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RC Pilot
Topic Author
Posts: 139
Joined: Sun Jul 22, 2001 11:21 am

How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 11:25 am

On a normal jet engine (where all the air goes through combustion and out the back where the back is just exaust) the trust reverser is to flap like things that bend in stopping all air going backwards and bouncing it off diverting it forward.

On a bypass
(some air goes through combustion and most of it goes around the engine portion straigh out the back where it mixes with engine exaust making an awsome amount of thrust)

from what I can see all that happens is the rear portion of the shroud moves backward and that is it.


I dont see where air is diverted forward. All I can see that shroud doing is making the bypassed air going out sideways.


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Photo © Daniel Werner









Can someone explain this to me.

Thanks

RC Pilot
 
777236ER
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 11:36 am

As well as the reverser cover moving backwards, airflow blocks come out to divert by-pass airflow out throught the sides and fowards. In reality, the air doesn't move directly forwards, but rather at an angle. Still, it is enough to slow the a/c down.

And then you have your A32X/A34X CFM reverser "petals" that should help divert more airflow forwards, as well as creating more drag to help slow down. There are pics of them in the databast, but frankly i'm too tired to look. I'll post them tomorrow  Big grin
Your bone's got a little machine
 
411A
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 11:37 am

As you can clearly see from the photo, the translating cowl has moved aft. What you cannot see are the blocker doors inside, which divert the FAN thrust forward (actually at an angle). Note that the hot stream is NOT diverted.
Works good, lasts a long time.
 
AA737-823
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 11:38 am

that's exactly what happens. THe bypass air goes out sideways. Because there is so much more air in the bypass than the combustor, more air is going out sideways than rearward.

Air going out sideways creates a lot of drag, picture the ambient air going straight backward at 160 mph and then bowing air sideways- that's where the drag comes in.

It is more effective than it sounds. However, on many of these planes, it will NOT move the plane backwards, I don't believe.

I could be wrong on that. I just don't think the air is moved forward enough.

Randy.
 
RC Pilot
Topic Author
Posts: 139
Joined: Sun Jul 22, 2001 11:21 am

RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 11:44 am

I guess that makes sense. I new the air coming out the engine wasn't diverted. I just didn't know the air came out at an angle.


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I believe this is the photo of the "pedal reversers" 777236ER was talking about
 
AA737-823
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 11:49 am

No, those aren't the ones he was talking about.

He is talking about the ones used only on Airbus products. A320s with CFM's have them.

Do a search. They're really wierd.

Randy
 
RC Pilot
Topic Author
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 11:50 am

Oh Im sorry. I thought that was what he ment about "pedal".

They look kind of like pedals I guess.

Sorry guys

Thanks for the posts.
 
RC Pilot
Topic Author
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 11:55 am

"Pedal Reverse"?



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Photo © Jason Taperell


 
RC Pilot
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 12:05 pm

Those are really wierd looking.

That uses the same concept of the 737-200's reversers except there are four
 
TWA717_200
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 12:22 pm

67 billion webpages and I can't find a single illustration.

Well, you can look on page 215 of Air Disaster, Volume 2!
 
 
RC Pilot
Topic Author
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 12:31 pm

click on the link and then click "a thrust reverser in action"
 
KCLE
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Thu Jan 03, 2002 12:49 pm

I don't know if this pic could help, but it shows the "cascades," the green pieces that the reversed air blows through.

 
777236ER
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RE: How Do By-pass Jet Engines Reverse Thrust Work?

Fri Jan 04, 2002 1:27 am

"Petal" reverser doors on A32X/A34X CFM-powered aircraft:

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Photo © Luis Rosa



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Photo © PixAir



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Photo © Saul Loeb



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Photo © Rajesh Changela



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Photo © Vasco Garcia



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Photo © Jorgos Tsambikakis



They provide more drag than standard reversers. Whether they're any good is debatable. They don't reducing landing distances significantly, and they'll definatly be heavier. They're an unusual design -- i don't think any other aircraft had them before the CFM56-powered Airbuses. Other CFM56-powered aircraft (737s) have the standard reversers.

Regards.
Your bone's got a little machine
 
akelley728
Posts: 2065
Joined: Tue Dec 07, 1999 12:35 pm

RE: How Do By-pass Jet Engines Reverse Thrust Work?

Fri Jan 04, 2002 3:16 am

Here is a closeup of the engines on that Iberia A320 that crash-landed last year.

You can clearly see the 'Petal' reversers:

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