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according to this picture

enter image description here

the P factor cuases airplane to yaw to the right but if pilot wants to pitch up , then p factor and gyroscopic precession acts on airplane at the same time but in opposite direction if propellers rotates counter clock wise in such manner : p factor makes the airplane to yaw to the right but gyroscopic precession makes the airplane to yaw the left

is that true?

sorry about my poor english language 🌹

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2 Answers 2

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That would be correct, as you can see from this video on Veritasium Youtube channel

Mind you, the pecession would only affect the plane for as long as it is rotating. P-factor is dependent on angle of attack, which of course would increase during pull, but when rotation stops, the "precession force" stops, and P-factor remains.

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    $\begingroup$ Precession is not, if I reacall correctly, mentioned in pilot training, so it must be negligible. I'm guessing P-factor is at least an order of magnitude greater. Sideslip would have some effect. In this case, flying "left side first", it would push the nose down. $\endgroup$
    – Jpe61
    Commented Sep 6, 2021 at 17:06
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    $\begingroup$ They may cancel each other in a transient condition, but only while yawing/pitching. Side slip will change the P factor's orientation somewhat, to the extent that the airflow has changed relative to the propeller axis. Say the flow is now coming from 7 o'clock due to side slip instead of 6. The P factor force orientation should move from 3 o'clock to 4 o'clock during the slip, to the extent that you have power on during the slip. $\endgroup$
    – John K
    Commented Sep 6, 2021 at 17:10
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    $\begingroup$ @Jpe61 precession forces can be much stronger, as you discover if you raise the tail of your C-180 very quickly on takeoff. and the nose swings hard from precession, but that's a brief transient state anyway. $\endgroup$
    – John K
    Commented Sep 6, 2021 at 17:12
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    $\begingroup$ @alireza The part of the disc with the greatest thrust is 3 o'clock looking from behind because the blade passing 3 has the highest angle when the prop axis is at a positive angle to the airstream. If you are slipping to the left, that is left wing down, with a positive AOA, the relative airflow goes from straight on from below, to offset to the left from below; 6 o'clock to 7 o'clock. The propeller disc sees its maximum blade angle shift from perpendicular to 6 o'clock to perpendicular to 7 o'clock, or from 3 o'clock to 4 o'clock. In that case P factor would create a slight NU tendency. $\endgroup$
    – John K
    Commented Sep 6, 2021 at 19:02
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    $\begingroup$ @JohnK in alizera's example the rotation of the propeller is opposite to "normal", as it is a pusher, the blade going downwards would be the blade at 9 o'clock. $\endgroup$
    – Jpe61
    Commented Sep 6, 2021 at 19:11
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They depend on different things. Gyroscopic precession occurs when you change the propeller's attitude- it causes a yawing tendency to the left when the counter-clockwise propeller is pitched up and to the right when it is pitched down. How big this effect is depends on how abruptly the pitch is changed.

P-factor depends on the current angle of attack of the propeller blades. Typically the plane is flown so that the descending blade has a higher angle of attack than the ascending blade, which causes it to produce more thrust. This causes a yaw to the right for a counter-clockwise propeller.

So both gyroscopic procession and p-factor can be in the same direction in some occasions. For instance, if the nose and angle of attack are initially high and they are quickly lowered, then both gyroscopic procession and p-factor will be to the right while the nose is being lowered.

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