Event CHI97IA041

Factual narrative

On December 11, 1996, at 1338 central standard time (cst), a Boeing 757-225, N603AU, operated as USAir Flight number 158, experienced an inflight cabin fire while at cruise altitude. The fire was extinguished by cabin attendants. The flight diverted to Hulman Field, Terre Haute, Indiana, and landed without further incident. The 14 CFR Part 121 passenger flight was operating on an IFR flight plan. The seven person flight crew and 177 passengers reported no injuries. The flight departed Phoenix, Arizona, at 1050 cst. Written statements from Flight 158's flight attendants said that they had noticed an electrical smell in the aft cabin while N603AU was parked at its passenger gate in Phoenix, Arizona. One flight attendant said there was a "...strong electrical smell..." in the rear of the airplane. She said she informed the first officer about the odor. The first officer came to the area where the odor was, according to the flight attendant. She said, "By the time he came back the smell had weakened somewhat." The flight attendant said the first officer thought the smell "...may have had something to do with starting the APU." According to the flight attendant, the first officer called a mechanic. She said the mechanic inspected the area in question and said there was nothing wrong. According to the captain of Flight 158, the flight was "...cruising at FL 370 when a flight attendant advised the cockpit that there was an unusual odor in the aft cabin." The captain said he suggested that the flight attendant pull the rear galley's circuit breakers to get rid of the odor. The odor had decreased, according to the captain. He said the flight attendant reported the odor's return a short time later. The captain said he looked into the situation and found an odor present in the aft cabin. He returned to the cockpit and lowered the aft cabin temperature. The captain said the flight attendant reported the odor was increasing and that smoke and fire were coming from the floor. He said an emergency was declared and the airplane made an emergency decent and landing at Hulman Field. Before landing, the flight attendant reported the fire had been extinguished. An on-scene investigation was conducted by a Federal Aviation Administration (FAA) Principal Maintenance Inspector (PMI). According to the PMI, "Just aft of seat 25ABC, there were 3 burned areas on the sidewall covering at points where corners of the vent panel touch the sidewall." Wiring in these areas was also found burnt. The wiring was associated with an audio entertainment system. The PMI said the system's circuit breaker had popped out. The airplane was ferried to Pittsburgh, Pennsylvania, for inspection and repair. The audio entertainment system was installed under a supplemental type certificate (STC) number SA5537NM. The STC had been granted to Hughes-Avicom International, Incorporated of Pomona, California, on March 5, 1992, by the FAA's Los Angles, California, Systems and Equipment Branch. A representative from the FAA's Pittsburgh, Pennsylvania, Flight Standards District Office (FSDO) participated in the inspection. He reported the following: 1) N603AU had electrical cables mis-installed at 6 different seat rows. 2) About half these cables exited the riser panel next to the floor and were incorrectly attached to the seat connection. 3) These cables exited jagged holes and had enough slack in them so that a passenger's foot could become entangled in them. 4) Other cables were jammed between the sidewall and riser panels. 5) Three cables had covering that was frayed with exposed wire. 6) Most of the cable exiting the riser panels had been routed to the seat while under the cabin carpeting. Three other Boeing 757-225's were examined by the Pittsburgh-based FAA PMI. He reported that each airplane had similar installation discrepancies. He said these discrepancies were counter to accepted maintenance practices and information contained in the STC. N603AU's audio entertainment system was installed by Sabre-Tech, Incorporated, Phoenix, Arizona. During conversations with a company representative it was said that the company's employees followed the STC's instructions during the system's installation. The STC holder was contacted regarding installation procedures stated on the STC's instructions and drawings. A representative from that company said that specific instructions on how to install the system's cable was not provided with the STC. He said they assumed that standard maintenance practices for wiring and cable installation would be followed. The STC stated, "Actual cable routing to be determined on aircraft." The STC did show that the cables were to be routed under the seat track cover next to the carpeting. This was not done on N603AU. Because of the incident on Flight 158, USAir decommissioned all the Boeing 757-225 audio entertainment systems until they are properly repaired. USAir developed a Campaign Directive (CD) that was accepted by the Pittsburgh-FAA/FSDO. The CD incorporates modifications to the entertainment system's installation. Each Boeing 757-225 equipped with the STC'd system will be modified according to the CD. Before departing on a scheduled passenger flight, a flight attendant noticed an electrical odor in the airplane's rear section. She advised the first officer, who consulted a mechanic. The mechanic found nothing wrong, and the flight departed a short time later. While en route, a flight attendant reported an electrical odor in the same area. After an investigation by the captain, the odor diminished, and the rear cabin temperature was lowered. Shortly after this action, smoke and fire were visible in the floor and side wall area. The captain declared an emergency and diverted to an alternate airport. During approach to the airport, the fire was extinguished, then an uneventful landing was made. Examination of the burned area revealed an audio-entertainment system cable had become shorted. Burning had resulted in minor damage to the airplane. Further investigation revealed that the cable had not been properly installed, and that the STC did not provide specific instructions for cable routing, except that it should be placed under a seat rail cover. Source: NTSB Aviation Accident Database (Pre-2008 Archive) Retrieved: 2026-02-12