#### Mike G

##### Junior Member

- Joined
- Jun 16, 2005

- Messages
- 1,678

- Location
- Lillebonne France

- Aircraft
- Owned Magni M16 now ELA 07

- Total Flight Time
- 550FW + 500 gyro

What Jean Claude is saying is that, if the rotor blades are infinitely stiff torsionally and/or have the CofG exactly at the centre of lift point chordwise, then an increase in load (say 2 G) increases Rrpm by 1.414 (square root of 2) and that increase in Rrpm increases the centrifugal/petal (depending upon your religion) force by the increase in Rrpm squared (1.414 squared = 2). Therefore when you look at the coning angle triangle of forces the vertical load force vector has increased by 2 and the centrif force vector has also increased by 2 so the coning angle remains unchanged.

Now in reality blades are not torsionally stiff and the chordwise CofG is probably not at the CofLift. So an increase in load will increase Rrpm and hence centrif force and that centrif force that is offset from the CofLift will twist the blade giving a positive twist if the CogG is behind (nearer the trailing edge) or a negative twist if the CofG is in front of the CofLift. This means that the blade pitch angle will cause the Rrpm to be higher (if pitch is reduced) or lower if pitch is increased and the coning angle centif force vector will be longer or shorter than the theoretical one hence decreasing or increasing the coning angle.

Mike