NTSB/AAR-02/01

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Factual Information 64 Aircraft Accident Report movement of the horizontal stabilizer, the CVR recorded the sound of the stabilizer-in-motion tone for 3 to 4 seconds. During the next several seconds, the load factor oscillated between 0.4 and 1.0 G, and the elevators moved to the trailing-edge-up direction from -0.4° to -7.0°, 123 consistent with control inputs being made to bring the nose up. • By 1609:42, the airplane had descended to approximately 29,450 feet and had accelerated to about 322 KIAS. At this time, the airplane’s pitch angle was -7.9° airplane nose down, and the elevators had moved to about a -8° position. The speed brakes deployed 1 second later and remained deployed for the next 1 minute 30 seconds. • At 1610:00, the airplane was accelerating through 343 KIAS (the airplane’s maximum allowable airspeed). At 1610:<strong>01</strong>.9, the CVR recorded the sound of the overspeed warning. • By 1610:16, the airplane had accelerated to 353 KIAS, the maximum airspeed it reached during the initial dive, and this airspeed remained nearly constant until 1610:23 as the airplane was descending through 24,200 feet. By this time, the airplane’s pitch angle had increased from -8° to -5° airplane nose down, and the elevators had moved to about a -11° position. • About 1611:13, the speed brakes were stowed. By this time, the airplane’s airspeed had decreased to 262 KIAS, and the airplane was maintaining an altitude of approximately 24,400 feet with a pitch angle of 4.4°. During the next 10 seconds, the airplane’s airspeed decreased to 254 KIAS. The airplane remained between 23,000 and 24,000 feet for the next 5 minutes, and the airspeed gradually increased to 335 KIAS. During this period, elevator movements ranged from between -7° to -9°. Airplane performance calculations indicated that a control column force of between about 130 and 140 pounds was required to recover from the dive. 124 • At 1614:44, the speed brakes deployed again, and the airplane’s airspeed began to decrease. • At 1617:50, the speed brakes were being stowed. By this time, the airplane had leveled off at approximately 18,000 feet, and the airspeed had decreased to 253 KIAS. At this time, the elevators were operating between -10° and -13°, and the airplane’s pitch angle was between -2° and 0°, with a constant indicated horizontal stabilizer angle of 2.5° airplane nose down. • At 1617:54, the CVR recorded the captain order deployment of the slats. About 1618:00, when the airplane was passing through 17,800 feet at 252 KIAS, the FDR recorded the extension of the leading edge slats. About 1618:05, the CVR recorded the captain order deployment of the flaps. About 3 seconds later, the flaps began extending to 11°, and the airspeed 123 The available range of the airplane’s elevators is from +15° to -25°. 124 As stated previously, this estimated force could be applied by either the captain, the first officer, or both.
Factual Information 65 Aircraft Accident Report decreased about 4 knots. The flaps remained at this value for about 20 seconds, during which time the airplane’s pitch angle was about 0°, with changes of less than 1°. About 1618:26, the CVR recorded the captain order retraction of the slats and flaps. During the 50 seconds after retraction of the slats and flaps, the airplane’s indicated airspeed increased from 245 to 270 knots, and the airplane climbed from approximately 17,400 to 17,900 feet with a pitch angle of about 4°. • Beginning at 1619:09, the FDR recorded small oscillations in elevator angle, pitch angle, and vertical acceleration values for about 15 seconds. • At 1619:21, the CVR recorded the sound of a faint thump. At 1619:21.5, the FDR recorded a 0.09° change, from 2.51° to 2.60°, in the horizontal stabilizer position (this was the first change in recorded horizontal stabilizer position since the one that coincided with the airplane’s initial dive from 31,050 feet about 10 minutes earlier) and elevator deflections increasing from -9° to -13°. Pitch angle and elevator oscillations ceased 2 seconds after the stabilizer position changed. • At 1619:29, the CVR recorded the captain order redeployment of the slats and flaps. At 1619:35, when the airplane was at an altitude of 17,900 feet, an indicated airspeed of 270 knots, and a pitch angle of 2°, the flaps were transitioning from 7° to 11°. • At 1619:36, the left elevator value was -12°, the right elevator value was -11°, and the load factor was 1 G. At 1619:36.6, the CVR recorded an extremely loud noise, and the FDR recorded a right elevator position of -25°. 125 By 1619:36.6, the load factor had increased to 1.45 Gs. At 1619:36.9, the pitch angle began to change to the airplane-nose-down direction, and the load factor decreased to 0.67 G. At this time, radar data detected several small primary returns. Within 3 seconds, the load factor quickly decreased to -3 Gs. The next several seconds of FDR data indicated a maximum airplane-nose-down pitch rate of nearly 25° per second. • By 1619:40, the airplane was rolling left wing down, and the rudder was deflected 3° to the right. • By 1619:42, the airplane had reached its maximum valid recorded airplane-nose-down pitch angle of -70°, and the load factor had increased to -1.45 Gs. At this time, the roll angle was passing through -76° left wing down. During the next 2 seconds, the load factor decreased to -2.1 Gs. • By 1619:45, the load factor had increased to -1.75 Gs, the pitch angle had increased to -28°, and the airplane had rolled to a -180° inverted position. Further, the airplane had descended to approximately 16,420 feet, and the indicated airspeed had decreased to 208 knots. 125 All subsequent recorded elevator values exceeded the physical ranges of the airplane’s elevator system and were considered invalid.
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Aircraft Accident Report Loss of Co
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National Transportation Safety Boar
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Contents iv Aircraft Accident Repor
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Contents vi Aircraft Accident Repor
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Figures viii Aircraft Accident Repo
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Abbreviations x Aircraft Accident R
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Executive Summary xii Aircraft Acci
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Factual Information 2 Aircraft Acci
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Factual Information 10 Aircraft Acc
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Factual Information 12 Aircraft Acc
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Factual Information 114 Aircraft Ac
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Analysis 126 Aircraft Accident Repo
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Conclusions 176 Aircraft Accident R
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Recommendations 182 Aircraft Accide
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Board Member Statements 188 Aircraf
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5. Appendixes Appendix A Investigat
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Appendix B 193 Aircraft Accident Re
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INTRA-COCKPIT COMMUNICATION AIR-GRO
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NTSB/AAR-02/01

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