Jet engine thrust with aircraft speed
 

There might be old threads on this subject, but I couldn't find any doing a quick search.

Anyway, the question is simply your take on jet thrust with forward speed. Reason why I am asking is I have found different answers (and I know it's probably engine type specific, i.e. turbojet, turbofan).

1. The JAA Learning Objectives in Powerplant wants you to state that jet engine thrust is fairly constant with engine speed.

2. The Performance notes in the JAA theory are also based on jet thrust constant with engine speed (thus Vx being close to Vmd for jet aircraft)

3. The Oxford Powerplant book have some diagrams where jet engine thrust almost halves within the subsonic speed range.

Any other suggestions? :)

Theroetically, a turbojet engine with a convergent duct where the airflow chokes at Mach 1 cannot have too much excess speed on the exhaust flow at high speed? What about a turbofan with a convergent-divergent duct?

Any light shed on this subject is greatly appreciated!!