c5load
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In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 1:46 am

When we fly and have to do a steep descent, we sometimes deploy the inboard thrust reversers to help slow us down. Do any civilian 4 engine airplanes do this as and emergency descent procedure?
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
T prop
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 2:00 am

I think DC-8 can on all 4 engines also Trident. Those and some Russian types maybe.

[Edited 2009-09-26 19:07:40]
 
timz
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 2:34 am

Many? Most? All? DC-8s were allowed to use full reverse on #2 and #3-- and not just for emergency, supposedly.
 
tdscanuck
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 2:58 am



Quoting Timz (Reply 2):
Many? Most? All? DC-8s were allowed to use full reverse on #2 and #3-- and not just for emergency, supposedly.

A few can do it, but they tend to be older designs. I'm not aware of any large Western jet since the 80's that can do it. Can't speak for the Russian designs...

Tom.
 
L-188
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 5:58 am

As far as the russians..


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I believe they usually carried power on the turbine so they didn't have to wait for the engines to spool up on a go-around.

I don't think I can come up with a high bypass engine that has this feature.
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tdscanuck
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 6:21 am



Quoting L-188 (Reply 4):
I don't think I can come up with a high bypass engine that has this feature.

I had that thought too. I almost wrote it down, then decided there were too many high-bypass fans out there that I couldn't be sure about.

Can anybody out there think of a (commercial) high-bypass fan that does in flight reverse?

Tom.
 
ImperialEagle
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 1:03 pm

quote=C5LOAD,reply=0]When we fly and have to do a steep descent, we sometimes deploy the inboard thrust reversers [/quote]

Are you speaking specifically about the C-5?
Interesting. I wonder what other high-bypass equipped military aircraft also have this capability?

I do not know whether the CFM equipped -8's have this capability.
The P&W -8's certainly use reverse thrust inflight. It was used often on the standard-bodied
-8's and is very effective.
"If everything seems under control, you're just not going fast enough!"
 
9VSIO
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 1:08 pm

Reverse Thrusters In Flight (by Jetblueguy22 May 9 2009 in Tech Ops)

Rather recent thread abt this...
Me: (Lining up on final) I shall now select an aiming point. || Instructor: Well, I hope it's the runway...
 
FWI747
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 1:27 pm



Quoting Tdscanuck (Reply 5):
Can anybody out there think of a (commercial) high-bypass fan that does in flight reverse?

IIRC CFM56 powered DC8 can do that too...
 
71Zulu
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 3:44 pm

Concorde could use thrust reversers on #2 and #3 in flight for descents as well...
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dispatchguy
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 5:52 pm

Only the older birds could do this, most civilian airliner flight manuals that I have seen have a specific prohibition against deploying a T/R inflight; and, due to system logic, its a near impossibility as you need weight on wheels to be able to close the interlock to deploy a T/R.

Lauda Air lost a B767 climbing out from Asia when his T/R deployed inflight back in 1991 or 1992

[Edited 2009-09-27 10:53:48]
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PGNCS
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 6:08 pm



Quoting Dispatchguy (Reply 10):
Only the older birds could do this, most civilian airliner flight manuals that I have seen have a specific prohibition against deploying a T/R inflight; and, due to system logic, its a near impossibility as you need weight on wheels to be able to close the interlock to deploy a T/R.

Lauda Air lost a B767 climbing out from Asia when his T/R deployed inflight back in 1991 or 1992

Good point about the Lauda accident.

All airliner types I have flown (727, 737, 744, 757, 767, DC-9/MD-80/MD-90, L-1011, A-320 family) have been prohibited from inflight reverser use, although as several have pointed out there are types capable and authorized to use inflight reverse. As you mentioned, most aircraft have interlocks that need weight on wheels (i.e. the aircraft needs to be on the ground) to deploy reversers, but some aircraft do not, relying on the intelligence of the pilots not to use the reversers in the air (e.g. DC-9); in my experience it has never been an issue either way.
 
c5load
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 9:59 pm



Quoting PGNCS (Reply 11):
All airliner types I have flown (727, 737, 744, 757, 767, DC-9/MD-80/MD-90, L-1011, A-320 family) have been prohibited from inflight reverser use

Usually T/R usage would only be reserved for 4 engine airplanes that way you have symmetrical thrust on the outboards. Three-engine airplanes could maybe get away with it by deploying the no.2 that way you still have even thrust.
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
JETPILOT
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 11:28 pm

The DC8 can reverse thrust in flight up to MCT on engines # 2/3. You can get idle reverse thrust on engines #1/4 when the gear is down. I used reverse thrust in flight once and the engine felt like they were going to rip off.
 
PGNCS
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RE: In-Flight Thrust Reverser Usage

Sun Sep 27, 2009 11:28 pm



Quoting C5LOAD (Reply 12):


Quoting PGNCS (Reply 11):
All airliner types I have flown (727, 737, 744, 757, 767, DC-9/MD-80/MD-90, L-1011, A-320 family) have been prohibited from inflight reverser use

Usually T/R usage would only be reserved for 4 engine airplanes that way you have symmetrical thrust on the outboards. Three-engine airplanes could maybe get away with it by deploying the no.2 that way you still have even thrust.

