Cyclic pitch should be applied to rotor blades in anti-phase, and other rotor model problems

[davidw65]

The animation of the rotor head operation is wrong, because, as shown it would not provide any pitch and roll control, in real life, as well as not matching the design of the real machine.

As animated, both blades have their pitch increased or decreased together, and what would be the swash plate assembly in a real helicopter, moves up and down the rotor shaft in time with the rotation. To actually generate a pitch or roll torque, particularly in a hover, one blade needs to pitch up at the same time as the other pitches down, so that there is excess lift on one side, and reduced lift on the other. In the R44, this actually achieved by the swash plate tilting, with its vertical position on the mast only being controlled by the collective. Only the pitch linkage rods actually need to reciprocate. This can be seen, for the actual R44 in https://www.youtube.com/watch?v=HxtXXuMhKKc

Also, the control rods that run down the cowling are shown as rotating with the rotor shaft, but in the real R22, which I think has the same basic design as the R44, doing that would tear big holes in the cowling, as the rods actually poke out through fixed holes in the top of the cowling. This is easy to see in https://www.youtube.com/watch?v=pPFgv8gIRtI

R44 Build: 20160104
Flightgear: 2017.3.1 Build 223
Open Scene Graph 3.4.0
Windows 10 Build 1703
amd64
ATI Radion HD 7700 Series OpenGL driver 4,5,13474

[davidw65]

Probably as a consequence of not understanding swash plates, the cyclic pitch is being applied as a pulse when one preferred blade is in the desired direction. It should be appled to both blades as they come into the right direction (different blades on each half rotation), and in practice would be more like a complete sine wave than pulses.

Also the the peak pitch variation seems to correspond to the cyclic stick direction, when, on a real helicopter it has to be applied about 90 degrees in advance.

That's because the differential lift doesn't directly pitch and roll the aircraft, but rather causes hte blades to go up and down, on the hinge at the top of the rotor head, with the result that the effective plane of the rotor, and therefore its thrust vector, changes, so as to pruduce a force that pushes the shaft over. This teetering of the rotor head, and the resulting sloping of the disk traced are not modelled at all. (It is always possible that modelling this correctly would overload the the simulator on older machines (like mine), as such it may be less important than the incorrect modelling of the swash plate and control rods,which are errors of commission).