United Airlines Flight 811 - Personal Investigation

Personal Investigation

Lee Campbell, a native New Zealander returning home, was one of the casualties on Flight 811. After his death his parents, Kevin and Susan Campbell, investigated the cause of the decompression independently of the National Transportation Safety Board. The Campbells' investigation led them to conclude that the design of the aircraft's cargo door latching mechanism was flawed.

As early as 1975, Boeing realized the aluminum locking sectors were of too thin a gauge to be effective and recommended the airlines add doublers to the locking sectors. In 1987 Pan Am Flight 125 outbound from London Heathrow Airport encountered pressurization problems at 20,000 feet (6,100 m), causing the crew to abort the flight and return to the airport. After the safe landing, the aircraft's cargo door was found to be ajar by about 1.5 inches (3.8 cm) along its ventral edge. When the aircraft was examined in a maintenance hangar, all of the locking arms were found to be either damaged or sheared off entirely. Boeing initially attributed this to mishandling by ground crew. To test this concern, Boeing instructed 747 operators to shut and lock the cargo door with the external handle, and then activate the door-open switch with the handle still in the locked position. Since the S-2 switch was designed to deactivate the door motors if the handle was locked, nothing should have happened. Some of the airlines reported the door motors did indeed begin running, attempting to force the door open against the locking sectors and causing damage to the mechanism.

Soon after the Pan Am incident in 1987, Boeing had issued a Service Bulletin notifying operators to replace the aluminum locking sectors with steel locking sectors, and carry out various inspections. In the United States, the FAA mandated this service by means of an Airworthiness Directive (AD) and gave US-flag airlines 18 months to comply with the AD. After the Flight 811 incident, the FAA shortened the time to 30 days.

In 1991, an incident occurred at New York's John F. Kennedy International Airport involving the malfunction of a United Airlines Boeing 747 cargo door. At the time, United Airlines' maintenance staff were investigating the cause of a circuit breaker trip. In the process of diagnosing the cause, an inadvertent operation of the electric door latch mechanism caused the cargo door to open spontaneously. This incident led to latch damage similar to that observed on the cargo door of Flight 811.

Two pieces of the Flight 811 cargo door were recovered from the Pacific Ocean on September 26, 1990 and October 1, 1990.