The Investigation Into the Loss of KC-135A 56-3592 Over Canada in 1989 Finally Provided Answers For Other Previous Losses
On Wednesday October 4th 1989, the crew of KC-135A-BN Stratotanker 56-3592 (CN 17341 MSN 31) was returning to their base at Loring Air Force Base (AFB) in far northeastern Maine after an overnight tanker mission. At about 0600 local time the aircraft exploded in midair over Perth-Andover near Carlingford, New Brunswick, Canada killing all four crew members aboard the aircraft. The wreckage was strewn over a wide area but large pieces came down on a hill along the west side of the Trans-Canada Highway north of Perth-Andover. This particular KC-135A had been delivered to the Air Force in November of 1957 and was nearly 32 years old, one of the few A models still in service at the time, and the last A model to be lost.
The investigation into the crash took several months as the wreckage took time to locate and process. When the investigation concluded the cause of the explosion was determined to be overheating of an aft body fuel tank pump operating in an empty fuel tank. When the overheated pump sparked it ignited the explosive fumes in the tank. But that wasn’t the end of the investigation. Those pumps were originally designed to work safely in fuel tanks that had been depleted or even emptied.
There were quite a few KC-135s lost under similar circumstances or with similar results. KC-135Q 58-0039 exploded in flight near Torrejon Spain in 1971. KC-135B 61-0331 was lost over the Pacific in 1971. KC-135A 60-0368 crashed on approach at Torrejon Spain in 1976, KC-135A 61-0296 crashed near K.I. Sawyer AFB in 1976. KC-135Q 60-0338 burned on the ramp at Plattsburg AFB. KC-135A 58-0031 exploded in flight near O’Hare airport in Chicago. Some of these losses were deemed to be directly related to the loss of 56-3592.
The root cause of the explosions, specifically the one of 56-3592 over Perth-Andover, was finally determined to be incorrectly repaired fuel pumps. The pumps were being inspected and repaired as needed (IRAN) and placed back into the supply pipeline at the Oklahoma City Air Logistics Complex (OKC-ALC) but the repairs were causing the pumps to overheat. KC-135 crews (all models) were instructed to keep 3000 pounds (about 450 gallons) of fuel in each body tank to prevent pump overheating.