Overhaul blunder behind in-flight 747-200 freighter fire

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After more than nine years, German investigators have revealed that a maintenance error caused an in-flight fire to break out on a Lufthansa Cargo Boeing 747-200 freighter's forward deck.

Several electrical circuit-breakers tripped as the aircraft reached its 31,000ft (9,450m) cruise altitude, after departing Sharjah. But while the crew sensed an electrical burning smell, and repeatedly checked the main deck, they could not detect anything untoward.

The 747, however, had sustained serious fire damage, for which evidence was discovered after the aircraft landed at Frankfurt. During the descent the crew had been unable to extend two of the slats and the approach was conducted at a speed 25kt (46km/h) higher than normal.

Examination of the lower cargo compartment revealed partially scorched insulation across the whole area of the oxygen bottles up to the main deck. There was a palm-sized hole in the dado vent box, with severe fire damage to nearby insulation, and there were smoke and heat traces on parts of the fuselage structure.

"The discovered smoke and heat traces and the damage indicate a cable fire with open flames - the flames themselves had gone out," says German investigation authority BFU.

It identifies the aircraft involved as a 747-200SF operated by Lufthansa after it was converted by Israel's Bedek Aviation Group. The dado boxes - which aid air circulation - were installed during conversion. However, these were larger than the originals and the BFU believes that, during a 2002 maintenance D-check in Singapore, necessary spacing from wiring bundles was not implemented when the dado box was reassembled.

Chafing of the wire bundle, which included a galley power line, led to a short-circuit and cable fire. The BFU adds that, probably during the D-check, the galley power line had been tied to the wire bundle for the flap control - against the manufacturer's design practices - resulting in the partial flap failure. BFU has just released the report into the 6 March 2003 event. The aircraft has subsequently been transferred to freight operator Evergreen.