Are return springs on a carburetor throttle mandatory or not? In many GA aeroplanes throttle control is connected mechanically to the throttle of carburetor via a cable. I read in some AFMs that in case of a cable failure, return springs will open the throttle so an engine will be at full power.
Is it mandatory to have those springs installed (a certification requirement or something) or it is optional? I'm asking about EASA regulations, but a reference to FAA regulations will also be helpful.
The FAA doesn't require it, but some carburettor manufacturers may have them. You can get return springs for Rotax engines, but only for non-certified aircraft and then again only to prevent throttle creep