Form a physical stand point engine thrust is just a force - the max thrust rating is the max force the engine can develop static thrust is when engine is still. This is not power.
The power developed by the engine(s) depends on airplane speed
Engine Power= Thrust x Speed = (total drag) x speed
For low drag designs and cruising in thin air a lower thrust is required for a given flight speed than when flying at sea level in a high drag aeroplane.
Drag is composed of profile and aerodynamic induced drag. Added togther gives (total drag) which equals the thrust required from the engine.
So you can see that thrust on its own is meaningless.
Watch out for units, in MKS system , Thrust is in Newtons, speed in meters/s gives power in watts ( divide by 1000 for kilowatts)
Where does this power ( energy) go? It goes into moving air ( air kinetic energy) and heating the airplane skin thru friction- in outer space where there is no drag no engine power is required.
Even with zero profile drag keeping an airplane in the air requires power becuase lift is a result of momentum exchange from the downwash created by the wings. So lift is no free lunch.
Last edited by b377; 11th March 2009 at 10:25.