Airworthiness Directives; Hoffmann Propeller Co. HO27( ) and HO4/27 Series Propellers

This amendment adopts a new airworthiness directive (AD) that is applicable to Hoffmann Propeller Co. HO27( ) and HO4/27 series propellers. This action requires installing improved propeller mounting bolts to a higher torque value, operating the airplane for one flight, checking the torque, and retorquing, as required, to the correct torque value. This amendment is prompted by reports of insufficient torque of propeller mounting bolts due to operating conditions, loads, and environmental conditions such as humidity and temperature. The actions specified in this AD are intended to prevent propeller mounting bolt failure, which could result in propeller separation and loss of control of the airplane.