AirWillie6475
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 11:01 am

How do the reversers work on the old engines like the ones in the MD80s? How do the normal ones work? How do the reversers work on turboprop. Also I am wondering why there is no sound during idle reverse? I tried to do a search but there weren't clear answers.
 
Newark777
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 11:08 am

Why grab a Heine when you can grab a Busch?
 
jeb94
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 11:14 am

On MD80s and many, many jet aircraft, the thrust reversers are the clam shell type. They open when reverse thrust is applied and redirect the exhaust back toward the front of the aircraft. Other jets use internal vanes that redirect thrust forward. For props, the blades reverse pitch. The prop continues rotating the same direction but because the prop angle changed, they are now providing thrust in the opposite direction.
 
khenleydia
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 11:15 am

On many of the older styles like 737-100s, exterior parts of the engine move into place behind the jet exhaust. This simply forces the jet exhaust the opposite direction. As to the newer styles, I really don't know how that works. As to props, I think the blades are turned so that they propel in the opposite direction.

I look forward to someone being able to explain all of them well.

KhenleyDIA
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hirisk
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 12:38 pm

on the47,57,67,77 the engines have sleeves on the outside that slide backwards forcing the exaust out and forwards to slow the a/c down. airbus has 4 doors per engine that open outwards to do the same thing.

personnaly,i love the clamshells on the 737/md88 Smile
happy contrails
 
eclipseflight7
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 12:48 pm

MG and NG 737's have cascade reversers, where part of the engine housing slides back. Here there is a load of vents (green, right?) facing upwards and forwards. From what I can tell the thrust then shoots out of these vents, and slows the aircraft down.
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NW747-400
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 1:19 pm

What most people don't understand is that thrust is not the exhaust velocity, its the force the exhaust creates on internal parts of the engine. Reverse thrust just means that the thrust being created inside the engine is counteracted by interferences placed in the exhaust stream to create a thrusting force in the opposite direction.

That being said, smaller, older turbofan airplanes (JT8) utilize a clamshell reverser which actually redirects air from both the fan duct and the core.

Most newer turbofans have aerodynamic type reversers (the ones that look like sleeves on the engine nacelle) that have a set of cascade turning vanes that redirect exhaust strictly from the fan duct while air moving through the core is unobstructed.
 
NW747-400
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 1:26 pm

With a turboprop, the engine itself does not actually reverse airflow, but the pitch of the propeller blades are changed so that the air is forced forward instead of aft.
 
khenleydia
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 2:44 pm

I remember that a long time ago I watched MD-80s (ish) in Dallas use their reverse thrust to back out from the gate. The last time I was down there, I noticed they are no longer letting them do that. At least not at the gates I was near. Do many planes have the ability to do that effectively? Do other airports let them?

KhenleyDIA
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NW747-400
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 2:48 pm

Powerbacks have become increasingly rare. Although I am not up to speed with the specific regulations at airports, the reduction in powerback operations is mostly a result of airlines changing their SOP's. Powerbacks lack the safety margins that pushbacks have simply because pilots can't look in the rearview to see whats behind them. Also on management's mind is the fact that powerbacks require just that...power. More power=more fuel consumption=bad doggie.
 
aeroweanie
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Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 3:15 pm

The DC-8 30 and 50 series had a portion of the nacelle that slid aft and then had two doors that rotated to form the reverser:


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Photo © Willam W. Sierra



I thought the DC-8 60 series had a cascade vane reverser, but these pictures shows a system similar to the 30 and 50 series:


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Photo © Werner Horvath



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Photo © Mike Primamore



The DC-9s and MD80s have big parts of the aft nacelle that pivot on four bar linkages to form buckets aft of the exhaust:


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Photo © Ben Wang



The MD90 has a portion of the cowl that slides to expose cascade vanes. An internal blocker door forces the fan air in the bypass duct through the vanes:


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Photo © Alastair T. Gardiner



