Thrust Reversers High/Low Speed

[newifr]

Could somebody please explain why Thrust Reversers are more effective during the high speed part of the roll out as opposed to when the aircraft is a lot slower?

Regards

newifr

[Intruder]

Been discussed before. You can search for it.

[FLEXPWR]

Well, that was a constructive first answer...

From my modest experience, sure someone would have better words than me to describe it, but do you feel the difference when you put your hand out the window of your car at 20 mph or 100 mph? Same goes for reversers. The basic concept is that drag will increase at the square of speed, so if you use the reversers say immediately at touch down at 140 kts, they will be 4 times as effective than at 70 kts. Of course this is over simplified, does not take into account ram effect, engine approach idle speed, etc.

Corrections and comments welcome,

Hope this helps. :ok:

Flex

[lomapaseo]

Some thoughts

at high speed there is a very large heat load on the brakes which can be partially offset by a high reverse thrust setting on the engine.

at low speed the thermal balance (heat-in vs heat-out) on the brakes is much less while high reverse thrust ends up getting in front of the engine and causing FOD.

I'm sure there are some more signifcant effects to come in this discussion

[Intruder]

Well, that was a constructive first answer...
Yep! Why waste time on an issue that has been discussed ad nauseum, especially when the OP gives NO indication that specific information is needed for specific purposes?

If you've been here for 9 years, you SHOULD understand that...

[Slasher]

I'm with Intruder. A lot of these posters appear to be simply
flight sim gamers like this one and I don't bother with 'em.

You can tell by the simplicity of the question construction.

For instance here's a typical example of the same question
being asked by a non-gamer -

Could somebody help me please? I'm studying Gas Turbine
Theory and I can't get my head around the physics of why
reverse thrust is more effective at higher speeds than lower
ones.

Also are cascade reversers more effective at lower speed than
the bucket variety? Thanks.