Clive,
Belated thanks for the shockwave explanation. Inevitably I must spend time with the basics.
Gordon,
Thanks for your explanation.
I always thought the intake momentum drag was one of the costs of bringing the air aboard. Hence the appearance of flt velocity in the expression.
However, since the air never slows down beyond about M0.5 at the engine face the air is never brought to rest relative to the aircraft. Does this mean that the momentum drag is really a function of axial vel at compressor entry also?
Have I gone off the rails here or is it something to do with airframe, ie inlet, and engine accounting?