Emirates773ER
Topic Author
Posts: 1318
Joined: Mon Jun 27, 2005 9:10 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:04 am

Why is it looking as if the engine has a cover missing on this take off flight?


View Large View Medium
Click here for bigger photo!

Photo © I-DISE - SpotIt



[Edited 2005-09-17 23:04:46]
The Truth is Out There ---- Face It!!!!!
 
Newark777
Posts: 8284
Joined: Thu Dec 02, 2004 6:23 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:06 am

That's the thrust reverser deploying right after the main gear touches down. And it's actually landing, not taking off.

Harry

[Edited 2005-09-17 23:07:03]
Why grab a Heine when you can grab a Busch?
 
dogfighter2111
Posts: 1867
Joined: Tue Nov 09, 2004 3:02 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:06 am

Err...

Actually, that aircraft is landing and that is the revers thrust  Smile

Thanks
Mike
 
Emirates773ER
Topic Author
Posts: 1318
Joined: Mon Jun 27, 2005 9:10 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:10 am

hmm.... can anyone explain reverse thrusters?
The Truth is Out There ---- Face It!!!!!
 
dogfighter2111
Posts: 1867
Joined: Tue Nov 09, 2004 3:02 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:11 am

It is like putting the engine in reverse to slow the aircraft down.

(Best way i can describe it)

Thanks
Mike
 
Emirates773ER
Topic Author
Posts: 1318
Joined: Mon Jun 27, 2005 9:10 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:16 am

Are reverse thrusters applied on all landing planes or speed is a factor while landing?
The Truth is Out There ---- Face It!!!!!
 
dogfighter2111
Posts: 1867
Joined: Tue Nov 09, 2004 3:02 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:20 am

Nearly all Landings use Revers Thrust.

There are 3 things that slow down an aircraft on landing:

Wheel Brakes
Reverse Thrust (Engine into Reverse  Smile )
Spoilers (Little Flaps that go up like / )

Thanks
Mike
 
DLKAPA
Posts: 7962
Joined: Wed Dec 03, 2003 10:37 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:24 am

The use of reverse thrust basically depends on what the airline's manual says. It's used to slow down the aircraft, though it isn't factored into the landing weights or approach/landing speeds when the dispatchers do the calculations because under normal conditions on an average runway (I say 7,000 feet or more), most planes should be able to stop in that distance with wheel and speed breaks. Obviously if its the 764 landing full at LGA it's gonna need some reverse thrust.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
flyf15
Posts: 6633
Joined: Tue May 18, 1999 11:10 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:25 am

The rear portion of the engine nacelle slides backwards, creating that gap you see. Air that would otherwise be shot out the back is now redirected and comes out of that slot in a angled forward direction, creating "reverse thrust"
 
whitehatter
Posts: 5180
Joined: Sat Jun 12, 2004 6:52 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:33 am



Click on the small pic above and you'll see the larger reversers in action on a 777-300ER (credits to Ringwayreports for the images)
Lead me not into temptation, I can find my own way there...
 
omoo
Posts: 650
Joined: Thu Jun 09, 2005 12:35 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 7:09 am

These new cowling can sure confuse people.
Fly Air Popobawa
 
DLKAPA
Posts: 7962
Joined: Wed Dec 03, 2003 10:37 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 7:11 am

Quoting Omoo (Reply 10):
These new cowling can sure confuse people.

Instead of redirecting the full engine thrust, the new cowlings only reverse the bypass flow. Think of it that way.
And all at once the crowd begins to sing: Sometimes the hardest thing and the right thing are the same
 
whitehatter
Posts: 5180
Joined: Sat Jun 12, 2004 6:52 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 7:13 am

Hardly new! The JT9D of the 1960s had a movable cowl, and some JT3D engines were fitted with a shorter version.
Lead me not into temptation, I can find my own way there...
 
jamesbuk
Posts: 3712
Joined: Mon May 02, 2005 11:52 pm

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 5:48 pm

i think the statement putting an engine in reverse is confusing as it gives the impression that the turbine turns the other way.
what really happens is some of the engine shell pulls back so it directs thrust forwards upsetting the aerodynamics and therefore slowing the aircraft this is the same with the bucket reversers they make a bucket at the rear of the engine and disrupt the aerodynamics
You cant have your cake and eat it... What the hells the point in having it then!!!
 
hawker
Posts: 103
Joined: Sun Aug 29, 2004 12:18 pm

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:11 pm

Quoting DLKAPA reply 11

Instead of redirecting the full engine thrust, the new cowlings only reverse the bypass flow. Think of it that way.