The DC-10 with CF6s started life with reverser buckets on the core exhaust and cascade vanes on the fan exhaust. The core reversers were eventually removed and they have just the fan cascade vanes:


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Photo © Michael Schmidt



The MD-11s have cascade vane reversers on the bypass air:


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Photo © Christian Waser - Aviapix Zurich/Worldwide



The 707 after turbofans were installed, had cascade vane reversers on the bypass and core exhausts:


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Photo © Marlene Leutgeb



The 727 started life with bucket reversers on the mixed exhaust. These were later replaced with cascade vanes:


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Photo © Joan Martorell



The Tay powered UPS 727-100s have buckets (apparently only on the #1 and 3 engines):


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Photo © Matt Barnette



The 737 Initial models started life with bucket reversers taken from the 727. It was found that when used, they caused the airplane to actually have a longer stopping distance! Boeing replaced them with an extended tailpipe and the same reverser as used on the DC-9:


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Photo © Bruce Leibowitz



737 Classics and NGs have cascade vane reversers on the bypass air:


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Photo © Jan Harald Olsen



The 747, 757, 767 and 777 have always had cascade reversers on the bypass duct air:


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Photo © William van Wanrooy




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Photo © Europix




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Photo © Europix




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Photo © TK



The Airbus A300, 310, 320 family, non-RR powered 330s and 340-500 and -600s all have cascade reversers on the bypass duct air:


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Photo © Tim Feise - APO Photos




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Photo © Avro




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Photo © Nik Deblauwe




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Photo © Brendan Vanderwerf



The A340s with CFM56s and RR powered 330s have doors that open and function both as blocker doors and reverser buckets:


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Photo © TK




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Photo © Mathieu Pouliot

 
Santhosh
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RE: Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 5:23 pm

During reverse thrusting in turbofan engines does they divert the complete thrust from the engine ie: air coming from both the inter core and and bypass section. Or do they only divert the bypass air into the front for slowing down the aircraft.

Thanx
George
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CRJ200Mechanic
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RE: Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 6:05 pm

Quoting Santhosh (reply 11):
During reverse thrusting in turbofan engines does they divert the complete thrust from the engine ie: air coming from both the inter core and and bypass section. Or do they only divert the bypass air into the front for slowing down


From what I know its only the bypass are that is directed forward by the cascade vanes. hope this helps
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HAWK21M
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RE: Thrust Reversers - How Do They Work?

Fri Feb 18, 2005 11:56 pm

Quoting Santhosh (reply 11):
do they only divert the bypass air into the front for slowing down the aircraft.


Depending on the Type of T/R used.
The Clamp shell [Bucket type] Reverses the Entire thrust.
The Cascade Vane types Reverse the Bypass Air only.
regds
MEL
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aeroweanie
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RE: Thrust Reversers - How Do They Work?

Sat Feb 19, 2005 2:10 am

HAWK21M:

Look carefully at the pictures I posted - in some cases, the cascade vane reversers are also used on the core flow.
 
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BALandorLivery
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RE: Thrust Reversers - How Do They Work?

Sat Feb 19, 2005 6:14 am

TO PUT IT SIMPLY

The thrust is re-directed, so insted of thrusting the a/c forward it is essentially thrusting it in other directions therefore slowing down the forward motion.
 
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HAWK21M
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RE: Thrust Reversers - How Do They Work?

Sat Feb 19, 2005 5:28 pm

Quoting AeroWeanie (reply 14):
Look carefully at the pictures I posted - in some cases, the cascade vane reversers are also used on the core flow.


Which pics are you refering to.Pls Identify the livery/no etc
regds
MEL
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B747FE
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RE: Thrust Reversers - How Do They Work?

Sun Feb 20, 2005 12:15 am

Quoting HAWK21M (reply 16):
Which pics are you refering to.Pls Identify the livery/no etc


B707/JT3, reply 10.

Regards,
B747FE.
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SATL382G
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RE: Thrust Reversers - How Do They Work?

