American Airlines Airbus Industrie A-300B4-605R A300B4-605 incident

Shortly after takeoff, as the flight climbed through 3,100 feet, the No. 1 engine fire warning activated. About 20 seconds later, the captain, who was the pilot flying, moved the No. 1 throttle to idle and asked the first officer to declare an emergency with air traffic control. About 47 seconds after the first officer identified the No. 1 engine fire warning, the captain asked the first officer to perform the engine fire emergency procedures checklist. The engine fire warning system deactivated because of fire damage to one of the fire loops, about 88 seconds after the fire warning activated and 2 seconds before the first officer moved the No. 1 fuel lever to the off position, shutting down the No. 1 engine. The flight crew did not notice the warning that the No. 1 fire loop system was inoperative. The engine fire warning system uses two loops. If one loop should no longer sense a fire or become inoperative because of fire damage, the engine fire warning will deactivate and a fire loop warning will be displayed to the flight crew. The flight crew must deactivate the faulty loop to regain the engine fire warning. The crew elected to stop the procedure after shutting down the No.1 engine because the fire light went out, and therefore did not activate the No.1 fire handle. Pressurized fuel continued to be supplied to the engine and feed the engine fire. The flight crew turned back to the departure airport. At 2,000 feet, about 3 minutes from landing, a flight attendant reported that a mechanic in the back had stated that the No. 1 engine was still smoking or on fire. The flight crew did not take any action and landed. About 1 minute after stopping, the captain ordered an emergency evacuation of the airplane, with instructions not to use the left overwing exits. About 1 minute 55 seconds after landing, the flight crew pulled the engine and auxiliary power unit fire handles and discharged the fire bottles into the No. 1 engine. In 1995, Airbus changed the engine fire procedure to allow for discontinuing the fire procedure and keeping an engine running at idle after an engine fire warning once the fire warning has gone out and after the throttle has been moved to idle. This change was made because of the high number of bleed air leak activated fire warnings. Postincident examination of the No. 1 engine showed that all the accessory gearbox idler adapter attachment bolt inserts had backed out, allowing fuel lines to unseat and spray pressurized fuel onto hot engine parts and ignite. On September 26, 1995, the accessory gear box idler adapter had been reworked per General Electric Aircraft Engine Service Bulletin 72-743 during engine overhaul at a vendor's facility. Smaller-than-required adapter bolt inserts had been installed.

Verbatim NTSB analysis and probable cause from the NTSB dataset