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Engine Cover Missing On This EK Pic?  
User currently offlineEmirates773ER From Pakistan, joined Jun 2005, 1448 posts, RR: 10
Posted (8 years 7 months 4 days 6 hours ago) and read 9210 times:

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


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Photo © I-DISE - SpotIt



[Edited 2005-09-17 23:04:46]


The Truth is Out There ---- Face It!!!!!
33 replies: All unread, showing first 25:
 
User currently offlineNewark777 From United States of America, joined Dec 2004, 9348 posts, RR: 30
Reply 1, posted (8 years 7 months 4 days 6 hours ago) and read 9191 times:

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?
User currently offlineDogfighter2111 From United Kingdom, joined Nov 2004, 1968 posts, RR: 1
Reply 2, posted (8 years 7 months 4 days 6 hours ago) and read 9182 times:

Err...

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

Thanks
Mike


User currently offlineEmirates773ER From Pakistan, joined Jun 2005, 1448 posts, RR: 10
Reply 3, posted (8 years 7 months 4 days 6 hours ago) and read 9149 times:

hmm.... can anyone explain reverse thrusters?


The Truth is Out There ---- Face It!!!!!
User currently offlineDogfighter2111 From United Kingdom, joined Nov 2004, 1968 posts, RR: 1
Reply 4, posted (8 years 7 months 4 days 6 hours ago) and read 9143 times:

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

(Best way i can describe it)

Thanks
Mike


User currently offlineEmirates773ER From Pakistan, joined Jun 2005, 1448 posts, RR: 10
Reply 5, posted (8 years 7 months 4 days 6 hours ago) and read 9117 times:

Are reverse thrusters applied on all landing planes or speed is a factor while landing?


The Truth is Out There ---- Face It!!!!!
User currently offlineDogfighter2111 From United Kingdom, joined Nov 2004, 1968 posts, RR: 1
Reply 6, posted (8 years 7 months 4 days 6 hours ago) and read 9101 times:

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


User currently offlineDLKAPA From , joined Dec 1969, posts, RR:
Reply 7, posted (8 years 7 months 4 days 6 hours ago) and read 9080 times:

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.

User currently offlineFlyf15 From , joined Dec 1969, posts, RR:
Reply 8, posted (8 years 7 months 4 days 6 hours ago) and read 9075 times:

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"

User currently offlineWhiteHatter From , joined Dec 1969, posts, RR:
Reply 9, posted (8 years 7 months 4 days 6 hours ago) and read 9053 times:



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)


User currently offlineOmoo From , joined Dec 1969, posts, RR:
Reply 10, posted (8 years 7 months 4 days 5 hours ago) and read 8966 times:

These new cowling can sure confuse people.

User currently offlineDLKAPA From , joined Dec 1969, posts, RR:
Reply 11, posted (8 years 7 months 4 days 5 hours ago) and read 8958 times:

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.


User currently offlineWhiteHatter From , joined Dec 1969, posts, RR:
Reply 12, posted (8 years 7 months 4 days 5 hours ago) and read 8951 times:

Hardly new! The JT9D of the 1960s had a movable cowl, and some JT3D engines were fitted with a shorter version.

User currently offlineJamesbuk From United Kingdom, joined May 2005, 3968 posts, RR: 4
Reply 13, posted (8 years 7 months 3 days 18 hours ago) and read 8690 times:

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!!!
User currently offlineHawker From Australia, joined Aug 2004, 105 posts, RR: 0
Reply 14, posted (8 years 7 months 3 days 18 hours ago) and read 8631 times:

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?


User currently offline777ER From New Zealand, joined Dec 2003, 11847 posts, RR: 18
Reply 15, posted (8 years 7 months 3 days 18 hours ago) and read 8631 times:
AIRLINERS.NET CREW
FORUM MODERATOR

The reverse thrust is kind of like air brakes. The Air flows throu and this causes a drag which slows the aircraft down

User currently offlineN754PR From , joined Dec 1969, posts, RR:
Reply 16, posted (8 years 7 months 3 days 15 hours ago) and read 8472 times:

Comne on, this topic must be a joke!

User currently offlineEK156 From United Arab Emirates, joined May 2005, 765 posts, RR: 2
Reply 17, posted (8 years 7 months 3 days 15 hours ago) and read 8412 times:

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 currently offlineHAWK21M From India, joined Jan 2001, 31573 posts, RR: 57
Reply 18, posted (8 years 7 months 3 days 13 hours ago) and read 8069 times:

http://www.airliners.net/discussions/tech_ops/read.main/124892/4/
regds
MEL



Think of the brighter side!
User currently offlineDeltaMD11 From United States of America, joined Dec 2002, 1701 posts, RR: 35
Reply 19, posted (8 years 7 months 3 days 13 hours ago) and read 7666 times:

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
User currently offlineLongHorn2000 From United States of America, joined May 2005, 12 posts, RR: 0
Reply 20, posted (8 years 7 months 3 days 11 hours ago) and read 6781 times:

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.


User currently offlineMytravel330 From United Kingdom, joined Aug 2005, 42 posts, RR: 0
Reply 21, posted (8 years 7 months 3 days 10 hours ago) and read 6190 times:

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.


User currently offline777WT From United States of America, joined Jan 2005, 874 posts, RR: 1
Reply 22, posted (8 years 7 months 3 days 10 hours ago) and read 5912 times:

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.


User currently offlineHawker From Australia, joined Aug 2004, 105 posts, RR: 0
Reply 23, posted (8 years 7 months 3 days 10 hours ago) and read 5815 times:

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?


User currently offlineSA006 From South Africa, joined Sep 2003, 1883 posts, RR: 55
Reply 24, posted (8 years 7 months 3 days 10 hours ago) and read 5652 times:

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
25 C680 : Most aircraft require the pilot to manually activate the thrust reverser. This depends on the design of the aircraft. Actions that happen upon touch
26 Post contains images MANTEC : 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. Tha
27 Sfuk : What about prop aircraft? Does the same apply? Do they even need it? Stu
28 Post contains images Gary2880 : !!!! yes, the Hercules, Dornier 328, J31/41.. And others can be put into reverse and will actually physically reverse themselves off a stand from sta
29 Post contains links Geo772 : Prop aircraft are able to reverse pitch the propeller. Here is a site about propeller aerodynamics. http://aerodyn.org/Propulsion/propeller.html As fo
30 Post contains images SA006 : 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 norm
31 Gary2880 : 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!) t
32 Starlionblue : 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
33 Post contains images HAWK21M : Remember....No Question is Foolish.Always Ask,cause at least you'll know the Answer. Cheers regds MEL
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