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Do "Gear" Tires Keep "Spinning" Inside Bay?  
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Posted (13 years 3 months 2 weeks 6 days 15 hours ago) and read 3179 times:

Hi guys. My question is... When an airliner "Takes Off" and the pilot retracts the landing gear, are the wheels still "Spinning" when they enter the wheel well bays?

When thinking back to the days when I worked on a ramp [a decade ago], all the aircraft that I worked with [mostly corporate], had "Spotless" wheel wells. I never thought to ask the pilots back then, so I'm wondering now if the pilots of retractables apply the brakes [once airborne] before raising the gear? Or does the aircraft's landing gear stop the tires automatically, if they stop at all?

I can only imagine that quite a mess could be made if an aircraft's tires are spinning at over 100 MPH inside their wheel wells, after they just lifted off a contaminated RWY covered in "Snow and Slush" or "Wet Mud and Gravel" etc!

Chris


"Just a minute while I re-invent myself"
33 replies: All unread, showing first 25:
 
User currently offlineIainhol From , joined Dec 1969, posts, RR:
Reply 1, posted (13 years 3 months 2 weeks 6 days 14 hours ago) and read 3011 times:

On the 172 we apply brakes before we retract the gear, this stops the main wheels spinning while in the wheel bay, however the nose wheel had a pad that stopped it spinning as it entered the bay.
Hope this helps,
Iain


User currently offlineWestern727 From United States of America, joined Jan 2007, 743 posts, RR: 4
Reply 2, posted (13 years 3 months 2 weeks 6 days 14 hours ago) and read 3001 times:

Most airliners have a "snubber" system, which applies the brakes to the wheels when the lever is thrown to retract the gear. So no, they don't spin in the wells.




Jack @ AUS
User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 3, posted (13 years 3 months 2 weeks 6 days 14 hours ago) and read 2962 times:

Thanks! Western727 / Iainhol. I am only "Type Rated" on fixed gear aircraft, and have not been up flying since this question entered my mind. The only Pilots I have to ask this today were you guys. Once again , Thanks for confirming what I thought must be true. Hopefully some airline Pilots or Mechanics etc, can give me more detail on how their jets work in this area.

P.S. The next time I'm out at YYZ doing some spotting at the "Departure" end of an active, I'm going to look real close [with binoculars] at the landing gear on airliners as it retracts, to see if they are dead stopped or not.

Chris








"Just a minute while I re-invent myself"
User currently offlineHeavyJet From , joined Dec 1969, posts, RR:
Reply 4, posted (13 years 3 months 2 weeks 6 days 13 hours ago) and read 2958 times:

On most larger aircraft, the main gear tires are automatically braked when the gear handle is raised. Gyroscopic forces would put tremendous loads on the landing gear if the tires remained "spinning" while being raised.

The nose gear is not subject to such gyroscopic forces while being raised and is normally braked by a snubber in the wheel well.


User currently offlineTygue From Canada, joined Jul 1999, 222 posts, RR: 0
Reply 5, posted (13 years 3 months 2 weeks 6 days 10 hours ago) and read 2927 times:

Once most aircraft rotate... the tires continue to spin until they are fully retracted. The nose gear is slowed by a large asbestos pad located in the wheel well. The main gear, however, continue to spin on their own until they come a stop. Unaided... no brakes... no pad... nothing.

This is speaking for large aircraft (Boeing/Airbus planes).


-Tygue


User currently offlineAmbasaid From , joined Dec 1969, posts, RR:
Reply 6, posted (13 years 3 months 2 weeks 6 days 6 hours ago) and read 2901 times:

Sorry Tygue,

But i disagree with you, the large Boeing aircraft which i am familiar with use residual brake pressure to slow and stop the spinning main wheels.

This is quite easily proven by the fact that with a brake deactivated or removed, the crew are required to leave the gear down for 2 minutes after takeoff in order for the wheels to stop spinning.

Heavyjet, I cant remember if the A300 is approved for gear down dispatch????


User currently offlineHAWK21M From India, joined Jan 2001, 31667 posts, RR: 56
Reply 7, posted (13 years 3 months 2 weeks 5 days 23 hours ago) and read 2869 times:

The B737s use Hydraulics thru the metering valve to automatically brake the main gear during retraction & simultanously disable the Antiskid system to Facilate this braking.

The nose gear has snubber pads to mechanically stop the wheels.

Gyroscopic forces of a spinning wheel can cause
difficulty in controlling the aircraft If they were left spinning in addition to chances of FOD on retraction into the wheel well.

regds.
HAWK.



