Gonzalo
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Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:07 pm

I was doing my usual tour for some of the aviation video channels, and I came across this video of a Tu-154 activating the thrust reverser well before the wheels touched the runway. I had the ( wrong? ) idea about all the commercial / civil aircraft had weight on wheels sensors, to prevent in flight deployment of the T/R ( I remember the case of a Lauda Air Boeing 767 crashed after an uncommanded T/R activation, with a high loss of lives )

Video :

https://www.youtube.com/watch?v=Yq5HLtdGeqE

Is this a characteristic of the Tu 154 ? Or was this particular aircraft on the video under some special condition ( MEL'd, Ferry flight to MX ) ?

Are there any other civilian / pax aircraft type / model that allows this ?

Thanks in advance.

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DocLightning
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:17 pm

Quoting Gonzalo (Thread starter):
Is this a characteristic of the Tu 154 ? Or was this particular aircraft on the video under some special condition ( MEL'd, Ferry flight to MX ) ?
Deploying The Thrust Reverser While Flairing? (by LH492 Jul 25 2006 in Civil Aviation)
Photo Question (by Kaitak744 Oct 24 2005 in Civil Aviation)

There are a few others. Presumably, the Tu154 locks out the reversers until the engines are at idle, although given that it's a 1960's Russian design, I'm not entirely sure about that.
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northstardc4m
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:18 pm

This was the case on a few jetliners:
DC-8 up to model 61
VC-10
IL-62
some models of Tu-134 and most is not all models of the Tu-154

Not common but if the plane is designed for it...
DC-8s had it only on engines 2 and 3, and some issues causing a couple crashes cause it to be disabled later on.
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Spacepope
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:18 pm

AFAIK a few other aircraft can do that too, including the IL-62. See at about 0:32 on this video: http://www.youtube.com/watch?v=N29ZFnQfm7I

Fuzzy memories make me think the DC-8 was also capable.
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BoeingGuy
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:29 pm

Quoting northstardc4m (Reply 2):
Not common but if the plane is designed for it...
DC-8s had it only on engines 2 and 3, and some issues causing a couple crashes cause it to be disabled later on.

The DC-8 in flight thrust reversers were intended to be used as speedbrakes. I don't think they were intended for use shortly before touchdown the OP was referring to. I'm not aware of crashed because of it. I experienced as a passenger as late as 1977 and thought I heard that the CFM engines on the -71s and -73 were also designed to used in reverse in flight.

Can you elaborate on the crashes and how in-flight thrust reverse used was disabled on the DC-8s?
 
migair54
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:29 pm

If i´m not mistaken the conconrde also could do to reduce speed, Russian planes as usual have some special features, they fly in somehow a different way from the western planes.

For example, when you see a russian plane taking off, for them getting speed first and then climbing is the procedure, but for western planes altitude is first then speed, if you think a bit in a place with a big clearway and no noise abatement it could be a good practice because in the Lift formula V is Square so increasing speed has a very big effect on lift.

But anyway, I´ve seen few Tu-154 and IL-62 mainly doing that. I think the pilatus porter can also do, but of course that´s not a jetliner.

Quoting northstardc4m (Reply 2):
DC-8s had it only on engines 2 and 3, and some issues causing a couple crashes cause it to be disabled later on.

i´m sure the forces generated in the pylon of the engines must have been terrible, they are designed to do let the engine pull the plane forward and not backward.
 
citationjet
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:33 pm

Here are other threads on this topic:
DC-8 And Reverse Thrust Use In Flight (by Ttailsteve Jul 3 2006 in Civil Aviation)

Thrust Reversers Before Touchdown? (by DocLightning Jul 7 2008 in Tech Ops)?threadid=232417&searchid=232483&s=DC-8+reverse#ID232483

Inflight Reverse Thrust On DC 8 (by 6YJCX Dec 4 2007 in Tech Ops)?threadid=211585&searchid=211930&s=DC-8+reverse#ID211930
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BlueShamu330s
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:34 pm

So I drive a 4x4. So what?! Tax the a$$ off me for it...oh, you already have... :-(
 
northstardc4m
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 6:35 pm

Quoting BoeingGuy (Reply 4):
Can you elaborate on the crashes and how in-flight thrust reverse used was disabled on the DC-8s?
http://www.airliners.net/aviation-forums/tech_ops/read.main/211585/

apparently all 4 engines could do reverse sorry... and I was under the impression that it was actually disabled, though apparently it was just airline policy.

And i'm finding more types:
Trident
Concorde
Tu-144
Jetstar
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Tristarsteve
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 7:38 pm

Quoting northstardc4m (Reply 8):
Trident

Ah de Havilland.
Now the Trident only had reverse on 1 and 3.
But they were deployed regularly in the descent as speedbrakes.
Then the aircraft could descend very fast. So fast that one Trident, I think it was the 2E did not have passenger oxygen fitted. In case of emergency, engines to idle, select reverse, descend nose down!
 
