rampguy
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When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 8:37 am

To all pilots.... Here is a question for you. Can any of you tell me when do the landing gears stop their spinning after lift off? I have been curious as to whether the pilot applies the breaks to stop the spinning or do you allow them to stop on their own even after they enter the wheel well and after the bay doors have closed? And if so, how long does it usually take? Thanks.
 
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cpd
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RE: When Do Landing Gears Stop Spinning After Take

Wed Mar 26, 2008 8:50 am

I think they have automated systems to stop it (which should be able to work once the plane no longer has weight on any of the wheels).

Concorde has brakes to do this as the gear is retracted. There are also systems to prevent the main brakes being applied until all wheels are moving at the same speed.

[Edited 2008-03-26 01:58:59]

[Edited 2008-03-26 01:59:36]
 
HAL
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 8:56 am

On most modern aircraft, moving the gear handle up not only starts the gear retraction, but also starts a gentle brake application on the mains. They should be pretty much stopped by the time they enter the wheel wells. Sometimes, especially with carbon brakes, this causes a small puff of brake dust to spew out:

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As for the nose gear, I don't know about other aircraft, but the 767 has a pair of pads in the wheel well that the nose tires rub against when retracted. These help slow the wheels to a stop in about ten seconds or so. The sound is quite noticeable from the cockpit, since the nose gear well is right below us.

HAL

[Edited 2008-03-26 01:58:10]
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Goldenshield
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 9:08 am



Quoting HAL (Reply 2):
As for the nose gear, I don't know about other aircraft, but the 767 has a pair of pads in the wheel well that the nose tires rub against when retracted. These help slow the wheels to a stop in about ten seconds or so.

I believe they are called "snubbers." As far as I know, all large (12,500+ lb.) transports have them, and they may be implemented in different ways depending on manufacture.
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ThirtyEcho
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 9:20 am

Well, if we start from the most simple example of a light twin or single, you don't want those wheels to be spinning when they go into the wells. On wet or snowy days, spinning wheels can throw water all over the gear assembly and the gear wells and doors; at altitude, this can freeze solid and make gear extension difficult at the end of the flight.

In addition, tires can pick up rocks and debris from the runway and hurl them into the airplane. All pilots are taught to tap the brakes after takeoff, prior to gear retraction.

In larger aircraft, this function is automated. In "big iron" there is the additional concern of gyroscopic forces if those big wheels remain spinning as they translate from a vertical plane to a horizontal plane of rotation.
 
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jetmech
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 9:34 am



Quoting HAL (Reply 2):
They should be pretty much stopped by the time they enter the wheel wells.

G'day Hal,

I think the idea may actually be to have the wheels stopped before the retraction sequence begins. This is to prevent imposing the massive gyroscopic forces (developed by the wheels being moved out of their plane of rotation) upon the landing gear structure.

Quoting HAL (Reply 2):
As for the nose gear, I don't know about other aircraft, but the 767 has a pair of pads in the wheel well that the nose tires rub against when retracted.

Same as the 747.

Regards, JetMech
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crjfixer
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 10:14 am

LOL anyone who had ever ridden in the cockpit of a CRJ knows the nose wheels dont stop for quite some time and if they arent balanced just right you can definately feel it when the gear goes up.
 
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vzlet
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 10:19 am

This Mustang's wheels are still spinning as they enter the wells:

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Birdwatching
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 6:02 pm

On most gliders I fly, particularly the ASK21 two seater, the wheels spin for a couple of minutes after take off. You don't hear it while being towed, but when you're free you get the loud spinning sound, which is kind of annoying when you want to enjoy the quietness of the glider's flight. I could stop the wheel with the brakes, but they are connected to the speed brakes, so I would lose some amount of altitude even if I do it really fast. On some K8s, I have a bicycle-style mechanic brake independent from the speed brake. I could use it to stop the wheel from spinning, but as far as I remember the spinning on the K8 stops during towing. I guess it depends on how easy the wheel turns and how new the plane (or the part) is.

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roseflyer
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RE: When Do Landing Gears Stop Spinning After Take

Wed Mar 26, 2008 6:58 pm

Quoting HAL (Reply 2):
As for the nose gear, I don't know about other aircraft, but the 767 has a pair of pads in the wheel well that the nose tires rub against when retracted. These help slow the wheels to a stop in about ten seconds or so. The sound is quite noticeable from the cockpit, since the nose gear well is right below us.

