# Strange airplane behavior

Guest

Several times with certain airplanes when i start to roll on the runway to take off the airplane does not go straight ahead in a straight line but rather it deviates to the left....????...any ideas why this might be?...it is driving me crazy and i havent got a clue why this is happening.

ARD-DC First Officer

which airplanes?

Tailhook Chief Captain

Anonymous wrote:

Several times with certain airplanes when i start to roll on the runway to take off the airplane does not go straight ahead in a straight line but rather it deviates to the left....????...any ideas why this might be?...it is driving me crazy and i havent got a clue why this is happening.

Some Props have a very sensitive throttle. If you apply it too sudden, especially when you're trying to get the aircraft rolling, it will pull to the left. That's realistic behaviour.

Yes, common in Props, its sort of like a Torque steer, caused by the rotation of blades.

A twisty joystick controlling the Rudder should help, or you can try using the keyboard. But the Rudder should enable you to steer!

Kurt Stevens (KurtPStevens) First Officer

It's called The "P Factor" and is an aerodynamic effect that causes propellor-driven planes to yaw when they are flown at high power and low speed (takeoff and climbout, for example.)

At low speeds, the plane flies at a substantial angle of attack, and so the airflow is not parallel to the plane's axis. Relative to the plane, the airflow is directed several degrees upwards. Now the prop axis is normally parallel to the plane's axis. As the prop rotates, on one side the blades are travelling upwards and on the other side they are travelling downwards. (On most planes, the prop turns clockwise, as seen from behind, so the left side goes up and the right side goes down.)

The upwards angle of the airflow causes the downward (right) side of the prop to have a greater airspeed and angle of attack than the upward (left) side. So the downward (right) side of the prop generates more thrust. Pull harder on the right side of the plane than on the left and the plane will yaw to the left.

This is one of the reasons why most real prop planes need a certain amount of right rudder to keep them straight during takeoff and climbout.

The other factor that requires right rudder on takeoff (in planes with clockwise props) is spiral propwash. The sideways component of the spiral propwash strikes the vertical stabilizer from the left (in conventional single engine configurations), also causing a yaw to the left. In general, the spiral propwash effect is a lot stronger than P-factor.

You also need right aileron to keep the plane straight to counteract the rotational torque from the engine(s).