Unlike hydrogen gasoline will ignite over a relatively narrow
  range of mixtures. 10:1 to about 18:1. The tank environment is
  always too rich to ignite the mixture.

  Paul Lamar

  Brings to mind the TWA 747 loss a number of years ago where government
  investigators concluded shorting wires in empty tank ignited jet fuel
  vapors
  causing explosion. I was skeptical from the start. Seems to me all 747
  aircraft that vintage would have been grounded immediately for
inspection.


  Al K

  My wife Robin worked for TWA in those days as a mechanic. All 747's
were
  inspected
  for loose or bare wires. Robin, due to her small size, spent many hours
  crawling
  around in fuel tanks. A nasty job. Nothing was found. It was common
  practice to take
  off with empty center tank if you did not need it. This reduced the
  stress on
  the wing spar. That meant thousands of successful
  747 take offs were made with empty center tanks. They also did their
  damnedest to
  ignite the mostly empty center tank on an old 747 with out success.

  IMHO it was shot down in error by the Navy and covered up by the
Clinton
  administration.
  Think of the political fall out if they admitted shooting it down in
error.

  Heck cars would be blowing up all over the place. Fuel flows through
  the pump past the armature and past the brushes.

  What they do with a fuel air bomb is first blow up the tank to
distribute
  the fuel in the air to roughly the proper mixture and then ignite the
  mixture
  with a flare. Then you get the really big bang. Forget the movies of
  cars and
  gasoline tank trucks blowing up.

  A can of gas will put out a match but don't ask me to demonstrate :)
  Do it with a robot.

Paul Lamar


    NOT a Match, but a cigarette, Virg


I've seen it done without igniting the fumes (cigarette).
Harold Lunt

If i remember correctly several days before the 747 was shot down the
Palestinians said if we did not stop backing Israel they would give us
something to think about.
Steve Hudson