SurClaro Flight Simulator Resources

harkonnen · Posted: Fri Sep 23, 2005 5:04 am Post subject: How does reverse thrust work?

I am now curious about the mechanics of reverse thrust. It can't possibly be the fans in those massive engines stopping suddenly and firing up in the opposite direction. Is it the way the air is taken in and redirected through the engine? Is there instant full power forward thrust provided? (It sure sounds like it while simming.) I suspect the reverse thrust doesn't equal full forward thrust. Thrust is measured in pounds of thrust provided, I think. I bet the engine opening animations in FS airliners provide a clue to this engineering delight but I'm sketchy on details on this one. Thanks for all the great feedback here BTW.

rd · Posted: Fri Sep 23, 2005 5:16 am Post subject:

Most of the reverse thrusters are obtained at the rear of the engine.

When put into reverse thrust ( R/T ) there are engine covers that swing rearward and then open, like to block the forward thrust, but these covers actually force the thrust air forward, toward the nose at full throttle, to help slow the plane down. There are other variations to use R/T. The engines do not go backwards, otherwise you would be able to move backwards. And everybody knows, planes don't have reverse :D

Ardie/rd

Max · Joined: 10 Dec 2004 Posts: 673 Location: LQSA

There are two major differences in today's engine reversers. One is called a CLAMSHELL reverser, usually found on Pratt & Whitney JT8Ds but also amny more engines that are tail mounted. While the engines mounted on the wings, (apart from the 737-200, which also has a clamshell reversed JT8D on the wings, which is always fun to watch) have a reverser called a Cascade system. The Clamshell reverser blocks the exaust on the rear of the engine, and directs it upwards and downwards with the so called reverse buckets. The Cascade reverser also blocks the exsaust, but it directs it a little more foreward and it has a specific mesh to direct the air forward (if you've seen that green mesh-kinda looking stuff under the reverser).

A little visual aid:

http://www.flightsim-pro.com/revs.jpg

Pilotwannabe · Posted: Fri Sep 23, 2005 2:06 pm Post subject:

Planes do have the ability to 'backup' themselves. I've seen it done. Its just most airports don't allow it to be done.

Commander Cool · Posted: Fri Sep 23, 2005 6:06 pm Post subject:

huh! :?
Could you care to explain this feat of engineering wannabe :?

Derek

Max · Joined: 10 Dec 2004 Posts: 673 Location: LQSA

On some aircraft, the reverse thrust is powerful enough to back up a light loaded airplane with parking brakes off. That's all.....and it is not allowed by any airport, and it isn't even counted as an ability of an aircraft, as it is a mis-use of an aircraft system.

bschott · Posted: Fri Sep 23, 2005 7:01 pm Post subject:

Some of the freeware aircraft will show you this ability if you are viewing from the outside. (most don't have the animation but some do)

Just tap your F2 key repeatedly while on the landing roll (or if you turn your damage/crash detection off, start up the engines at the gate and do the same)

Commander Cool · Posted: Fri Sep 23, 2005 8:00 pm Post subject:

Oh right thanks max, I knew that, I thought he meant an actual reverser on its own.

Derek

Pilotwannabe · Posted: Fri Sep 23, 2005 9:36 pm Post subject:

Personally, I think if an aircraft is ABLE to do something, it should be counted as an ability, where it is a misused system or not...
Surfers surf on waves, is the ability of the wave to provide the momentum to the surfer a misuse of a wave just because waves aren't there for surfers? And therfore the ability of doing said action by the wave is not an ability at all?

Not arguing, just bringing my two cents to the table :)

dakine503 · Joined: 28 May 2005 Posts: 11 Location: USA

I have actually seen this done in STL. An MD-80 used the thrust reverse to push back from the gate. I wondered about it myself. If not allowed to do that, why in the world would they let them? Surely everyone at the ramp saw this. :roll:

brettr10 · Posted: Mon Sep 26, 2005 9:27 pm Post subject:

I've seen it done for real as well but on military aircraft..C-130 and C-17. It's quite something to see when you see how fast they can backup but obviously the rules are very different for this type of operations. They've got some monster reverse thrusters. In fact on a steep ingress to the airfield the C-17 hangs on the thrust reversers. It's an amazing site.

wheelright · Joined: 15 May 2004 Posts: 169 Location: KDNL/KAGS

I was on a plane when the reverse from the gate trick was done. No TUG available, mega delays and the weather window was closing. The Cpt. told us to hang on as we were about to experience something very rare. He was given clearance by both the airport and his company for the unassisted back-up. Traveling in the summertime can cause some real messes.

Also, anyone notice that they've gone back to single engine taxi since fuel costs started climbing? They don't start the second engine until they are almost to the runway and upon landing they shut one down as soon as they're clear of the runway.

bschott · Posted: Tue Sep 27, 2005 2:17 am Post subject:

wheelright wrote: I was on a plane when the reverse from the gate trick was done. No TUG available, mega delays and the weather window was closing. The Cpt. told us to hang on as we were about to experience something very rare. He was given clearance by both the airport and his company for the unassisted back-up. Traveling in the summertime can cause some real messes.

Also, anyone notice that they've gone back to single engine taxi since fuel costs started climbing? They don't start the second engine until they are almost to the runway and upon landing they shut one down as soon as they're clear of the runway.

You know I noticed that too. I thought it was just Northwest doing that, but it seems United does it too. I do some 'plane-spotting' here at the local airport and the first time I saw this, I thought there must have been engine problems, but during the day every aircraft that landed or took off seemed to be doing the same.

Very strange. One would think they would need to stress the other engine more to get the same thrust both would supply, and then they had the 'swivel' issue when the thrust is imbalanced.

Too much thinking, head hurts.

myheadspinsincircles · Posted: Tue Sep 27, 2005 2:14 pm Post subject: .

huuh? how does that work? if one engine is off wouldn't that make them go spinning? well not spinning but turning u know what i mean... and if they keep the wheel straight wouldn't that create a lot of pressure on the wheel's support bars n stuff....how exactly do planes turn anyways? i mean in engineering terms...like....big servos? like a car? something different?

Max · Joined: 10 Dec 2004 Posts: 673 Location: LQSA

Hydraulic servos and a steering wheel on captain's left and copilot's right side. Most of the ATR 72's lamost always taxi with only one engine, and it doesn't send them spinning, they just use the wheel to turn, and you wouldn't believe how little input it actually needs to keep it straight.

You probbably think that a landing with one engine off is also impossible??