PDA

View Full Version : Do faired wheels rotate in flight ?


Bajab
12th Feb 2019, 20:00
I have been told that out of balance faired wheels can induce vibrations in the plane during the flight.
This implies that faired wheels do rotate during the flight.

Is is this the case?

pattern_is_full
13th Feb 2019, 15:22
Simple, non-retractable faired wheels (e.g. C172, Grumman Cheetah) can rotate in flight. That doesn't mean they always do.

The bottom of the wheel sticks out of the fairing into the slipstream, and thus can be spun by the passing air, like a stream waterwheel. https://en.wikipedia.org/wiki/Water_wheel#/media/File:Stream_waterwheel_simple.svg (https://en.wikipedia.org/wiki/Water_wheel#/media/File:Stream_waterwheel_simple.svg)

Mass of the wheel, axle lubrication, roughness of the tire tread, and aircraft speed will all affect whether the force is enough to spin the wheel.

I've never felt vibrations, myself.

Complex wheels that are faired into the fuselage once retracted (e.g. 737) won't have the same asymmetrical force, and usually are braked to a standstill during the retraction process.

DaveReidUK
13th Feb 2019, 16:39
Simple, non-retractable faired wheels (e.g. C172, Grumman Cheetah) can rotate in flight. That doesn't mean they always do.

The bottom of the wheel sticks out of the fairing into the slipstream, and thus can be spun by the passing air, like a stream waterwheel. https://en.wikipedia.org/wiki/Water_wheel#/media/File:Stream_waterwheel_simple.svg (https://en.wikipedia.org/wiki/Water_wheel#/media/File:Stream_waterwheel_simple.svg)

Mass of the wheel, axle lubrication, roughness of the tire tread, and aircraft speed will all affect whether the force is enough to spin the wheel.

I've never felt vibrations, myself.

Complex wheels that are faired into the fuselage once retracted (e.g. 737) won't have the same asymmetrical force, and usually are braked to a standstill during the retraction process.

Another configuration is a semi-retractable mainwheel that retracts in the fore-and-aft plane. From what I recall of the Shorts commuters, they don't alarm the passengers by rotating when retracted. :O

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/636x533/landing_gear_fa7e0f5702b901c03cd05f1bd3d05b2c05117b90.jpg

That may have been a result of snubbers in the bay, it's been a long time ...

eckhard
13th Feb 2019, 21:01
Makes for a much smoother gear-up landing too!
Didn’t the Anson, C-47 and B-17 have a similar design?

ZeBedie
13th Feb 2019, 21:08
Some British WW2 era types had cups mouded into the tyres to make them rotate after gear extension, with the intention of saving tyre wear.

ehwatezedoing
13th Feb 2019, 21:38
Makes for a much smoother gear-up landing too!
Didn’t the Anson, C-47 and B-17 have a similar design?
C-47 does and also have "Wheel spinning stopper" in its wheel bays. A sort of a thick lanyard with metal pads on it.

Chu Chu
13th Feb 2019, 22:53
The A-10 (Warthog) gear has a similar design as well.

B2N2
13th Feb 2019, 23:13
On light aircraft brakes always drag a little.
I’ve never seen or felt wheels turn in flight.
Difficult to draw but it’s not that hard to visualize that faired wheels barely have any air pressure on them because of the air being deflected by the wheel pants.


https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/432x288/f2370cda_d994_4539_8651_21d139b30b45_f852363b16514e295d6243b 46df41d84d1598ea5.jpeg