ESDU 85015:2006

ESDU 85015 first explains the definitions of propeller thrust and efficiency in free air, discussing the contributions to losses from blade profile drag and induced effects, the latter split further into those arising from axial and swirl velocities. The influence of propeller design on free air efficiency is considered. Then the effects of propeller installation, in tractor or pusher configuration, on propeller thrust and airframe drag is discussed for propeller-nacelle and propeller-nacelle-wing combinations, and the different thrust definitions commonly applied to the tractor propeller-nacelle situation in the US and UK are explained. The interference effects due to cooling air inlets, and turbine engine exhaust jets, are also considered. The simple axial momentum theory is presented and used to establish the axial variation of the axial velocity, streamtube diameter and static pressure for a practical range of thrust coefficients. A thrust/drag accounting framework is provided in ESDU 85017.