On January 10, 2014, an Eurocopter AS350B3 helicopter, registration N3948A, crashed near Encino, Texas, resulting in one serious injury and two minor injuries. The aircraft was being operated by US Customs and Border Protection (CBP) for a law enforcement patrol flight.
What happened
The flight originated from McAllen International Airport (KMFE) at approximately 0610 central standard time. While conducting a patrol to assist ground agents, the pilot descended from 800 feet to 150 feet above ground level (AGL) to hover on a southerly heading. As the helicopter began drifting southeast, the pilot attempted to reposition the aircraft by performing a left climbing turn.
During this maneuver, the pilot reported feeling the wind catch the tail, followed by a slight shimmed sensation. The helicopter then entered a rapid left spin. The pilot applied full right pedal and attempted to accelerate in an effort to regain control, but the aircraft continued the left spin and impacted trees and terrain. The pilot noted hearing a sound similar to the low rotor RPM horn prior to the impact.
The investigation
Investigators examined the wreckage, which was located on a ranch approximately 50 miles north of KMFE. The fuselage came to rest on its right side, and there was evidence of a post-impact fire. The examination of the airframe and engine revealed that both had a total time of 1,397 hours.
Mechanical analysis of the transmission and main rotor system showed that the transmission supports were broken and the 'Starflex' rotor hub had broken arms. Damage to the main rotor blades was consistent with ground impact. The tail rotor gear box remained attached, and the tail rotor blades were inspected, with one blade showing damage and separation.
Data from the Digital Engine Control Unit (DECU) and the Vehicle Engine Monitoring Display (VEMD) were reviewed. The VEMD recorded an overtorque event, a free turbine overspeed event, and a gas generator overspeed event. These events occurred within seconds and were consistent with the impact sequence and the engine producing power at the time of impact. No pre-impact mechanical failures were identified that would have prevented normal operation.