Eastern Air Lines Flight 375

Investigation

Investigators, including Operations Group Chairman Bobbie R. Allen with the Civil Aeronautics Board (CAB, the predecessor of the NTSB) determined that engines two and four had each ingested at least one bird, and that engine one had ingested at least eight. The bird damage caused the number one propeller to autofeather and the engine to shut down at the same time that damage to engines two and four prevented them from developing full power at a critical stage of flight. The aircraft, unable to climb, went into a stall. The power interruption to the port engines probably caused the left wing to stall; the wing dropped and the aircraft crashed into the water. There was also evidence that birds had crashed into the windscreen, reducing the pilots' visibility; in addition, bird remains had clogged the pitot tubes, making the pilots' airspeed indicators unreliable.

It was eventually determined that turboprop engines such as those on the Electra were highly sensitive to damage from bird strikes. The CAB recommended to the Civil Aeronautics Administration (CAA, the predecessor of the FAA) that steps be taken to reduce the damage caused by bird strikes to turbine engines, and that ways be found to reduce the populations of birds around airports.

However, another possible factor that came to light later was a maintenance defect in the copilot's seat. During civil litigation by the family of a deceased passenger, it was discovered that the airplane's maintenance records showed that the adjustable seat had accidentally slid backward during a takeoff about six weeks prior to Flight 375. Rather than perform the proper repair of replacing a metal rod, a mechanic used a strand of wire. A subsequent maintenance check on September 19 showed that the copilot's seat would not lock in any position; it was left in that condition. Expert testimony during the trial claimed that the co-pilot of Flight 375 (who during an emergency would typically be flying the plane while the pilot attempts to locate and solve the problem) most likely pushed the rudder pedal to compensate for unexpected yaw. In doing so, it was surmised that this foot pressure caused the seat to slide backward, which caused him to inadvertently pull back on the yoke. This nose-up condition could have been the decisive stall that caused the final plunge into the water.