celestar
Topic Author
Posts: 494
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Advancement In Engine Thrust Reverser?

Tue Sep 07, 2010 9:21 am

I wonder what kind of improvement engine maker has done to the commercial engine thrust reverser design. Recently, I flown on an old 737-300 and it brings back the old day memory of how loud the thrust reverser can be. That is also the case with current 747-400 My question is, are they some sort of advancement on new engine on B777 (RR or GE) or on A330 (RR or PW or GE) because the noise generated during thrust reverser application was significantly lower and sometime you could hardly feel or hear them. Very interested to know what had been done to the engine design?
 
tdscanuck
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RE: Advancement In Engine Thrust Reverser?

Tue Sep 07, 2010 4:12 pm

Quoting celestar (Thread starter):
I wonder what kind of improvement engine maker has done to the commercial engine thrust reverser design.

For a while it was essentially nil, since the reverser companies were different than the engine companies. Some of the engine companies created or purchased reverser companies (GE & RR) but they operate as semi-independent divisions. But two of the biggest vendors today (Spirit Aerospace & Goodrich) aren't tied to any engine company.

Quoting celestar (Thread starter):
My question is, are they some sort of advancement on new engine on B777 (RR or GE) or on A330 (RR or PW or GE) because the noise generated during thrust reverser application was significantly lower and sometime you could hardly feel or hear them.

A lot of that is the use of idle reverse...the modern large twins can stop perfectly happily on most runways without using reversers at all, so they often deploy them but don't spin up the engines.

CFD has also considerably improved the design of the cascade vanes in sliding sleeve reversers (and I assume the petals in petal reversers) to improve reverse thrust efficiency, which gives you an automatic noise drop anyway.

Tom.
 
prebennorholm
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RE: Advancement In Engine Thrust Reverser?

Tue Sep 07, 2010 11:04 pm

Quoting celestar (Thread starter):
...the noise generated during thrust reverser application was significantly lower and sometime you could hardly feel or hear them.

At more and more airports - especially in Europe - the use of reversers is now forbidden due to noise regulations. Mostly it works the way that the reversers are engaged, and the engines are spun up slightly above idle. It doesn't provide any noticeable brake force, but it does provide a much faster spin up in case of accidental wheel brake failure.

Wheel brakes have become a lot better, so nowadays reversers are mostly treated as sort of backup for the wheel brakes. In older days reversers provided the cheap way to save wear on the wheel brakes.
Always keep your number of landings equal to your number of take-offs
 
flyboy80
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RE: Advancement In Engine Thrust Reverser?

Wed Sep 08, 2010 1:44 am

I love the thrust reversers on the 737, 757, 767, and A320. Always seems when they are deployed, and the engines are spooled up, they "rattle" the flap assembly- sometimes very violently- during the breaking action. I've never noticed this on tail mounted engine types, and I would assume because there is no turbulent air being generated around the assembly itself because of engine placement. The Airbus seems to have a large gap between the spoilers and the flap and that must contribute to the shaking as well.

Has anyone witnessed thrust reverse on the Ejet aircraft? If so, does the flap assembly tend to shake like the 737s and airbus twins?
 
kimberlyRJ
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RE: Advancement In Engine Thrust Reverser?

Wed Sep 08, 2010 6:26 pm

Hey hey

I miss the noise of reverse thrust on all (okay, most/some ish) flights I crew... It was always nice to hear when landing at LHR or LGW it was a very nice welcome ‘home’  

These days in the UK reverse is not often used (well at the bigger airports) and when it is it's idle or maybe just above.

A lot of pilots seem to use idle reverse – I am sure this means that if reverse thrust is suddenly needed it would be quicker to arrive?

There are a few airports around the world our pilots seem to use plenty of reverse thrust (depending on the runway) no matter what the conditions, but the runways tend to be quite far away from any urban areas etc.

Last year I was quite amazed when I flew with Monarch Airlines on an Airbus A300-600R from LGW to KGS on a night flight. On landing (in heavy rain) the aircraft stopped amazing quickly without any use of reverse thrust (not even idle).

From what I understand the runway is 7,874ft long and we landed on runway 32 and took the first exit so we used around 4000ft (ish) amazing in heavy rain and no reverse thrust in fact we slowed down so quickly it was very uncomfortable (or maybe I am just so used to sitting facing backward – as I’m cabin crew).

After that landing the Airbus A300-600R gained a lot of my respect, well its brakes did!

An example that reverse thrust can’t make that much difference? Though I was surprised to pilots did not idle them just in case!

Question, do pilots from certain airlines or certain countries tend to use reverse thrust no matter what the airport recommends? Or local conditions?

Is there any airline policy on this matter? Or the use of idel?

Kimberly
 
tdscanuck
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RE: Advancement In Engine Thrust Reverser?

Wed Sep 08, 2010 8:37 pm

Quoting kimberlyrj (Reply 4):
A lot of pilots seem to use idle reverse – I am sure this means that if reverse thrust is suddenly needed it would be quicker to arrive?

