Faulty maintenance blamed in MD engine fire

 - April 30, 2009, 11:51 AM

Two veteran American Airlines pilots, who in the words of the NTSB were “not having a good day,” nevertheless used “some exceptional stick-and-rudder skills” to get their crippled MD-82 safely back to Lambert-St. Louis International Airport (STL) after experiencing an in-flight engine fire during the airliner’s departure climb on Sept. 28, 2007.

During the return to STL, the nose landing gear on Flight 1400 failed to extend because of the loss of hydraulic pressure, so the pilots executed a single-engine go-around and lowered the nosegear using the emergency procedure. After the crew completed an emergency landing, the two pilots, three flight attendants and 138 passengers deplaned on the runway. No injuries were reported, but the airplane was substantially damaged by the fire.

The NTSB determined that the engine fire probably stemmed from an unapproved and improper procedure used by mechanics to start the left engine manually. The fire was prolonged and the safety of the MD-82 further jeopardized by how the crew handled the emergency, including a two-minute interruption to the engine-fire checklist.  

According to the Safety Board, the use of an inappropriate manual engine-start procedure led to the uncommanded opening of the left engine air turbine starter valve and a subsequent left engine fire, which was prolonged by the flight crew’s interruption of an emergency checklist to perform nonessential tasks. Contributing to the accident were deficiencies in American’s Continuing Analysis and Surveillance System (CASS) program, the airline’s internal maintenance system.

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 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 takeoff.

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 deal effectively with the emergency.

The Board was particularly concerned about the fact that the crew repeatedly interrupted their completion of the emergency checklist items with lower-priority tasks, and this interruption–coupled with cascading systems failures–increased the pilots’ workload. The Safety Board also criticized the cockpit crew for a communications breakdown with the flight attendants.

NTSB acting chairman Mark Rosenker described the episode as an accident where things got complicated quickly and where flight crew performance was important. “Unfortunately,” he said, “the lack of adherence to procedures ultimately led to many of this crew’s in-flight challenges.”

Pre-existing Problem Not Solved

In examining the maintenance issues, investigators found that in the 13 days before the accident flight, the aircraft’s left engine air turbine starter valve had been replaced 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 American’s CASS did not discover the repeated failures to address the issue.

“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.”

Although it deemed the captain’s decision to initiate a go-around to be “a reasonable choice,” the NTSB faulted the crew for the “lack of a sterile cockpit” while taxiing and for their response to the engine-fire warning light. Noting that while the pilots were “seasoned” and “professional,” Rosenker said, “What I heard on the CVR [cockpit voice recorder] seems to belie that.”