What about the wheels after t/o?

[Cargo_ramp]

Bit of a silly question..but what happens to the wheels after the A/c takes off? Do they automatically brake, and stop spinning before they retract into the wheel well, or do they just wine down?

[ausdoc]

The pilot usually applied the brakes to stop the wheels before retracting them. There are a few good reasons for not retracting them while they are spinning.

Spinning wheels have a slightly greater diameter due to the centrifugal forces. This can cause them to interfere with the wheel wells.

Spinning wheels can flick a lot of debris (stones, mud, rubber) into the the wheel wells and all of the equipment situated in there.

Retraction of fast-spinning wheels often involves moving them out of their plane of rotation. This induces gyroscopic effectes which can dramatically shorten the life of the wheel bearings, etc.

Hope this helps.

[Willit Run]

I believe ausdoc is used to flying the smaller planes.
In the transport world, the tires are auto matically braked, by the brake system. If the pilot hit the brakes, they would spin the tires on the rims and knock them out of balance. The main gear tires are braked with very low pressure, and the nose gear tires ususally have a "snubber" that the nose tires rub against.
Thats it simplified!!!

[ausdoc]

Thanks Willit,

Yep, the smaller ones for me. Wasn't sure what the original question related to.

Cheers,
ausdoc

[tykon]

Cargo Ramp. From an engineering perspective. I will tell roughly what happens to a 737NG. Pilot selects up. "A" system pressure retracts the landing gear, and at the same time "A" system "up" pressure is ported to the brakes through the brake metering valve, which has a solenoid for stopping the brakes when wheels retract. This bypasses the anti skid system, as if it didnt, the wheels would keep unlocking as it would think it is in a skid.

When pilot selects down, there is no brake pressure at all, so they are free to spin up.

As said before, the nose uses pads to brake the nose wheels.

If the tyres were to throw tread on the up selection, there is a little tube near the wheel well cutout on each side, that, supposedly if the tyre threads separate, will be ruptured by the wayward tread, and this will dump "some" "A" system up pressure so the gear will not retract any further, but to prevent a total loss of "A" system, there is a fuse that will shut off this fluid loss when it detects excessive flow.

Hope this helps, and if I"m wrong about anything, do tell me, as I"m only working from memory.