Summary
This supplemental NPRM revises an earlier proposed airworthiness directive (AD), for McCauley Propeller Systems model 4HFR34C653/L106FA propellers. That proposed AD would have required a onetime fluorescent penetrant inspection (FPI) and eddy current inspection (ECI) of the propeller hub for cracks. That proposed AD resulted from reports of 3 hubs found cracked during propeller overhaul. This supplemental NPRM would require the same inspections. This supplemental NPRM results from reports of 7 additional hubs found cracked during propeller overhaul, totaling 10 cracked hubs. We are proposing this supplemental AD to prevent failure of the propeller hub, which could cause blade separation, damage to the airplane, and loss of control of the airplane.