Landing Gear

[Guest citybus2200]

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

[John_Cillis 2,406]

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

[Guest Tim W]

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

[E 0]

>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."

[badderjet 181]

>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

[badderjet 181]

>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

[Guest tinman]

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. :)

[Dark Moment 0]

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

[Guest Philip Olson]

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

[Dark Moment 0]

<<>>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

[Guest tinman]

LMAOThanks Mark and Philip. Same sense of humor we use on the young apprentices at work ;). I am taking notes for when the next one starts work fresh out of college! :D

[Guest Philip Olson]

Mark, yes I do mean to tell you that they expell the liquid in flight, what do you think the blue stuff when you flush is for? It is antifreeze, so the runways do not get broken or people get hurt on the ground. You can't tell me that you have not noticed that the oceans are blue, it is from everyone flushing over the ocean, the antifreeze has tinited the water. And as far as the captains walk around, that is the reason he does it before the passengers board the craft, so he does not get "blue". You were perhaps right though about one thing and that is your sudden showers while laying on the beach, it probably is an aircraft trying to maintain it's proper weight. If you wish to test this idea we can charter a flight and bring along a GPS and flush at the appropriate time over a specially picked persons house }( and get feedback from that person. Tinman, for you yes, I engage in that type of behaviour quite a bit. what type of industry are you in, I'd be happy to send you some of my better ones if you would like them? Several of my past employers tried stuff like this on me when I was younger but they almost never worked, much to their chagrin, because I could think very quickly on my feet and would realize what was possible or real and not. Take care you all and smile!!Philip

[Guest tinman]

I am an AME (aircraft maintenance engineer) in Canada, which is equivalent to an FAA IA certification. I am always up for some aviation humor!

[Guest Philip Olson]

I will put together a list for you, I'll post it here but I'll also send it to you in a private message so if you happen to miss the post you can still read it. It may take me a couple of days as I was just informed that the next two days are going to be very busy for me. When the boss speaks I must listen! The sofa is really hard on my back!Talk to you soon, Philip