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neilking
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Reverse Thrust Engagement

Sun Aug 14, 2005 11:40 pm

Is it true that, on some airliners, reverse thrust can be set to deploy automatically when the main gear touches the ground (like the spoilers)?

Also, are aircraft fitted so that the crew can't apply power with the thrust reverser levers raised until "the system" has confirmed that both (or all) sets of reverser gills are opened so as to prevent an inadvertent thrust situation?

Any pilots out there who can explain to me how R/T works on, say, an Airbus?

Thanks, Neil
 
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N405MX
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 1:23 am

Quoting Neilking (Thread starter):
Is it true that, on some airliners, reverse thrust can be set to deploy automatically when the main gear touches the ground (like the spoilers)?

On the A320 you put the thrust levers on iddle, and the reverse levers on "armed" position (you lift them), when touch-down, the reverses deploy automatically, then the pilot just have to move the thrust levers backward so he can apply more reverse thrust.

Cheers
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HAWK21M
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 2:21 am

Reverse Thrust

Above is only the Bucket type.
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neilking
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 2:34 am

Did one of the forum moderators move this thread from Civil Aviation to Tech Ops?
 
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HAWK21M
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 2:38 am

Quoting Neilking (Reply 3):
Did one of the forum moderators move this thread from Civil Aviation to Tech Ops

If they did,You'll recieve an Email stating that.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
SlamClick
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 2:43 am

I am not aware of any airliner on which the reversers can be set to deploy automatically.

In all cases that I am aware of (six type ratings and an instructor on two other types) it is done manually by the pilot flying.

I know of at least two types where they can be extended in flight. I said "can" and not "should" by the way.

The picture HAWK21M provided for the clamshell type is pretty close to what the "cascade" type of reverser is like. Instead of clamshell buckets across the whole exhaust they do this:

A part of the cowling slides aft, uncovering a set of cascade grates which are angled forward. Reaching full aft position it moves internal "blocking doors" into the fan duct and directs the fan air through the cascades which angles it forward.

Cascade type reversers on high-bypass fan jets get an increase in forward thrust from the engine core exhaust, while spooling up in reverse, which must be offset by reverse thrust from the fan air. That makes them perhaps slightly less efficient.

With both types, if you come out of reverse too quickly the reversing mechanism will stow with the engine still at high RPM and you will get a forward thrust boost for a moment. Usually we will linger for a moment at reverse idle until the engines unspool, before closing the reversers.
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neilking
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 3:56 am

Thanks for all the replies, guys.

Yes I got an e-mail saying my thread had been moved to Tech/Ops - they're very strict here on A.Net!

Replies seem quite conflicting - N405MX says yes and SlamChick says no.

I only asked because I watched a vid on FL350.com of an A330 landing and the R/T gills (is that the right word?) opened before the nosewheel was down.

Although that's not to say power was applied before the nosewheel was down. But if it was (automatically), would that not cause a massive nose down pitch?

If R/T engages automatically on touch down, could this not cause a stress-ful situation in a "bounced" landing in gusty conditions?

Any further replies welcome.

Neil
 
Matt72033
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 4:04 am

reverse thrust can only be activated on the ground, this is usually garunteed by a weight on wheels switch that puts the aircraft in 'ground mode' sometimes also when the MLG wheels spin up, all of which located in the MLG

i'm sure this is a very simplistic explanation, but someone out tehre will be able to give you a better idea.
 
neilking
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 4:17 am

Thx Matt

The question I'm looking for an answer to here is, can a modern airliner be set to a mode whereby, when the MLG detects weight (touchdown), the R/T gills (or clamshells - only on older jets like the 732??) open automatically and the engines automatically spool up to give R/T?

i.e. R/T happens "automatically" on touchdown totally "hands-off" from the flight crew?

May be I misunderstood previous replies (and/or never understood in the first place?)

Neil
 
DH106
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 5:40 am

I have a photo in a book somewhere of an IL-62 crossing a threshold still 20ish feet in the air with it's buckets already open. Very short runway perhaps ?  Smile
The Il-62 is not exactly renowned for it's short field performance Maybe the ex. Soviet types have less rigorous safeties on reverser deployment.
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PhilSquares
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 5:52 am

Quoting Neilking (Reply 8):
The question I'm looking for an answer to here is, can a modern airliner be set to a mode whereby, when the MLG detects weight (touchdown), the R/T gills (or clamshells - only on older jets like the 732??) open automatically and the engines automatically spool up to give R/T?

