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787 Thrust Reverser Question  
User currently offlinePHX787 From Japan, joined Mar 2012, 7859 posts, RR: 19
Posted (2 years 4 months 2 weeks 3 days 22 hours ago) and read 9216 times:

Hi all, ran a search, couldn't find much on it


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How does that thrust reverser work? It looks almost seamless. Does the entire cowling move back when the thrust reverser is activated?


Thanks, Z


我思うゆえに我あり。(Jap. 'I think, therefore I am.')
27 replies: All unread, showing first 25:
 
User currently offline817Dreamliiner From Montserrat, joined Jul 2008, 2555 posts, RR: 2
Reply 1, posted (2 years 4 months 2 weeks 3 days 21 hours ago) and read 9210 times:

Im not sure how much plane spotting youve done, but to answer your question, other aircraft have similar thrust reverse systems so its not really new:


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It works by diverting the air being drawn in by the fan outside the core, out through that opening when the cowling slides back. Also yes the back part of the cowling slides back entirely.

This should help give a basic idea if you dont understand:

http://en.wikipedia.org/wiki/Thrust_reversal

[Edited 2012-07-11 18:33:20]


Reality be Rent. Synapse, break! Vanishment, This World!
User currently offlineyeelep From United States of America, joined Apr 2011, 669 posts, RR: 0
Reply 2, posted (2 years 4 months 2 weeks 3 days 20 hours ago) and read 9161 times:

Its a translating sleeve/cascade type T/R, very common. When the sleeve translates aft there are blocker doors that move into the fan bypass airflow to redirect it through the cascades ( the black parts you can see in the OP pict.).

User currently offlinejetmech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 3, posted (2 years 4 months 2 weeks 3 days 20 hours ago) and read 9135 times:

Quoting PHX787 (Thread starter):
Quoting yeelep (Reply 2):

It works as illustrated in the following diagram.



This arrangement is very similar to that I've seen on many CF6's. Some of the earlier RB211's had a slightly different design where the blocker doors were actuated by pushrods instead.

http://www.youtube.com/watch?v=bvpj1BV-sCk
http://www.youtube.com/watch?v=dZ-wh8Kuh1M

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlinePHX787 From Japan, joined Mar 2012, 7859 posts, RR: 19
Reply 4, posted (2 years 4 months 2 weeks 1 day 4 hours ago) and read 8731 times:

Quoting 817Dreamliiner (Reply 1):
Im not sure how much plane spotting youve done,

Not much where I'm up and close to the planes

Quoting jetmech (Reply 3):

That's what I was looking for. Thanks!

I've seen thrust reversers operate on the A343 and the A320 for example which the cowling opens outward and that diverts the thrust but i wasn't sure how this one worked.



我思うゆえに我あり。(Jap. 'I think, therefore I am.')
User currently offline817Dreamliiner From Montserrat, joined Jul 2008, 2555 posts, RR: 2
Reply 5, posted (2 years 4 months 2 weeks 1 day ago) and read 8664 times:

Quoting PHX787 (Reply 4):
That's what I was looking for. Thanks!

I've seen thrust reversers operate on the A343 and the A320 for example which the cowling opens outward and that diverts the thrust but i wasn't sure how this one worked.

Have you tried using the search function or even google? This answer would have been there.



Reality be Rent. Synapse, break! Vanishment, This World!
User currently offlineAA737-823 From United States of America, joined Mar 2000, 5913 posts, RR: 11
Reply 6, posted (2 years 4 months 1 week 5 days 21 hours ago) and read 8320 times:

Quoting PHX787 (Reply 4):
I've seen thrust reversers operate on the A343 and the A320 for example which the cowling opens outward and that diverts the thrust but i wasn't sure how this one worked.

Those are called pivot-doors. They're lighter weight than the translating cowl, because there are far fewer parts, and also fewer actuators. A CFM-56 on a 737 has six actuators, three for each cowl half, while the CFM on an A320 has just four, one for each pivot door.

Quoting 817Dreamliiner (Reply 5):
Have you tried using the search function or even google? This answer would have been there.

You're quite the rude snob today, aren't you? If you don't have anything nice to say..... as the saying goes.

Quoting PHX787 (Thread starter):
How does that thrust reverser work? It looks almost seamless. Does the entire cowling move back when the thrust reverser is activated?

For reference, all in-production Boeing aircraft use this design. Many Airbus do as well, though the Rolls on the 333, and the CFM on the 320 use the pivot doors.


User currently offline817Dreamliiner From Montserrat, joined Jul 2008, 2555 posts, RR: 2
Reply 7, posted (2 years 4 months 1 week 5 days 21 hours ago) and read 8308 times:

Quoting AA737-823 (Reply 6):
You're quite the rude snob today, aren't you? If you don't have anything nice to say..... as the saying goes.

I didnt say anything mean, I was only suggesting that he should have done a search before asking such a question. The forums here has a good amount of information regarding different aspects of aviation, in this case the tech/ops forum would have something related to thrust reversers that has been previously discussed. Even if he didnt find anything here, he could have used a search engine like google to find what he needed. If you didnt like how I answered then thats just your problem. Theres nothing wrong with telling someone to do a google search.



