The fatal crash of a 1985 Enstrom 280FX, N86235, during a training flight on January 26 in Erie, Colo., triggered an FAA emergency Airworthiness Directive 2015-04-51 on February 12. Witnesses reported that the main rotor blades separated from the helicopter before impact. The instructor and his student were killed. The emergency AD mandates magnetic particle inspections (MPI) of main rotor blade spindles with 5,000 or more hours' time in service (TIS) or an unknown number of hours' TIS for cracking before further flight for all piston-engine models of Enstroms. It also applies to Enstrom Model 480 turbine singles S/Ns 5001 to 5006 with main-rotor spindle part numbers 28-14282-11 or 28-14282-13.
Enstrom CEO Tracy Biegler told AIN that the company had not received any reports of spindle cracks through February 16 and called the 5,000-hour TIS limit for inspections "extremely conservative." He said the company's helicopters "have a very good safety record."
The emergency AD is estimated to apply to a total of approximately 323 U.S.-registered helicopters, and it supersedes Enstrom Service Directive Bulletins 0119 and T-050 issued February 11. Inspection results must be reported to the FAA within 72 hours. The FAA estimates the cost of each inspection at $1,318 and a cost of $8,504 to replace a spindle if required. The inspections must be performed by a Level II or Level III inspector. According to the FAA, the preliminary crash investigation indicates the blades separated due to a spindle crack at the last thread of the spindle-retention nut, a crack that had “existed, undetected, for a significant amount of time before the separation.” The FAA said the emergency AD was an “interim action.”