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I recently flew on an A320, and during takeoff when the aircraft was rotating, I heard a loud rattling noise. If I had to guess I would say it came from the gear below but I can't be sure. I was sitting slightly behind the wings. The noise stopped when we lifted off the runway.

Edit: The noise sounded a bit like a stick shaker, a loud vibration.

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    $\begingroup$ Does this answer your question? What is this sound from Airbus aircraft before take off? $\endgroup$ – Pondlife Mar 7 at 15:00
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    $\begingroup$ @Pondlife I'm not so sure about the duplicate. The PTU has more of a barking sound, not a rattling. It should also not activate during rotation since there shouldn't be any pressure difference between the yellow and green systems at that time. $\endgroup$ – Bianfable Mar 7 at 15:08
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    $\begingroup$ Maybe the runway just wasn't even? $\endgroup$ – PerlDuck Mar 7 at 15:18
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    $\begingroup$ Definitely not the barking PTU sound, I heard that one too during engine startup but this was different. Sounded too rough to be the runway, but I guess that's a possibility. $\endgroup$ – Jaque Mar 7 at 15:25
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    $\begingroup$ @Bianfable I'm not sure either, but it seemed at least somewhat possible. This is why we (mostly) need multiple votes to close; it's completely possible that I'm wrong 😃 $\endgroup$ – Pondlife Mar 8 at 19:05
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Rattling that disappears after liftoff is normally associated with a vibrating tire transmitting vibrations up through the airframe, and causing some sort of interior panel that is a bit loose to rattle in sympathy. On most airliners the brake system applies the main wheel brakes momentarily, once weight-off-wheels, to prevent the usual spin down vibrations during retraction (Nosewheels normally use a friction brake that contacts the tire when it's fully up for the same purpose). So if the wheel is shaking and making other things shake it will stop as soon as you're airborne.

Airliner wheel assemblies are usually statically balanced vertically like motorcycle tires, not dynamically balanced on machines like car tires (I shudder to think of the cost of a dynamic balancer that can do wheels that big). You can have a vibration mode that comes in at a certain tire RPM, so all of a sudden starts to shake, then you lift off and the brakes are tapped by the braking system to stop the wheels, and the vibration stops.

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