Correct. It takes a few seconds for the reverser to deploy, and reverse idle is usually higher than ground idle, so you can get up to full reverse thrust much more quickly if you're already in idle reverse.

Tom.
 
pilotpip
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RE: Advancement In Engine Thrust Reverser?

Sun Sep 12, 2010 2:04 am

Quoting kimberlyrj (Reply 4):
There are a few airports around the world our pilots seem to use plenty of reverse thrust (depending on the runway) no matter what the conditions, but the runways tend to be quite far away from any urban areas etc.

Last year I was quite amazed when I flew with Monarch Airlines on an Airbus A300-600R from LGW to KGS on a night flight. On landing (in heavy rain) the aircraft stopped amazing quickly without any use of reverse thrust (not even idle).

From what I understand the runway is 7,874ft long and we landed on runway 32 and took the first exit so we used around 4000ft (ish) amazing in heavy rain and no reverse thrust in fact we slowed down so quickly it was very uncomfortable (or maybe I am just so used to sitting facing backward – as I’m cabin crew).

After that landing the Airbus A300-600R gained a lot of my respect, well its brakes did!

An example that reverse thrust can’t make that much difference? Though I was surprised to pilots did not idle them just in case!

Question, do pilots from certain airlines or certain countries tend to use reverse thrust no matter what the airport recommends? Or local conditions?

Is there any airline policy on this matter? Or the use of idel?

Modern antiskid brakes are very efficient and actually do better as they heat up due to being carbon brakes versus metallic. Also, reversers are not taken into consideration in performance calculations and can be deferrered with no penalty. To be perfectly honest, 99% of passengers have no idea how strong airliner brakes really are. If I wanted to use max braking on the aircraft I fly (ERJ-170) you would likely end up with a bruise from the seatbelt. Our aircraft don't have autobrakes but even on short runways like MDW I don't have to give a full application.

It also heavily depends on the type of reverser employed. Cascade style reversers only change the direction of the bypass air. They redirect it sideways more than forward and they decrease effectiveness as you slow. They also increase risk of FOD ingestion as you slow. Clamshells have a much more pronounced aerodynamic effect as well as redirecting all air.

My airline requires use of full reverse on every landing. It's an operational requirement in our SOP. Not really a fan of it because there are plenty of times where you don't need it, like landing on 22R at ORD where they want you to turn off at the end, but I do it anyway. Usually in a case like that I just bark 'em, let them spool up to max and then return to idle reverse quickly.

As for airport requirements, there aren't any in the US that I can think of that have any sort of ban against them and you can bet if I were at an airport that did, and I needed them I would use them.

There are situations where they're particularly useful like wet or snow-covered runways because quite frankly, you want everything you have helping you stop in those situations and the anti-skid might be doing it's job keeping the wheels spinning versus skidding.
DMI
 
bond007
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RE: Advancement In Engine Thrust Reverser?

Sun Sep 12, 2010 10:32 am

Quoting prebennorholm (Reply 2):
At more and more airports - especially in Europe - the use of reversers is now forbidden due to noise regulations.

I'm not sure 'forbidden' is correct, unless I'm mistaken. Many airports have regulations concerning the use of anything but idle reverse, but on contaminated runways or whenever there is a safety issue, there is no restriction on their use.

Quoting pilotpip (Reply 6):
Also, reversers are not taken into consideration in performance calculations and can be deferrered with no penalty.

Well, for accelerate-stop distances on contaminated runways they can, right?

Bond
I'd rather be on the ground wishing I was in the air, than in the air wishing I was on the ground!
 
bonusonus
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RE: Advancement In Engine Thrust Reverser?

Mon Sep 13, 2010 2:28 pm

Quoting kimberlyrj (Reply 4):
Question, do pilots from certain airlines or certain countries tend to use reverse thrust no matter what the airport recommends? Or local conditions?

I've noticed that many airliners use significant reverse thrust at smaller airports (and not just on short runways). It seems like the only reason is to slow down faster to be able to hit the earlier taxiway turnoffs. Can anyone confirm using them for this purpose?
 
aerotech777
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RE: Advancement In Engine Thrust Reverser?

Wed Sep 15, 2010 6:38 pm

Hi,

Wondering which thrust reverser (petals or cascades) provides more stopping distance?

During high speed RTO, if one engine fails or dispatched inoperative can the crew use the thrust reverser for the operating
engine(s)?

Feedback appreciated
 
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bikerthai
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RE: Advancement In Engine Thrust Reverser?

Wed Sep 15, 2010 7:01 pm

Quoting aerotech777 (Reply 9):
ondering which thrust reverser (petals or cascades) provides more stopping distance?

As I recall, the cascades are more efficient in terms of airflow because the blocker doors covers more of the fan flow and the cascade vanes does a better job of re-directing the flow. You can only cover so much with the pedals. However, I think the petal design is simpler, less expensive, and might even be lighter. I'm familiar with the cascades but not the petals design

bikerthai
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