Newark777 From United States of America, joined Dec 2004, 9348 posts, RR: 33 Reply 1, posted (7 years 8 months 1 week 2 days 20 hours ago) and read 8009 times:
That's the thrust reverser deploying right after the main gear touches down. And it's actually landing, not taking off.
Dogfighter2111 From United Kingdom, joined Nov 2004, 1968 posts, RR: 1 Reply 2, posted (7 years 8 months 1 week 2 days 20 hours ago) and read 8000 times:
Err...
Actually, that aircraft is landing and that is the revers thrust
Dogfighter2111 From United Kingdom, joined Nov 2004, 1968 posts, RR: 1 Reply 4, posted (7 years 8 months 1 week 2 days 20 hours ago) and read 7961 times:
It is like putting the engine in reverse to slow the aircraft down.
Dogfighter2111 From United Kingdom, joined Nov 2004, 1968 posts, RR: 1 Reply 6, posted (7 years 8 months 1 week 2 days 20 hours ago) and read 7919 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 )
Spoilers (Little Flaps that go up like / )
DLKAPA From , joined Dec 1969, posts, RR: Reply 7, posted (7 years 8 months 1 week 2 days 20 hours ago) and read 7898 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.
Flyf15 From , joined Dec 1969, posts, RR: Reply 8, posted (7 years 8 months 1 week 2 days 20 hours ago) and read 7893 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"
Jamesbuk From United Kingdom, joined May 2005, 3968 posts, RR: 5 Reply 13, posted (7 years 8 months 1 week 2 days 9 hours ago) and read 7508 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!!!
Hawker From Australia, joined Aug 2004, 105 posts, RR: 0 Reply 14, posted (7 years 8 months 1 week 2 days 8 hours ago) and read 7449 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?
EK156 From United Arab Emirates, joined May 2005, 765 posts, RR: 3 Reply 17, posted (7 years 8 months 1 week 2 days 5 hours ago) and read 7230 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!!!!
DeltaMD11 From United States of America, joined Dec 2002, 1698 posts, RR: 38 Reply 19, posted (7 years 8 months 1 week 2 days 3 hours ago) and read 6484 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
LongHorn2000 From United States of America, joined May 2005, 12 posts, RR: 0 Reply 20, posted (7 years 8 months 1 week 2 days 2 hours ago) and read 5599 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.
Mytravel330 From United Kingdom, joined Aug 2005, 42 posts, RR: 0 Reply 21, posted (7 years 8 months 1 week 2 days 1 hour ago) and read 5008 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.
777WT From United States of America, joined Jan 2005, 874 posts, RR: 1 Reply 22, posted (7 years 8 months 1 week 2 days ago) and read 4730 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.
Hawker From Australia, joined Aug 2004, 105 posts, RR: 0 Reply 23, posted (7 years 8 months 1 week 2 days ago) and read 4633 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?
SA006 From South Africa, joined Sep 2003, 1883 posts, RR: 56 Reply 24, posted (7 years 8 months 1 week 2 days ago) and read 4470 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
-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 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 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 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 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 HAWK21M: Remember....No Question is Foolish.Always Ask,cause at least you'll know the Answer. Cheers regds MEL
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