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Hydraulic "dust"?

Tue Aug 31, 2004 1:11 pm

Can someone explain this photo to me ?
Look closely at the landing gears......

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RE: Hydraulic "dust"?

Tue Aug 31, 2004 1:22 pm

Carbon dust more likely.
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RE: Hydraulic "dust"?

Tue Aug 31, 2004 3:52 pm

Upon retraction of the landing gear brakes would be applied automatically to stop the wheels from spinning before it enters the fuselage... Smile So it should be carbon dust as NKP has stated.

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RE: Hydraulic "dust"?

Tue Aug 31, 2004 8:59 pm

?? That is just an illusion in my opinion. You guys sure it just isn't exhaust??

I didn't think the wheels were stopped outside the fuselage either. I thought there was a "stopper" in the wheel well that contacts the tire to stop it.



I will correct myself here. In the 777 sys book it says that the main wheels are indeed stopped prior to entering the wheel well (center hyd sys for all you tech nuts). The front wheels have no brakes, and are stopped when they rub against spin brakes in the nose wheel well.

Looks like the carbon dust is a winner!

[Edited 2004-08-31 14:14:09]
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RE: Hydraulic "dust"?

Tue Aug 31, 2004 9:16 pm

Large aircraft usually apply the brakes (automatically in some cases) to stop the wheels before they enter the well. The nose wheels may have an internal contraption to stop them (as on the older A320's - deleted from at least some of the newer ones - not required, I guess).
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RE: Hydraulic "dust"?

Tue Aug 31, 2004 10:52 pm

At liftoff, the wheels are spinning at high RPM and with the weight suddenly on them, their diameter is somewhat larger than you are accustomed to seeing. As has been stated the mains on most large aircraft are automatically braked before they enter the well. The main gear well on most airliners is home to hydraulic reservoirs and lines, flight control linkage and even fuel lines. Stopping the rotation outside this confined space is a good idea.

Landing gear that retract fore or aft into a well can be stopped with snubbers fitted in the gear well. These stop the rotation by applying friction on the tread surface.
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RE: Hydraulic "dust"?

Wed Sep 01, 2004 12:16 am

Auto retract braking is normally used to stop the Main wheels prior to entering the retracted position.The black smoke visable looks like carbon dust.
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RE: Hydraulic "dust"?

Wed Sep 01, 2004 12:18 am

One of the more common systems uses return hydraulic pressure from the retract lines to apply the brakes stopping the main wheels on takeoff. On gear retracting in a straight line the most common is the spin-down brake pads mounted in the top of the wheel well.
The reason is that gear retracting tangentally to the spin direction creates significant side loads due to the gyro effect of the wheel and tire assembly moving or retracting at right angles to the spin direction. Also if the tire is shreadded it will damage the aircraft if it enters the wheel well spinning.
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RE: Hydraulic "dust"?

Wed Sep 01, 2004 8:24 am

It's brake dust. There was a thread on this subject just a few weeks ago. Pretty informative.
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