Says Evidence Of Electrical Arcing Present Despite AD Compliance

The National Transportation Safety Board reported Wednesday its investigation into a wing fuel tank explosion on a Transmile Airlines B-727 airplane in Bangalore, India, on May 4, 2006, is ongoing. The Directorate of Civil Aviation of India is leading the investigation; the U.S. is participating as the country of manufacture. An NTSB-led team was on-scene in India and also traveled to Malaysia from May 24 to June 2.

As Aero-News reported, the accident occurred while the Malaysian-registered cargo airplane was waiting to be towed for a return flight to Subang, Malaysia. None of the four people aboard were injured.

The evidence indicates that an explosion in the left wing fuel tank destroyed the structural integrity of the wing. Had this explosion occurred in flight, it would have resulted in the catastrophic failure of the wing and the airplane would have crashed.

Investigators found evidence of damaged wiring and electrical arcing within the left wing fuel tank in an aluminum conduit tube that carried 115V AC electrical power to the fuel pump (see photos).

Wire arcing within the conduit routed through the fuel tank was previously recognized as a potential ignition source, and the accident airplane had been modified in accordance with an FAA Airworthiness Directive (AD). The AD required removal of the wires from the conduit, inspection, and re-installation of the wires or replacements into the conduit after insertion into a protective plastic sleeve.

This, however, did not prove to be sufficient to prevent the Bangalore accident.

This accident illustrates that ignition sources continue to exist and fuel tank explosions continue to occur in both wing and center wing fuel tanks despite the corrective efforts of government regulators and industry.

The Safety Board continues to believe the best protection against fuel tank explosions is to eliminate the flammable conditions inside the fuel tanks through design changes such as nitrogen-inerting systems, as per NTSB Safety Recommendation A-96-174.

FMI: www.ntsb.gov