EAD Expanded, Now Affects Over 300 Aircraft

On February 12, 2015, the FAA issued EAD 2015-04-51, which was prompted by a fatal accident. Preliminary results of the investigation indicated that the accident was caused by a crack in the spindle which resulted in the main rotor blade separating from the helicopter. The crack was discovered at the last thread of the spindle retention nut threads.

While the investigation could not determine when the crack initiated, it was able to determine that the crack existed, undetected, for a significant amount of time before the separation. EAD 2015-04-51 required, before further flight, conducting a magnetic particle inspection (MPI) to determine if a crack exists in any spindle that has 5,000 or more hours time-in-service (TIS) or where the hours TIS of the spindle is not known. If there was a crack in the spindle, EAD 2015-04-51 required replacing it before further flight. EAD 2015-04-51 also required reporting the inspection results to the FAA within 72 hours.

Since EAD 2015-04-51 was issued, inspection reports received by the FAA indicate approximately 20% of the spindles had evidence of cracks. The inspection reports include spindles with cracks at less than 5,000 hours TIS. With analysis of available data, the agency have determined the need to expand the applicability to include spindles with 1,500 or more hours TIS.

The EAD covers Enstrom Helicopter Corporation (Enstrom) Model F-28A, 280, F-28C, F-28C-2, F-28C-2R, 280C, F-28F, F-28F-R, 280F, 280FX helicopters, all serial numbers; and Enstrom Model 480 helicopters with a serial number (S/N) 5001 through 5006; with a main rotor spindle (spindle), part number (P/N) 28-14282-11 or P/N 28-14282-13.

The FAA is issuing this EAD because after evaluation of all the relevant information and determined the unsafe condition described previously is likely to exist or develop in other products of these same type designs.

The EAD requires, before further flight, conducting an MPI to determine if a crack exists in any spindle that has 1,500 or more hours TIS or where the hours TIS of the spindle is not known. If there is a crack in the spindle, this EAD requires replacing it before further flight. The MPI of the spindle must be conducted by a Level II or Level III inspector qualified in the MPI method in the Aeronautics Sector according to the EN4179 or NAS410 standard or equivalent. This EAD also requires, within 72 hours, reporting certain information to the FAA.

The EAD affects 323 helicopters of U.S. Registry and that operators may incur the following costs to comply with this EAD. Inspecting the spindles will take about 15 work-hours per helicopter and reporting the required inspection information will take about 0.5 work-hour. We estimate an average labor rate of $85 per work-hour, for a total cost of $1,318 per helicopter and $425,714 for the U.S. fleet. Replacing a spindle will cost $8,164 for parts and no additional work-hours.

(Image from file)

FMI: EAD