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Red Panda
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Reversing Thrust In Mid Air

Fri Jun 25, 2004 5:06 pm


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Is this 747 really reversing thrust when still so up high above the ground? If yes, what happened to this 747? Would pilots try to slow down an overspeed aircraft by reversing its thrust in mid air? I do not believe so, but what is this picture showing then?

r panda
 
tekelberry
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 5:21 pm

If you look at previous pictures of the same airplane, the engine looks the same. It was probably just a small part that needed to be replaced that wasn't painted to blend in with the rest of the engine.
 
ZKSUJ
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 5:35 pm

Is it even possible to reverse thrust in mid air? Don't they have some thing that would stop it cause it may be unsafe?
 
fritzi
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 5:58 pm

ZKSUJ, yes they do.

Some aircraft can use reverse thrust in-flight though. DC8 (idle), Concorde (inboard idle), prop aircraft, IL-62, ...

In 1991, a Lauda B767-300 crashed in Thailand after an in-flight thrust reverser deployment on the #1 engine. Shortly before the aircraft was torn apart mid-air, the crew had recieved a message on the EICAS about a T/R problem, but the crew opted to continue the flight. All lives were lost
 
ZKSUJ
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 6:05 pm

Wow, thanks Fritzi for clearing that up.
 
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United_fan
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 9:27 pm

Doesn't the main gear have to be on the ground before you can use reverse thrust and ground spoilers? I remember seeing a pic somewhere of an Illusin (sp?) on finals with a thruster open?
"Suspicion is a matter of opinion"
 
Braniff1960
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 10:12 pm

I knew I had seen this before.

Guess it's true!






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[Edited 2004-06-25 15:14:32]
nothing like the smell of jet exhaust!
 
akelley728
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 10:18 pm

United_Fan:

Yes, it was common practice with the older version of the Illyushin IL-62 to have their clamshell reversers deploy before touchdown, as a way of making the landing shorter, I guess.

You can see it in this photo:

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longhauler
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 10:18 pm

Some aircraft are certified for in-flight reverse, as some above have stated. Usually this is in place of Spoilers/Speed Brakes.

For the aircraft that are not certified for in-flight reverse, it would take a series of failures for it to happen.

At low speeds however, it is not as devastating as you might think, and it is practised in the Simulator all the time. That is, speeds below 250 knots.

As it was considered very unlikely, jet aircraft were never tested at high speed reverser deployments. However, the Lauda Air B767-300 that had that problem above 300 knots resulted in, as we all know, very bad results. As a consequence, aircraft are now tested for reverser deployments at all speed/mach regimes.

The heading picture of the B747SP, appears to have an unpainted part, not a reverser deployment.
Just because I stopped arguing, doesn't mean I think you are right. It just means I gave up!
 
flyingbronco05
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RE: Reversing Thrust In Mid Air

Fri Jun 25, 2004 10:19 pm

Never Trust Your Fuel Gauge
 
RDUDDJI
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RE: Reversing Thrust In Mid Air

Sat Jun 26, 2004 4:44 am

me thinks the effects would be somewhat worse than slamming your car into reverse while going 80mph!
Sometimes we don't realize the good times when we're in them
 
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clickhappy
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RE: Reversing Thrust In Mid Air

Sat Jun 26, 2004 4:54 am

doubtful. Most planes would be at (near) idle power over the threshhold, judging by the noise (im not a pilot)
 
HaveBlue
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RE: Reversing Thrust In Mid Air

Sat Jun 26, 2004 4:56 am

Another nice thing about the picture of the 747... its cousin the C-5 can be seen in the background.
 
md80fanatic
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RE: Reversing Thrust In Mid Air

Sat Jun 26, 2004 5:10 am

That Russian plane pictured above only has two of it's four engine TR deployed. The other two are providing forward thrust.
 
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Starlionblue
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RE: Reversing Thrust In Mid Air

Sat Jun 26, 2004 10:00 am

Reverse in the air is normally only used for rapid descents. In the case of many airliners, if there is a decompression, fastest time to safe altitude is basically point the nose down and use airbrakes + idle reverse to make sure you don't get into overspeed (that would be bad). Apparently this also makes the airframe vibrate violently.

For some military transports like the C-17, reverse and full flaps is used for tactical descents at up to about 14000 ft/min.

"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
MrFord
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RE: Reversing Thrust In Mid Air

Sat Jun 26, 2004 12:56 pm

Another thing about the Lauda Air 767 crash :

While the reverse vanes opened, the engine was still producing cruise thrust (probably about 78-80% N1). So, all the bypass thrust going backward was suddenly going forward, and on only one engine, so here you get the 'swiving' effect.

At idle, opening reverse vanes mostly kept bypass thrust (or any thrust with a clamshell type) to propulse the plane by send it (the air) sideward, with little if any backward thrust.
"For radar identification throw your jumpseat rider out the window."
 
VS340
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RE: Reversing Thrust In Mid Air

Sat Jun 26, 2004 1:30 pm

Many years ago there was an accident in Winnipeg where a 732 crashed after one thrust reverser opened up during a go around attempt. All on board died.

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