Page:NTSB Aircraft Accident Report, United Airlines Flight 389.pdf/34

 of the stabilizer. Because the pawl is located in such a position as to be protected from damage during impact a possibility exists that the crew actuated the pawl to stop an unwanted nose up maneuver of the aircraft. It is also possible that the crew initiated an aircraft nose up maneuver just prior to impact and that impact forces caused a subsequent movement of the control column that activated the stabilizer brake and displaced the pawl. However, the position of the stabilizer jack screw in a 0.5 unit aircraft nose up at impact would indicate the pawl position was probably the result of impact. The low torque of the stabilizer trim actuator and the failure of the four flight spoilers to pass a cold soak test are not considered to be in causal relationship to this accident. The worst possible result of this situation would be one or more spoilers failing to extend when selected to the extended position. This would cause an unexpected and unwanted roll condition. However, the evidence indicates that the spoilers were in the down or retracted position at impact and thus an unwanted roll probably was not a problem to the crew. Furthermore, the review of pilot reports of spoiler difficulties indicated they were a high altitude phenomena. The crew of this flight indicated no concern in their last radio contact with the approach controller and were within l5 seconds of impact at the time of the last transmission. The crew had already descended below their assigned altitude of 6,000 feet and the accident was about to occur. Lastly, the evidence indicates the aircraft initially struck the water in a normal descent attitude.

Examination of the recovered components of the hydraulic system reveal no evidence of pre-impact malfunction. The four anti-icing valves were recovered in the closed position which indicates the anti-icing system was "off" at impact. One pilot's directional indicator showed that the course selected,