The four crewmembers of the Ellsworth AFB B-1 bomber that crashed Aug. 19 in Montana are lucky. Considering there were several explosions caused by burning fuel while in flight, the time they had to eject was probably just seconds, if that.
The subsequent investigation blamed a fold down baffle that broke free, puncturing the main fuel line which caused a massive leak of thousands of gallons of fuel into the plane. That fuel came in contact with a hot precooler duct, setting off a chain reaction of explosions that destroyed the plane.
In a November 1988 crash with similarities to the August loss, the four crew members were also lucky to survive.
A crew was practicing touch and go landings at Dyess AFB, Texas when a fire started in a wing, knocking out two engines and destroying control equipment. Crash investigators were not able to determine how the fire started; but they noted a “design deficiency” that allowed fuel to flow from the overwing fairing (wing gas tank) to a precooler which was hot enough to ignite the gas.
Fuel leaks, commonly called weeping and seeping, have occurred in B-1 bombers regularly. With nine separate fuel tanks in various locations in the fuselage and wings, there are a lot of places where things could go wrong as fuel always flows between tanks to maintain aircraft balance. Then you add the swept wing design … complex with a lot of moving parts. The stress of flight and even weather also can come into play in a fuel leak.
At times, the Air Force grounded the bomber fleet due to leaks. On at least occasions (one at Dyess that resulted in the fleet being grounded; the other at Ellsworth), maintenance airmen swept the wings too far forward, rupturing fuel tanks.
Fuel leaks were more common in the bomber’s early deployment days. The biggest fuel leak issue plaguing the bomber was in the initial design of the fuel cells, options left out to cut the bomber’s weight. In the early days of operation (the B-1 became operational in 1986), there was an average of one fuel leak every five hours of flight time. Over the years, design changes and aggressive maintenance routines cut the average time between leaks. But the leaks still persist.