Currently, helicopter developers are hindered seriously by the lack of a ‘Sprag clutch’.
Current ‘workarounds’ are unsatisfactory.
What is a "sprag clutch’.
A sprag clutch is a one-way It resembles a roller bearing but, instead of cylindrical rollers, non-revolving asymmetric figure-eight shaped sprags or other elements allowing single direction rotation, are used. When the unit rotates in one direction the rollers slip or free-wheel, but when a torque is applied in the opposite direction, the sprags tilt slightly, producing a wedging action and binding because of friction.
Helicopters
A sprag clutch is used in many designs to transfer power from the engine to the main rotor. In the event of an engine failure, the sprag clutch allows the main rotor to continue rotating faster than the engine so that the helicopter can enter autorotation.
Wikipedia.
In a nutshell.
The engine can power the rotor.
The rotor cannot power the engine.
In the event of an engine or gearbox seizure, the rotor doesn’t seize up as well.
After starting the engine, it is a ‘checklist item’ that is NO-GO if it doesn’t function. Functionality is checked by looking for a needle split, when the throttle is rolled off from 100% towards idle.
Solution for Asobo.
parameter
sprag_clutch =
description
When this parameter is set to 1 (TRUE) engine torque drives the rotor. The rotor cannot drive the engine.
Default value is 0 (FALSE).
parameter
sprag_clutch_direction =
description
A value of 0 (FALSE) here will maintain the default rotational direction of the helicopter blades, which is clockwise (when viewed from above). Setting this to 1 (TRUE) will reverse that rotation, so anti-clockwise.
Default value is 0…
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Stu