistent with these statements
being spoken relatively quietly. For additional information, see the section titled, “Audio Information
Recorded by First Officer’s Hot Microphone.”
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An airplane’s normal load factor is approximately perpendicular to the airplane’s wings. Although
the terms “vertical load factor,” “vertical acceleration,” and “normal load factor” are often used
interchangeably, for the purposes of this document, the term “load factor” is used.
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A G is a unit of measurement of force on a body undergoing acceleration as a multiple of its weight.
The normal load factor for an airplane in straight and level flight is about 1 G. As the load factor decreases
from 1 G, objects would become increasingly weightless, and at 0 G, those objects would float. At load
factors less than 0 G (negative G), loose objects would float toward the ceiling, and, at -1 G, those objects
would accelerate toward the ceiling.
NTSB/AAB-02/01
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