Regionals Update: ATR 42 prop failure draws action from NTSB

 - July 11, 2008, 6:37 AM

The NTSB has recommended that the FAA require inspections of Hamilton Sundstrand 568F propellers in service for more than six years or 11,700 hr, after a propeller blade separated from its hub on an ACES Colombia ATR 42-500 on January 12. The recommendation covers serial numbers 1 through 1698 and calls for an immediate determination of a new inspection and repair threshold.  

The prop separation occurred roughly five minutes after takeoff from Cartegena, Colombia, on a scheduled flight to Bucaramanga, Colombia. After shutting down the  number-two engine, the crew returned to Cartegena for an emergency landing. None of the four crew and 37 passengers suffered injuries, and the airplane sustained only minor damage to the engine’s cowling.

A preliminary investigation by Colombian authorities revealed that one of the prop’s six blades separated through the metal base just outboard of the hub. An adjacent blade sustained a fracture through the composite airfoil. Closer examination revealed that the separation resulted from a fatigue fracture of its base, or “tulip,” originating in an area of widespread corrosion. Because compression wrap and sealant material conceal the area of the prop’s fillet radius, a major inspection performed to current requirements would not detect such corrosion. The NTSB recommends the removal of the compression wrap as part of the revised inspection procedures.