BoeingGuy
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 7:40 pm

Quoting Tristarsteve (Reply 9):
So fast that one Trident, I think it was the 2E did not have passenger oxygen fitted. In case of emergency, engines to idle, select reverse, descend nose down!

I can't imagine that. It's still like 3 minutes from cruise to 10,000 feet.
 
MH017
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 8:37 pm

Flew once a Syrian YAK-40, and they applied the (single) thrust-reverser before touch-down at DAM...
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longhauler
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 8:48 pm

Quoting Tristarsteve (Reply 9):
So fast that one Trident, I think it was the 2E did not have passenger oxygen fitted.

Actually, it was the other way around. The Trident One, and the Trident Three did not have passenger oxygen (in Britain, I am not sure about export models), the Trident Two did.

Same thing with most versions of the BAC-111, no passenger oxygen.
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tdscanuck
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 18, 2012 10:55 pm

Quoting Gonzalo (Thread starter):
I had the ( wrong? ) idea about all the commercial / civil aircraft had weight on wheels sensors, to prevent in flight deployment of the T/R

They all have systems to prevent inadvertent T/R deployment. Those aren't always weight-on-wheels sensors. The 737, for example, can deploy off the radio altimeter (and hence can deploy in a very thin range of "in-the-air").

Tom.
 
737tdi
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RE: Thrust Reverser Deployment Before Touchdown

Wed Dec 19, 2012 12:01 am

Quoting tdscanuck (Reply 13):
They all have systems to prevent inadvertent T/R deployment. Those aren't always weight-on-wheels sensors. The 737, for example, can deploy off the radio altimeter (and hence can deploy in a very thin range of "in-the-air").

Tom





Tom: I believe once the "sync-loc" mod. was installed the reversers can not and will not deploy until weight on wheels. You can pull the handle but nothing will happen until then.

As far as the DC-8 the inboard reversers can be deployed at any time. There is a mechanical lock off of the nose landing gear to prevent deployment of the outboard reversers. I have flown many test hops where this system was verified and it feels like you hit a wall when those CFM-56-2s are reversed in flight. Remember the DC-8 does not have speedbrakes so they use the reversers to slow.
 
PGNCS
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RE: Thrust Reverser Deployment Before Touchdown

Wed Dec 19, 2012 1:06 am

Quoting tdscanuck (Reply 13):
Quoting Gonzalo (Thread starter): I had the ( wrong? ) idea about all the commercial / civil aircraft had weight on wheels sensors, to prevent in flight deployment of the T/R
They all have systems to prevent inadvertent T/R deployment. Those aren't always weight-on-wheels sensors. The 737, for example, can deploy off the radio altimeter (and hence can deploy in a very thin range of "in-the-air").

Tom.

The DC-9 series has nothing to inhibit inflight deployment (WoW or RA, etc.) other than good sense. In over 10,000 hours on the aircraft I have never seen it be an issue. Of course the throttle does have to be at idle first, so I suppose you could make the argument that this interlock is a system to prevent inadvertent deployment, though it will NOT prevent inflight deployment regardless of altitude.
 
tdscanuck
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RE: Thrust Reverser Deployment Before Touchdown

Wed Dec 19, 2012 1:32 am

Quoting 737tdi (Reply 14):
Tom: I believe once the "sync-loc" mod. was installed the reversers can not and will not deploy until weight on wheels. You can pull the handle but nothing will happen until then.

The sync-lock is triggered by microswitches on the T/R deploy handles...the sync-locks will release as soon as you pull up on the handles. They're there to prevent a Lauda-type incident by providing an independent level of redundancy in the actuation hardware. The sync-locks will not prevent an intentional deployment.

Assuming that the pilot pulls the levers (releasing the sync locks), another relay needs to actuate to command hydaulic fluid to the actuators. The ground for that relay can go through two paths...one is the air/ground system (basically weight-on-wheels) and the other is the radio altitude from the flight control computer (less than 10'). Either path is sufficient to allow deployment so if you're on the ground (specifically, the air/ground relay is in ground) or the FCC thinks you're less than 10' from the ground, the T/R's will deploy.

If you have access, check out 737 AMM SDS 78-34-00 for more details.

The key to most T/R systems is preventing *inadvertent* deployment. Many aircraft will inhibit deployment in flight regardless what the crew says but all of them don't want the T/R's to ever deploy unless the flight crew wants them to.

Tom.
 
XXXX10
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RE: Thrust Reverser Deployment Before Touchdown

Sat Dec 22, 2012 9:20 am

Quoting Tristarsteve (Reply 9):

Not sure about the TU144
I may be wrong but AFAIK there where no T/R on this bird. I beleive a parachute was used on landing !
 
