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Old 28th Apr 2022, 14:10
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Originally Posted by Reely340 View Post
A properly designed cyclic mechanism would - for example for pure forward cyclic input - tilt the swashplate in a way that pure fwd action results……..=> I recall that Bell has some experience building helos, so why do they use that "crossmixing cam" at all?
The easy part is designing the mechanical controls to provide pure lateral and longitudinal input to the swash plate.

The hard part, is the nonlinearities of the rotor performance with changes in forward speed, center of gravity, downwash over the fuselage, deflection in the transmission mounts, etc.

Prior to flight testing of a new helicopter design, manufactures often produce prototype bell cranks of slightly different ratios to allow for adjustment of control sensitivity. As mentioned before, swashplates can be adjusted to couple lateral with longitudinal.

For larger helicopters equipped with stability augmentation systems like the 429, many of these nonlinearities or taken out by the SCAS actuators.

Engineers that don’t like the inability to exactly predict helicopter performance and handling qualities, quit their jobs and design fixed wing airplanes. :-D

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