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Old 03-10-2012, 08:39 PM
  #23  
shdw
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Joined APC: Jun 2009
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Originally Posted by JamesNoBrakes View Post
Most texts explain that torque causes a left yaw during takeoff roll due to more pressure/drag on the left tire as a result of the left rolling tendancy.
Regarding torques effect on rollout, I'm not sure, I can't claim one way or another. What I know is I've not read a statement like the one made in PHAK from any source I'd consider reputable on this subject. Though the concept makes intuitive sense, I wonder if its magnitude is negligible.

Where I run into a mental block with the scenario PHAK presents is that full aileron for a crosswind departure doesn't exhibit an appreciable effect on the need, or lack of need, for rudder during the rollout. I would guess at the later portion of the takeoff roll, with speed on the order of 40-50 knots, full aileron would yield a far greater rolling force than engine torque forces.

The spiraling slipstream, if significant to any extent, will go "backwards", how's that going to be some kind of major influence with a twin?
If the props are counter rotating, as many are, then spiraling slipstream can be ignored. However, so could the effects of torque on wheel weight and p-factor.

If the twin has a critical engine, then slipstream and torque effect would come back into play. As well as p-factor when in flight.

due to how much negative p-factor can affect an aircraft (it's not directly related to the aircrafts AOA, it's directly related to the aircrafts flight path vs props flight path, which are very different obviously).
That is why I said fuselage AOA. Which isn't exactly accurate as most engines are canted downward a few degrees. In other words, p-factor at the initial start of the rollout, prior to raising the nose, would present with a right yawing tendency.
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