One of the problems of the difference between scheduled and real world performance of the R22 is the sensitivity of its small main and tail rotor blades to blade condition. Worst case scenario is warm humid day in summer and the leading edges plastered with bugs.The effects of humidity is not scheduled in the performance graphs as it used to be in old marginal performance helicopters (piston Whirlwinds for instance) and from memory could be up to 5 percent from dry to humid air. Cleaning the leading edges every sortie is a pain but can add the equivalent of about 5 bhp. Doesn't sound much but is the difference between a cushion creep and a more comfortable takeoff.