Sasha
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RE: Thrust Reverser Deployment Before Touchdown

Sat Dec 22, 2012 1:54 pm

Yak-40 also could do this. not sure about Yak-42. landed in one last sunday - it didn't use it  
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Fabo
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RE: Thrust Reverser Deployment Before Touchdown

Sun Dec 23, 2012 1:58 am

IIRC YK42 does not have reversers - at all.
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atct
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RE: Thrust Reverser Deployment Before Touchdown

Tue Dec 25, 2012 4:05 am

Quoting BoeingGuy (Reply 10):

There are also regs (someone else will have to find em) that say how many O2 masks are required per passenger. I was a flight attendant on a US regional and though we "briefed" the masks, we did not have more than 1 for each 10 passengers on board the aircraft.

atct
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DualQual
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RE: Thrust Reverser Deployment Before Touchdown

Thu Jan 03, 2013 9:42 pm

Quoting tdscanuck (Reply 13):

IIRC (haven't really looked at that system page in a while) it's 10feet on the RA you can deploy the reversers on the 737. I don't know why anyone would want to do that but you could.
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longhauler
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RE: Thrust Reverser Deployment Before Touchdown

Fri Jan 04, 2013 3:39 am

Quoting tdscanuck (Reply 13):
They all have systems to prevent inadvertent T/R deployment. Those aren't always weight-on-wheels sensors. The 737, for example, can deploy off the radio altimeter (and hence can deploy in a very thin range of "in-the-air").

That must have been later B737s, the B737s I flew (-200, and -200ADV) required positive oil pressure and weight on wheels to power the hydraulics to work.

In fact, some of them also had a squat switch in the nose wheel as well, which also had to be activated. Makes sense, the -200 had huge buckets and in a nose high attitude, you could scrape them on the ground.
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tdscanuck
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RE: Thrust Reverser Deployment Before Touchdown

Fri Jan 04, 2013 3:03 pm

Quoting longhauler (Reply 22):
That must have been later B737s, the B737s I flew (-200, and -200ADV) required positive oil pressure and weight on wheels to power the hydraulics to work.

Yes, I was talking -300 and onwards. -100/-200 had a totally different reverser system.

Tom.
 
Kaiarahi
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RE: Thrust Reverser Deployment Before Touchdown

Fri Jan 04, 2013 9:35 pm

Quoting BoeingGuy (Reply 4):
Can you elaborate on the crashes

NZ lost a DC-8 at AKL on a training flight when a TR was activated on a touch-and-go. My father was an FE with NZ at the time and scheduled to be on that flight, but was swapped out for other duties.
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BA777
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RE: Thrust Reverser Deployment Before Touchdown

Sat Jan 05, 2013 10:30 am

Yep thats correct on the 737 you can deploy them just before touchdown, a Captain did it last week and it made for a very....commercial landing!
 
fsnuffer
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RE: Thrust Reverser Deployment Before Touchdown

Sat Jan 05, 2013 2:30 pm

While at Offutt there were rumors RC-135 pilots were deploying TR during the flare and it was called a "Shemya Short Landing". Since I never took a flight to Shemya, it is only second hand.
 
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longhauler
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RE: Thrust Reverser Deployment Before Touchdown

Sat Jan 05, 2013 3:57 pm

Quoting Kaiarahi (Reply 24):
NZ lost a DC-8 at AKL on a training flight when a TR was activated on a touch-and-go. My father was an FE with NZ at the time and scheduled to be on that flight, but was swapped out for other duties.

When I hear stories like this, I often think of fate.

My father was supposed to be the Second Officer of the Trans-Canada DC-8 that was lost at YUL in 1963, but the crew's inbound flight was late and a reserve crew was used instead. When I asked him about that, he just said, "If I were on the aircraft, it wouldn't have crashed, I guess it was meant to crash!"

Maybe it was the same in your Father's case. His hand on the thrust levers might have had a different weight, angle, etc ... and the T/R would not have been activated.
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Kaiarahi
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RE: Thrust Reverser Deployment Before Touchdown

Mon Jan 07, 2013 6:21 pm

Fate for sure! I can't find the accident report archived anywhere, but the story within NZ at the time was that the training captain (left seat) may have hooked his finger around the "leg" of #4 throttle (rather than the knob) and pulled it back aggressively (they were doing engine out drills), causing the TR to jerk up and deploy. If he'd had his hand on the top of the throttle, it likely wouldn't have happened. As I recall the report, there was a recommendation for better TR lever mechanical protection, but I don't remember if it was implemented. I do remember that when I was learning to fly Hercs a few years later, simulated engine out training was done with a smooth throttle retardation - the AKL accident was still fresh in everyone's mind.
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Kaiarahi
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RE: Thrust Reverser Deployment Before Touchdown

Mon Jan 07, 2013 7:39 pm

Whoops - training captain was right seat .... And in the DC-8, they were actually called "thrust brakes", rather than TRs.

[Edited 2013-01-07 12:34:27]
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