I think that is the same on all Boeing planes. Nose gear does not have brakes. I remember reading a flight squawk when that mechanism failed and the pilots complained about a noise under the flight deck for about 5 minutes after takeoff.

The main wheels will be stopped with brakes before entering the wheel well. Especially on the smaller jets, there are many many components inside the wheel well. A piece of tread coming off a tire spinning in the wheel well could do a lot of damage and take out a hydraulic system. There is a small prevention mechanism located as the tire enters the wheel well that is supposed to break off if there is a loose tread flying around and cause the gear to automatically extend. I have never heard of that little mechanism every being used though.

[Edited 2008-03-26 12:00:22]
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andz
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Mar 26, 2008 7:08 pm

I have noticed on a Dash 8 that the wheels are still spinning furiously when they disappear inside the wheel well.
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Buzz
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Mar 27, 2008 6:33 am

Hi Ramp Guy, Buzz here. I'm trying to recall which airplane... most likely a Boeing ... where I learned that the "spare" hydraulic pressure coming off the retract actuator is ported to the brakes to gently drag the MLG wheels to a stop. That's the pressure coming out of the retract actuator , not the pressure going in to shove the wheels into the wheel well. For some reason I recall a number of a couple hundred PSI.

Like some of the other guys have said, the NLG has brake pads that the nose tires rub up against. It's an item we used to check for wear on the B check.

Make more sense?

g'day
 
rampguy
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Mar 27, 2008 8:35 am

Thanks Buzz for the info. As you can tell, I am by no means a pilot, just a ramp rat. lol I think I'll just stick with loading the bags and let the rest of you take the controls in the driver's seat.
 
kimberlyRJ
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Mar 27, 2008 8:45 am

Hey

Just completed a long haul pond crossing, so bare with me on this one…

When an aircraft taxi’s the breaking system (pads etc) create heat which can sometimes build up, especially after landing or on an aborted take off.

When an aircraft (heavy) has taken off, the gear is retracted and the wheels are ‘slowed down’ and then stopped. What’s happening to the heat? I know while the gear is retracting air will be passing at great speed but once fully retracted there will be no air movement.

I remember last summer on a very hot day I took off on a B744 heading for LAX. After a normal taxi and a normal (ish a little long) take off the pilots left the gear down for ages! It was three and a half minutes before the gear was retracted, I remember well as I timing it and thinking ‘Capt is about to tell me we have a problem’ just as the gear went up. Nothing happened after that stage, I mean not straight away, so there did not seem any clear reason for keeping the gear down, other then for calling them?

I would have asked him but the Capt was horrible!

Kimberly

Ps. I’m loving LHR T5
 
3MilesToWRO
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Mar 27, 2008 9:04 am



Quoting Kimberlyrj (Reply 13):
When an aircraft (heavy) has taken off, the gear is retracted and the wheels are ‘slowed down’ and then stopped. What’s happening to the heat? I know while the gear is retracting air will be passing at great speed but once fully retracted there will be no air movement

Not much air movement, but anyway there's some and additionaly the brakes will be warming all the rest of the plane - starting from gear parts and (theoretically) finishing at radome and top of fin  Smile

What's more, it's not the same braking as when you need to dissipate the kinetic energy of 100 Tons moving 100 km/h. It only needs to lose energy of 100 kg wheels rotating 10 times a second. For a brake system able to do the first, the second case is a piece of cake.
 
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HAWK21M
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Mar 27, 2008 9:25 am

Most modern day Airliners use the Auto retract braking,that ports Hyd pr to the MLG Brakes just before it enters the MWW.For the NLG wheels there are Snubbers pads to stop the rotation by friction.

regds
MEL
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roseflyer
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Mar 27, 2008 1:37 pm



Quoting Kimberlyrj (Reply 13):
When an aircraft (heavy) has taken off, the gear is retracted and the wheels are ‘slowed down’ and then stopped. What’s happening to the heat? I know while the gear is retracting air will be passing at great speed but once fully retracted there will be no air movement.

It eventually disappaits in the wheel well. One problem is that the heat from the brakes does heat the air in the tires which causes them to expand. It is actually quite impressive how much a tire can grow and shrink. Once the airplane is near cruise though, the wheel well gets quite cold. There isn't a problem with heat.

The problem with heat is after landings. The brakes do need some time to cool after landing before the plane is safe to take off again. This usually is brief enough not to matter, but short turn times and short flights can cause problems with brake heat.
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Bartonsayswhat
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Mar 28, 2008 6:13 am

With regards to leaving the wheels down after take off to let the brakes cool, is this done on any 737 as the wheels are exposed letting air run over them?
 