What are you talking about? ALL of the aircraft I mentioned have reverse thrust on all engines. None, including the 747-400, is approved for inflight reversing; all are approved to use the reversers on the ground to slow the aircraft during landing (or RTO).
 
c5load
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RE: In-Flight Thrust Reverser Usage

Mon Sep 28, 2009 12:09 am



Quoting PGNCS (Reply 14):
What are you talking about? ALL of the aircraft I mentioned have reverse thrust on all engines. None, including the 747-400, is approved for inflight reversing; all are approved to use the reversers on the ground to slow the aircraft during landing (or RTO).

Yes, I know all of the airplanes you mentioned have reverse thrust capabilities on the ground, but I am talking about using them in the air. Like I said, with a two-engine jet, you obviously can't use them inflight. But a 4-engine airplane, you could use them in-flight to slow yourself down in a steep or emergency descent. When you deploy them, just the drag helps slow you down. You obviously don't spool them up in reverse.
"But this airplane has 4 engines, it's an entirely different kind of flying! Altogether"
 
Viscount724
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RE: In-Flight Thrust Reverser Usage

Mon Sep 28, 2009 12:26 am



Quoting L-188 (Reply 4):
As far as the russians..

Also the Tu-154, however I believe the Tu-154 and IL-62 only use reversers very close to the ground, unlike the DC-8. If memory correct, the IL-62 only has reversers on the outboard engines, and the Tu-154 only on engines 1 and 3.


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PGNCS
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RE: In-Flight Thrust Reverser Usage

Mon Sep 28, 2009 12:51 am



Quoting C5LOAD (Reply 15):
Quoting PGNCS (Reply 14):
What are you talking about? ALL of the aircraft I mentioned have reverse thrust on all engines. None, including the 747-400, is approved for inflight reversing; all are approved to use the reversers on the ground to slow the aircraft during landing (or RTO).

Yes, I know all of the airplanes you mentioned have reverse thrust capabilities on the ground, but I am talking about using them in the air. Like I said, with a two-engine jet, you obviously can't use them inflight. But a 4-engine airplane, you could use them in-flight to slow yourself down in a steep or emergency descent. When you deploy them, just the drag helps slow you down. You obviously don't spool them up in reverse.

But that's not what you said in your reply 12. You said "Usually T/R usage would only be reserved for 4 engine airplanes that way you have symmetrical thrust on the outboards. Three-engine airplanes could maybe get away with it by deploying the no.2 that way you still have even thrust."

The Trident could use inflight reverse; and evidently Concorde and the DC-8 could use inflight reverse on the #2 and 3 engines. I have not flown any of those three aircraft, so I have no firsthand knowledge of the operational limitations associated with them. What I do know is that regardless of which of these aircraft we are discussing, symmetrical thrust is possible in either forward of reverse thrust. It is, as I correctly pointed out, not permitted on any of the airliner types I have flown including the 4-engined 747-400. Most of the aircraft I mentioned have interlocks that prevent inflight reverse; some don't.
 
ImperialEagle
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RE: In-Flight Thrust Reverser Usage

Mon Sep 28, 2009 3:00 am



Quoting JETPILOT (Reply 13):
engine felt like they were going to rip off.

Ah, but the -8 is a tough old bird.

The only time I experienced in-flight reverse thrust on a stretched -8 was a -61 of UA's on a flight from Denver to Reno. We dove in over the Truckies with the inboards roaring.

It was very common to use reverse thrust on the standard-bodied -8's. If ATC pulled a fast one on you, you could loose altitude and/or speed in a hurry. It was always very dramatic.
I have fond memories of threading the eye of the needle in a -51 series, diving through afternoon thunderstorms on the way into MCO. Awesome!
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JETPILOT
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RE: In-Flight Thrust Reverser Usage

Tue Sep 29, 2009 9:31 am

One of the -8's in our fleet was an old UA -61. Maybe it was the same plane. Our company for some reason prohibited revrse thrust in flight. I never got an explanation as to why. But I had to do it just once. Captains discretion.... you know the deal. Nothing as tough as the DC8!
 
Bellerophon
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RE: In-Flight Thrust Reverser Usage

Tue Sep 29, 2009 5:26 pm

C5LOAD

...Three-engine airplanes could maybe get away with it by deploying the no.2 that way you still have even thrust...

On a three-engined jet aircraft I flew (HS121) - which was approved for the use of reverse thrust in the air - there was no thrust reverser fitted to No.2 engine, so it would have been rather hard to have used it in the manner you suggest.

Reverse thrust was fitted only on Nos. 1 & 3, and could be used on the ground or in the air, on either or both engines, subject to various operational limitations.

On a more general note, having also flown a four-engined jet aircraft on which reverse thrust in the air was permitted, allow me to say this, about both types:

    * The use of reverse thrust in the air, on only one engine, if necessary, was permitted.

    * There were several operational limitations on the use of reverse thrust in the air.

    * These limitations sought to guard against the achieving or maintaining of very high rates-of-descent when near the ground.

    * These limitations sought to give the pilot adequate time to shut down an engine should one fail to come out of reverse thrust, when commanded, in the air.

    * The most passenger friendly way of using reverse thrust in the air was to use it to decelerate as well as descend, that way a relatively level pitch attitude / cabin floor could be maintained.

On both types, the principal area one had to be very careful about, when using reverse thrust in the air, was to allow oneself sufficient time and height above the desired level-off altitude to cancel reverse thrust, reduce the RoD and then level off without pulling 4g !


Best Regards

Bellerophon
 
borism
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RE: In-Flight Thrust Reverser Usage

Tue Sep 29, 2009 6:59 pm

Qatar has civilian C-17s, so yes.

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