I would not have thought that thrust deflectors deflected the hot portion of the exhaust, which would not do either the reversers or the airframe much good. But does that mean the hot part of the exhaust is still pushing the plane forward?

Is the roar you hear when the thrusters are deployed on landing due to the engines speeding up, or just the sound of the diverted air? Are the engines at idle?
 
777ER
Crew
Posts: 9853
Joined: Fri Dec 19, 2003 5:04 pm

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 6:11 pm

The reverse thrust is kind of like air brakes. The Air flows throu and this causes a drag which slows the aircraft down
 
N754PR
Posts: 2909
Joined: Mon Oct 04, 1999 10:03 pm

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 8:54 pm

Comne on, this topic must be a joke!
Bush, your a sad, sad man.
 
EK156
Posts: 646
Joined: Mon May 09, 2005 8:01 pm

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 9:18 pm

Quoting N754PR (Reply 16):
Comne on, this topic must be a joke!

Why do you think it is a joke? Some of us are not as clever as you are and would like to know more.... please excuse us if we are ignorant.... We deeply appologise and will make sure we never ask any questions in your presence again!!!!
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 10:53 pm

I may not win often, but I damn well never lose!!! ;)
 
DeltaMD11
Posts: 1678
Joined: Sat Dec 07, 2002 4:56 am

Engine Cover Missing On This EK Pic?

Sun Sep 18, 2005 11:29 pm

The idea that the "engine is put into reverse" isn't exactly correct. The type of thrust reverser seen in the above picture is called a cascade reverser. Part of the engine cowling slides back and the engine bypass flow is directed forward. For the most part reverse thrust in and of itself is not very effective in slowing the aircrafts' speed down on the runway, thats what the wheel brakes are for. The idea behind reverse thrust, as it is with the spoilers, is to reduce the lift generated by the wings therefore putting more weight on the wheels (giving more breaking power in the process) thereby helping to slow the aircraft down.

Other types of reversers that I can think of off the top of my head would be clamshell reversers (most commonly associated with the PW JT8D, but are used widely on other engines as well), and the petal-type reversers seen on the CFM56 and many other engines as well where doors deploy around the engine cowling allowing bypass air to flow through them as well.
Too often we ... enjoy the comfort of opinion without the discomfort of thought. - John Fitzgerald Kennedy
 
LongHorn2000
Posts: 12
Joined: Mon May 02, 2005 5:25 am

Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 12:51 am

The negative thrust from the thrust reverser doesn't come so much from pointing the exhaust forward. In fact, I don't think that there is a large forward component to the exhaust as it exits during thrust reverse. I think that it is mainly directed perpendicular to the engine axis.

However, if you look at the forces in an engine during it's operation you will then see how the thrust reverse actually works. In an engine you've got the fan and compressor which pressurize the air before it goes into the combustor and the turbine (or bypassed). In the fan and compressor section there is tremendous pressure that manifests itself in a force pushing the airplane backwards. Under normal operation the process of burning and exhausting through a nozzle (or just exhausting through a nozzle for the bypass) results in a much larger force pushing the airplane forward (thrust). When the thrust reversers are deployed, it effectively removes this force by angling it perpendicular to the engine axis. However, the forces acting on the fan and compressor are still pushing backwards. This opposite force increase as engine RPM increases.
 
mytravel330
Posts: 42
Joined: Sun Aug 28, 2005 8:30 pm

Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 1:49 am

Quoting N745PR REPLY 16
Comne on, this topic must be a joke!

It might be a joke to you but for some of the people on here who may not be up to engineer status its all about finding out things and it would be cool if you could do that with a bit more respect, not everyone knows every nut and bolt on an airplane as im sure you dont,please be more considerate in your replies, if you have nothing constructive to say then leave it out.
 
777wt
Posts: 828
Joined: Wed Jan 19, 2005 7:45 am

Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 2:16 am

Quoting Hawker (Reply 14):
I would not have thought that thrust deflectors deflected the hot portion of the exhaust, which would not do either the reversers or the airframe much good. But does that mean the hot part of the exhaust is still pushing the plane forward?

Is the roar you hear when the thrusters are deployed on landing due to the engines speeding up, or just the sound of the diverted air? Are the engines at idle?

