Maximum speed -Pro craft

The standard approach for prop-driven aircraft is to assume that engine and propeller together produce a power (as opposed to thrust) output that is independent of speed. Calculations analogous to those carried out above for the jet aircraft, but based on power rather than drag, lead to formulae for maximum speed, absolute ceiling, and so on. The resulting equations do not however lend themselves
to simple closed-form solutions, and generally, iterative solutions need to be found.
Suppose the maximum engine shaft power output is P_max. The propeller will convert this to useful propulsive power with an efficiency η ; the useful available propulsive power is thus given by
                                                            P_av = η P_max