727LOVER
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Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 2:32 am

I believe the answer is NO--the Lauda Air crash!! But my co-worker (a non-aviation type) insists that it is a normal routine to reverse thrust while airborne. Set him straight please.  Smile/happy/getting dizzy
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SlamClick
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 2:43 am

Depends on the type of aircraft.

The DC-8 used the reversing of two engines in flight as a speed brake.
I have seen them popped in the flare on other types but they did not fully deploy and spool up until after touchdown.
With some, it might be a very bad thing.
Happiness is not seeing another trite Ste. Maarten photo all week long.
 
CHRISBA777ER
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 2:48 am

I know of several people (unrelated to each other) who claim that on the approach into a well known Southern Californian international airport, (San Diego) that its perfectly normal for the aircraft to "turn the engines off completely so there is no engine sound at all" on approach, and that the aircraft goes into reverse on very short finals (before - and they were very specific about this) the gear touches down. All three people are amateur interested aviation types - anyone else heard of this. FYI the occurence happened on a 737 all three times, Southwest, United, and Alaska in case it matters...
What do you mean you dont have any bourbon? Do you know how far it is to Houston? What kind of airline is this???
 
c172heavy
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 2:51 am

727LOVER:

There are a number of previous posts on this subject that you can access througth the SEARCH pulldown at the top of the page, but the simple answer seems to be yes, it is POSSIBLE. But not generally accepted, other than in the flare, as SlamClick pointed out.
"How's that working out for ya?....Bein' clever?"
 
goboeing
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 2:54 am

I think they have great imaginations!  Smile Maybe bad eyes and ears too? If you stand right under a jet, sometimes it's surprisingly quiet but not that quiet! And they'd have to re-start the engines during this maneuver, it sounds like!

Nick

Edit: I am referring to CHRISBA777ER's post.

[Edited 2004-11-17 18:55:24]
 
Bellerophon
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 2:54 am

727LOVER

Sorry, but you're the one who may just need a little straightening out! Big grin

Concorde, Trident (HS121) and DC-8 were three types that could use reverse thrust in the air.

I have used reverse thrust in the air many times over the years, and whilst the approval to use reverse thrust in the air may be an unusual feature, that exists on only a few types, on those aircraft for which its use is approved, it is both a safe and useful feature, with none of the problems that some would have you believe.

The use of reverse thrust in flight on a type where it is not approved, is a completely different matter, and is about as stupid an action as is possible in aviation.

Should you survive, you deserve all that's coming to you.

Regards

Bellerophon

[Edited 2004-11-17 18:56:26]
 
2H4
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 2:57 am

I believe the C-17 has this capability as well.


2H4
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miamiair
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 3:27 am

The IL-62 will crack the buckets prior to touchdown.
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timz
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 3:30 am

"Concorde, Trident (HS121) and DC-8 were three types that could use reverse thrust in the air."

On the two inners for the DC-8-- ditto for the Concorde?

Just on the center engine for the Trident?

And no twin can use reverse in the air?


[Edited 2004-11-17 19:31:22]
 
avt007
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 5:28 am

ChrisBA777ER- I've also known pax to ask F/As on an F28- "Why is the engine shut down?", thinking that since the inlet guide vanes aren't turning, the engine must be off. One F/A told that she replied that it was to save fuel during cruise, and the pax bought it! Don't believe anything a passenger tells you, even if they like airplanes, chances are 98% they are mistaken.
 
air2gxs
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 5:41 am

Chances are that if the aircraft is not certified for inflight reverser it will be impossible, under normal, non-malfunction circumstances, to deploy the recersers. The aircraft I'm familiar with have an air/ground circuit interlock (electrical) that prevents reverser deployment in the air.
 
efohdee
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 6:26 am

What about turboprop aircraft? Can any turboprops reverse thrust inflight??
 
avt007
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 6:44 am

Yes, some turboprops can reverse inflight, often with disastrous results. There was a mod a few years back on the Dash8 to cause a Godawful horn to sound if you selected a power lever setting below flight idle. However, it is still possible to use reverse. I've read of incidents and accidents where reverse was accidently used on descent, resulting in prop overspeed, and at least once, propellor and gearbox failure, i.e. falling off the aircraft.
 
skysurfer
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 9:39 am

Wasn't there a DHC-5 Buffalo that crashed at an airshow a couple of years back (Farnborough???) due to the props being selected to 'reverse' pitch??

