Lufthansa Cargo B742 near Sharjah on Mar 6th 2003, cable fire on board

Last Update: August 21, 2012 / 13:52:10 GMT/Zulu time

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Incident Facts

Date of incident
Mar 6, 2003

Classification
Report

Aircraft Registration
D-ABZA

Aircraft Type
Boeing 747-200

ICAO Type Designator
B742

A Lufthansa Cargo Boeing 747-200 freighter, registration D-ABZA performing a freight flight from Sharjah (United Arab Emirates) to Frankfurt/Main (Germany) with 3 crew, had just reached FL310 after climbing out of Sharjah when autopilot B, autothrottle and electrical power supply for the galley dropped offline by themselves, altimeter #2 changed to stand by mode, and circuit breakers for galley power control, trailing edge flaps asymmetry and fail, alternate leading edge flaps drive #1 and #4, alternate inboard trailing edge flap drive and inboard flap control tripped. The crew was able to re-engage autopilot, autothrottle and altimeter #2, but did not attempt to reset the circuit breakers. A slight smell of burnt wires was noticed in the cockpit, the flight engineer noticed a stronger smell in the galley of the main deck, however, no indications of smoke or fire were noticed. As no further systems were affected the crew decided to continue the flight but checked the galley every 15 minutes. On approach to Frankfurt slats #1 and #3 could not be extended, the trailing edge inboard flap indicators remained in the position retracted even though the flaps did extend. The crew used an approach speed 25 knots higher than normal and managed a safe landing at Frankfurt.

Germany's Bureau for Aviation Accident Investigation (BFU) released their final report concluding the causes of the serious incident were:

The cause for the cable fire was an insufficient distance between the dado vent box at STA 780 and the wire bundle running behind it. The short circuit and cable fire were caused by the continued chafing of a bolt of the dado vent box with a wire bundle for the power supply for the galley. The faulty re-assembly of the dado vent box in connection with the wire bundle running behind it probably occurred during a D Check in Singapore in 2002.

The non-existent separation of supply lines with other lines caused the partial failure of the flaps.

The air circulation between the main and lower deck through the dado vent boxes probably aided the extension of the fire.

The BFU reported that after landing and unloading of the cargo the wall panels in the lower cargo compartment were removed. The whole area of the oxygen bottles showed partially scorched insulation. Further removal showed the aluminium structure of the dado vent box STA 780 close to the cargo deck had received a hole of about 5 by 10 centimeters/2 x 4 inches as result of fire. Two wire bundles running behind the box and the insulation showed signs of severe fire damage. Smoke and heat traces were found within the pressurized fuselage structure. Underneath the vent box an area of one square meter of insulation was scorched. The oxygen bottles for the flight crew remained undamaged.

The BFU reported the damaged wire bundles contained the power supply for the upper galley (up to 150kVA, 3 phases at 115V), one other contained 80 wires for various aircraft systems like flap and slat control, ice protection and cargo handling.

When the other dado boxes were checked a number were found chafing against the cables behind them. The wire bundles had been installed in 1985, the boxes were later added in 1992 during reconstruction.

The BFU reported that the dado boxes were several inches wider than the original. In addition, contrary to the delivery status, the supply line for the upper galley was connected with the wire bundle for flap control through a plastic cable tie. This practise was not compliant with the manufacturer's standard design practises.

The BFU reported the reconstruction was carried out by Bedek Aviation Group in Israel. Two more aircraft of the operator had been reconstructed by this organisation, checks of these two aircraft showed that the wires behind the dado vent boxes were extra insulated.

The BFU analysed the damage indicated a cable fire with open flames had occurred, the flames extinguished by themselves. The primary power supply to the upper galley was found damaged in a way that caused a short circuit. This caused damage to the parallel wire bundle and tripped several circuit breakers causing the flap indication to be faulty and the malfunction of parts of slats.

The cable fire was likely caused by chafing of one of the dado vent box's bolts with the wire bundle containing the power supply lines for the upper galley.

In 2002 a D check of the aircraft had been conducted. The BFU assumes that the dado boxes were removed and the wire bundles loosened as is common during such checks. It is likely that during re-installation the necessary distance between box and wire bundles was not adhered to.
Incident Facts

Date of incident
Mar 6, 2003

Classification
Report

Aircraft Registration
D-ABZA

Aircraft Type
Boeing 747-200

ICAO Type Designator
B742

This article is published under license from Avherald.com. © of text by Avherald.com.
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