The Flaming Coffin nickname was a disparaging term apparently coined in the US when the DH4 was being tested in preparation for production over in the United States. DH4 A7532 was sent over as a pattern for manufacture and to test out and as you probably know, the Liberty-engine US version made some changes to the design based on the reports written after that DH4 was assessed. It's that assessment which was the catalyst for the nickname, as the report was fairly critical of the DH4, claiming the French Breguet was a better day bomber. The Flying Coffin nickname is often mistakenly thought to refer to the fact that the DH4 was prone to fire in the air, but that is not the reason for the nickname, and most RFC crews completely disagreed with the assessment and didn't use that nickname, they were in fact very fond of the aircraft in most cases. Most casualties were due to the fact that a lot was asked of the DH4 crews, flying deep penetration missions over Germany for several hours, so it actually did very well under the circumstances.
The real reason for the nickname is that the location of the fuel tank on the DH4 (between the pilot and the rear gunner, which changed on the US version) could potentially lead to a grim fate for pilots if the thing crash landed. What could happen is the weight of the fuel in the tank would cause it to carry on traveling forward under momentum as the aircraft came to an abrupt stop in a forced landing or crash, thus it could break loose from its mountings and carry forward, pinning the pilot between the fuel tank and the engine. If that happened and the fuel tank ruptured, it might possibly spill fuel onto a hot engine part and cause a fire, which would cremate the pilot since he would be pinned to the hot engine by the fuel tank and unable to escape. Thus he would be in a 'flaming coffin'. The truth is, if a crash was severe enough to do that, he'd probably be dead anyway.
So in reality, that's more based on fear than an actual probability, as the kind of fuel carried by the DH4 is actually fairly hard to ignite if simply spilled onto a hot metal part, oil on the other hand will often quite easily burn. You can try that for yourself (be careful though); tip a small amount of petrol into a dish and drop a lighted match into it; the fuel will most likely put the match out rather than ignite. This is because fuel like that tends to have to 'mist' in order to ignite, i.e. fuel vapour is far more likely to ignite. So in the case of the DH4, you would have to have some sort of flame at the engine and the fuel tank rupturing in the crash, and throwing a fuel/air mixture into the flame to really have a good chance of igniting things. That could certainly happen, but merely spilling petrol on a hot engine would not necessarily do it. This is why modern aviation fuels are often designed to 'gel' if they get a shock, in the hope that they will not mist and ignite if a fuel tank ruptures in a crash. You have probably seen the very famous NASA test footage of a Boeing 707 airliner being remotely piloted and belly landed in the US desert onto some spikes intended to rip open the wing fuel tanks, where it rolls over and is engulfed in a fireball. That test was part of the research into such fuel ignition, amongst other things.
You can try that experiment for yourself too (wear an apron): Get a bowl of custard, place it on a table and thump your fist hard into it. You'd expect it to splash everywhere, but that doesn't happen because the shock you deliver to the custard forces it to gel.
Wiseman: When you removed the book from the cradle, did you speak the words?
Ash: Yeah, basically.
Wiseman: Did you speak the exact words?
Ash: Look, maybe I didn't say every single little tiny syllable, no. But basically I said them, yeah.
Last edited by Chock; 5 November 2009 at 09:35 AM.