CcrlR
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Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 9:56 am

I was learning in class about the types of reverse thrusters the Clamshell type(like on the MD-80, 737-200, 727, 717,etc) and the cascade(like on the 737-300 to 900, IAE's on the A320 and others), but what about the ones CFM and Rolls Royce where they have these doors that open, are they the clamshell or another type?

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ACDC8
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 10:59 am

Quoting CcrlR (Thread starter):
but what about the ones CFM and Rolls Royce where they have these doors that open, are they the clamshell or another type?

I believe that they are called "buckets", but I could be wrong.

Quoting CcrlR (Thread starter):
and the cascade(like on the 737-300 to 900, IAE's on the A320 and others

So the normal reversers are "cascades"?
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320tech
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 11:28 am

I believe the thrust reversers on the CFM-56 on the A320 are called the "normal" type.  Wink

All we ever call them is the blocker door type.

Buckets, I believe, are the style used on DC-9's and 737-200's. Could be wrong about that, but they are shaped vaguely like buckets.
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AR1300
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 11:31 am

Weren't there 3 types: The A340 style, the The 732 style(MD-80, etc) and the 738 style?

Mike
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ACDC8
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 11:40 am

This is how I understand it:

Clamshell...

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Bucket...

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Cascade...

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Please correct me if I'm wrong.
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citation501sp
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 1:24 pm

From where I sit I've refered to them in this manner.

Clamshell / Buckets = DC-9s 737-100/200 etc Diverts both bypass and exhast flow. Heard this from an old Mohawk/Allegany/USAir Mech. he was working on DC-9 before I was born. he always refered to them as buckets.


Cascade = CFM 56 powered 737s etc Diverts only Bypass air

a subset of Cascade is the Petal Door, type which is that certain Airbus's use the the A340 in reply4. again Diverts only bypass air.



We could confuse matters more and add the early DC-10s which not only has cascade reversers but also a set of mini clamshells to reverse the core exhast too...
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ACDC8
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 2:48 pm

Maybe this will help...
Thrust Reverse Types (by Baw2198 Feb 15 2004 in Tech Ops)

Clamshell/buckets: B737-200/MD80 types
Cascade: B777/B747 types
Petal: CFM-56 engines A340/some A320's
 Smile
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Jetlagged
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 7:32 pm

Just to confuse things, the 737-200 reversers are also known as target type reversers.

Clamshells and buckets are distinctly different. Clamshells are often internal to the jetpipe, deflecting the airflow back through cascade vanes. They usually make a spherical shape when closed. Buckets are usually external devices where a piece of the engine casing moves over the exhaust to deflect the air. Buckets are, well, bucket shaped. The 727 had a combination of both clamshells and buckets (called deflector doors in that aircraft).

http://www.boeing-727.com/Data/systems/infothrustreverse.html

What has been referred to as the cascade vane type in posts above is also often called the translating sleeve type. This utilises a combination of internal blocker doors, cascade vanes and a translating sleeve. Cascade vanes are also associated with some clamshell designs, so don't define the design really.

Concorde had an external clamshell reverser, called an eyelid.

So the name of the reverser type is not that well defined, and the terminology used depends on the aircraft or engine manufacturer
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jush
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 8:49 pm

Just for me: I do like the clamshell that looks so old fashioned historical and not properly working at all.
Having said that AFAIK they are more effiicent than cascades right?

Regards
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KensukeAida
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 9:24 pm

Quoting Jetlagged (Reply 7):
Just to confuse things, the 737-200 reversers are also known as target type reversers.

Target and Clamshell are two DIFFERENT things. 737-100s and early -200s had clamshell reversers, but the majority of -200s switched to target type when it was found that the clamshells really didn't work worth a damn (and tended to lift the aircraft off the ground, which is counterproductive).

You can see the difference between a target and a clamshell on this page:

http://www.b737.org.uk/powerplant.htm

Scroll down towards the bottom.

- John
 
KensukeAida
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 9:28 pm

Quoting ACDC8 (Reply 4):
This is how I understand it:

Clamshell...




That's a target type. Not a clamshell. A clamshell is what you'd find on a 727 or a DC-9, but NOT a 737-200.

- John
 
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RE: Types Of Thrust Reversers On Engines

Fri Oct 14, 2005 10:59 pm

Quoting KensukeAida (Reply 9):
Target and Clamshell are two DIFFERENT things.

I realise that. No need to shout. ACDC8 referred to them as clamshells, not me. You'll notice I referred to the 727 as having clamshell reversers, and the early 737s shared the same system. The pictures on the website you refer to show the external deflector doors, but not the internal clamshell doors. My 727 link shows a cross section through the JT8D showing both items.

