Lan Ding Gere
13th Aug 2002, 12:38
A silly question,
What would be the temparature and speed of the exhaust from one of the jet engines on a 744 be for a plane that is taking off. How is ilbs of thrust eqate to mph ?
If a jet is travelling at say 100mph, would the exhaust speed be 100mph ?
How can it be measured ?
Fokker-Jock
13th Aug 2002, 19:25
If any aircraft was flying at 100 kts the exhaust gas would be a lot higher in order to maintain equilibrium to drag. However, it's much easier to refer to thrust or exhaust gas as a force and then see how much an engine is required to give to maintain a given speed.
The force from the engines must always (assuming constant speed and altitude) be the same as the total amount of drag on the airplane.
The speed of the exhaust is dependant upon many factors such as nozzle area, temperature etc. because the force created is equal to the weight of the air being thrown aft times the speed at which it is thrown plus the speed at which the aircraft is travelling.
But I believe your question is too complex to explain and to calculate as it depends on ALOT of factors; Aircraft frontal area, wing design, drag characteristics, temperature, air pressure, humidity, position, aircraft weight + a hundered other factors I have no competence of explaining. Just to calculate the drag; here is the formula:
(Cdi x S x ˝rV2 + CDp x S x ˝ r V2)
Good luck !
The thundering sound you hear when an aircraft takes-off is an indication that the air thrown aft of the engines are supersonic and therefore over appx 1100 km/h.