Incident Overview
On October 1, 2008, at approximately 1840 Pacific daylight time, a Eurocopter AS350 B3 helicopter, registration N172AE, was substantially damaged during a hard landing at Blaine Municipal Airport in Blaine, Washington. The helicopter was registered to the US Department of Homeland Security and operated by Customs and Border Protection (CBP) as a public use flight. The commercial pilot and flight instructor on board were not injured.
Flight Details
The flight originated from Bellingham, Washington, at 1815 as a local training flight under visual meteorological conditions. No flight plan was filed. The pilots were conducting a series of practice emergency procedures as part of an annual proficiency evaluation.
Sequence of Events
After completing two landings, the instructor announced they would conduct manual governor operations and switched the governor from "auto" to "man" while on the downwind leg to runway 32. Following a left 360-degree turn, the pilot initiated an approach with the intention of performing a slide-on landing. On final approach, the pilot felt slightly high and increased the rate of descent to intercept a flatter approach profile.
At about 80 feet above ground level (agl), the pilot increased throttle and raised the collective slightly to maintain the flatter approach. Shortly thereafter, he noticed rotor rpm (NR) decaying below the green arc and applied throttle. As NR continued to decay, the low rotor rpm warning horn sounded near 360 rpm. The pilot continued increasing throttle, and NR stabilized at 350 rpm at about 40 feet agl. Describing the descent through 20 feet agl, the pilot attempted to increase throttle and collective to arrest the rate of descent when "it felt like the bottom fell out," resulting in a hard landing on the asphalt runway in a slight nose-high attitude.
The flight instructor reported hearing the low rotor rpm horn and noticing NR slowing through 350 rpm as the helicopter descended through about 20 feet agl. He placed his left hand over the left collective twist grip but stated that "before I could react to correct the situation," the helicopter struck the ground. The instructor added that he believed he saw the throttle twisting in the decreasing rpm direction before he placed his hand on the twist grip.
Post-accident Examination
A Federal Aviation Administration (FAA) inspector examined the helicopter at the accident site. The tail boom was found partially bent, and one main rotor blade was damaged. Neither the commercial pilot nor the flight instructor reported any mechanical anomalies with the helicopter prior to the accident.