Attn. Nick /
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Ex PanAm 747 pilot, then based JFK, I had many friends flying 747s with TWA. We often compared our procedures and discussed our airplanes and their differences, as I was often instructing in classrooms or simulators at the PA Academy in Miami... I now fly 747s in Argentina, manager pilot training, and when TW 800 crashed, no need to tell you, we were in contact about the facts and... theories.
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No need to say, all ex-PanAm flight crews, like myself, immediately thought about "foul play", a bomb, a missile... after all, PanAm, as well as TWA, were considered by terrorists as the perfect targets representing the USA when overseas. It took me a long time, until the final report by the NTSB, to believe that TW 800 went down with a CWT explosion... Remember Lockerbie.
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That the explosion occured at some 13,500 feet in the climb, is no surprise. TW 800 was dispatched from JFK to CDG, with wing tanks and reserves near full, but no extra fuel was required nor loaded in the CWT. The plane had landed in JFK arriving from Europe, with the usual residual fuel remaining in the CWT. And yes, that fuel was warm, because of the A/C packs used on the ground at JFK. How warm...?
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An AFM 747 limitation is "maximum fuel temperature" for Jet A or Jet A-1 to be 54.5ēC in the tanks. The fuel is generally warmer in the CWT because of the A/C packs. You said that fuel cools off rather fast... well, it cools off (not so fast, but it does cool) in the wing tanks, not much in the CWT...
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There is no "CWT fuel temperature" that we can read in the 747. We can read fuel tank temperature for tank nē1, or for each separate engine feed. here in Argentina, if the fuel gets very cold on our very long flights (minimum temperature for Jet A or A-1 limit is 37ēC in our limitations), we sometimes keep 2 or 3,000 kilos of fuel in the CWT until needed to be used to warmup the engine feed lines, if needed. I know that after 10 hrs in cruise, that fuel remains rather warm in the CWT, maybe 10 or 20ēC warmer than wing tanks.
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However uneducated we pilots and flight engineers are in the 747, it is very likely that the CWT exploded when the F/E on the flight operated the "scavenge pump". Why...? With PanAm, as well as with TWA, our F/E's SOP performed after passing 10,000 feet in the climb, was to activate the scavenge pump to "suck the last drops" of an "empty" CWT and transfer that fuel into the nē2 main tank. Many of us believe that this, triggered the explosion, probably with a short in that electrical wiring or motor. So, 13,500 feet makes sense...
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I know that UAL F/Es used to do same SOP, but at 18,000 feet in climb... and here in Argentina, we did that scavenge, to complete our "after takeoff checklist" at flap retraction at some 3 to 5,000 feet if our CWT was empty. No need to tell you that we no longer do such a procedure... If a few liters of fuel remain in the CWT, well, who cares...? -
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A few years ago, smartass as I am, with my Zippo lighter, and filled it with a few drops of Jet A-1. I could never use it again, and had to buy a new one. Jet fuel is extremely difficult to light-up. At PanAm, we flew many military MAC flights contracts, and the Air Force often delivered Jet B fuel (JP-4). For that fuel, we had a lot of limitations, such as maximum pressure for fueling, and maximum temperature reduced to 43ēC...
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Thank you for your input about steel tanks, it is appreciated. However good the "Discovery Channel" is, obviously it is for the general public.
Happy contrails