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Guest Philip Olson

Landing Gear

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In reality, during the landing and takeoff, does the wheels of the airplane have any motion?How many times does the wheels need to change after the landing and take off?

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OK I'll bite. And if these are serious questions than.....Oh hell I don't know.In my reality the wheels have a lot of motion. It's called spinning. :)How many times does the wheels need to change?. Um as many times as they get dirty?? Maybe I'm missing the question. Maybe a language barrier??Care to try again ??Bobby

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I am sorry, I think you must be misunderstood my meaning. Obviously I know the wheels "spins". But does it have any power to make the wheels in moving? And, how often do they replace the tires?

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Gotcha now, Hong Kong Busperson,To my knowledge there are no aircraft out there that "drive" through the wheels; brake, yes, and independently, but not drive. Usually the main wheels will simply roll along happily waiting for a touch of the brakes now and again or a lot of brakes if the pilot cocks up the takeoff. However, the nose wheel is usually steerable, and in the case of an aircraft like the DC-3, the tail wheel can either be left to rotate freely on its axis for taxiing or be locked for takeoff/landing so that it doesn't wobble all over the place. Don't think there are any steerable tail wheels ... there may be.As for wear and tear ... someone else will have to answer that. It's obviously going to depend on the aircraft and the usage. And who is looking after it.Mark "Dark Moment" Beaumonthttp://www.swiremariners.com/newlogo.jpg

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So, that means all aircraft's tail wheels have no supporting power to make them spins. Basically they stay at neutral where there is no small engine (something like that) in a airplane that enable the tail wheels to spin(move)?

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Some aircraft (Airbus?) have little fins on the inside of of each wheel. When wheels are lowered on App, the air rushing over them makes the wheels spin and is supposed to reduce wear on the tyres by reducing the friction at the instant the tyre makes contact with the runway. I understand there is a brake/axle-assembly cooling effect here too.Cheers,Paulhttp://www.strontiumdog.plus.com/sbird.jpgOfficially licenced by British Airways plc for use of name and logo[p]AMD XP2800+ Barton, Gigabyte GA-7NNXP nForce2, 1Gig Crucial PC3200 DDR 400MHz, Gainward 128 MB GF4-4200, SB Audigy, 3 x WD Caviar SE[/p]

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If so, how often do the tires need to be replace since it's worn so quickly?

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It all depends upon the landings and the braking action. It also depends upon the quality of the tires. Some will lat longer than others, just like on a car. Different treads, different material, etc. In my own experience, I had brand new tires on a pa-128 and landed hard and 'rode' the breaks after landing 'hot'. The steel belts were showing thru after one landing and needed to be replaced. I had to pay for them and the cost for 2 new tires was only 32.00. These being training tires, really didn't expect much wear from these.keith

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How deep is the tread of a boeing aircrafts? If you say it depends on the braking and weight. Wouldn't a boeing aircraft tread will last shorter and need to be replace since it is very heavy and need to brake harder?

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All landing gear to my knowledge is free spinning. It takes the power of the engine to make the aircraft move forward. If you want to turn you apply differential breaking (one side at a time, left, right) or you use the rudder which is conected to the nose wheel or tail wheel (depending on your gear configuration).Pretty simple, nothing fancy....The tires get replaced like car tires, when the tread is worn down. This all depends on the usage of the tires. Space shuttle tires I think get changed after every flight. But you didn't ask about the space shuttle. Maybe someone who knows about Boeing aircraft could tell you how offten the tires get changed on an airliner.

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I see... I should've post a question specifically on how often do a boeing aircraft replace its tires, right?

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Actually if you look inside of the wheel wells of Boeing planes (maybe airbus too), you will see large pads inside that stop the wheels from spinnng once they are retracted inside the plane. This so they will not continue to spin inside the plane and cause a gyro effect that could affect control of the plane.

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Don't know about large aircraft, but in real-world advanced GA aircraft I was raught to touch the toe brakes to stop wheel spin before retraction.

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Then how is it going to effect the trim just to stir a drink in an anticlockwise direction in Northern Hemisphere?

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<<>> - Dark MomentHow could it get effected by just stir a drink though?

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"How could it get effected by just stir a drink though?"He was joking.

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Funny, that reminds me of when I was about 12 years old. My dad was a pilot in the RAF and one half term I was driving with my uncle and I asked him why didn't you take off from a standing start like a plane. i.e. run up the power and release the brakes! It seemed like a good question at the time to me!RgdsTimhttp://www.cambridgeflyingclub.com/images/timavatar2.jpg

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>I see... I should've post a question specifically on how>often do a boeing aircraft replace its tires, right?I'm guessing at frequency, but I'd wager a military cargo tire was changed maybe once a year due to wear. (really hard to say, as it was always a different tire needing changing and really, really dependent on usage and how rough of terrain it'd been landed on). On a military bomber... the frequency was probably much longer between changes. As to stopping the spin, on military aircraft the tires retract against essentially a piece of thick rubber in the wheel well known as a "spin brake."