Again, the answer is NO!
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air2gxs
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 6:08 am

Some terminology:

The gills are cascade panels or vanes. The part of the cowl that moves aft is called the translating sleeve.


Reverse thrust must be selected by the flight crew. On aircraft I'm familiar with (B727, B747, B757, B767, MD11 & A300) the reverse levers will not even come up into the idle detent unless the throttles are at idle. Then the main gear needs to be on the ground, therefore the reversers can be deployed with the nose in the air.

According to N405MX, the A320 apparently has a system similar to the auto speedbrake system. I have no knowledge of the A320, so I won't comment.

TIn the DC8 reverse thrust can be selected in the air. With flaps up only 2 & 3 can be selected to reverse. With flaps down, all 4 can. We have banned the use of reverse thrust in the air (except in emergencies) due to the abnormal stresses exerted on the structure.
 
PhilSquares
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 6:39 am

Quoting Air2gxs (Reply 11):
According to N405MX, the A320 apparently has a system similar to the auto speedbrake system. I have no knowledge of the A320, so I won't comment.

There is no auto reverse in the 320/330/340 family of aircraft. I can't think of a single transport category aircraft that has an auto-reverse system.
Fly fast, live slow
 
neilking
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 7:12 am

Thx Air2 and Phil

Think I'm getting the picture that there is no modern airliner with "auto reverse"

Thx for the replies, Neil
 
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Starlionblue
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 8:01 am

Quoting Neilking (Reply 6):
Yes I got an e-mail saying my thread had been moved to Tech/Ops - they're very strict here on A.Net!

I agree. And that's part of what makes it a great board.

Quoting Neilking (Reply 6):
R/T gills (is that the right word?)

Nope, but I like it Big grin As Air2Gxs says, they're called panels or vanes.

Quoting Matt72033 (Reply 7):
reverse thrust can only be activated on the ground, this is usually garunteed by a weight on wheels switch that puts the aircraft in 'ground mode' sometimes also when the MLG wheels spin up, all of which located in the MLG

Many types allow T/R in the air, including the C-17 (where it is regularly used operationally) and the DC-8.
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SlamClick
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 9:24 am

Quoting Matt72033 (Reply 7):
reverse thrust can only be activated on the ground,

Perhaps on some types, but there are plenty of others where they can be opened in flight.

Quoting Neilking (Reply 6):
I only asked because I watched a vid on FL350.com of an A330 landing and the R/T gills (is that the right word?) opened before the nosewheel was down.

That was our standard landing in the A-330. Get the mains on, pop the reversers then fly the nose gently (sometimes) to the runway. You would not be getting any real thrust until the nosewheel was on, anyway. If one engine should flame out on its way past reverse idle, you'd have nosewheel steering as well as rudder authority to see you through the uncomfortable moment of asymmetric reverse.
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Matt72033
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RE: Reverse Thrust Engagement

Mon Aug 15, 2005 8:51 pm

Quoting SlamClick (Reply 15):
Perhaps on some types, but there are plenty of others where they can be opened in flight

yeah, sorry, im aware that there are certain types but i was just speaking generally......sorry
 
troubleshooter
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RE: Reverse Thrust Engagement

Tue Aug 16, 2005 10:47 am

On the 737 the thrust reverser can be deployed below 10ft RA.
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bri2k1
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RE: Reverse Thrust Engagement

Tue Aug 16, 2005 11:43 am

Quoting Neilking (Reply 8):
only on older jets like the 732??

In general, high-bypass turbofan engines employ cascade-style reversers. The high ratio of bypass air mass flow to core flow makes them highly effective.

I don't know which engine types or reverser configurations were available on any particular 737 variant.

I believe many business-class jets built today have lower bypass ratios and are equipped with clamshell-style reversers.

Others will know more. I'm curious though -- why the fascination with thrust reversers? They aren't that impressive. Their use is optional and never calculated into landing figures. Most landings are conducted with only idle reverse -- they are barely counteracting the forward thrust at that point, but they can be spun up if they're really needed. Only, they would have a hard time stopping an airliner. Especially when at higher weights as operated by (profitable) carriers, the wheel brakes are the most effective, and to me, most impressive kinetic energy dissipators on the plane. Barring my rant, you can rest assured there are numerous other threads regarding thrust reversers here, and you can read as much as you'd like.

When thrust reversers are impressive, to me, is when they're engaged in air. At least one US Air Force type can deploy the inboard two engines' reversers in flight, and safely achieve a 6000 FPM descent rate!
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HAWK21M
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RE: Reverse Thrust Engagement

Tue Aug 16, 2005 4:41 pm

Quoting Troubleshooter (Reply 17):
On the 737 the thrust reverser can be deployed below 10ft RA.

