Boeing 767-324, G-OOBL
During pre start-up checks, a burning smell was identified in the rear of the aircraft cabin. Following investigation by the captain, it was decided to disembark the passengers. During the disembarkation, it was reported that the aircraft was on fire. The captain made a MAYDAY call to ATC, switched off all aircraft power and exited the aircraft. Examination revealed that the unloader check (non-return) valve between the potable water tank and the potable water air compressor had failed which allowed moisture/liquid into the air compressor which in turn, caused the air compressor to lock-up. The thermal cut-out switch associated with the electric motor that powered the potable water air compressor cycled until it eventually welded/fused in the ON position allowing a constant supply of electrical power to the compressors’ motor causing it to severely overheat.
Boeing 767-324, G-OOBL 10-09.pdf (282.44 kb)