To: Grey Area
After looking at the diagram I came to the conclusion that not all helicopters have a 90-degree precession angle. It is not that they weren’t designed to have a phase angle of 90-degrees it is that through a combination of design related problems in the dynamics and rotor blade systems the phase angle will vary. I have to believe that or, I will have to download my memory of the Cheyenne helicopter. It too was designed to have a 90-degree phase angle but the rotor system had a tendency to deviate from the 90-degree phase angle. Sometimes it was in excess of 90-degrees and sometimes it was less than 90-degrees. This was caused by a combination of things that included the design of the blades and the stiffness of the blades along with speed and gross weight.
The problem manifested itself in different ways. On some occasions the helicopter would not fly in the direction the cyclic was displaced and on two occasions the rotorblade divergence from the selected flight path was so extensive that the blades hit the fuselage.
It took two years to develop a fix that would eliminate the deviation from the selected flight path. They designed a system that compared the movement of the cyclic stick to the movement of the blades. If there was a deviation between input and response the system would send a signal to the servos via the autopilot and the servos would correct the pilots input to get the desired response at the rotor. This is very similar to the system used on the Lynx at least as it was described to me. The system used on the Cheyenne employed an Electro mechanical feedback loop and it was rife with single point failures that could cause the loss of the aircraft. The program was cancelled and two years later the Apache came on the scene.
Now, with that out of the way please tell me how the control inputs are made to the rotorhead from the fixed servos to the rotating rotorhead on the Lynx if there is no swashplate. Pictures would be appreciated.
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The Cat