Prevailing Cultural / Organizational Factors

At the time of the accident, the McDonnell-Douglas Model DC-10 was relatively new in airline service. The airplane design also incorporated relatively new technology in many systems with which flight crews were unfamiliar. Just prior to the fan separation event, the flight crew was discussing the autothrottle system, and where the engine rotor speed signals for the autothrottle originated. This discussion led to a quickly organized experiment to determine the signal source. The experiment resulted in all three engines accelerating to speeds which had not been commanded by the flight crew, and had the immediate effect of initiating the interactive mode on the number 3 engine and the rapid separation of the inlet and fan.

Experimenatation of this type, while not authorized, has been noted during the course of other investigations involving new aircraft and/or technologies. Knowledge of system interactions and basic system function is important for a flight crew and fundamental to the proper conduct of flight operations. However, it is more appropriately conducted during initial aircraft evaluation and dedicated flight testing, not revenue service. This flight crew, while exercising their normal curiosity about their airplane, inadvertently triggered an unexpected event that led to the destruction of one engine and the accident sequence of events.

Back to top