The FAA this week published a new airworthiness directive (2015-SW-014-AD) governing the inspection intervals to check for cracks on the main rotor spindles of piston-and turbine-powered Enstrom helicopters, effective June 2. The FAA is shortening the mandated initial inspection interval to 1,500 hours time-in-service (TIS) from the previous requirement of 5,000 hours it imposed on an emergency basis in February (2015-04-51) following the fatal crash of an Enstrom 280FX in Erie, Colo., on January 26. A preliminary investigation indicated that a spindle crack at the last thread of the retention nut threads caused the main rotor to separate from that helicopter.
The emergency AD required magnetic particle inspections (MPI) on spindles with more than 5,000 hours and that the results be reported back to the FAA. Twenty percent of the spindles inspected had evidence of cracks, including those with less than 5,000 hours TIS, prompting the FAA to revise the AD and impose the 1,500-hour limit and order that the MPI be conducted before further flight. The FAA estimates the AD will affect 323 helicopters in the U.S., with inspections costing $1,318 and spindle replacement another $8,164 per helicopter.