3MilesToWRO
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Mar 28, 2008 8:04 am

The outside of one wheel is. But not the brakes themselves. Additionaly the wheels are certainly made as "invisible" for airflow as possible. So it shouldn't be much difference compared to completly hidden gear.
 
A/c train
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Mar 28, 2008 8:45 am

Metered Hyd pressure is fed to the brakes from the retract circuit and the nose wheels have spin brakes. Some aircraft such as A320 are not allowed to takeoff with brake temps of 300 +, a way of cooling on others is to prolong gear retraction. Option on some aircraft are brake fans.
 
KELPkid
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Mar 28, 2008 11:01 am



Quoting Vzlet (Reply 7):
This Mustang's wheels are still spinning as they enter the wells:

In fact, if you tap the brakes in the P-51 after leaving the runway, your next landing will result in a noseover if you land with the wheels down  Wow! (I forget the exact technical reason for that, but it's definitely on the "don't do this" list!).
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sprout5199
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Mar 28, 2008 12:31 pm



Quoting KELPkid (Reply 20):
In fact, if you tap the brakes in the P-51 after leaving the runway, your next landing will result in a noseover if you land with the wheels down (I forget the exact technical reason for that, but it's definitely on the "don't do this" list!).

I bet its because the pads don't release from the rotor(there is no return spring like on a drum brake---did the P-51 use disc brakes?). So when the tire hit the pavement, the brakes wouldn't release right away, and you get a nose over.
I had a caliper stick on a Jeep Grand Wagoneer once, the pad dragged enough to make the rotors glow orange. thank god I had to pi$$ to cool it down before it melted all the grease in the bearings, but smelled real bad.

Then again I could be wrong(not that has ever happened, I thought I was wrong once, turns out I was incorrect about that. duck 

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askr
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RE: When Do Landing Gears Stop Spinning After Take

Fri Mar 28, 2008 1:06 pm



Quoting RoseFlyer (Reply 16):
It eventually disappaits in the wheel well. One problem is that the heat from the brakes does heat the air in the tires which causes them to expand. It is actually quite impressive how much a tire can grow and shrink. Once the airplane is near cruise though, the wheel well gets quite cold. There isn't a problem with heat.

Aren't aircraft wheels filled with nitrogen?
AFIK nitrogen has very little thermal expansion, so the tires won't grow so much compared to an identical wheel filled with just plain air.
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FlyASAGuy2005
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Mar 28, 2008 1:18 pm

I remember reading this in a book but on the CR2, on wheels up, fluid is sent to the breaking system and that's how they are stopped. Is that right?
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rwessel
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Mar 28, 2008 6:58 pm



Quoting Askr (Reply 22):
Aren't aircraft wheels filled with nitrogen?
AFIK nitrogen has very little thermal expansion, so the tires won't grow so much compared to an identical wheel filled with just plain air.

Very often they are filled with nitrogen and I believe it's required for airliners. But the expansion of essentially all gases for a particular temperature change is basically identical in this sort of application. And even if there were a meaningful difference between the gasses present, air is already 78% nitrogen, so that would dampen any such effect. OTOH, there isn't any such effect, as the other two major gasses in air (oxygen 21%, and argon 1%), don't have major differences from nitrogen in the temperature and pressure ranges we're talking about.

The main advantages for nitrogen in tires are the displacement of oxygen and water vapor (and the other trace gasses), which can degrade the materials in the tire. Worse, water vapor can freeze, causing mechanical damage to the tire and rim (which would actually reduce the pressure in the tire a bit more than expected, but the total amount of water vapor is quite small).

Pure nitrogen gas is also a bit lighter than air (about 3.3%), which, according to a quick back of the envelope calculation, works out to something like 10lbs total for all 18 wheels on a 747.
 
474218
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Mar 28, 2008 8:35 pm



Quoting RampGuy (Thread starter):
landing gears stop their spinning

I have been watching this item for days and no one has had the right answer yet:

The landing gear never spins so it doesn't have to stop. Only the wheels and tires spin.
 
Viscount724
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 2:15 am

Quoting RoseFlyer (Reply 9):
Quoting HAL (Reply 2):
As for the nose gear, I don't know about other aircraft, but the 767 has a pair of pads in the wheel well that the nose tires rub against when retracted. These help slow the wheels to a stop in about ten seconds or so. The sound is quite noticeable from the cockpit, since the nose gear well is right below us.

