History of Flight
On July 11, 2008, at 1232 eastern daylight time, a Schweizer 269C-1, N61425, was substantially damaged when it collided with terrain during a forced landing near Northumberland, Virginia. The certificated commercial pilot and the passenger were not injured. Visual meteorological conditions prevailed for the local flight that originated at Hummel Field (W75), Saluda, Virginia. No flight plan was filed for the aerial survey flight conducted under 14 Code of Federal Regulations Part 91.
The pilot reported that the helicopter was full of fuel and hovering 100 feet above ground level when it encountered a headwind registering 20 knots on the airspeed indicator. The helicopter shuddered, the nose yawed to the right, and application of the left anti-torque pedal had no effect as the helicopter began to rotate around the main rotor mast. The pilot initially increased collective pitch to climb away from trees, then applied forward cyclic to lower the nose and increase forward airspeed. This slowed the rate of rotation during descent, but upon ground contact, the landing skid caught and the helicopter rolled onto its side.
The pilot stated that he did not run out of pedal; rather, he had no left or right pedal effectiveness. Examination of GPS track data showed an S-shaped track that eventually oriented the helicopter into a quartering-tailwind condition above the crash site.
Personnel Information
The pilot held a commercial pilot certificate with a rating for rotorcraft helicopter and a private pilot certificate for airplane single engine land. His most recent second-class medical certificate was issued on May 29, 2008. He reported 424 total flight hours, with 200 hours in helicopters, nearly all in make and model.
Aircraft Information
The helicopter's most recent annual inspection was completed on July 3, 2008, at 4,657 aircraft hours. The pilot reported about 4 flight hours between the inspection and the accident.
Meteorological Information
At 1240, weather recorded at Middle Peninsula Regional Airport (KFYJ), 20 miles west of the site, included clear skies, visibility 10 miles, wind from 160 degrees at 5 knots, temperature 30°C, dewpoint 20°C, and altimeter 30.09 inHg.
Wreckage and Impact Information
Examination in Clayton, Delaware on August 5, 2008, revealed that the main rotor blades had been removed. Cyclic and collective control continuity was established from controls to main rotor head. Tail rotor control continuity was established from pedals to tail rotor, but rigging could not be positively established due to airframe deformation and a break at the tailboom forward bulkhead attachment with overload fracture signatures. Tail rotor drive continuity was decoupled at the main transmission output due to impact; locknut safety wire was broken and threads exposed. The tail rotor driveshaft and gearbox were removed; main transmission pinion drive spline was secure and undamaged; driveshaft couplings were intact with no damage or abnormal wear. The tail rotor pitch control was undamaged with no abnormal wear; tail rotor blades showed minor tip cap damage. The belt drive transmission was intact and undamaged; electrical power actuated the linear clutch smoothly. The main transmission rotated smoothly to the main rotor head when turned by hand. Engine start using battery power and the helicopter's fuel system resulted in immediate idle; acceleration to 2,500 rpm showed manifold pressure 11 inches and oil pressure in normal range; magneto check was within parameters.
Additional Information
Examination of performance planning charts indicated that atmospheric conditions provided in-ground-effect performance up to 2,000 feet mean sea level; out-of-ground effect charts were not available or required. The U.S. Army's TH-55A Operator's Manual described loss of tail rotor effectiveness (LTE) as a situation involving loss of effective tail rotor thrust without drive system break, likely occurring at hover due to out-of-ground effect hover, high pressure altitude/high temperature, adverse wind conditions, engine rpm below 2900, or improperly rigged tail rotor. Indications include a slow starting right turn unresponsive to full left pedal. The procedure is to lower collective to regain control and touchdown. FAA Advisory Circular 90-95 described LTE as a critical low-speed aerodynamic characteristic resulting in uncommanded rapid yaw, not related to maintenance malfunction, occurring in all single main rotor helicopters below 30 knots. Conditions include high-power, low-airspeed environments with left crosswind or tailwind. At airspeeds below translational lift, the tail rotor provides nearly 100 percent directional control; if thrust is unavailable, the aircraft yaws right. Recommendations include avoiding tailwinds and out-of-ground effect hover, and being aware of wind direction and velocity.