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>Funny, that reminds me of when I was about 12 years old. My>dad was a pilot in the RAF and one half term I was driving>with my uncle and I asked him why didn't you take off from a>standing start like a plane. i.e. run up the power and release>the brakes! >>It seemed like a good question at the time to me!Yeah, why not!! :-hah Just press the clutch (highest gear), go full throttle (ouch) and then release the clutch slowly... Except the tire squeaking at least the sound will be similar, huh? (oh just the RPM sound might be of a bit higher pitch... hehe) :-lol

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>and cause a gyro effect that could affect control of the plane. I wonder why though. I mean, as soon as you lift the ground, with or without braking, they won't turn much longer anyway, huh? :-hmmm So why that additional braking pads? By the way, do you know any picture source of those? I would like to see what these look like.Thanks manEtienne :-wave

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People, sit back and be educated. As a licennced AME, here are the answers you all seek.There are such things as "steerable" tailwheels, though I have only seen them on light GA aircraft, the larger planes are usually free-castering. One that comes to mind is the PA-36 Pawnee, there are bridles with springs attatched to the tailwheel, which is tied into the rudder system.Some aircraft have "fins" on the wheels for pre-touchdown spinups, and there are also airframe spin up turbines as well, which will spin wheels up inside the gearwell. Not a common system, but the Cessna Citation 500/550/560 uses this setup on the nosewheel. It is activated by a switch in the cockpit, but these systems are prone to breaking, and are VERY expensive to repair, so they are commonly removed from the aircraft all together.As far as tire replacement, each aircraft is different, and each company usually sets thier own guidelines. Tires on the big birds are not cheap, so ops and maintenance are set to maximize the life of tires. Generally, most companies will run them until chords are showig, but some don't. Another point to keep in mind is damage to the tires from FOD (forign object damage). Any time a cut in a tire cuts into the chords, the tire is rejected. Likewise if there is any damage to the sidewall of the tire. I have seen tires with over 80% tread rejected due to damage. I know from experience that the SAAB 340 is hard on tires, and they get changed more often than some people change thier underwear.Aircraft landing gear IS free spinning. Taxiing is accomplished through rudder input, tiller input (large aircraft are NOT steered with the rudder, but a seperate hydraulically actuated hand tiller), and differential thrust and braking.Some aircraft have pads in the wheelwells to stop spinning tires, others, as stated, usually use a quick tap of the brakes before retraction. As far as the gyro effect theory, that is a load of BS (think about it....if that were true, the same effect would prevent yaw control after the plane lifted off and the wheels were still spinning with the gear extended).The reason for stopping the wheels on retraction is that there are generally a LOT of systems in the wheelwell, from hydraulics to pneumatics, electrics, etc.. Imagine the problems that would occur if a tire spinning at 130mph in a wheelwell were to burst, or more likely, a rock caught in the tread of the tire broke free and shot like a bullet and ruptured a hydraulic line or snapped a wire.The tire slowdown is necessary because the wheel WILL spin for a long time after it leaves the ground. Simple theory of gyros. Keep in mind, on the big birds, the wheels and tires weigh several hundred pounds, are spinning at an enormous rate of speed, and since they are no longer on the ground, do not have the aid of friction to slow them down.Hope I enlightened a few of you. :)

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So I was right about stirring the drink then. Tell me, is there a risk of the plane being over takeoff weight if people have two lumps of ice rather than one?Great post, thanks, we've all learned something after all in this thread!Mark "Dark Moment" Beaumonthttp://www.swiremariners.com/newlogo.jpg

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No Mark, and I can't believe that you would ask this, I thought that you would know better. They carefully weigh everything, including the ice before take off so as to assure no over weight situations on take off. Now if a passenger, or all of them gets two lumps of ice during the flight the ice will be converted to water which will be consumed and then most people will expell this extra liquid before the flight is over. Once the passenger flushes the toilet that extra weight is then ejected from the aircraft thereby insuring no over weight situations upon landing. The airlines have data tables that tell them the exact percentages of passengers that probably will not use the rest room during flight so they know exactly how to control a potential over weight situation and normally will avoid 3 lumps of ice on most flights. If you need more information on this I'll drop it in the mail to you. :-)Philip

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<<>>Now come on, Philip. This is a serious forum. Are you expecting me to believe that yer average Jumbo Jet has a hole in the bottom just like its passengers? "Please do not use the lavatories during our stopover in Iceland, ladies and gentlemen ... if it freezes on the way out it might crack the runway" or "Ladies and gentlemen, please do not use the lavatories until the Captain has finished his walkaround".Of course, if you're right, that would account for those sudden short rainshowers I've experienced whilst sunbathing on the beach by Princess Juliana Intl., St. Maarten ...Mark "Dark Moment" Beaumonthttp://www.swiremariners.com/newlogo.jpg

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