Any info or corrections are very welcome

Cheers

In the dark you can't see ugly, but you can feel fat
 
USAFHummer
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RE: Reverse Thrusting In The Air--possible?

Thu Nov 18, 2004 9:56 am

The NASA Gulfstream II is also modified to enable inflight reversing, which it needs while simulating shuttle approaches...

Greg
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747NUT
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RE: Reverse Thrusting In The Air--possible?

Fri Nov 19, 2004 1:01 am

I believe the 737 NG can deploy T/R 10 feet above ground.
It gets its signal through the radio altimeter
If it's not broken, don't fix it !
 
FredT
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RE: Reverse Thrusting In The Air--possible?

Fri Nov 19, 2004 4:10 am

Which may e g reflect off clouds. Hm. You sure?

Cheers,
Fred
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cancidas
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RE: Reverse Thrusting In The Air--possible?

Fri Nov 19, 2004 5:22 am

i've engaged the reverser on the C208 caravan inflight a few times. this was only for a matter of a few seconds to slow down on a steep final. (flaps full and spoliers up)

now some people tend to mix up reversers and reverse thrust. it is possible to open the reversers to use them as speed brakes. the IL-62, TU-154, C-5A and C-17 come to mind. to my knowledge, the only a/c that is actually capable of using reverse thrust inflight is the NASA gulfstream.
"...cannot the kingdom of salvation take me home."
 
greasespot
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RE: Reverse Thrusting In The Air--possible?

Fri Nov 19, 2004 5:52 am

Real simple. If you shut the engines down you have no reverse thrust. In reverse thrust the engines are still running...

GS
Sometimes all you can do is look them in the eye and ask " how much did your mom drink when she was pregnant with you?"
 
c172heavy
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RE: Reverse Thrusting In The Air--possible?

Fri Nov 19, 2004 3:03 pm

Skysurfer:

Is this the a/c you speak of?


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If so, the only cause of crash given in the Remarks was a strong, gusty tailwind and a steeper than normal approach. (Farnborough, 1984)
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HAWK21M
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RE: Reverse Thrusting In The Air--possible?

Fri Nov 19, 2004 4:32 pm

I remember a discussion many years ago at work about if T/R could be delibrately operated on a B732, & yes it could provided a sequence of actions were performed,Like using the T/R override,Landing gears Down,Thrust levers at Idle & Reverse thrust levers deployed.
Although under normal circumstances there were safety features In built to prevent an accidently or errornously deployment.
regds
MEL
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TripleDelta
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RE: Reverse Thrusting In The Air--possible?

Fri Nov 19, 2004 4:42 pm

Miamiair is right. Il-62s do, sometimes, open the reversers to slow down on final.


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Probably during fast or high-angle approaches they need to slow down and slow down quickly. Though I assume the stress in the engine pylon is great, plus the pylon having to carry 2 engines...
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747NUT
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RE: Reverse Thrusting In The Air--possible?

Fri Nov 19, 2004 7:20 pm

"Which may e g reflect off clouds"

I presume you are referring to the rad alt reflecting off clouds ?
Not likely otherwise you would be getting all sorts of GPWS warnings going off during flight, can you imagine the chaos with a "pull up, pull up" warning at 30 000 feet ?

Cheers Mike
If it's not broken, don't fix it !
 
Bellerophon
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RE: Reverse Thrusting In The Air--possible?

Sat Nov 20, 2004 2:20 am

Timz

...On the two inners...ditto for "the"...( Embarrassment , ouch!)...Concorde?...

Correct.

And traditionally just "Concorde".  Big grin


...Just on the center engine for the Trident?...

No, not on the centre engine, only on engines 1 & 3.

Best Regards

Bellerophon
 
Aviadvigatel
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RE: Reverse Thrusting In The Air--possible?

Sun Nov 21, 2004 10:49 pm

Keep an eye out for the new series on Discovery Wings - Classic British Aircraft. On the show with the VC10 and Trident, on ex Trident pilot talks about when he used reverse thrust in flight to descend from 20,000 feet in 3 minutes for a late landing approval.

