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## Left turning tendencies

• abdullah
• Topic Author

### abdullah created the topic: Left turning tendencies

Hey everyone, i’ve heard from many people that the bob tait forums are a great help so i figured i’d give this a shot.

At the moment, most of the content in CADA i am understanding well, however i really am struggling to understand the left turning tendencies and how i can differentiate between them.

torque reaction, slipstream effect, gyroscopic precession and asymmetric blade effect.

can anyone help me better understand this? and is there a simple way to differentiate them?

also some examples of questions i may get would be great!

• Posts: 2449

### bobtait replied the topic: Left turning tendencies

One thing to remember is that they are very much related to whether the aircraft is a nose-wheel or tail-wheel aircraft.

Slipstream and torque occur for ALL aircraft. Slipstream produces a yaw to the left as the spiraling slipstream strikes the fin and rudder pushing the tail to the right.

Torque is the natural reaction that makes the aircraft roll opposite to the propeller rotation. It's really just the well known law of physics that says 'for every action there is an equal and opposite reaction".

P factor (or Asymmetric Blade effect) and Gyroscopic precession is most noticeable in tail-wheel aircraft.

P factor occurs because, while the tail-wheel is on the runway, the propeller is advancing at an angle to the oncoming relative airflow. That means that the down-going propeller blade has both a higher speed of airflow and a higher angle of attack. That produces a yaw to the left.

Gyroscopic precession is noticeable only WHILE THE TAIL IS BEING LIFTED and the propeller is forced to change its plane of rotation. See RPL/PPL Volume 1 page 64 and/or CPL Aerodynamics Page 36.

• abdullah
• Topic Author

### abdullah replied the topic: Left turning tendencies

when you say slipstream and torque are for all aircraft, do you also mean p factor and gyroscopic precession only occurs in tailwheel aircraft? or only just more common.

thank you for the response bob!

• Posts: 2449

### bobtait replied the topic: Left turning tendencies

P factor and gyroscopic effect will be present whenever the propeller disk is advancing at other than 90° to the airflow.

This is most noticeable in a tail-wheel aircraft because, when the tail wheel is on the ground, the propeller disk is tilted away from the perpendicular. In a nose-wheel aircraft the propeller disk is pretty well in the perpendicular position all the time.

So P factor and gyroscopic precession during take-off are more noticeable in a tail-wheel aircraft.

However, in any aircraft these effects will be present during flight with high angles of attack or abrupt changes in pitch attitude such as during aerobatic manoeuvres. Aerobatic aircraft actually rely on gyroscopic precession to allow the performance of some advanced manoeuvres! Do a search on Google for 'lomcevak', an airshow manoeuvre that relies entirely on gyroscopic precession.

Questions on this topic usually relate only to the take-off itself.