A long time ago some early planes were equipped with thrust reversers that actually reverse the cold air section and the hot turbine exhaust section (two separate reversers in one) but that caused problems with the hot section reverser (I don't know specifically but something associated to the heat and the hot air being sucked back into the engine)

Now today's engines are mostly casade type thrust reversers while most private jets, 727's and early 737's use clamshell thrust reversers which is more effective but takes more abuse for what it's designed for.

When the thrust reversers are deployed by pulling the throttles to idle and the front levers raised, it only goes up to between 20% to 50% max of the total engine power, no more.
80% of the thrust in normal flight is produced by the cold section flow, only 20% is produced by the hot section flow.
So only the 80% section which is the cold flow, is actually reversed.

Think of a turboprop (propellers driven by a small turbine engine via a gearbox or shaft), they can reverse their blades to produce negative thrust but no reversers on the hot section of the engine.

The roar you're hearing after the engines reversers have deployed is both the engine and the diverted air at the same time.
Think about it, the air is trying to change direction almost about 120 degrees from the intake path.


Some airlines are cutting back on the use of reversers when they're not needed for landing on a long runway, they just put it in idle and deploy the reversers but don't add power while in reverse, in this case just idle air flow is being bleed off from forward thrust and isn't doing much but it's already in reverse if they need to add power in a instant to stop quickly instead of waiting for the reverser to deploy then the power can be added.

Thrust reversers does pose problems for the engines, they are:
FOD (Foreign Object Damage) from sucking up whatever is on the runway and the blades strikes it.
Shorten engine life due to higher EGT (Exhaust Gas Temp.) while in reverse.
 
hawker
Posts: 103
Joined: Sun Aug 29, 2004 12:18 pm

RE: Engine Cover Missing On This Ek Pic?

Mon Sep 19, 2005 2:22 am

I would still like to know, in my pathetic ignorance, what a pilot does on landing with reverse thrust. Once the wheels start rotating the spoilers automatically deploy and reverse thrust is selected.

Does that then mean the throttles are then advanced or left at idle?

If they are advanced, I assume they only go to a certain setting. Once the speed reduces to a certain amount then the throttles are put back to idle and the brakes applied. Is that right?
 
SA006
Posts: 1818
Joined: Tue Sep 16, 2003 3:28 am

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 2:37 am

Quoting Hawker (Reply 23):
Does that then mean the throttles are then advanced or left at idle?

Idle thrust is issued 10 feet before touchdown (in some cases , the computer shouting "RETARD" at the pilot) This means that the engines should be at idle thrust. After touch down , reverse is applied and I think the throttles are locked at idle. Someone correct me if I am wrong  Smile

-SA006
Proudly South African
 
c680
Posts: 425
Joined: Sat Apr 23, 2005 6:03 am

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 2:52 am

Quoting Hawker (Reply 23):
Once the wheels start rotating the spoilers automatically deploy and reverse thrust is selected.

Most aircraft require the pilot to manually activate the thrust reverser. This depends on the design of the aircraft. Actions that happen upon touch down are usually dependent on a "squat switch." Its design is to detect weight on the wheels, not rotation of the wheels.

Quoting Hawker (Reply 23):
Does that then mean the throttles are then advanced or left at idle?

That depends on the action of the pilot. Both are possible. Simply deploying the thrust reverser will give significant stopping power without the need to spool up the engines, which makes quite a bit of noise.

Quoting Hawker (Reply 23):
If they are advanced, I assume they only go to a certain setting.

No, they operate just like throttles - full range of settings, but frequently there is a Max setting that is less than full engine power. Again, this depends on the airplane you are talking about - many designs exist.

Quoting Hawker (Reply 23):
Once the speed reduces to a certain amount then the throttles are put back to idle and the brakes applied. Is that right?

You can, but it is poor practice. Brakes and Thrust reverser are two separate systems. They are usually operated independently of one another. Basic rule of thumb is to "get on the brakes" early in the landing process, as they provide the majority of stopping power. Also, if you have a brake failure, you know about it early enough to do something about it (use emergency brakes, more thrust reverse, etc)

Your questions are good ones, and they also illustrate why pilots of aircraft over 12,500 Gross Weight get type ratings for each type of aircraft they fly: They can be very different from one another (Concorde vs. Beech 1900)
My happy place is FL470 - what's yours?
 