Sun Feb 20, 2005 1:03 am

Excellent post AeroWeanie!!
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HAWK21M
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RE: Thrust Reversers - How Do They Work?

Sun Feb 20, 2005 2:12 pm

Quoting B747FE (reply 17):
B707/JT3, reply 10.


Interesting & Educational.Thanks.
What Turbofan Powerplant replaced the JT3Ds Turbojets on the B707.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
aeroweanie
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RE: Thrust Reversers - How Do They Work?

Mon Feb 21, 2005 3:49 pm

HAWK21M:

The JT3Ds were turbofans - they replaced JT3Cs on the 707 (and 720). The 707s also flew with JT4s and RR Conways. The Conways were turbofans. I think the JT4s were only turbojets.

SATL382G:

Thanks!
 
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HAWK21M
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RE: Thrust Reversers - How Do They Work?

Tue Feb 22, 2005 2:31 am

Quoting AeroWeanie (reply 20):
e JT3Ds were turbofans

Any idea what was the bypass ratio on the JT3C/JT3D.
regds
MEL
I may not win often, but I damn well never lose!!! ;)
 
B2707SST
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RE: Thrust Reversers - How Do They Work?

Tue Feb 22, 2005 4:13 am

Quoting HAWK21M (reply 21):
Any idea what was the bypass ratio on the JT3C/JT3D.


The JT3D's BPR as about 1.4:1. The JT8D was between 1:1 and 1.8:1.

--B2707SST
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undehoulli
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RE: Thrust Reversers - How Do They Work?

Tue Feb 22, 2005 7:18 am

What powers the thrust reversers varies with aircraft type too. In the ERJ they are hydraulically-actuated clamshell reversers while in the CRJ they are powered by 14th-stage engine bleed air. I don't know about other types of aircraft, my guess is most are hydraulic.
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HAWK21M
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RE: Thrust Reversers - How Do They Work?

Wed Feb 23, 2005 12:59 am

Quoting B2707SST (reply 22):
The JT3D's BPR as about 1.4:1. The JT8D was between 1:1 and 1.8:1.

And the JT3D.
regds
MEL
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Jomgelborn
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RE: Thrust Reversers - How Do They Work?

Thu Jul 11, 2013 3:46 am

When reverse thrust is activated, is the throttle always all the way off? Or can you throttle up for extra reverse thrust even though the core exhaust may not be redirected?
 
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Starlionblue
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RE: Thrust Reversers - How Do They Work?

Thu Jul 11, 2013 4:02 am

Quoting Jomgelborn (Reply 25):

When reverse thrust is activated, is the throttle always all the way off?

There's a fail-safe mechanism that makes it impossible to start reversing unless the throttles are idle first. On Boeing the throttles have to be all the way back to idle or the reverse levers can't be moved. On Airbus the throttles go through idle and then back into the reverse range. (On turboprops there's a beta range.)

If you want more power on reverse, you lift the reverse levers more on Boeing or pull back more on Airbus.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Jomgelborn
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RE: Thrust Reversers - How Do They Work?

Thu Jul 11, 2013 4:16 am

How come a light aircraft with a piston engines don't use reverse thrust like turbo props do? Seems like it would help to stop as fast as possible. Or if the breaks failed, you could use it.
 
SAAFNAV
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RE: Thrust Reversers - How Do They Work?

Thu Jul 11, 2013 4:28 am

Quoting Jomgelborn (Reply 27):
How come a light aircraft with a piston engines don't use reverse thrust like turbo props do? Seems like it would help to stop as fast as possible. Or if the breaks failed, you could use it.

I'd say to keep down complexity and therefore costs.
Just not needed on smaller aircraft.
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Starlionblue
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RE: Thrust Reversers - How Do They Work?

Thu Jul 11, 2013 5:04 am

Quoting SAAFNAV (Reply 28):
Quoting Jomgelborn (Reply 27):
How come a light aircraft with a piston engines don't use reverse thrust like turbo props do? Seems like it would help to stop as fast as possible. Or if the breaks failed, you could use it.

