Page:CAB Accident Report, American Airlines Flight 383.pdf/12

– 11 – at the coordinate time point of 83 minutes 14 seconds corresponding to a heading of 238 degrees. This mark was not plotted because verification of this prior engraved mark over the last 15 seconds was considered impossible due to a foil aberration.

The acceleration excursions noted throughout the readout were consistent with the maneuvers being performed and, except for the last 50 seconds of flight, no significant turbulence activity was noted. During the last 50 seconds of flight the G trace activity was suggestive of light turbulence computed to be less than 14 feet per second.

In an effort to derive additional information from the flight recorder readout, the recorder data was utilized to develop an envelope of possible engine power/aircraft configuration combinations during the last six minutes of flight. Aerodynamic and mathematical techniques were employed to compute the various thrust and aircraft configuration combination possibilities that would be consistent with the flight recorder parameters of specific points in the descent. It was possible to establish that for the descent from 5,000 feet to 2,000 feet, the only compatible aircraft configuration was; flaps retracted, gear up, spoilers extended, and thrust at idle. For other time intervals during the approach many combinations of these variables would have been consistent with the flight recorder data, and the actual configuration of N1996 for these time intervals could not be conclusively established. However, the study did indicate that with the exception of the level off at 2,000 feet where some thrust would have been required to correlate with the recorder data, the entire descent, 7,000 feet to impact, could have been made at or near idle thrust, gear up and with wing flap extension at or near the AA normal operating flap extension speed schedule.

1.12 Aircraft Wreckage

Examination of the aircraft wreckage at the crash site indicated the first impact was made by the right wing with a tree at an altitude of 665 feet m.s.l. which is approximately 225 feet below the published field elevation. Evidence based on tree damage in the swath path substantiates that the aircraft was in a level attitude on a heading of 235 degrees at the point of initial impact. The aircraft attitude at nose impact was determined to be five degrees noseup; the measured terrain upslope angle at this point was 9.6 degrees. The aircraft slid a distance of 340 feet relatively intact through scrub trees and ground foliage before impacting and coming to rest amidst a group of larger trees.

The major airframe structure and all flight control surfaces were found in the wreckage area. There was no evidence of any inflight separation of the aircraft structure or components.

Examination of the flight control system revealed no evidence of failure or malfunction prior to impact. The horizontal stabilizer was found at a setting of