Reality be Rent. Synapse, break! Vanishment, This World!
User currently offlinepoLOT From United States of America, joined Jul 2011, 2314 posts, RR: 1
Reply 8, posted (2 years 4 months 1 week 5 days 20 hours ago) and read 8284 times:

Quoting AA737-823 (Reply 6):
Those are called pivot-doors. They're lighter weight than the translating cowl, because there are far fewer parts, and also fewer actuators. A CFM-56 on a 737 has six actuators, three for each cowl half, while the CFM on an A320 has just four, one for each pivot door.

What is the disadvantage with them then? If they are lighter and perform equally I would figure that all new designs would have this type of reverse thrust design. It can't be just a patent issue in Boeing's case, Airbus used the cowl type for the A380 on both engine types.


User currently offlineBoeEngr From United States of America, joined Feb 2010, 321 posts, RR: 35
Reply 9, posted (2 years 4 months 1 week 5 days 20 hours ago) and read 8280 times:

If a Tech/Ops forum on an aviation site is not the place to ask technical questions about aviation, we're all in trouble...

 


User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 10, posted (2 years 4 months 1 week 5 days 9 hours ago) and read 8178 times:

Quoting 817Dreamliiner (Reply 7):
I was only suggesting that he should have done a search before asking such a question.

Often times, it is easier and faster to ask the guys who know then try to find it on the web.

Quoting poLOT (Reply 8):
What is the disadvantage with them then? If they are lighter and perform equally I would figure that all new designs would have this type of reverse thrust design.

The disadvantage is that the doors are not as efficient in diverting the flow. The cascades provide more control in where you want to direct the reversed flow.

The picture that jetmech showed did not show the different angles to which the cascade direct the flow. Along the circumference of the nacelles, the cascades direct the flow in different direction. In one or two area, the cascades are actually blocked off to prevent the flow from impinging on the aircraft (body or wheels) or blow air in front of the airplane where FOD may get ingested back into the engines.

Also, I am not sure if the pivoting doors close out as much fan air as the cascade type doors. If someone have an axial view of a pivoting door compared to translating cowl doors deployed, it may be useful.

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 11, posted (2 years 4 months 1 week 5 days 6 hours ago) and read 8092 times:

Quoting poLOT (Reply 8):
What is the disadvantage with them then? If they are lighter and perform equally I would figure that all new designs would have this type of reverse thrust design.

Cascade reversers provide better reverse thrust performance and scale up better. If you use petal reversers (aka pivot reversers) and you want to go up to 777 size you're pretty much screwed. Using cascade reversers across the board means you're just working with one design (this may be a legacy from Boeing having a centralized nacelle design group for all models for a long time).

Tom.


User currently offlinePHX787 From Japan, joined Mar 2012, 7859 posts, RR: 19
Reply 12, posted (2 years 4 months 1 week 4 days 4 hours ago) and read 7815 times:

Quoting 817Dreamliiner (Reply 7):

Montserrat? How is it?  
Quoting bikerthai (Reply 10):
The disadvantage is that the doors are not as efficient in diverting the flow. The cascades provide more control in where you want to direct the reversed flow.

That might explain why the AF343 that was landing at CVG used the entire runway, but the DL777 at CVG used about half of it, while landing (back when both of those planes operated at CVG) I get it. Thanks!



我思うゆえに我あり。(Jap. 'I think, therefore I am.')
User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 13, posted (2 years 4 months 1 week 4 days 1 hour ago) and read 7764 times:

Quoting PHX787 (Reply 12):
AF343 that was landing at CVG used the entire runway, but the DL777

There may be more issue involved with the example you gave (Landing weight of aircraft, 4 smaller engines vs 2 larger engines, how good were the brakes etc.) .

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineDocLightning From United States of America, joined Nov 2005, 20242 posts, RR: 59
Reply 14, posted (2 years 4 months 1 week 3 days 23 hours ago) and read 7741 times:

Quoting tdscanuck (Reply 11):
Cascade reversers provide better reverse thrust performance and scale up better. If you use petal reversers (aka pivot reversers) and you want to go up to 777 size you're pretty much screwed.

The A330 Trent 700s (which aren't *that* much smaller than on the 777) use them. I wonder why?


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17118 posts, RR: 66
Reply 15, posted (2 years 4 months 1 week 3 days 22 hours ago) and read 7724 times:

Quoting PHX787 (Reply 12):
That might explain why the AF343 that was landing at CVG used the entire runway, but the DL777 at CVG used about half of it, while landing (back when both of those planes operated at CVG) I get it. Thanks!

Probably not due to reversers. Brakes and landing weight have a far bigger effect.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 16, posted (2 years 4 months 1 week 3 days 20 hours ago) and read 7687 times:

Quoting DocLightning (Reply 14):
The A330 Trent 700s (which aren't *that* much smaller than on the 777) use them. I wonder why?

RR has a long history of doing their own nacelles, unlike the other two engine makers. Did they do the A330 nacelle? That may be a contributor but I don't know why they would have chosen that trade.

