N427ALBell 407 · 1997

On June 4, 2012, about 0955 eastern daylight time, a Bell 427, N427AL, sustained substantial damage after an inflight bird strike, main rotor vibration, and hard landing near Indiantown, Florida. The private pilot, commercial copilot, and three passengers received minor injuries. The helicopter was registered to Southern Aviation Systems, LLC, and operated by a private individual. Visual meteorological conditions prevailed and no flight plan was filed for the 14 Code of Federal Regulations Part 91, executive/corporate flight, destined for Ocala International Airport-Jim Taylor Field (KOCF) Ocala, Florida. The flight originated from the Palm Beach International Airport (PBI), West Palm Beach, Florida, about 0930.

According to the pilot, approximately 25 minutes into the flight, while on a heading of 330 degrees and at an altitude of 800 feet mean sea level (msl), he maneuvered the helicopter to avoid colliding with several large birds. The pilot felt something impact the upper right side of the helicopter near the main rotor mast area. Immediately following the impact, the helicopter started shaking violently, and became difficult to control. The pilot elected to land in an open field. Descending through 300 feet msl, the shaking became more pronounced and the helicopter became uncontrollable. At 50 feet msl, the aircraft went into a left spin and impacted the ground and rolled over on its left side. All onboard were able to exit the helicopter on their own.

Examination of the helicopter by a FAA inspector and a representative of the airframe manufacturer revealed that the tail boom separated about three feet aft of the attachment point to the fuselage. The collapse of the left mail landing gear and subsequent tail boom departure from the airframe was consistent with a dynamic rollover by the helicopter.

Pitch change links connected the swash plate at the lower end to the main rotor blade pitch horns at the upper end. According to a NTSB metallurgy laboratory report, the orange square and red triangle-coded links were fractured approximately 1.25 inches from the end closest to the pitch horns where the tube was internally threaded. The fracture surfaces were oriented approximately 45 degree to the longitudinal axis of the tube and had a rough appearance, consistent with tensile overstress fractures. The orange tube had an inward dent approximately 0.75 inch below the fracture. The rod ends that connected the blue diamond and green circle-coded links to the swash plate were bent forward in the direction of rotation (clockwise direction as viewed beneath the mast looking up) and fractured in the thread roots. The fracture surfaces had a rough irregular appearance. The deformation and appearance of the fracture surfaces were consistent with bending overstress fracture. The main rotor blade pitch horns were fractured and twisted on the blue diamond and green circle-coded blades. The ends of the pitch horns were still connected to the upper fittings of the pitch links. The fracture surfaces were at approximately 45° angles to the longitudinal axis of the arm and they had a rough appearance, consistent with an overstress fracture.

All four main rotor blades separated from the hub due to contact with the ground or other helicopter components. Ground scars by the main rotor blades were verified through paint marks and gouges in the dirt.

Evidence of bird remains were present on components of the rotor head, two of the four pitch change rods, and the tail rotor. Each pitch change rod with bird remains was separated from one of their attach points respectively. The bird remains were removed and sent to the Smithsonian Institute for bird identification. According to the report, male and female Black Vulture DNA was found on the pitch control rods, pitch control linkages, and the tail rotor.