Taking off in a straight line!!

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8 years 1 month ago #8385 by
Can anyone answer this question?

When a model is taking off under max or near max power, it veers to the left. This is invariably explained as a result of torque reaction from the prop and is countered with right rudder.
The question is how does a torque about the roll axis, (prop reaction) get translated to a torque about the yaw axis, (veer to the left) when both wheels are firmly on the ground preventing any roll movement?

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8 years 1 month ago #8386 by AlanF
Replied by AlanF on topic Taking off in a straight line!!
Have a google for P factor.

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8 years 1 month ago #8387 by
Replied by on topic Taking off in a straight line!!
Thanks Alan

There is quite a lot on the subject.
To minimise the effect, the implication is to raise the tail as quickly as possible with a tail dragger and keep a tricycle layout level for as long as possible. Also with a trike undercarriage, the plane will only veer left when the nose is raised to lift off.

Is this true?

Could this effect also generate a pitching torque from a side wind?

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8 years 1 month ago #8393 by AlanF
Replied by AlanF on topic Taking off in a straight line!!
You're right Ron , there is a huge amount on the subject of P factor, Gyroscopic precession, spiral slipstream and torque effects.

Logically P factor must always have an effect anytime the prop disc is at an angle to the airflow. How much effect that has on the aircraft must depend on what other forces are acting at the time.

For a tail dragger at take-off I would imagine that gaining forward speed as quickly as possible without tipping the nose would be the way to reduce the yaw effect.

For a trike, by the time the nose is raise you already have a reasonable air speed so P factor and spiral slipstream effects are already reduced relative to the aerodynamic forces provided by the wings, tail plane and fin.

A question for the experts: What effect does P factor etc have when doing a stall turn?

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8 years 1 month ago #8397 by DavidTappin
Replied by DavidTappin on topic Taking off in a straight line!!
Alan asks

A question for the experts: What effect does P factor etc have when doing a stall turn?


I don't profess to being a particular expert but I would have thought that, since at the point of ruddering over in a stall turn, the motor will be close to idle the effect would be negligible.

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8 years 1 month ago #8398 by MikeSeale
Replied by MikeSeale on topic Taking off in a straight line!!
I guess it's a no flying day when we're pondering things we have no control over?

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