I think that is the same on all Boeing planes. Nose gear does not have brakes. I remember reading a flight squawk when that mechanism failed and the pilots complained about a noise under the flight deck for about 5 minutes after takeoff.

The noise of the nose gear retracting is also very noticeable if you're sitting in the forward cabin of a 747 where the gear retracts almost under your seat.

[Edited 2008-03-28 19:17:01]
 
tdscanuck
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 2:34 am



Quoting Rwessel (Reply 24):
The main advantages for nitrogen in tires are the displacement of oxygen and water vapor (and the other trace gasses), which can degrade the materials in the tire.

It also avoids the exploding wheel problem. I'm not sure if this occurs with today's rubber formulations, but older rubbers would offgas when they got really hot. With air in the tire, you could end up with a flammable mixture inside the tire that would get up to its autoignition temperature and boom...really flat tire.

Tom.
 
motopolitico
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 5:26 am



Quoting Rwessel (Reply 24):
Pure nitrogen gas is also a bit lighter than air (about 3.3%), which, according to a quick back of the envelope calculation, works out to something like 10lbs total for all 18 wheels on a 747.

So why not use pure Helium? Helium, being a noble gas, is even less reactive, and would be even lighter than nitrogen. Imagine the weight savings!

 stirthepot   duck 
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tdscanuck
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 7:10 am



Quoting Motopolitico (Reply 28):
So why not use pure Helium? Helium, being a noble gas, is even less reactive, and would be even lighter than nitrogen. Imagine the weight savings!

Imagine the cost increase and how much more often you'd have to fill the tires due to greatly increased diffusion rates.

Tom.
 
rwessel
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 7:32 am



Quoting Motopolitico (Reply 28):
So why not use pure Helium? Helium, being a noble gas, is even less reactive, and would be even lighter than nitrogen. Imagine the weight savings!

You'd, in fact, save about 250lbs (total, all 18 wheels), but a single fill of the tires will cost you about $1200. And it would leak like crazy with any sort of normal tire. I suspect you'd give up more weight than that trying to get things adequately impermeable and with decent seals.
 
roseflyer
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 8:31 am



Quoting Motopolitico (Reply 28):
So why not use pure Helium? Helium, being a noble gas, is even less reactive, and would be even lighter than nitrogen. Imagine the weight savings!

That idea does keep getting thrown out there, but the diffusion rate just does not make it work. Helium would leak very quickly out of the tires. Aircraft tires are pressurized to over 200 PSI IIRC. Helium can find its way through the rubber. Nitrogen is a much larger molecule and won't leak as quickly.
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panserbjorne
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 9:10 am



Quoting Rwessel (Reply 24):
Quoting Askr (Reply 22):
Aren't aircraft wheels filled with nitrogen?
AFIK nitrogen has very little thermal expansion, so the tires won't grow so much compared to an identical wheel filled with just plain air.

Very often they are filled with nitrogen and I believe it's required for airliners. But the expansion of essentially all gases for a particular temperature change is basically identical in this sort of application. And even if there were a meaningful difference between the gasses present, air is already 78% nitrogen, so that would dampen any such effect. OTOH, there isn't any such effect, as the other two major gasses in air (oxygen 21%, and argon 1%), don't have major differences from nitrogen in the temperature and pressure ranges we're talking about.

The main advantages for nitrogen in tires are the displacement of oxygen and water vapor (and the other trace gasses), which can degrade the materials in the tire. Worse, water vapor can freeze, causing mechanical damage to the tire and rim (which would actually reduce the pressure in the tire a bit more than expected, but the total amount of water vapor is quite small).

Pure nitrogen gas is also a bit lighter than air (about 3.3%), which, according to a quick back of the envelope calculation, works out to something like 10lbs total for all 18 wheels on a 747.

Another important reason for filing up the tires with nitrogen....to reduce the risk of fire...there were few incidents regarding this,that is why they implemented the usage of nitrogen
 
panserbjorne
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 9:13 am



Quoting 474218 (Reply 25):
Quoting RampGuy (Thread starter):
landing gears stop their spinning

I have been watching this item for days and no one has had the right answer yet:

The landing gear never spins so it doesn't have to stop. Only the wheels and tires spin.

Haha....Good one there....I guess nobody noticed it,we were so into explaining the facts about the tires and wheels,that we didn't realise what does the topic is about... Big grin  Silly
 
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HAWK21M
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 9:34 am



Quoting 474218 (Reply 25):
The landing gear never spins so it doesn't have to stop. Only the wheels and tires spin.