A lot of people refer to the 737-200 reverser as having bucket deflectors. AFAIK, the only thing which differentiates a target type reverser is that it translates aft as well, rather than simply closing off the jetpipe. There are no vanes to guide the airflow.
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ACDC8
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RE: Types Of Thrust Reversers On Engines

Sat Oct 15, 2005 10:47 am

Perhaps someone out there would care to post some examples of reversers with the CORRECT terminology. I have posted a few examples which are apparently incorrectly labeled. So please, have a go at it. I'm trying to learn a few things on this site and some photos and the appropriate labels would be very helpful.
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HAWK21M
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RE: Types Of Thrust Reversers On Engines

Sat Oct 15, 2005 1:20 pm


Clampshell type [B737-100 & Earlier -200][Pneumatically powered]


Target type [B737-200][Hydraulically operated]

regds
MEL
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ACDC8
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RE: Types Of Thrust Reversers On Engines

Sat Oct 15, 2005 5:32 pm

Thanks HAWK! Those are the same pics as on the link that John provided. So lets see if I've got this right (finally ...  Wink ) :

-Clamshell B727
-Target (or bucket) B737-200
-Cascade B777
-Petal A340

Is this correct?
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RE: Types Of Thrust Reversers On Engines

Sat Oct 15, 2005 11:41 pm

Quoting ACDC8 (Reply 14):
-Target (or bucket) B737-200
-Cascade B777

Not quite, target reverser is not necessarily the same as buckets. Cascade vanes are part of the 727 clamshell system too, so it's not really a type of reverser. The triple seven and most other big fans use the translating cowl/blocker door system.
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KensukeAida
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RE: Types Of Thrust Reversers On Engines

Sun Oct 16, 2005 7:15 am

Jetlagged is correct. Clamshell, cascade, and petal, work more or less the same by diverting bypass air. The difference is in the physical movement of the reverser doors.

Target (and bucket?) are the odd men out because they divert everything including the engine thrust. They were only used on a few planes like the 737-200s, and the some fighter jets like the Panavia Tornado.

Which brings up an interesting question....

If clamshell and cascade work more or less the same, how come cascade/clamshell work on the 737 Classics, NGs, and the 727s, but not the 737-200s? Everything I've read suggested that there were serious problems with clamshells on the early 737s, which necessitated them switching to target.

Does it have to do with wing mounted JT8D's being different somehow than tail mounted ones?

- John

[Edited 2005-10-16 00:34:35]
 
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RE: Types Of Thrust Reversers On Engines

Sun Oct 16, 2005 9:32 am

Quoting KensukeAida (Reply 16):
Jetlagged is correct. Clamshell, cascade, and petal, work more or less the same by diverting bypass air. The difference is in the physical movement of the reverser doors.

Hate to correct you when you say I'm right, but clamshell and bucket reversers reverse all the airflow too. They are almost always mounted in the jetpipe area. It's only translating sleeve and petal types which reverse fan air only.

Quoting KensukeAida (Reply 16):
If clamshell and cascade work more or less the same, how come cascade/clamshell work on the 737 Classics, NGs, and the 727s, but not the 737-200s? Everything I've read suggested that there were serious problems with clamshells on the early 737s, which necessitated them switching to target.

The 737 engines are very close to the ground, so this may have been why the 727 style reverser did not work so well. They switched to a design where the exhaust is deflected at an angle to the vertical, reducing the lifting effect of blasting the air straight down and up. 737 Classics (-300/400/500) and NGs do not have clamshell reversers. They have the translating cowl design.


Look, there are so many design variations, and each manufacturer tends to use nomenclature slightly differently. It's very hard to generalise like this. Take each design on its merits, or lack of, and don't get too hung up on what each is called.
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ACDC8
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RE: Types Of Thrust Reversers On Engines

Sun Oct 16, 2005 10:33 am

Quoting Jetlagged (Reply 15):
Not quite, target reverser is not necessarily the same as buckets. Cascade vanes are part of the 727 clamshell system too, so it's not really a type of reverser. The triple seven and most other big fans use the translating cowl/blocker door system.

That's it I give up!  Wink

Seriously though, I appreciate all your guys information and help on this subject. It's always refreshing to learn more.
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HAWK21M
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RE: Types Of Thrust Reversers On Engines

Sun Oct 16, 2005 5:02 pm

Quoting Jetlagged (Reply 17):
The 737 engines are very close to the ground, so this may have been why the 727 style reverser did not work so well. They switched to a design where the exhaust is deflected at an angle to the vertical, reducing the lifting effect of blasting the air straight down and up

The reason for the Angled Installation on B732 was Because When verticallly mounted.During R/T operation.The Airflow deflected downwards used to lift the Aircraft & make braking Less effective.
regds
MEL
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stirling
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RE: Types Of Thrust Reversers On Engines

Sun Oct 16, 2005 5:51 pm

If I can, allow me to add a couple more THRUST REVERSER Types; #4 and #5:

#4)

I will call this one The "Barn Door":


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#5)

I will call this one "Wright Brothers Chic":


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Honorable Mention.

#6) I know there's an official hoity-toity word for it, I'll just call it "Jump? How High Sir?":


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KensukeAida
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RE: Types Of Thrust Reversers On Engines

Mon Oct 17, 2005 2:29 am

Am I the only one here finding this an unusually confusing topic?  Sad

- John

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