This article from Flight Global recently posted may also interest you:
By Darren Shannon in Washington DC
An investigation of the 4 May explosion of a Transmile Airlines Boeing 727-200 freighter’s left wing during towing at Bangalore airport has found evidence of damaged wiring and electrical arcing within the wing’s fuel tank.
“Had this explosion occurred in flight, it would have resulted in the catastrophic failure of the wing and the airplane would have crashed,” it adds.
“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,” says the NTSB.
It adds: “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.”