Accident Description
On April 28, 2021, at approximately 1324 eastern standard time, a Bell 429 helicopter, registration N53DE, was destroyed in an accident near Eden, North Carolina. The commercial pilot was fatally injured, and two passengers sustained serious injuries. The flight was operated as a Title 14 Code of Federal Regulations Part 91 aerial observation mission.
The helicopter was equipped with a GPMS Foresight MX Health and Usage Monitoring System (HUMS) that captured position, attitude, acceleration, rotor speed (Nr), and engine data during the flight. The HUMS data showed the helicopter departed Danville, Virginia, at about 1233 and flew cross-country southwest into North Carolina. By 1245, the helicopter was conducting a powerline patrol around Eden, flying at an altitude of about 100 feet above the terrain, gaining altitude during turns and between line inspections.
During the final minutes of flight, the helicopter was traveling at an airspeed between 50 and 60 knots parallel to powerlines at an altitude between 700 and 775 feet mean sea level. Rotor speed was near 100%, torque varied between 15% and 25%, and engine gas generator (N1) speeds were between 84% and 88%.
A utility lineman seated in the front left seat recalled that the pilot was reversing course in a banking right turn when he heard a very loud, “cannon-like” noise, and within seconds the helicopter was heading into the trees. Several ground witnesses observed the helicopter flying low over trees along powerlines; one saw it make a right turn before disappearing behind trees. Others described a steep left turn from their vantage point, but the helicopter was actually in a right turn. Witnesses saw the underside and skids before it slid at an angle downward and disappeared into the woods.
Wreckage and Impact
The helicopter impacted wooded terrain at an elevation of 570 feet and came to rest on a heading of about 251° magnetic, approximately 393 feet from the powerlines. A post-crash fire damaged the majority of the fuselage. The debris path was about 200 feet long on a 245° heading, with pieces scattered in multiple directions.
All major components were accounted for. The main rotor hub remained attached, and main rotor blades exhibited impact damage with a “broom straw” appearance at the spars. Three separated leading edge pieces near the tip ends were found. The tail boom fractured into multiple pieces; the tail rotor was partly separated due to fracturing of the output shaft. The tail rotor drive shaft showed fractures and cuts; a 34-inch section was found embedded vertically in the ground.
Flight control system components were examined; servo actuators showed no preimpact anomalies. Both engines (Pratt & Whitney PW207D1) were examined and revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation. Usable data could not be retrieved from the electronic engine controls due to thermal and impact damage.
Flight Data and Investigation
The accident helicopter was not equipped with a cockpit voice/flight data recorder, which was an available option. ADS-B data from the FAA was used alongside HUMS data. However, abnormalities in the recovered HUMS data made attitude and acceleration data unreliable.
A performance study using HUMS, ADS-B, weather data, and published Bell performance data indicated the helicopter was not near the edge of its operating performance envelope for speed, altitude, or temperature. Weather at the time was clear with 10 statute miles visibility. The pilot’s postmortem toxicology showed no findings of a contributory nature. The autopsy report attributed the cause of death to smoke inhalation and thermal injuries with blunt forces contributing.
A LIDAR scan conducted by Duke Energy recorded the location of powerlines and surrounding terrain. Analysis of the accident flight path using HUMS and LIDAR showed the helicopter’s distance from the treetops increasing near the end of recorded data.