Ok, but the fuel cell on a bomber is bigger than on a fighter, it also tends to carry alot more ordnance. Fires generally happen 1 of 3 ways.
Your paper/cloth airplane caught on fire by a tracer.... so it burns a fairly long time before either loosing lift, or setting the pilot or gas tank on fire.
Your fuel bag is leaking, and it isnt self sealing, and a tracer round hits some of the leak, leading back to the bag, and boom.
Your engine is leaking oil, rinse repeat with either tracer round or heat of the engine, this is a slow burn, if any burn at all, the pilot simply bails out due to lack of visibility and cockpit filling with smoke.
Problem with bombers, is their fuel bags, their oil coolers, their engines and there thin skin, are all in the exact same place, on the really thin wing. You light that engine up, the fuel bag is close behind if the wing simply doesnt disentegrate from the impact stresses and heat of the fire anyway.
Where a 190, whose engine is way out front, and fuel way in back and out on the wings, or take an american fighter aircraft with self sealing fuel bags......
I doubt HT
is going to sit back and do the math on potential damage locations, actual fuel storage characterisitcs on each airframe type, tracer vs non tracer, and do some sort of crazy formula for it. It is just easier to say... if your airplane is on fire, you got 3-6 seconds to get the heck out.