MANTEC
Posts: 56
Joined: Sat Mar 19, 2005 5:41 am

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 4:09 am

Quoting N754PR (Reply 16):
Comne on, this topic must be a joke!

Thanks to all of you for explaining the use of reversers.....I didn't think the thread as a joke and I for one am grateful for the clarification.

Thanks again Guys!!

 bigthumbsup 
 
sfuk
Posts: 129
Joined: Mon Sep 12, 2005 9:30 pm

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 4:16 am

What about prop aircraft? Does the same apply? Do they even need it?

Stu
 
Gary2880
Posts: 1856
Joined: Wed Aug 18, 2004 8:52 pm

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 5:18 am

Quoting SA006 (Reply 24):
(in some cases , the computer shouting "RETARD" at the pilot)

 rotfl   rotfl   rotfl  !!!!

Quoting Sfuk (Reply 27):
What about prop aircraft? Does the same apply? Do they even need it?

yes, the Hercules, Dornier 328, J31/41.. And others can be put into reverse and will actually physically reverse themselves off a stand from stationary instead of using a tug.

sounds bloody horrible though.
Patriotism is the last refuge of the scoundrel :- Samuel Johnson
 
Geo772
Posts: 439
Joined: Thu Jul 15, 2004 11:40 pm

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 5:27 am

Prop aircraft are able to reverse pitch the propeller.

Here is a site about propeller aerodynamics.
http://aerodyn.org/Propulsion/propeller.html

As for engines that use the cascade type reverser many aircraft could in theory reverse themselves. However in today's age of high fuel prices and airlines very much conscious of their bottom line this is a feature that goes unused.
Flown on A300B4/600,A319/20/21,A332/3,A343,B727,B732/3/4/5/6/7/8,B741/2/4,B752/3,B762/3,B772/3,DC10,L1011-200,VC10,MD80,
 
SA006
Posts: 1818
Joined: Tue Sep 16, 2003 3:28 am

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 5:33 am

Quoting Sfuk (Reply 27):
What about prop aircraft? Does the same apply? Do they even need it?

Props such as ATR's , Dash 8's etc feather. "Feathering" occurs when the propellers are moved to a flat angle thus creating no pushing power. In normal flight , props are set at an angle to provide movement. Again , correct me if I am wrong please  Smile

-SA006
Proudly South African
 
Gary2880
Posts: 1856
Joined: Wed Aug 18, 2004 8:52 pm

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 5:45 am

Quoting Geo772 (Reply 29):
in theory reverse themselves.

ahh more than theory, and far from unused. Eastern Airways does it all the time at ABZ, (at the prices they charge the cost isn't really a factor!) they ask the ATC for a 'powerback' instead of the usual 'pushback'

I once stood in front of a Do328 as it reversed its self.. Sounds so loud and unhealthy

[Edited 2005-09-18 22:48:14]
Patriotism is the last refuge of the scoundrel :- Samuel Johnson
 
User avatar
Starlionblue
Posts: 17049
Joined: Fri Feb 27, 2004 9:54 pm

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 6:23 am

Quoting Emirates773ER (Reply 3):
hmm.... can anyone explain reverse thrusters?

I think they've been explained reasonably well. But if you nitpick reverse thrusters are not found on aircraft. They are found on spaceships. Thrust reversers, on the other hand, ARE found on aircraft.

Quoting Dogfighter2111 (Reply 6):
Nearly all Landings use Revers Thrust.

Most commercial airliner landings use some reverse thrust, or idle reverse, but not "nearly all".
"There are no stupid questions, but there are a lot of inquisitive idiots."
 
User avatar
HAWK21M
Posts: 29867
Joined: Fri Jan 05, 2001 10:05 pm

RE: Engine Cover Missing On This EK Pic?

Mon Sep 19, 2005 4:01 pm

Quoting MANTEC (Reply 26):
Thanks to all of you for explaining the use of reversers.....I didn't think the thread as a joke and I for one am grateful for the clarification

Remember....No Question is Foolish.Always Ask,cause at least you'll know the Answer.
Cheers  bigthumbsup 
regds
MEL
I may not win often, but I damn well never lose!!! ;)

Who is online

Users browsing this forum: Baidu [Spider], EA CO AS, flyingclrs727, glen, Google [Bot], HALtheAI, hinckley, JJV, qf789, smokeybandit, vv701 and 216 guests