What happened
On November 23, 2012, an American Eurocopter AS350B3 2B1 helicopter, registration N3984A, was involved in an accident near Newfield, Arizona. The aircraft, operated by the Department of Homeland Security, was conducting a routine air patrol mission when the pilot decided to land in a confined area approximately two miles north of the U.S./Mexico border for a lunch break.
The pilot landed the aircraft in a patch of dried mud containing potholes and cattle hoof prints. After landing, the pilot performed a stability check and lowered the collective to the full down position. With the engine at 100% power, the pilot applied cyclic and collective friction to prevent control movement but did not engage the collective lock. While reaching behind the seat to retrieve a lunch bag, the pilot experienced a momentary loss of situational awareness.
During this period, the nose of the helicopter became light and pitched upward. The pilot applied forward cyclic to correct the pitch and maintain skid contact with the ground. This triggered vertical dynamic oscillations consistent with ground resonance. It is believed that at least one ground resonance strap may have been positioned in a pothole, losing contact with the ground.
In an attempt to regain stability, the pilot applied positive collective to lift the aircraft. As the helicopter ascended, it lurched into a nose-low attitude, causing the lower wire strike blade to strike the ground and create a pivot point. The pilot then made an aggressive aft cyclic movement with positive collective input. This caused the tail skid to strike the ground, pushing the vertical fin and tail rotor gearbox upward and severing the tail rotor drive shaft. The aircraft then entered an uncommanded left yaw and spin, which continued until the pilot reduced the collective. The helicopter eventually touched down in a nose-up attitude on its skids. The pilot, the sole occupant, sustained one minor injury and was not killed.
The investigation
Investigators from the CBP and American Eurocopter examined the wreckage and found significant damage to the tail cone, vertical fins, tail rotor drive train, and tail rotor blades. The engine was noted to produce a grinding noise when rotated.
An examination of the cockpit camera, an Appareo Vision 1000, revealed that the device had been unplugged and had not recorded any data since September 22, 2012. Consequently, no cockpit video or audio from the accident was available for review.