Thrust Reversers High/Low Speed
Thread Starter
Join Date: Jul 2011
Location: Australia
Posts: 25
Likes: 0
Received 0 Likes
on
0 Posts
Thrust Reversers High/Low Speed
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
Regards
newifr
Join Date: Jun 2002
Location: Vega Constellation
Posts: 286
Likes: 0
Received 0 Likes
on
0 Posts
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.
Flex
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.
Flex
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
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
Join Date: May 2000
Location: Seattle
Posts: 3,196
Likes: 0
Received 0 Likes
on
0 Posts
Well, that was a constructive first answer...
If you've been here for 9 years, you SHOULD understand that...
Join Date: Feb 1998
Location: Formerly of Nam
Posts: 1,595
Likes: 0
Received 0 Likes
on
0 Posts
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.
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.
