15-25 seconds, random within that range, wold work.
I still like my ideas better.
Particularly the forcing the pilot to ride it down once it became uncontrollable as punishment for trying to fight in a burning aircraft.
I do agree it should be the same for all aircraft as it would be practically impossible to actually determine each aircraft's burn rate and pattern when the fuel tank was ignited by a .303, 7.7mm, 7.92mm, 12.7mm, 13mm, 13.2mm, 20mm, 23mm, 30mm, 37mm and so on.
