Accident Overview
On May 7, 2013, at about 1149 mountain daylight time, a Bell 206L-1 helicopter, registration N20Z, sustained substantial damage when it struck the ground near La Junta, Colorado, following an in-flight loss of tail rotor control. The aircraft was engaged in an aerial observation flight under 14 CFR Part 91, operated by Corporate Aircraft Services and registered to Helicopters Inc. The pilot and two passengers were not injured.
Flight Details
The flight originated from La Junta Municipal Airport (LHX) at approximately 1135 for the purpose of videotaping a pipeline corridor. The pilot reported maintaining altitudes between 50 and 100 feet above ground level at ground speeds of 45 to 55 knots, with no hover commands and forward flight throughout. After one flight, the helicopter landed at LHX for refueling, adding 50 gallons of fuel. Upon departure, the flight path continued southwest over flat rural terrain with low vegetation.
Loss of Control Sequence
At about 1200, the helicopter experienced an uncommanded left yaw lasting 1–2 seconds, then returned to straight flight. A passenger noted an engine torque spike from 55% to 115%, accompanied by a change in engine pitch. After another 1–2 seconds of straight flight, an uncommanded right yaw began and continued until impact. The pilot stated he treated the event as a loss of tail rotor effectiveness (LTE), lowering the collective, reducing throttle, and attempting to keep the helicopter level while cushioning the landing. After touchdown, the helicopter rolled onto its left side.
Postaccident Examination
The wreckage was moved to a maintenance facility. The fuselage was largely intact with impact crushing. The engine rotated freely with no internal failure evidence. The main rotor gearbox remained attached; the mast was bent at the gearbox exit, with swashplate control connections broken in a manner consistent with postimpact overload. No preimpact defects were found in the remainder of the control system. The tail boom separated at two locations approximately 3 and 4 feet forward of the tail rotor gearbox, consistent with main rotor blade impact. The tail rotor driveshaft exhibited multiple separations due to postimpact damage. The tail rotor gearbox rotated freely with no defects. The tail rotor control pushrod showed breaks consistent with postimpact damage from main rotor blade contact. Except for these breaks, the tail rotor control system functioned normally with no preimpact defects. The postaccident examination revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation.
Weather and Video Data
At 1153, LHX reported wind from 320° at 11 knots gusting to 16 knots, visibility 10 statute miles, clear skies, temperature 24°C, dew point 0°C, altimeter 29.91 inHg. The pilot provided a video recording from a handheld camera mounted on a monopod extended out a left-side window. The NTSB Recorder's Laboratory extracted embedded GPS data from the video. Data began at about 1135 near Cheraw, Colorado (4 nm north of LHX) and ended at about 1149 roughly 6 nm south-southwest of LHX. The flight progressed southward for about 8 nm, then turned to a heading of about 153°, then further east to 126°. About one minute before the recording ended, the helicopter was at 37 knots ground speed, 4,265 feet MSL, on a heading of 126°. Using reported wind, airspeed was calculated between 22 and 26 knots. About 30 seconds before end, ground speed was 31 knots at 4,296 feet MSL on heading 128°, with calculated airspeed between 16 and 20 knots.
Video review showed uneventful observation until 1148:28, when wind noise was recorded and the camera jerked slightly. Wind intensified intermittently until 1148:49, when the helicopter began an increasing right yaw. At 1148:54, yaw continued to increase; the camera was retracted. About one second later, the view showed the helicopter inverted. The helicopter descended and impacted the ground at 1148:57.
Helicopter Flying Handbook Reference
According to FAA-H-8083-21A, loss of tail rotor effectiveness (LTE) is defined as an uncommanded, rapid yaw toward the advancing blade that does not subside. The handbook notes that low-speed aerial filming and pipeline patrols are high-risk activities for LTE due to difficulty determining wind direction and speed at low altitudes. It describes weathercock stability affected by tailwinds from 120° to 240° clockwise from the nose, where the helicopter may begin an uncommanded turn. If a right yaw develops with the tail in this region, the yaw rate can accelerate rapidly. The handbook emphasizes maintaining positive control of yaw rate and full attention to flying in such conditions.
No probable cause was determined by the investigation.