Motor train
In aircraft, the motor train refers to the installation of the propeller shaft offset by a certain angle relative to the longitudinal axis . For example, if the propeller is turning clockwise, a motor pull to the right is selected, and if the propeller is turned to the left, a motor pull to the left. This is also increasingly used, especially in model aircraft construction .
In single-engine models, the propeller pushes air backwards along the fuselage, the so-called propeller jet . The rotation and friction of the propeller do this in a kind of corkscrew motion. The rudder unit , which serves to stabilize the aircraft around the yaw axis and its control, therefore experiences an uneven flow, as does wing parts (particularly close to the fuselage) and the horizontal stabilizer . In addition, the counter-torque of the motor on the aircraft causes a roll torque opposite to the direction of rotation of the propeller . Furthermore, the so-called P-factor causes negative effects under certain conditions. Accordingly, the aircraft with a clockwise engine running under load with a neutral rudder position and without engine pull would have the tendency to initiate a left turn. In order to ensure an even flow on the rudder unit (and at the same time to counteract the two other phenomena mentioned), an appropriate motor train is selected.
Compensating for the yaw moment by setting the vertical stabilizer at a non-zero angle is inexpedient because the propeller jet is greatly reduced or absent when the engine is throttled or stopped, and the aircraft then has a corresponding tendency to turn. In addition, the compensating moment would be speed-dependent with a changed rudder setting angle, which is advantageously not the case with the motor pull.
See also
swell
- Herbert Groß: Aviation Knowledge; 2nd Edition; Motorbuch Verlag; Stuttgart 2005; ISBN 3-613-02378-4