No, as long as you are pulling positive G's, your angle of attack is positive. It has nothing to do with pitch angle. Edit: Oh you meant flying upside down, no

No, as long as you are pulling positive G's, your angle of attack is positive. It has nothing to do with pitch angle. Edit: Oh you meant flying upside down, not doing a loop? Yeah, negative AoA is not the same as positive AoA. It makes sense to distinguish them because, unless the wing uses a symmetric airfoil, it will behave differently in the two cases. Given that you also calculate the lift vector as a function of AoA, and for anything to make sense the lift vector is antiparallel in the two cases, the AoA would also be negative.