Thanks for all the replies to this, and to David and John for their input. David I know you flew F3A aerobatics for some time (as I did) so you can appreciate my obsession with motor thrust lines. Regarding your theory I wonder has anybody flown the Kingcat full chat straight and level and hit the engine "kill" switch for an abrupt stop on the engine?. Should not this cause an immediate nose up?. If this were to happen would this prove your theory?. Thanks again, Paul.