INVESTIGATORS SAY that two fuel probes recovered from the site of the crash of Trans World Airlines Flight 800 show no signs of electrical arcing which could have caused the centre fuel-tank explosion which brought down the Boeing 747-100 on 17 July, killing 230 people.

One of the probes displayed "petalling" characteristic of metal damaged by an explosion, but this was caused when the hot probe hit the water, investigators believe. A probe recovered several weeks ago showed no signs of explosive damage. The crash site is to be trawled for the remaining four probes and other small debris.

The US National Transportation Safety Board (NTSB) believes that an explosion in the near-empty centre fuel-tank may have brought down the 747, but it does not know whether the accident was caused by a malfunction, a bomb, or a missile. The NTSB plans to blow up the centre tank of an old 747 to help determine whether such an explosion could have brought the aircraft down.

Boeing analysis suggests that a fuel-tank explosion alone would not have been sufficient cause for the aircraft to break up. Tests show that a fuel-tank explosion could produce an overpressure of 0.69-1bar (10-15lb/in2), while a pressure of 2-2.76bar would be required to cause the fuselage structure to fail, as in the TWA accident.

The US Federal Aviation Administration in 1972 proposed the purging of empty fuel tanks with inert gas to prevent explosions, but the precaution was rejected by airlines as being too expensive. Boeing argues that fuel-tank components such as probes are de-signed to eliminate the possibility of their sparking-off explosions.

Source: Flight International