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Guest Pittsburgh

Wheel spin up

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Guest Pittsburgh

Hi, A question for the pros: When retracting the gear after take-off, are the wheels stopped from spinning prior to entering the wheel wells or are they allowed to spin until the run out of energy? Also, are the wheels put in motion prior to touch down in order to minimize the wear on them?Thanks,BoazEKCH

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Guest mpauli

Hi BoazAs far as I know it depends on the aircraft. I know that the gears on the big airliners (such as B747, B777, MD11, A340-A330) are stoped as soon as you move the gear lever. I think the smaller plane's wheels aren't stoped, but not sure.And No, I know no arcraft which wheels are set in motion prior to touch down. But again, I don't know them all! ;-)CheersMartin

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Hi Boaz,The main gear tyres are stopped. The brakes are applied automatically when you retract the gear. As the nosewheel is not equipped with brakes, the tyre will be rotating as it is stowed in the wheel well. THere is, however, a rubber block that stops the tyre after retraction.The wheels are not spun up during extension. On touchdown, the wheels will spin up from 0 to landing speed.There are many reasons why the wheels aren't spun up. Here are just a few:tyre wear during landing is minimal _compared_ to tyre wear during taxi! Take a heavy B747-400, when it turns the tyres are stressed more than during multiple landings!the cost of adding a mechanism (be it electrical or air driven) is not worth the reduction in wear.additional equipment required to turn the wheels may result in higher drag -> fuel penalty.the wheels are very heavy, and when a turning object is turning, it created a gyro effect. Therefore, you may experience quite a bit of handling difficulties.Regards,Mark

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"As the nosewheel is not equipped with brakes, the tyre will be rotating as it is stowed in the wheel well. THere is, however, a rubber block that stops the tyre after retraction."I don't think they're rubber, Mark. They appear to be made of a fibrous-type material (probably fire-resistant, but, according to the manual, contain no asbestos). Of course, after many takeoffs, they might have a coating of rubber on them ;-) The two resistive pads (one for each wheel) are mounted on springy metal brackets attached to the roof of the wheel well.The Alternate braking system is used to stop the main wheels spinning (i.e. c/o Hydraulic system A).Cheers.Ian.

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Guest wkzzo

The material is known as a "phenolic" block.The material is made by applying heat and pressure to layers of paper or glass cloth impregnated with synthetic resin. Its used in alot of places on the AC, electrical isolation ,rub-strips for flap seals, wing to body fairings, cable guides, ect.... It does feel like a dense wood though.

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Thanks, Wallace.Interesting stuff (the phenolic material... and your material) :-)Cheers.Ian>

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Guest Hawkeyeted

I thought it was called a "Micarta" block? Pieces of Mica pressed together under heat/pressure. Used where friction points are (i.e flight control cable/pullys, or where a flight conrtol cable passes through a spar/rib). Maybe I'm thinking of something different.....

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