Page:CAB Accident Report, American Airlines Flight 383.pdf/13

– 12 – 5-1/2 degrees airplane noseup which is in the normal range. No reliable trim settings could be obtained for the aileron and rudder controls due to extensive impact damage to these components. The nose gear, two main landing gears and tail skid were found in the retracted and locked position.

The trailing edge flaps were in the 25-degree extended and locked position at impact as determined from the aileron lockout actuator and flap jackscrew measurements. All of the leading edge devices were found in the full extended position. All in-flight and ground spoilers were retracted.

The hydraulic and electrical systems were examined thoroughly and no evidence was found to indicate any pre-impact failure or malfunctions. No determination could be made as to the operating condition of the pilot static or autopilot systems due to severe impact and ground fire damage. Both air-condition pack shutoff valves were found in the open position.

All three engines were recovered from the wreckage. The Nos. 1 and 3 engines had separated from the fuselage during the final impact sequence while the No. 2 engine remained attached to its engine mount in its proper location.

Subsequent disassembly and inspection revealed that the three engines had ingested tree wood, mud, and twigs during the impact sequence. This debris was distributed from the air inlet section through the turbine sections of each engine. The No. 1 engine high compressor assembly was damaged extensively with the seventh, eight, and ninth stage blades all broken off at the blade platform. Blades were also broken in the tenth, eleventh, and thirteenth compressors stages and all blades not broken were bent in a direction opposite to rotation. The No. 3 engine compressor section was damaged extensively with stator vanes and fan blades bent or broken. Those blades not broken were bent in a direction opposite to rotation. Evidence of rotation on the No. 2 engine was established by mud and debris which was wiped in the track of the first stage fan blades. There was no significant damage to the compressor or turbine assemblies and the engine was free to rotate.

Metal impingement was noted on the combustion chamber heads, nozzle guide vanes and turbine sections of all three engines. Impingement was heaviest on the first stage turbine blades and diminished progressively through the remaining stages.

The engine pressure ratio (EPR) transmitters, one for each engine, were recovered completely undamaged. Testing of these units indicated that all were within calibration tolerance; however, no valid information could be obtained as to engine power settings at impact.

The complete examination of all three engines revealed no evidence of any failure, malfunction, or operating distress prior to impact.

All of the flight and engine instruments located in the cockpit were either damaged severely or destroyed by impact forces or fire. None of the recovered instruments could be functionally tested due to the severity of the damage incurred.

The two VHF navigational receivers installed on the aircraft were recovered but because of damage, the selected frequencies could not be obtained. Only one badly distorted radio frequency selector control panel was recovered. Positions of the