The issue is heat. With so much fuel, eventually any fire will become so hot it can't be put out.
Not really. The issue is getting enough of the bunker grade up to a high enough temperature to sustain a fire. One bomb hit with HE isn't going to do it. The energy of the situation doesn't work. Even if 100% of the heat from an HE bomb were transferred to the fuel (which it won't be... the transfer will be more like 0.5% to 1.0%) it's not enough to raise the temperature of that much bunker grade to make it volatile. You need multiple hits, or else you need something like WP or Thermite.
The Ploesti raid load out provides a good example of the calculations of the sort of effort required to get a sustained fire in a target environment that had ALOT more volatiles than ordinary bunker grade.
The PR fire is a lousy example. The PR tanks were not full of bunker grade fuel. The tanks weren't double walled like the military ones at PH, and none of the PR tanks were surrounded by high berms.
I'm not sure you and I are on the same page when it comes to bombing. Hitting moving ships from altitude can be challenging. Hitting stationary ships when they are trying to kill isn't quite as challenging. But hitting or even coming within a lethal 1500-2000 feet on something the size of a fuel tank and any practical altitude.
In the real actual war, Kates did not regularly display that kind of accuracy when level bombing. As for 1500-2000 feet being lethal to an oil tank, that is a made up number. No basis in reality. US strategic bombing raids relied on direct hits or strings of hits within 300 feet to be really effective on targets such as refineries that had much more volatile stuff around than bunker grade. As a matter of pragmatics, since a B-17 could not reliably hit within 1000 feet of a target, you had to use groups of B-17s to do the job. A group of Kates is less effective at that sort of thing than any two B-17s. You're not going to get the results you seem to think KBs Kate drivers could obtain. They might get luck and nail one. They won't set it alight without multiple hits and incendiaries in the mix.
Ever wonder why ships catch fire after getting hit by a bomb?
No, I don't wonder at it.
It's not like they are getting hit with napalm.
They are full of explosives, flammable paint, rags, solvents, and more interestingly, things like oxy bottles, acetylene bottles, alcohol bottles, avgas, and diesel. That's the stuff that burns when ships are hit. Bunker grade is extremely difficult to get a sustained burn going. Several Japanese CAs were horridly damaged because their burning oxy bottles and fuel set off their torpedoes.
If an explosion in a tank full of bunker grade was good enough to get 'er done, USS North Carolina and USS Saratoga would have sunk the first time each was torpedoed. Bismarck would have burned after her encounter with Hood and PoW. Sorry fella. Bunker grade doesn't burn half so easily as you imagine.
It's enough to make metal burn, let alone dried paint, chairs, humans or if you are real unlucky explosives or fuel. And don't think that 3000F magically goes away. Just think how long it takes your chicken pot pie to cool off from 165F?
Actually, most of it DOES immediately go away. It's not magic. It's called "blast" and mostly results in heating up alot of atmosphere that first compresses and heats, then expands and goes away. No magic required.
On this remark, I'm simply going to quote that USN veteran who spent some 40 years studying the combat capabilities of pretty much everything. "Fifty-caliber incendiary machine gun bullets could have wiped them out. "
He was incorrect. As with most such assertions you have to ask whether it was the kind of thing he'd have studied closely (it wasn't). A better source of information on this is the USSBS analyses of strategic bombing efforts on oil industry targets in the 3rd Reich and on the margins of the Japanese empire.
I can imagine reasons to say things like that in an investigative proceeding. It's kind of like reading Ceasar's account of his Gallic campaign. The more he talks up Vercingetorex, the greater Ceaser's victory is seen to be. I think with Nimitz (and many other writings from the period) you can find a motive for distracting the Senate's eye off the ball. In re PH, it takes the reader's eye away from "Look what happened when we screwed up" to "It could have been worse."
Anyhow, no way a few incendiary rounds from a .50cal or even a whole bunch of exploding 20mm hits would do the job. It's all about the energy. How much bunker grade in the tank, how much energy required to heat it enough to get a self-sustaining fire. An ordinary HE bomb won't do it.
Bursting the tanks and adding thermite would definitely do it. But thermite was not the sort of thing KB ever carried.
