One of the major issues with helicopter design is that the effective speed of the rotor tips vary by twice the forward speed of the helicopter as it swings arou

One of the major issues with helicopter design is that the effective speed of the rotor tips vary by twice the forward speed of the helicopter as it swings around from back to front to back again. The rotor going from back to front experiences a speed that is the tip speed due to rotation plus the forward speed of the helicopter. As it swings around to the front and then towards the back it experiences a speed that is the speed of the tip due to rotation minus the forward speed of the helicopter. So if your helicopter is going at 200 mph and your rotors - which have been noted here several times need to stay below the speed of sound - are going at say 400 mph at the tip, then the rotor tip speed varies from 200 mph to 600 mph on every single rotation. It’s hard (for me) to imagine an air-breathing engine that could operate efficiently with its intake air speed changing that much that frequently. Much less a ramjet which has no turbines or anything to even out the intake velocity and which normally wants to operate well above the speed of sound.