The National Transportation Safety Board determined today that an engine fire on an American Airlines jetliner was probably due to an unapproved and improper procedure used by mechanics to manually start one of the engines. The fire was prolonged and the safety of the aircraft further jeopardized by how the flight crew handled the emergency. A flawed internal safety management system, which could have identified the maintenance issues that led to the accident, was cited as a contributing factor.
On September 28, 2007, at 1:13 p.m. CDT, American Airlines flight 1400, a McDonnell Douglas DC-9-82 (MD-82), N454AA, experienced an in-flight left engine fire during departure climb from the Lambert-St. Louis International Airport (STL). During the return to STL, the nose landing gear failed to extend, and a go-around was executed. The flight crew conducted an emergency landing, and the two flight crewmembers, three flight attendants, and 138 passengers deplaned on the runway. No occupant injuries were reported, but the airplane sustained substantial damage.
The investigation revealed that a component in the manual start mechanism of the engine was damaged when a mechanic used an unapproved tool to initiate the start of the #1 (left) engine while the aircraft was parked at the gate at STL. The deformed mechanism led to a sequence of events that resulted in the engine fire, to which the flight crew was alerted shortly after take-off.
The Board examined how the flight crew handled the in-flight emergency and found their performance to be lacking. The captain did not adequately allocate the numerous tasks between himself and the first officer to most efficiently and effectively deal with the emergency in a timely manner. The Board was particularly concerned with how the crew repeatedly interrupted their completion of the emergency checklist items with lower priority 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 V. Rosenker. "Unfortunately, the lack of adherence to procedures ultimately led to many of this crew's in-flight challenges."
In examining the maintenance issues, investigators found that in the 13 days prior to the accident flight, the aircraft's left engine air turbine starter valve had been replaced a total of six times in an effort to address an ongoing problem with starting the engine using normal procedures. None of valve replacements solved the engine start problem and the repeated failures to address the issue were not recognized or discovered by the airline's Continuing Analysis and Surveillance System (CASS). "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. Following the appropriate maintenance procedures would have gone a long way toward preventing this mishap."
As a result of the investigation, the Safety Board issued a total of nine safety recommendations. The Board asked the Federal Aviation Administration (FAA) to 1) evaluate the history of air start-related malfunctions in MD-80 airplanes to determine if changes to the cockpit warning system are warranted; 2) ensure that pilots are trained to refrain from interrupting the completion of emergency checklists with nonessential tasks; 3) ensure that MD-80 operators train crews on the interaction of systems involved in engine fire suppression; 4) and 5) ensure that crews are trained to handle multiple emergencies simultaneously; 6) require that crews be trained to prepare the aircraft for an emergency evacuation after a significant event away from the gate; 7) provide flight and cabin crews with the latest guidance on effective communications during emergencies; and 8) 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. A synopsis of the Board's report, including the probable cause, conclusions, and recommendations, is available on the NTSB's website. The Board's full report will be available on the website in several weeks.