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I have a question about the procedure to jack the aircraft for wheel replacement. According to the manual, it required to set the Parking brake OFF before starting jacking at the Main Landing Gear.

I curiously wonder if the brake is set OFF to let the wheels on the other landing gear could rotate freely on its axle.

Why don't we keep the parking brake ON to prevent the aircraft moving and slip out of the jack?

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    $\begingroup$ Thanks for your comment. I have read that question. However, my question is about setting braking OFF before jacking aircraft which happens in a short period of time. $\endgroup$
    – dingdingdong
    May 3, 2020 at 10:13
  • $\begingroup$ Probably makes things easier to get the old wheel off & the new wheel on. $\endgroup$
    – Ralph J ♦
    May 3, 2020 at 13:19
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    $\begingroup$ Absolutely NOT a duplicate. $\endgroup$
    – Ralph J ♦
    May 3, 2020 at 13:21
  • $\begingroup$ @dingdingdong Oh yes, of course. Absolutely my mistake. I must have completely misread "jacking" as "chocking" or something like that. $\endgroup$
    – Noah Krasser
    May 3, 2020 at 14:23
  • $\begingroup$ Does this answer your question? Why are parking brakes not used for parking jetliners? $\endgroup$
    – KorvinStarmast
    May 3, 2020 at 21:25

1 Answer 1

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The wheel is removed with the PB depressurized so that the discs are free to float (both rotationally and slightly axially) when the wheel is being slid off, to prevent any potential binding of the disc projections where they engage the slots in the bore of the wheel as the wheel is pulled out. If the discs are locked in place by brake engagement, any off-axis movement of the wheel unit as it's being slid off could jam it on the discs, making it really hard to pull off.

When the procedure is started, the airplane is chocked at the other gears, so the parking brake is already made redundant at this point. As a former aviation technical writer in another life (not Airbus), I would say it was done that way for work flow purposes (getting all the cockpit related precautions out of the way before you start the procedure) because you don't need the PB on once chocked, and you're going to have to release it anyway, so it's done during the preparation steps prior to the actual jacking.

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