Accident Details
On April 27, 2017, about 1330 eastern daylight time, a Robinson R44 II, registration N728CB, operated by Chesapeake Bay Helicopters, was substantially damaged during a collision with terrain while maneuvering near Newton, North Carolina. The commercial pilot and a crewmember sustained minor injuries. The flight was a local aerial observation flight conducted under 14 Code of Federal Regulations Part 91. Visual meteorological conditions prevailed, and a company flight plan was filed. The flight originated from Concord Regional Airport (JQF), Concord, North Carolina, about 1225.
Pilot and Crewmember Accounts
The pilot reported performing a pipeline patrol at 500 ft above ground level and an airspeed of 70 knots. During the patrol, the crew observed a right-of-way infraction and circled the location at the same airspeed and altitude. While extending the circling pattern, the pilot felt a shudder in the controls; simultaneously, the nose of the helicopter yawed right and the helicopter began to spin. The pilot immediately lowered the nose in an attempt to increase forward motion, but the rate of spin increased. He then attempted to set up for an autorotation and avoid residences and utility wires. The helicopter subsequently impacted the ground, and the pilot shut down the engine and exited. The crewmember reported that while on pipeline patrol, they circled to photograph construction work. While circling, the helicopter lost control and spun two or three times before impacting the ground.
Wreckage Examination
Examination of the wreckage revealed substantial damage to the helicopter. Tail rotor driveshaft continuity was confirmed from the tail rotor blades to the main rotor. Continuity was also confirmed from the left anti-torque pedal to the tail rotor. A section of right anti-torque pedal control tube was found bent and separated. The separated section of control tube was retained for metallurgical examination, which revealed that the separation was consistent with overstress due to impact forces. No preimpact mechanical malfunctions were identified.
Maintenance
The helicopter's most recent 100-hour inspection was completed on March 10, 2017. At that time, the airframe and engine had accumulated 1,873.6 total hours of operation. The helicopter had flown an additional 43.6 hours from the time of the inspection until the accident flight.
Meteorological and GPS Information
The recorded wind at an airport located about 10 miles northwest of the accident site, at 1253, was from 190° at 8 knots. Review of GPS data provided by the operator revealed that after completion of the first left circuit and the beginning of the second left circuit, the helicopter's ground speed slowed to about 1 mph at a GPS altitude of 1,223 ft (about 500 ft above ground level). At that time, the GPS track indicated a northerly course, with an approximate 8-knot tailwind. The track subsequently indicated a transition from a left circuit to a right turn.
Relevant FAA Advisory Circular and Safety Notice
The Federal Aviation Administration issued advisory circular (AC)-90-95, "Unanticipated Right Yaw in Helicopters," during February 1995. The AC stated that loss of tail rotor effectiveness (LTE) is a critical, low-speed aerodynamic flight characteristic that can result in an uncommanded right yaw rate that does not subside on its own and, if not corrected, could result in loss of aircraft control. It also noted that LTE is not related to a maintenance malfunction and may occur in varying degrees in all single main rotor helicopters at airspeeds less than 30 knots. The AC provided recommendations to reduce the onset of LTE, including avoiding tailwinds when maneuvering between hover and 30 knots, avoiding out-of-ground-effect hover and high-power demand situations such as low-speed downwind turns, and being especially aware of wind direction and velocity when hovering in winds of about 8–12 knots. Recovery techniques included applying full left pedal, moving cyclic forward, and reducing power if altitude permits, with autorotation as a possible course of action if rotation cannot be stopped and ground contact is imminent. Additionally, Robinson Safety Notice SN-34 addressed aerial survey and photography flights and provided cautions about such flights below 30 knots airspeed.