Think of the brighter side!
User currently offlineAmbasaid From , joined Dec 1969, posts, RR:
Reply 8, posted (13 years 3 months 2 weeks 5 days 18 hours ago) and read 2851 times:

Hawk21M,

Can you please explain what you mean by

Gyroscopic forces of a spinning wheel can cause
difficulty in controlling the aircraft If they were left spinning


How do spinning wheels interfere with aircraft control?


User currently offlinePanman From Trinidad and Tobago, joined Aug 1999, 790 posts, RR: 0
Reply 9, posted (13 years 3 months 2 weeks 5 days 14 hours ago) and read 2836 times:

Go back to your basics on gyroscopes.

All gyroscopes have 2 properties.

Rigidity and precession.

Rigidity is the tendency for the gyro to remain pointed in one direction.

Precession is the property whereby if a force is applied to a gyro it is felt 90 degrees perpendicular to the point of application.

You now have the main gear wheels spinning at very high RPMs and so acting like a gyro. Select retract and you now have a force acting on the axis of the gyro trying to move it along the lateral axis of the airplane, this force is felt at 90 degrees from the point of application so basically along the longitudinal axis of the aircraft. Now imagine you have a 747 with it's 16 wheel main gear. You have 16 forces all acting along the longitudinal axis of the aircraft, You now have an aircraft that is bucking like a rodeo horse. Not nice to control and with the different rotational speeds of each wheel (assuming that they all slow down at different speeds) it would be very hard to trim this aircraft.

Hope that helps.

PanmaN


User currently offlineGalaxy5 From United States of America, joined Mar 2000, 2034 posts, RR: 25
Reply 10, posted (13 years 3 months 2 weeks 5 days 13 hours ago) and read 2828 times:

the main tire on the plane i fly (C-5 galaxy ) use snubbed brake pressure through a anti-rotation valve and the spinning is sensed by spin-up detectors. once the brake handle is placed to up the brake pressure is applied and wheel rotation is stopped then the MLG retraction sequence is initiated if the anti-rotation vlv fails then the wheels must spin down by themselves ( takes approx 2 min ) before the gear retracts. the nose gear retracts regardless it doesnt require spin down because it retracts straight back and the gyroscopic forces are minimal. hope that helps.  Smile/happy/getting dizzy


"damn, I didnt know prince could Ball like that" - Charlie Murphy
User currently offlineL-188 From United States of America, joined Jul 1999, 29791 posts, RR: 58
Reply 11, posted (13 years 3 months 2 weeks 5 days 1 hour ago) and read 2789 times:

I remember reading about a crash of a C-109 (Tanker B-24) in India during the war when the gear was selected up when the aircraft was "flying" flying but the wheels where still on the ground. The brakes automaticly stop the wheels from spinning and it caused enough drag that it brought the aircraft back down. Since the airplane was full of aviation fuel it exploded on hitting. I think all of the crew save one was killed. And he was really badly burned.


OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.
User currently offlineFBU 4EVER! From Norway, joined Jan 2001, 998 posts, RR: 7
Reply 12, posted (13 years 3 months 2 weeks 4 days 22 hours ago) and read 2781 times:

Panman's explanation on gyroscopics is very good and to the point.
I believe it was in the late 40's or early 50's that experiments were performed with wheels that would spin up before landing so as to save wear upon touch-down.Needless to say,the gyroscopic forces put paid to that idea.Would have liked to hear the pilot's comments as they found out!!!



"Luck and superstition wins all the time"!
User currently offlineFDXmech From United States of America, joined Mar 2000, 3251 posts, RR: 34
Reply 13, posted (13 years 3 months 2 weeks 4 days 18 hours ago) and read 2770 times:

Amongst other reasons, theoretically, even if it were feasable to spin the wheels prior to touchdown. This would create many more problems than it would solve. Foremost in my mind is the fact that initial wheel spin up is a critical input to many systems such as antiskid, autospoilers, autoland systems and the like. A very important mode transition parameter indeed.


You're only as good as your last departure.
User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 14, posted (13 years 3 months 2 weeks 4 days 6 hours ago) and read 2733 times:

1. The A300 automatically applies main gear brakes for three seconds at gear retract command.
2. "Gyroscopic Forces" have nothing to do with it. The wheels need to be stopped when they enter the wells, to avoid damage to the gear.
3. Spaceman, I don't know where you ever found a "spotless" wheel well. Most of the airliner wells I've seen are nasty with Skydrol, dirt, grease, and general crud...



"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3700 posts, RR: 34
Reply 15, posted (13 years 3 months 2 weeks 4 days 1 hour ago) and read 2721 times:
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The 747 brake sytem applies 400 psi to the brakes as the main gear is retracted.

User currently offlineHeavyJet From , joined Dec 1969, posts, RR:
Reply 16, posted (13 years 3 months 2 weeks 3 days 18 hours ago) and read 2709 times:

DC10hound,

>>"Gyroscopic Forces" have nothing to do with it. The wheels need to be stopped when they enter the wells, to avoid damage to the gear.<<

Care to elaborate?