Not if the mod to include the NLG on grd thru the added nose Air-Grd sense is implemented.
Enabling the T/R deployment only when all Three Gears are on the Ground.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
Airgypsy
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RE: Reverse Thrust Engagement

Wed Aug 17, 2005 12:04 pm

Troubleshooter is correct on the 733. 10 feet radar altimeter was the arm for the TRs. It was because the TRs were slow to deploy and the engines are not renown for their acceleration from idle or even flight idle. The 732 got the switch moved to the nose gear after a 732 parked in a gas station after a long landing at RDU. If those short little mains won't "get on" (because he's floating down the runway) the pilot can push the nose on and delploy the TRs.
I've seen the film of a C-5 doing the emergency breakaway from a tanker with #2 and #3 reversers deployed in flight. Drops off the boom like a rock!
Have fun and stay off the brakes on those powerbacks.
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HAWK21M
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RE: Reverse Thrust Engagement

Wed Aug 17, 2005 4:46 pm

Quoting Airgypsy (Reply 20):

Any link to the relevant SB.
regds
MEL
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troubleshooter
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RE: Reverse Thrust Engagement

Thu Aug 18, 2005 4:31 am

Quoting HAWK21M (Reply 21):
Any link to the relevant SB.

Hawk, I´m not sure if there´s an existing SB. I was refering to the 737NG (I don´t know the classics) and there the T/R can be deployed below 10 ft RA without any air/ground signal.

Is there a difference to the classic 737?
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HAWK21M
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RE: Reverse Thrust Engagement

Fri Aug 19, 2005 1:26 am

Quoting Troubleshooter (Reply 22):
Is there a difference to the classic 737

On our Aircraft there was a Mod done to prevent T/R deployement until all Three Gears are on the Grd.Provided by an additional Air-Grd sense at the Nose gear Lh wheelwell operated by the PPI cable to the Nose Gear steering Mechansim.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
highflyer9790
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RE: Reverse Thrust Engagement

Wed Aug 24, 2005 6:45 am

does anyone have a diagram of a 747 RT bucket like the one MEL gave us?
121
 
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HAWK21M
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RE: Reverse Thrust Engagement

Wed Aug 24, 2005 9:10 pm


The closest I could get.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
neilking
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RE: Reverse Thrust Engagement

Sun Sep 04, 2005 3:35 am

As the person who started this thread, can I thank all the contributors for their very interesting replies.

Rgds, Neil
 
abbs380
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RE: Reverse Thrust Engagement

Sun Sep 04, 2005 4:10 pm

Its been many years, but IIRC, on the DC-8 Series 63. Originally you could get full reverse on all 4 engs. in flight. Then after a while they came out with a s/b to mod the a/c so you could only get full power on the i/b engs and idle on the ob/s. To get full reverse on all 4 you had to be on the ground with the nose strut compressed. The mechanism which controlled this was a cable operated cam shaft located in the center pedestal, which blocked reverse throttle travel until the nose strut was compressed.

The reversers were translating sleeve bucket type, which deflected both fan and core flow. In an emergency there was a provision to stow the buckets even with the translating sleeve deployed so you would have immediate foreward thrust.
 
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HAWK21M
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RE: Reverse Thrust Engagement

Sun Sep 04, 2005 6:32 pm

Quoting Abbs380 (Reply 27):
Then after a while they came out with a s/b to mod the a/c so you could only get full power on the i/b engs and idle on the ob/s.

What prompted the SB.
regds
MEL
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abbs380
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RE: Reverse Thrust Engagement

Mon Sep 05, 2005 5:00 pm

Mel, Im not sure what prompted the sb but I think it was related to what Air2gxs said in reply 11, abnormal stress. I think he is describing a re-engined DC-8 whereas I am talking about the old smoky, noisy, version.

By coincidence we had an A300 come in tonight with no 2 engine i/b reverser half stuck in full reverse while the o/b half was stowed. As the a/c pulled in I was standing by the gpu ready to hook up the power cord when suddenly (I thought at first) a huge gust of wind hit me. After I hooked up the cord and the engs. were shut down the wind went away, duh, then I realized what happened. The Capt. said they didn't get an unlocked light until the engs. were shut down, but I suspect it was on all the time since they came out of reverse but they just didn't notice since it was a slow day at the airport and they used all the rwy. and just rolled into parking.

