Hirobo HI0404543 Auto-Rotation Torque Limiter for SX Series Helicopters  [HI0404543]

Auto-rotation torque limiter overview

This HIROBO HI0404543 auto-rotation torque limiter is an RC-scale replacement part intended for use in helmet-style helicopter rotor assemblies where the limiter controls autorotation torque transfer. It is listed as a common part for Eagle, Freya, EX and SX series helicopters and serves the tuning and safety role during autorotation practice and emergency descent testing.

Functionally, the limiter moderates the torque transmitted between the rotor head and drivetrain under low-load or free-spinning conditions, helping to stabilise rotor deceleration during autorotation. The part is designed to be swapped in place of the factory limiter using the existing mounting points and original fasteners to retain factory alignment and rotor tracking.

When fitting, confirm the unit aligns with the helicopter's existing interface and that no additional modifications to the head or shaft are required. After installation, verify rotor free-play and conduct a ground test hover to confirm predictable autorotation response before flight tuning or high-stress manoeuvres.

This torque limiter is a direct-access replacement for pilots focused on autorotation behaviour and rotor slowdown consistency, use it to restore or adjust autorotation feel while keeping factory mounting and alignment intact.