whip stalls
 

... are prohibited in Cessna 172's / 152's, and I presume any other light aircrat.

Is that because of excessive negative g's being developed ?

What would be a guesstimate on the amount of g's developed ?

Mike

A "whip stall" is apparently the same as a tail slide, if that helps anyone actually answer the question... (sorry, I can't answer it myself).

Definition of a whip stall

NOUN: A usually intentional stall in which a small aircraft enters a vertical climb, pauses, slips backward momentarily, then drops nose downward.

The transition from vertical up to vertical down is actually around zero "G".

I think the problem for non-rated aircraft is the possibility of reverse air flow during the tail-slide, with associated probable control snatch.

You can stop control snatch by holding the controls tightly. But if you didn't, the elevator / rudder would probably be damaged quite badly, as the C152 control stops are very small and very close to the hinge line. Perhaps Mr Cessna is just playing safe with what is after all only a semi-aerobatic aircraft?

The 172 on the other hand is not aerobatic at all as far as I know, although it is spinnable.

To answer the original post, although the transition from up to down is approx 0g, the pendulum effect after transition to vertical down can give ±2g in my limited experience. Not enough to hurt a 152. Can't say it makes me feel great though...