Anyway, TR/S are maintenance intensive.
 
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HAWK21M
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RE: Reverse Thrust Engagement

Mon Sep 05, 2005 5:14 pm

Quoting Abbs380 (Reply 29):

Surprisingly no Indication.After landing when the R/T Levers were stowed.Does the A300 use Proximity Switches for sense.
regds
MEL
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abbs380
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RE: Reverse Thrust Engagement

Tue Sep 06, 2005 11:11 am

MEL, no prox detectors. On the CF6-80a2 they use conventional switches for stow/deploy ind. They are located in the center drive unit on each side of the eng. In this case we changed the i/b cdu and all checks ok.
 
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HAWK21M
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RE: Reverse Thrust Engagement

Tue Sep 06, 2005 4:58 pm

Quoting Abbs380 (Reply 31):
On the CF6-80a2 they use conventional switches for stow/deploy ind

Do you have a pic of these convential switches on the CF680A2s.
regds
MEL
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SuseJ772
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RE: Reverse Thrust Engagement

Wed Sep 14, 2005 3:23 am

Quoting SlamClick (Reply 5):
I know of at least two types where they can be extended in flight. I said "can" and not "should" by the way.

Just out of curiosity, which types can be extended in flight? Wasn't this a suspected reason for the Egypt Air crash? What good could come out of allowing an aircraft the capability of deploying in air? It seems to me this would be instant crash - but I am sure I'm missing something.

Quoting DH106 (Reply 9):
I have a photo in a book somewhere of an IL-62 crossing a threshold still 20ish feet in the air with it's buckets already open

I have seen this picture as well, so I am not doubting the claim. But what I am wondering is why didn't this instantly force the nose of the plane straight down? Or at least stall? What am I missing here? Thanks guys!
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HAWK21M
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RE: Reverse Thrust Engagement

Wed Sep 14, 2005 4:23 am

Quoting SuseJ772 (Reply 33):
Quoting DH106 (Reply 9):
I have a photo in a book somewhere of an IL-62 crossing a threshold still 20ish feet in the air with it's buckets already open

I have seen this picture as well, so I am not doubting the claim. But what I am wondering is why didn't this instantly force the nose of the plane straight down? Or at least stall? What am I missing here? Thanks guys!


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Hows it on the VC-10
regds
MEL
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Jetlagged
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RE: Reverse Thrust Engagement

Wed Sep 14, 2005 4:46 am

Quoting SuseJ772 (Reply 33):
Just out of curiosity, which types can be extended in flight? Wasn't this a suspected reason for the Egypt Air crash? What good could come out of allowing an aircraft the capability of deploying in air? It seems to me this would be instant crash - but I am sure I'm missing something.

DC-8, HS Trident, Il-62 and Concorde are some that spring to mind. I believe it was possible to select thrust reverse in flight on the 727, but not an approved procedure. It was used as a way to increase rate of descent in the DC-8 and Trident. As I understand it idle reverse thrust was the limit. On the Il-62 it appears to be used to control approach speed. I don't know which Egypt Air crash you refer to, but Lauda Air lost a 767 due to uncommanded reverse thrust deployment in flight.

Quoting SuseJ772 (Reply 33):
I have seen this picture as well, so I am not doubting the claim. But what I am wondering is why didn't this instantly force the nose of the plane straight down? Or at least stall? What am I missing here?

The exhaust air is deflected sideways as much as it is deflected forwards, so it shouldn't cause the wings to stall. There's no reason why the nose would be forced straight down, but if selected asymmetrically it would be dangerous. The Il-62 probably only has reverse idle selected, in which case the bucket is acting like an airbrake.
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F14D4ever
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RE: Reverse Thrust Engagement

Thu Sep 15, 2005 5:26 am

Quoting Bri2k1 (Reply 18):
thrust reversers ... aren't that impressive.

You forgot the "IMHO". As in "IMHO the video clips of max reverse over at flightlevel350 are fun to watch."

Quoting Bri2k1 (Reply 18):
Most landings are conducted with only idle reverse

At least 90% of the flights I've taken have utilized Max Reverse.

Quoting Bri2k1 (Reply 18):
they would have a hard time stopping an airliner.

