Strange how the brain can begin to dust off some of its old pages. I recall that the old Jet Provost 3 wasn’t allowed to be aerobatted or spun if there was any fuel in the tip tanks and if that was part of the sortie profile it was normal to take off with “half tips” so they would be empty by the time you climbed to minimum entry altitude. One of the pre spinning checks was to confirm that the main gauge reading had begun to decrease. At least I think that’s correct…..it’s 44 years since I last flew one and a year longer since I nearly killed myself by inadvertently flick rolling then spinning one inverted from a badly botched aerobatic manoeuvre (had I not previously recovered from one in a C150 as mentioned earlier I might not be here writing about it).
A similar cockup in a JP (Strikemaster in fact) may well have been a factor in the sad demise of an ex Harrier display pilot of my acquaintance, quite some years later.