User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3700 posts, RR: 34
Reply 17, posted (13 years 3 months 2 weeks 3 days 18 hours ago) and read 2712 times:
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I would have thought that was self explanitory. Imagine a spinning burst tyre with long bits of rubber hanging off the remains.

User currently offlineHeavyJet From , joined Dec 1969, posts, RR:
Reply 18, posted (13 years 3 months 2 weeks 3 days 16 hours ago) and read 2701 times:

I meant the ("Gyroscopic Forces" have nothing to do with it) part of it.

I know all about bursting tires (tyres)in the wheelwells, especially close to hyd lines and reservoirs etc, etc.

I'm not trying to start an argument. I'm hoping to learn something new from someone who may know more than I.


User currently offlineMr Spaceman From Canada, joined Mar 2001, 2787 posts, RR: 9
Reply 19, posted (13 years 3 months 2 weeks 3 days 15 hours ago) and read 2698 times:

Well, like I originally posted, most of the aircraft [90%], that I worked with were "Corporate Jets/Turbo Props", so maybe they were just simply easier and quicker to clean up inside [because they were smaller]. Any time that I was hooking up a tow bar, or pulling a gear pin etc, I would be impressed on how clean the wheel wells were. Good maintanance personnel I guess. Either way, that's what made me wonder if the wheels were stopped?...The lack of [OK, "a lot"] of dirt.

Chris




"Just a minute while I re-invent myself"
User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 20, posted (13 years 3 months 2 weeks 2 days 6 hours ago) and read 2668 times:

Heavy Jet:
No, I don't care to elaborate. As VC-10 says, it is self explanatory. (Thanx VC!  Smile)



"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineDc10hound From United States of America, joined Dec 2000, 463 posts, RR: 5
Reply 21, posted (13 years 3 months 2 weeks 2 days 6 hours ago) and read 2664 times:

Mr Spaceman:
I know what you mean, I like clean jets, too!!



"Eagles soar. But weasels never get sucked into jet intakes.."
User currently offlineAmbasaid From , joined Dec 1969, posts, RR:
Reply 22, posted (13 years 3 months 2 weeks 1 day 23 hours ago) and read 2647 times:

Dc10hound,

I think that you may find that Heavyjet was asking about this statement "Gyroscopic Forces" have nothing to do with it.

This certainly isn't self explanatory, why wont you elaborate?


User currently offlineHeavyJet From , joined Dec 1969, posts, RR:
Reply 23, posted (13 years 3 months 2 weeks 1 day 17 hours ago) and read 2638 times:

>>No, I don't care to elaborate<<

Didn't think you knew what you were talking about!

If you can't explain yourself, why bother posting.


User currently offlineVC-10 From United Kingdom, joined Oct 1999, 3700 posts, RR: 34
Reply 24, posted (13 years 3 months 2 weeks 1 day 17 hours ago) and read 2636 times:
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I have to agree Dc10hound that gyroscopic effect would not be a consideration as you are retracting the gear along the rotational axis, unless it is a HS Trident.
Precession is only a factor if you twist the gyro around its axis.


25 EssentialPowr : Ever ride a bike? Most physics books call it angular momentum... Hey Teygue...You're wrong (totally). Mains are braked on Boeings, Lears, and Airbuses
26 Post contains images Tygue : *pulls out the FCOM3 for the B757-200 and the A330-200* I was wrong. My sincere appologies. And I quote: "During gear door opening, main gear wheels a
27 HeavyJet : >>And by the way... the gyroscopic forces of 8 tires inside a 230,000kg aircraft are negligable.
28 Post contains images Ambasaid : Tygue, Thanks for the explanation, I will try to find you a Boeing AFM or MEL page reference this morning, but note that I did say "This is quite easi
29 Post contains images Tygue : Judging by your profile, it sounds like you have a good number of hours in your books I'm not too sure what you're talking about... (possibly because
30 EssentialPowr : Why no one has offerred the the calculation of the Moment of Inertia of, say, a tandem 757 whel assembly at 140 kts perpendicular to the axis of rotat
31 EssentialPowr : Nose GEar snubbers - if installed, aren't Asbestos...typically they're rubber; then smooth metal after the rubber's gone (EMB135/45). And yes, out of
32 Ambasaid : Tygue, This is taken from the B757 Dispatch Deviations Guide. MEL 32-41-1 Wheel Brakes. A: One brake may be deactivated with a deactivation tool provi
33 VC-10 : Just a thought........If gyroscopic forces are such a problem when retracting the gear why are there no controlability problems with the 2 or 3 hugely
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