TO power per hour?
Taking up the number of take-offs per hour, there's a limitation on certain components of some Bells (205/212+others?) based upon RIN. You'll find it mentioned in small type in Bell publications.
I'm not familiar enough with these types to know exactly what a RIN is or how it's calculated, but I always had the impression it was related to the number of 'high power events' the rotor system was subjected to per hour (average). Presumably these 'high power events' were within regular limits, and yet somehow impacted upon the life of some components.
Anybody got more detail?