Tires are mounted on the hubs which form a wheel when combined so the "Wheel" spins.Wheel is part of the LG.....so that explains.
 Smile


But on the topic The term used is "Auto retract braking"

regds
MEL
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panserbjorne
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 9:56 am



Quoting HAWK21M (Reply 34):
Tires are mounted on the hubs which form a wheel when combined so the "Wheel" spins.Wheel is part of the LG.....so that explains.

Well I hope you know the difference between car spinning,and it's wheels spinning,so I guess u may apply the same to landing gear spinning,and the wheels spinning. If the landing gear spins,and by the time it finishes the first spin,it would have cut the fuselage into two.... Big grin
 
kimberlyRJ
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Mar 29, 2008 3:27 pm

Hello

Quoting RoseFlyer (Reply 16):
The problem with heat is after landings. The brakes do need some time to cool after landing before the plane is safe to take off again. This usually is brief enough not to matter, but short turn times and short flights can cause problems with brake heat

Don’t I know it, while back we had to wait 40 minutes on a hot dry summers day after aborting a fully loaded B744 at LHR for the breaks to cool down enough to safe limits.

Kimberly
 
Valkyrie01
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RE: When Do Landing Gears Stop Spinning After Take Off

Sun Mar 30, 2008 9:04 pm



Quoting HAWK21M (Reply 34):
But on the topic The term used is "Auto retract braking"

I am used to gear retract braking
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baron95
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RE: When Do Landing Gears Stop Spinning After Take Off

Mon Mar 31, 2008 4:55 am

When I was learning to fly light retractable gear aircraft, only one instructor insisted that I tapped the breaks just prior to moving the gear handle to the retract position - no other instructors ever told me to do so.

The one that did is the best instructor I ever had and I am glad he shaped my flying career from early one. His reasoning was to reduce gyroscopic forces, particularly in planes where the gears change directions in complex ways (e.g. some Cessna planes). It never occurred to me to ask - and what about the nose wheel that has no breaks.

I have kept this routine of tapping the break then retracting the gear for the above reasons, but also for a more tangential reason. As you can tell by my username, I frequntly fly Beech Barons, and on those planes there are several different combinations of gear/flaps switch locations, causing many a pilot to retract the gear on the ground (during roll out or for the ill advisable touch and go).

Since I only retract the gear after tapping the breaks (after take-off on positive rate of climb or after stopped clear of the runway), If I tried to retract it say during a touch and go, while on the ground, it would be a wake-up call having the breaks applied on the go part. If I were about to make a mistake on on roll-out (unlikely since I don't touch anything til clear and stoppe), I'd hope that at least having the breaks pressed would put enough weight on the mains to trigger that presure switch on the landing gear mechanism.

Anyway, a bit off topic, but I wanted to share that and acknowledge a great instructor.

Back on topic - it sounds to me like a bad design and/or procedural practice to have a bunch of spinning wheels retract into the fuselage of a plane - particularly in contaminated runways and such. I hope automated systems or pilots are applying breaking before/during retraction on at least the main wheels which at 2/3 or more of them.
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Kay
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Apr 02, 2008 3:26 pm



Quoting Kimberlyrj (Reply 13):
When an aircraft (heavy) has taken off, the gear is retracted and the wheels are ‘slowed down’ and then stopped. What’s happening to the heat?



Quoting RoseFlyer (Reply 16):

It eventually disappaits in the wheel well.



Quoting 3MilesToWRO (Reply 14):
Not much air movement, but anyway there's some and additionaly the brakes will be warming all the rest of the plane - starting from gear parts and (theoretically) finishing at radome and top of fin Smile

What's more, it's not the same braking as when you need to dissipate the kinetic energy of 100 Tons moving 100 km/h. It only needs to lose energy of 100 kg wheels rotating 10 times a second. For a brake system able to do the first, the second case is a piece of cake.

Perhaps in normal situations, the heat of the brakes are not an issue after the wheels have been retracted. But there has been a plane crash because of this (in very abnormal circumstances though). I tried to find it on the web but couldn't. Here is the sequence:

- Aircraft is about to take off, but the chosen runway is foggy.
- The captain has the ingenious idea to continue taxiing down the runway while dissipating fog with his engines on high-thrust, balancing the thrust with high brake pressure to stop the acceleration.
- After dissipating the fog on part of the runway, the captain backtracks back to the runway start and initiates take off.
- Shortly after the gear is retracted in the air, a fire engulfs the gear bays.
- The plane crashes due to.. well, fire.

