-- UA562 / 3May70 Boeing 727-100, N7027 UA ship # 7527, center fuel tank "exploded" during refueling. Parked on ramp, MSP, then number Gate 24. Wx: 53 deg F, wind 290/ 8. Fueling had been in progress for eight minutes when a LOUD sharp BANG sounded (like a fire cracker); fuel vapor and smoke seen ejected from Left Wing Tip near Tank Vent and fuel dump outlet [witnessed from outside by S/O, Oz mechanic, and the fueller]. Fueling was stopped; S/O disconnected electrical power from the buses, APU then was shutdown. Inspection: explosion in #2 Tank (center) ... presumed static discharge within #2 tank induced by presence of steel clamps and bolt assembly . . . Investigation revealed that fuellers at MSP used 450 gpm rate ... F/A's inside cabin were asked about the sound (explosion), but they perceived only a bump as if someone had hit the a/c with a belt-loader. ...
I had heard stories from old 727 techs of hearing a tank explosion (low fuel level, ACM's running, high OAT), they said they heard a loud THUMP. FLT 800, EWIS was driven by this allthough with many stories told about tank explosions (with no breach) I do not believe it was the cause of flt 800. None the less it had never been linked to HF key. Our now standard wiring practices are a good thing.