RV4Ker,
Positive G is maintained throughout the loop, so the engine is not aware that it's upside down in relation to earth.....Having said that, the vid clip was taken in Australia.....I do not have large enough _ _ _ _ to try the same manoever....
Same reason we can loop and roll the RV4's (With pos G applied), but to remain inverted, need to have inverted oil system fitted and inverted fuel pick-ups.... :D (Rattex would also need fuel injection to remain inv)
So that's two planes you need to test in Slummies now !