Anyone remembers the details of this accident?

Kay
 
BAE146QT
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RE: When Do Landing Gears Stop Spinning After Take Off

Wed Apr 02, 2008 5:16 pm



Quoting RoseFlyer (Reply 9):
I think that is the same on all Boeing planes.

I believe that a front brake set was optional on the 727. Other than that, I believe you're right.
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3MilesToWRO
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Apr 03, 2008 12:23 pm



Quoting Kay (Reply 39):

And what you describe (yes, I think I remember reading about it) is exactly dissipating the energy of 100T @ 100 knots (random numbers, of course, order of magnitute matters). Only you dissipate it before it builds into kinetic, but rather right at the stage of energy being provided by engines. What the pilot did was for the brakes, approximately, the same as aborted takeoff.
 
Kay
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Apr 03, 2008 1:50 pm



Quoting 3MilesToWRO (Reply 41):
And what you describe (yes, I think I remember reading about it) is exactly dissipating the energy of 100T @ 100 knots (random numbers, of course, order of magnitute matters). Only you dissipate it before it builds into kinetic, but rather right at the stage of energy being provided by engines. What the pilot did was for the brakes, approximately, the same as aborted takeoff.

Agree (therefore, the procedure mentioned above whereby after an aborted take off, one must wait, and cannot take off immediately and raise the gear, which might cause a fire in the gear bay).

But I was surprised, when I read about this accident, that a fire can actually start because of this although it is clear that it was a dumb idea. Some accidents (and the waste of hundreds of lives) have a very "random" feel to them!!

Kay
 
474218
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RE: When Do Landing Gears Stop Spinning After Take Off

Thu Apr 03, 2008 3:13 pm

There is another reason the main landing gear wheels are stop before they are stowed in the wheel wells:

The gyro effect the mass of the spinning wheels has on the landing gear. The spinning wheels have a tendency to keep the landing gear extended, by stopping the wheels the hydraulic retract actuator does no have to work as hard.
 
panserbjorne
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Apr 04, 2008 5:17 am



Quoting Kay (Reply 39):
Anyone remembers the details of this accident?

I dont really remember the accident,but i do know that there is a procedure to leave the gears down right after the lift off,the purpose is to cool the wheels off before retracting it.I think this procedure applies if you are deferring wheel well fire detection system.
 
QANTAS747-438
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Apr 04, 2008 6:27 am

I work for WN, and as explained to me by a MX guy, on our 737s there is a ring around the wheel well that has layered rubber squares. They extend about a foot or so into the wheel well. When the landing gear comes up, the spinning tires rub up against the layered rubber buffers and stop spinning.

[Edited 2010-05-01 13:54:43 by srbmod]
My posts/replies are strictly my opinion and not that of any company, organization, or Southwest Airlines.
 
Kay
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Apr 04, 2008 8:48 am

Everytime I look inside a landing gear well I get fascinated and scared at the same time.

Kay

[Edited 2010-05-01 13:55:20 by srbmod]
 
rwessel
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RE: When Do Landing Gears Stop Spinning After Take Off

Fri Apr 04, 2008 8:59 am

Quoting QANTAS747-438 (Reply 45):
I work for WN, and as explained to me by a MX guy, on our 737s there is a ring around the wheel well that has layered rubber squares. They extend about a foot or so into the wheel well. When the landing gear comes up, the spinning tires rub up against the layered rubber buffers and stop spinning.


I dunno, these look too light to really do much to stop the wheel, the look more like spray shields to me...

[Edited 2010-05-01 13:56:05 by srbmod]
 
tdscanuck
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Apr 05, 2008 5:55 am



Quoting QANTAS747-438 (Reply 45):
I work for WN, and as explained to me by a MX guy, on our 737s there is a ring around the wheel well that has layered rubber squares. They extend about a foot or so into the wheel well. When the landing gear comes up, the spinning tires rub up against the layered rubber buffers and stop spinning.

Those are aerodynamic seals to improve airflow over the wheelwell. The gear is already stopped by the brakes before it makes contact with the seals.

Tom.
 
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HAWK21M
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RE: When Do Landing Gears Stop Spinning After Take Off

Sat Apr 05, 2008 1:56 pm



Quoting Kay (Reply 46):
Everytime I look inside a landing gear well I get fascinated and scared at the same time.

on my 1st day at work during a major check I remember looking insde a B737 MWW & wondering.Today it seems so simple.
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MEL
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