I'd say to keep down complexity and therefore costs.
Just not needed on smaller aircraft.

If nothing else you'd need a variable pitch prop. The smallest planes don't have one because it is an added cost, more weight, more maintenance...

As for light props with variable pitch props, they can stop on pretty short runways as it is. Even with failed brakes light planes don't need a lot of runway.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Airgypsy
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RE: Thrust Reversers - How Do They Work?

Thu Jul 11, 2013 3:30 pm

Reverser types are:
Target type - The clam shells block the path of the exhaust and deflect it slightly forwards.
Cascade type: - A clamshell in side the exhast "plugs" the tail pipe and the exhaust is forced out of cascade vanes in front of the "plug" or as the aft fan cowl moves aft (most common) blocker doors are plulled out to block the fan air and the fan air is forced out through cascade vanes. Some airlines deploy these blocker door reversers at the gate to prevent fan rotation while parked.
Reversable propeller type - The governor system piston is moved to a position that sets the propeller at a negative blade angle and forces the air forward instead of backwards.
Backing off the gate. Atlanta Hartsfield in the only airport actually designed for "powerback" operations.
Full reverse with feet flat on the floor. Forward thrust to halt the aircraft. Application of brakes in reverse could tip the aircraft on its tail.
 
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HAWK21M
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RE: Thrust Reversers - How Do They Work?

Thu Jul 11, 2013 6:48 pm

Quoting Airgypsy (Reply 30):
Full reverse with feet flat on the floor. Forward thrust to halt the aircraft. Application of brakes in reverse could tip the aircraft on its tail.

This needs to be mentally played over and over again......only use fwd thrust to stop a power back.
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802flyguy
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RE: Thrust Reversers - How Do They Work?

Fri Jul 12, 2013 3:29 am

"Thrust Reversers - How Do They Work? "


Usually, quite well, thank you!


(Sorry couldn't resist)
 
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CALTECH
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RE: Thrust Reversers - How Do They Work?

Sun Jul 14, 2013 2:19 am

The DC-10s early in their history, had a core reverser in addition to the fan reverser, that had a troubled service life until they were removed. IIRC, at least one blew off when reverse thrust was engaged.

UNITED Would Be Nice
 
JAGflyer
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RE: Thrust Reversers - How Do They Work?

Sun Jul 14, 2013 2:31 am

Here is an EXCELLENT video showing the blocker doors opening/closing on an engine with cascade thrust reversers.

https://www.youtube.com/watch?v=bvpj1BV-sCk
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Clydenairways
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RE: Thrust Reversers - How Do They Work?

Tue Jul 16, 2013 3:19 pm

Quoting CALTECH (Reply 33):
The DC-10s early in their history, had a core reverser in addition to the fan reverser, that had a troubled service life until they were removed. IIRC, at least one blew off when reverse thrust was engaged.

The L1011 Tristar had something similar in the beginning, but these too were later removed.
 
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Starlionblue
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RE: Thrust Reversers - How Do They Work?

Wed Jul 17, 2013 12:15 am

Here's a video of Steve inspecting the rear turbine of a 737 with clamshell reversers. Don't try this at home kids. http://www.youtube.com/watch?v=yz3AC93DvDo
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
Viscount724
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RE: Thrust Reversers - How Do They Work?

Wed Jul 17, 2013 11:57 pm

Quoting Jomgelborn (Reply 25):
When reverse thrust is activated, is the throttle always all the way off? Or can you throttle up for extra reverse thrust even though the core exhaust may not be redirected?

Just curious, how did you find this 8-year-old-thread to ressurect it?
 
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Pellegrine
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RE: Thrust Reversers - How Do They Work?

Thu Jul 18, 2013 6:34 am

Quoting Viscount724 (Reply 37):
Just curious, how did you find this 8-year-old-thread to ressurect it?

I was about to say,

W
O
W
oh boy, here we go!!!

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