An unapproved and improper procedure used by mechanics to manually start the left engine on an American Airlines jetliner on Sept. 28, 2007, probably caused a fire that forced an emergency landing, the NTSB determined today.
The Board also found that the flight crew’s handling of the emergency prolonged the engine fire and further jeopardized the safety of the flight. Finally, the NTSB cited as a contributing factor American’s flawed internal safety management system (SMS), which, it said, could have identified the maintenance problems that led to the accident.
During the incident in question, American Airlines Flight 1400, a McDonnell Douglas MD-82, experienced an in-flight left engine fire during departure climb from St. Louis Lambert International Airport. During the return to St. Louis, the nose landing gear failed to extend, and the crew executed a go-around. The flight crew successfully conducted an emergency landing, and the two flight crewmembers, three flight attendants and 138 passengers deplaned on the runway. No one suffered injuries, but the airplane sustained substantial damage.
The investigation revealed that a mechanic damaged a component in the manual start mechanism of the left engine with an unapproved tool while the aircraft sat at the gate in St. Louis. The deformed mechanism led to a sequence of events that resulted in the engine fire.
The Board examined how the flight crew managed the in-flight emergency and found that the captain did not effectively allocate the numerous tasks he and his first officer needed to conduct to deal with the emergency in a timely way. The Board expressed particular concern with how the crew repeatedly interrupted their completion of the emergency checklist items with less vital tasks.
“Here is an accident where things got very complicated very quickly and where flight crew performance was very important,” said NTSB acting chairman Mark Rosenker. “Unfortunately, the lack of adherence to procedures ultimately led to many of this crew’s in-flight challenges.”
Investigators also found that in the 13 days before the accident flight, mechanics had replaced the aircraft’s left engine air turbine starter valve six times in an effort to address an ongoing problem with starting the engine using normal procedures. None of the valve replacements solved the engine start problem, and the airline’s Continuing Analysis and Surveillance System (CASS) did not recognize or discover the repeated failures.
“The airline’s own internal maintenance system, the purpose of which is to catch maintenance and mechanical issues that could lead to an incident or accident, failed to do what it was designed to do,” said Rosenker. “And that allowed this sequence of events to get rolling, which ultimately resulted in the accident.”
The Safety Board has issued nine safety recommendations as a result of this investigation. Specifically, the Board asked the FAA to evaluate the history of air start-related malfunctions in MD-80s to determine the need for changes to the cockpit warning system; ensure that pilots receive training that stresses they refrain from interrupting the completion of emergency checklists with nonessential tasks; ensure that MD-80 operators train crews on the interaction of systems involved in engine fire suppression; ensure that crews receive training in handling multiple emergencies simultaneously; require training related to the preparation of the aircraft for an emergency evacuation after a significant event away from the gate; provide flight and cabin crews with the latest guidance on effective communications during emergencies; and require Boeing to establish an interval for servicing an engine component.
The Board also recommended that American Airlines evaluate and correct deficiencies in its CASS program.