Tom.


User currently offlineDocLightning From United States of America, joined Nov 2005, 20242 posts, RR: 59
Reply 17, posted (2 years 4 months 1 week 3 days 17 hours ago) and read 7630 times:

Quoting tdscanuck (Reply 16):
RR has a long history of doing their own nacelles, unlike the other two engine makers. Did they do the A330 nacelle? That may be a contributor but I don't know why they would have chosen that trade.

The Trent 700 nacelle is of a classic Trent design with the the bypass duct running the full length of the engine.


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This shows the general arrangement with the clamshell doors clearly visible. I can't find one with them deployed.


User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 18, posted (2 years 4 months 1 week 3 days 9 hours ago) and read 7551 times:

Quoting DocLightning (Reply 14):

The A330 Trent 700s (which aren't *that* much smaller than on the 777) use them. I wonder why?

Aren't some of the A380 T/R the doors type also? And they also only have two engines with reverser.

Quoting tdscanuck (Reply 16):
That may be a contributor but I don't know why they would have chosen that trade.


As we all know, the TR are not essential for certification of the aircraft.

So, basically you are trading the cost/efficiency of the doors vs the wear and tear on the brakes. Someone would have to dig up the brake replacement cycle of a door T/R aircraft vs a cascades TR aircraft and work out the various cost involved . . . along with the weight delta, fuel burn impact, maintenance etc . . .   

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineDocLightning From United States of America, joined Nov 2005, 20242 posts, RR: 59
Reply 19, posted (2 years 4 months 1 week 3 days 8 hours ago) and read 7524 times:

Quoting bikerthai (Reply 18):
Aren't some of the A380 T/R the doors type also? And they also only have two engines with reverser.

AFAIK, both RR and EA engines on the A380 are the petal-type.


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RR on the left, EA on the right


User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 20, posted (2 years 4 months 1 week 3 days 7 hours ago) and read 7509 times:

Quoting DocLightning (Reply 19):

Hum, if you are right, then there may be something about the cascades type being more efficient if it was used exclusively on the A380 (because the outboard engines do not have T/R).

bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlineDocLightning From United States of America, joined Nov 2005, 20242 posts, RR: 59
Reply 21, posted (2 years 4 months 1 week 3 days 7 hours ago) and read 7507 times:

Quoting bikerthai (Reply 20):
Hum, if you are right, then there may be something about the cascades type being more efficient if it was used exclusively on the A380 (because the outboard engines do not have T/R).

Not sure that's the reason. I suspect ground clearance is a bigger issue.


User currently offlineGatorman96 From United States of America, joined Dec 2005, 874 posts, RR: 0
Reply 22, posted (2 years 4 months 1 week 3 days 6 hours ago) and read 7496 times:

Quoting bikerthai (Reply 20):
Hum, if you are right, then there may be something about the cascades type being more efficient if it was used exclusively on the A380 (because the outboard engines do not have T/R).

bt

BT,

I believe the A380 doesn't have outboard T/R's because the engines hang over the width of the runway in many cases. If they did, they could kick up FOD into the inboard engines and wings.



Cha brro
User currently offlinebikerthai From United States of America, joined Apr 2010, 2170 posts, RR: 4
Reply 23, posted (2 years 4 months 1 week 3 days 4 hours ago) and read 7453 times:

Quoting Gatorman96 (Reply 22):
I believe the A380 doesn't have outboard T/R's because the engines hang over the width of the runway in many cases. If they did, they could kick up FOD into the inboard engines and wings.

Understood. My inference is because it doesn't have the outboard T/R, it then have to go to a more efficient design for the inboard T/R to make up some of the difference.

Quoting DocLightning (Reply 21):
Not sure that's the reason. I suspect ground clearance is a bigger issue.

Could be . . .

But from this angle on a different airplane, its seems that you can design a door that will open and not extend beyond the lower part of the nacelle.

http://en.wikipedia.org/wiki/File:Easyjet_thrust_reversers_arp.jpg

Then again, you lose efficiency.


This is a great shot of how a cascade type door, blocks the whole fan duct.

http://www.flickr.com/photos/wbaiv/2736667356/

I can't seem to find a comparable picture of one for the door type.


bt



Intelligent seeks knowledge. Enlightened seeks wisdom.
User currently offlinetdscanuck From Canada, joined Jan 2006, 12709 posts, RR: 80
Reply 24, posted (2 years 4 months 1 week 3 days 2 hours ago) and read 7403 times:

Quoting DocLightning (Reply 19):
AFAIK, both RR and EA engines on the A380 are the petal-type.

The pictures in your post clearly show cascade reversers, not petal reversers.

Tom.


25 Post contains links and images jetmech : There actually appears to be quite a few gaps with the deployed petal type TR. View Large View MediumPhoto © Brandon Archer Regards, JetMech
26 bikerthai : Good picture. That's what I'm thinking. Although they may be able to optimize the coverage by locating the gap at the struts support and cutting the
27 DocLightning : Sorry! I meant to say "cascade."
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