After many, many iterations, the National Transportation Safety Board (NTSB) investigation ended with the adoption of their final report on August 23, 2000. In it they concluded that the probable cause of the accident was “an explosion in the center wing fuel tank (CWT), resulting from the ignition of flammable fuel/air mixture in the tank. The source of the ignition could not be determined with certainty, but, of those evaluated in the investigation, the most likely was a short circuit originating outside of the CWT that allowed excessive voltage to enter through the electrical wiring.
It seems the NTSB and Boeing dismissed electrostatic discharge (ESD) as probable cause and, instead, latched onto wiring short circuit. In so doing they created a highly improbable scenario. Aircraft systems utilize low voltages ranging from 24 VDC to 30 VDC. By what means this range can transform into an “excessive voltage spike” without auto-inductive means in the indication system is beyond me. What am I missing?
Probable cause points to unruly, electrostatic energy and not a wiring short. Air conditioning (A/C) units had been operating at full capacity while the aircraft sat on the tarmac for six (6) hours in a hot July sun, thus lowering temperatures internal to the aircraft and raising ESD levels because of it. The units, which are adjacent to the CWT, had vaporized residual fuel within the tank through heat transfer. A bomb had been created waiting to explode. The fuse, it can be said, was the energy traversing the electrical wiring from the cockpit of the 747 to the fuel level sensor. By way of contrast the short-circuit notion seems to have been something pulled out of thin air.
Realistically, the pilot had made an altitude change to 15,000 feet, as instructed by the air controller. TWA 800 had likely met its fate upon reaching that altitude, but what was the cause? Most likely it was ESD from pilot, or co-pilot, to gauges and switches on the instrument panel. Electrostatic voltage above several thousand volts had produced a spark that found its way to the fuel sensor in the CWT and caused the explosion. Supportive of that was the pilot had noticed that the fuel gauge to Engine #4 was behaving erratically. It would be surprising if he did not tap the gauge, as most persons would be prone to, and in so doing sparked the panel. The energy would seek the path of least resistance to systems "ground". It’s anyone’s guess where that path might be, and how many lesser discharges had occurred in flights before. It is frightening, but bear in mind that electrostatic voltage build-up was in proportion to the time the Boeing aircraft was on the tarmac prior to take-off. Six hours is not only ridiculous, it is inhuman. Imagine!