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The Socata TB10 checklist indicates that you should touch the brakes after lift-off. I assume this is to stop the wheels from turning, but why?

In a retractable gear aircraft this would make sense to avoid using anything in the wheel-well to stop the wheels and potentially causing damage or generate heat (as a side note, I think some airliners actually have brake-pads in the wheel wells for this purpose). However, the TB10 is not equipped with retractable gear.

The TB10 and TB20 are very similar, and it might be a case of copy & paste between the two POHs (the TB10 POH also lists V-speeds for "flaps and landing gear retracted").

Do spinning wheels have an adverse effect on aerodynamics (or handling in general)? I would assume, if anything, they'd produce less drag. And as a cherry on top, I'd also assume they'd start spinning again fairly quickly, as only the lower part of the wheels are protruding out in to the air flow.

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An instructor I sometimes fly with constantly taps the brakes just after take-off when we fly in my 182. His reason is mainly out of habit; he's a former regional carrier ATP. –  mah May 4 at 21:19
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depending on the condition of the runway (grass, dirt) and tires, rotating wheels can induce a little shaking in a DA-20. As a rule, I always step on the brakes after lift off to stop that annoying vibration –  Radu094 May 4 at 21:26
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I'll tap the brakes in the Cherokee if I feel a vibration that I think is related to the gear (though the one you're most likely to feel is the nose wheel, which has no brake...) - If that stops the vibration I know the main wheel bearings may need attention. –  voretaq7 May 4 at 23:12

4 Answers 4

This answer to another question has a link suggesting that the spinning wheels may be sufficiently large gyroscopes to affect handling of the aircraft. That was however on a larger aircraft and higher speed (Lockheed Constellation). I don't know whether that effect would be observable on TB10.

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On a Cessna 172, spinning wheels do create vibrations. Once the brakes are hit the vibrations stop. It could be due to the wheel balancing.

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This would be my answer. To stop the vibrations that can especially agitate unknowing passengers. –  Magnetoz May 5 at 15:40
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Can you do more to convince readers that on a Cessna 172, spinning wheels do create vibrations? Is this documented somewhere? –  Articuno May 5 at 22:47

So the physicist in me tells me that the reason for this is a cool little thing called angular momentum.

Remember back when you were a kid, first learning to ride a bike? At some point you realized that the more speed you have, the more stable you are on your bicycle. This is because of angular momentum.

So imagine your up in the air, and you have to wheels rotating at 75 rpm (assuming a takeoff speed of 55KIAS, no headwind, and a tire diameter of 18 inches). You have a decent amount of angular momentum fighting any maneuver that the aircraft wants to make.

Consistency is key in safety in aviation. The difference in ground speed for a takeoff could vary from the Vr KIAS ± max head/tail wind. That's enough to significantly alter the dynamics of a maneuver.

--EDIT--

If you want to know how much you are affected by this angular momentum, check out the question I posted on the physics stack exchange.

http://physics.stackexchange.com/questions/111353/what-is-the-inertia-caused-by-angular-momentum-when-twisted-on-its-rotating-axi/111422

Angular Momentum

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To the person who downvoted: why? Care to share? –  Brian Wheeler May 5 at 2:59
    
I think this answer could be improved by doing more to convince us that "that's enough to significantly alter the dynamics of a maneuver". How much angular momentum is there? How relevant is that to flight maneuvers? Does any reliable source agree with you? –  Articuno May 5 at 3:52
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Actually, gyroscopic effects make very little contribution to the stability of bicycles, as shown by experiments by David Jones in the late 1960s. For more details, see Lowell and McKell, *The Stability of Bicycles (American Journal of Physics, vol 50, no 12, pp. 1106-12, 1982; PDF). –  David Richerby May 5 at 18:46

Spinning wheels are not a problem in fixed undercarriage aircraft, there's no good reason to tap the brakes after takeoff if the gear is nailed down. I suspect you answered your own question when you theorized that they may have simply copied that part of the manual.

From a wear perspective you may save some wear on the bearings by stopping the wheels spinning, but since you are using the brake pads to do it it's likely less overall wear just to let them stop naturally.

CLimbout is a busy time, anything that adds workload without a benefit shouldn't be on a checklist. I'd say you are probably safe to ignore that in a TB-10, however that is just my opinion and it may be worth contacting a TB-10 club and asking them what they think.

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