Programme is on Tuesday nights at 9pm (UK), and repeated on some other evenings. Knowing Wings, it will probably be repeated for the next 5 years!
 
planespotting
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RE: Reverse Thrusting In The Air--possible?

Mon Nov 22, 2004 11:10 am

When i sat in on a new hire ground school at southwest one of the new guys asked the instructor if they could use reverse thrust while still in the air. the response is as follows:

"thats a good question. Now that reverse thrust lever you pull, thats a mechanical/hydraulic switch type thing isn't it? What do you suppose the chances of each engine going to reverse thrust at the exact time are? What if they were each about a thousandth of a second apart? The airplane would have one engine going at about 50% N1 and the other going about 75% N1 in reverse. What do you suppose the consequences of the airplane being violently yawed in the direction of the positive engine 10 feet off the ground are? Yes it is possible to put reverse thrust in while in the air, but do you want to be the test pilot that finds out?"
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2H4
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RE: Reverse Thrusting In The Air--possible?

Mon Nov 22, 2004 3:51 pm

I remember a discussion many years ago at work about if T/R could be delibrately operated on a B732, & yes it could provided a sequence of actions were performed,Like using the T/R override,Landing gears Down,Thrust levers at Idle & Reverse thrust levers deployed.


I've experimented with this in the 737-200 simulator and remember achieving 15-20,000 fpm descent rates by spooling the engines up with the buckets out and pushing the nose over to fly just under the barberpole. Not sure the buckets would stay attached to the aircraft in actual flight, but it was fun in the sim.


2H4
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tbanger
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RE: Reverse Thrusting In The Air--possible?

Mon Nov 22, 2004 4:47 pm

The Saab 340 has what is known as "Flight Idle Overide Stop". What does it do? Well exactly that!

There is a stop that activated via a microswitch prevents the power levers entering beta power whilst the aircraft is in flight. This is determined via the WOW or Weight On Wheels switch.

In an emergency, the pilots can pull a knob up which allows the stop to be overidden. Hence the name Flight Idle Overide Stop.

With the power levers at flight idle, those two enormous fans become giant airbrakes. I would hate to be in a position to require the use of reverse on one of these babies.....lol.

 
747NUT
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RE: Reverse Thrusting In The Air--possible?

Mon Nov 22, 2004 11:23 pm

" The airplane would have one engine going at about 50% N1 and the other going about 75% N1 in reverse.What do you suppose the consequences of the airplane being violently yawed in the direction of the positive engine 10 feet off the ground are? "

T/R can only be activated when the throttles are at idle (there is a gate that prevents them from being deployed in anything above idle) and only once the T/R is deployed will it only allow you to take power by pulling the T/R levers up further. So having both engines at different power settings are prevented.

If it's not broken, don't fix it !
 
10mid
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RE: Reverse Thrusting In The Air--possible?

Tue Nov 23, 2004 7:37 am

In a turboprop, a lot of the propwash goes over the horizontal stabilizer. Going into reverse, which on some planes is physically possible, disturbs the airflow on the horizontal stabilizer, causing the hose to drop suddenly. Disastrous when just feet off the ground.

In the words of John Hazlet, Director of Maintenance at Ameriflight, "You can do it. But you might as well shove a pistol up your ass and kiss your ass goodbye."
 
Slcpilot
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RE: Reverse Thrusting In The Air--possible?

Tue Nov 23, 2004 9:46 am

Here's another plane that was designed for the use of reverse thrust in flight. It was supposedly capable of ridiculously steep descents....



I never saw it fly, and I think that feature played a part in it's demise....

SLCPilot

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jetstar
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RE: Reverse Thrusting In The Air--possible?

Tue Nov 23, 2004 11:27 am

On the Lockheed JetStar, while reversers were not certified for use in flight, there was no real safety features to prevent this. All it took was the throttle brought back to idle and then the reverse lever could be pulled up and the reverser buckets would deploy.

Some pilots just before touchdown with the power levers back to idle would deploy the buckets and once the main wheels were on the ground they would pull up on the reverse levers to bring the engines back up to speed.

This probably saved a few hundred feet of runway because of the time delay from wheel touchdown when the reversers would be deployed until the reversers were fully extended and power could be brought up again.




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