lars1
I have never had anything to do with the R-22 but understand the 124HP is main transmission limit. A way to work out how much power the fan pulls out of the engine is to get hold of the Lycoming Operators Manual for the particular model engine fitted. In there you will find a graph giving the RPM, MAP and HP of the base engine (no cooling fans, generators, vacuum pumps etc). Look that up with Robinsons 124HP figures and you should find the Lycoming chart will give you a higher figure. The difference will be the cooling fan HP + generator + any other ancillaries the engine is driving. Good luck and hope I'm clear enough.