Posted for "Giffen A Marr" <gamarr@charter.net>:

 
 There are frangible valves available out there for the fuel lines. They have
 been used on helicopters for many years. Their use came about from crash
 survivability testing done by the military. The reason was that on
 helicopters, most of the fuel was carried below the floor of the cabin and
 very close to the CG. The fuel tanks were puncture resistant bladders,
 connected by hoses with the frangible fittings in the line. If the fitting
 pulled apart, it automatically sealed the line. Rollover valves were also
 installed in the vent lines.
 
 Giff Marr
 LIVP/20B 35%