Action
Notice of proposed rulemaking (NPRM).
Summary
The FAA proposes to supersede Airworthiness Directive (AD) 2021-23-17, which applies to all Hoffmann GmbH & Co. KG (Hoffmann) model HO-V 72 propellers. AD 2021-23-17 requires amending the existing aircraft flight manual (AFM) by inserting abnormal propeller vibration instructions, visual inspection and non-destructive test (NDT) inspection of the propeller hub and, depending on the results of the inspections, replacement of the propeller hub with a part eligible for installation. Since the FAA issued AD 2021-23-17, further investigation by the manufacturer revealed that cracks found on propeller hubs likely resulted from propeller blade retention nuts that were not tightened using published service information during blade installation. This proposed AD would retain the required actions of AD 2021-23-17. This proposed AD would also require a maintenance records review and, depending on the results of the maintenance records review, tightening of each propeller blade retention nut to specific torque values. Depending on the results of the maintenance records review, this proposed AD would require physically inspecting the propeller blade for shake. If any axial play is detected during the performance of the inspection, this proposed AD would require the removal of the propeller from service and the performance of an NDT inspection of the propeller hub. The FAA is proposing this AD to address the unsafe condition on these products.