Incident Overview
On January 30, 2016, at about 1000 central standard time, a Helicopteres Guimbal Cabri G2 helicopter, registration N503DS, collided with terrain while hover taxiing at Beaumont Municipal Airport (BMT), Beaumont, Texas. The helicopter, owned by 503 Delta Sierra, LLC and operated by Neches Helicopter Training, LLC, was conducting a day visual flight rules personal flight under 14 CFR Part 91. No flight plan was filed, and visual meteorological conditions prevailed. The flight had originated from BMT at about 0830.
Pilot Report
The pilot reported that after completing a local area flight, he was hover taxiing to the ramp on a heading of about 065 degrees. While clearing the taxiway, the helicopter encountered a small gust of wind, which the pilot described as a tailwind. He corrected the resulting left rotation with approximately one-quarter of right tail rotor pedal, noting an airspeed of about 20 knots and an altitude of about 10 feet.
About one second later, a second, stronger gust occurred. The pilot applied full right tail rotor pedal, but the helicopter continued to rotate left. He nudged the cyclic right to follow the left spin and regain control. Although he stopped forward momentum, the left skid contacted the ground, causing the helicopter to roll left and impact terrain. The helicopter rotated left twice, terminating near its original heading. The pilot characterized the event as a loss of tail rotor effectiveness (LTE).
The pilot reported wind conditions at the time as 14 knots gusting to 24 knots from 220 degrees. He verified no preimpact mechanical failures or malfunctions with the airframe or engine that would have precluded normal operation.
Aircraft Damage
The helicopter sustained substantial damage to the fuselage, main rotor system, tailboom, and tail rotor system. The pilot and sole passenger were not injured.
Additional Information
According to the manufacturer, the Cabri G2 was tested in wind conditions higher than the required 17 knots and exhibited no LTE. The flight manual states that a wind speed of 35 knots at all headings was demonstrated at sea level, and 25 knots at all headings at maximum reduced weight for in-ground-effect hover.
Helicopteres Guimbal Service Letter SL 12-001, addressing yaw control, notes that the Fenestron tail rotor design is immune to stall and vortex-ring state (LTE). It provides guidance on pedal inputs during approaches and spot-turns.
A previous accident involving a Cabri G2 on October 26, 2011, in Gloucestershire, UK, involved loss of yaw control during landing, engine power loss, and hard landing. The AAIB report cited pilot belief that slow application of right pedal caused the accident; the manufacturer suggested prolonged yawing could cause engine stoppage due to fuel sloshing. No preimpact mechanical anomalies were found.
The FAA Helicopter Flying Handbook defines LTE as an uncommanded, rapid yaw toward the advancing blade, caused by aerodynamic interaction, not mechanical failure.