They're not intended to stop the airliner, but to slow it down while saving wear and tear on the brakes.
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HAWK21M
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RE: Reverse Thrust Engagement

Thu Sep 15, 2005 1:27 pm

Can the VC-10s deploy T/Rs in Air too.
regds
MEL
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wing
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RE: Reverse Thrust Engagement

Thu Sep 15, 2005 5:52 pm

Quoting N405MX (Reply 1):
On the A320 you put the thrust levers on iddle, and the reverse levers on "armed" position (you lift them), when touch-down, the reverses deploy automatically, then the pilot just have to move the thrust levers backward so he can apply more reverse thrust.

I really would like to learn the source of this information.
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jumbojim747
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RE: Reverse Thrust Engagement

Thu Sep 15, 2005 8:35 pm

Quoting SlamClick (Reply 5):
I know of at least two types where they can be extended in flight. I said "can" and not "should" by the way.

Hey Slam i thought after the lauda incident they would make this action almost impossible to achieve.
What good reason would an aircraft manufacturer have for an inflight deployment of reversers.
Cheers
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mrocktor
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RE: Reverse Thrust Engagement

Fri Sep 16, 2005 12:16 am

Quoting JumboJim747 (Reply 39):
Hey Slam i thought after the lauda incident they would make this action almost impossible to achieve.
What good reason would an aircraft manufacturer have for an inflight deployment of reversers.
Cheers

Trouble is the 767 was not designed to open the reversers in flight. To be honest, I would imagine no aircraft is designed to be capable of opening reversers at cruise speed.

On the other hand, reversers could be used during approach as drag devices, with the advantage of not messing as much with the wing's stall characteristics as spoilers do. Several older aircraft have this capability.

In modern aircraft, with huge turbofans mounted way ahead of the wing leading edge, this is not practical. Reverse airflow from the engine near the wing leading edge can really mess with the plane's stall behavior.

Requirements for the protection against T/R opening in flight have driven an extreme level of complexity in the interlocks: the required data to allow command of the T/R - such as weight on wheels, airspeed, wheel speed, thrust setting, radio altitude - and the mechanisms themselves, consisting of three independent locks, shutoff valves and other precautions, are extremely involved.

I have become skeptical as to the true benefit of thrust reversers, with the cost and weight associated to them and the advent of carbon brakes that take high temperatures so much better than steel.

mrocktor
 
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jumbojim747
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RE: Reverse Thrust Engagement

Fri Sep 16, 2005 9:30 am

Quoting Mrocktor (Reply 40):
have become skeptical as to the true benefit of thrust reversers, with the cost and weight associated to them and the advent of carbon brakes that take high temperatures so much better than steel.

SO have i.
Great explanation and thank you
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Jetlagged
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RE: Reverse Thrust Engagement

Fri Sep 16, 2005 1:45 pm

Quoting Mrocktor (Reply 40):
Trouble is the 767 was not designed to open the reversers in flight.

But it had been certified as safe in that condition. However, the problem for the Lauda Air 767 was that the left engine went into reverse at climb power and at high IAS. Had the engine gone into reverse at a lower IAS or power setting the crew might have had time to respond.

Since the accident, the effects of reverse thrust on lift and drag have been required to be included in all simulator data packages so that crews have a chance to be trained in such scenarios more realistically.

.
The glass isn't half empty, or half full, it's twice as big as it needs to be.
 
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N405MX
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RE: Reverse Thrust Engagement

Sun Apr 26, 2009 5:02 pm



Quoting PhilSquares (Reply 12):
There is no auto reverse in the 320/330/340 family of aircraft. I can't think of a single transport category aircraft that has an auto-reverse system

I didn´t say it´s an auto-reverse, actually I wrote the reverses got armed, still the pilot has to move the thrust levers from iddle to reverse; as far as I know the plane don´t reverse by itself on the A318/319/320.

Quoting PhilSquares (Reply 10):
Quoting Neilking (Reply 8):
The question I'm looking for an answer to here is, can a modern airliner be set to a mode whereby, when the MLG detects weight (touchdown), the R/T gills (or clamshells - only on older jets like the 732??) open automatically and the engines automatically spool up to give R/T?

Again, the answer is NO!

Indeed, NO, still the pilot has to rev up the engine and the reverses open only in the ground, don´t remember the exact weights for the plane for the gear switch to "know" that the plane is on the ground, actually because of that it´s why the hard touchdown is better than a soft landing.

Best regards.
Life is what happens when you have other plans.....
 
PGNCS
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RE: Reverse Thrust Engagement

Wed Apr 29, 2009 1:17 am



Quoting Jetlagged (Reply 35):
I believe it was possible to select thrust reverse in flight on the 727, but not an approved procedure.

It is definitely possible and definitely prohibited in the DC-9.

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Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos