Accident Overview
On March 26, 2022, at 1715 eastern daylight time, a Robinson R44 helicopter, registration N288L, was substantially damaged during an accident near Myrtle Beach, South Carolina. The pilot and three passengers were not injured. The flight was conducted under Title 14 Code of Federal Regulations Part 91 as a sightseeing tour.
Pilot Report
The pilot reported that he had been flying tours all day, totaling about 40 flights, with all but two in another company helicopter. The accident helicopter had also been flown about 40 flights by another pilot earlier that day. After a shift change, the accident pilot performed a preflight inspection and took a break due to wind conditions. After the break, he completed one uneventful flight in the accident helicopter. On the accident flight, shortly after takeoff at about 500-700 ft above ground level, the helicopter began vibrating. The pilot described the vibration as "very violent, like a brick in a [clothes] dryer, but three times more violent." The vibration seemed to come from behind him, shook the airframe in all directions, and was not isolated to any one control. The pilot noticed erratic tachometer rpm readings and that the helicopter was no longer climbing. He entered an autorotation and confirmed a full split of the engine/rotor tachometer needles. The vibration continued throughout the autorotation. During the approach, he flared and pulled collective to cushion the landing; the helicopter landed on its skids and slid on pavement before impacting a dirt mound and rolling onto its left side. Neither the pilot nor passengers were injured.
Post-Accident Examination
Initial examination by a Federal Aviation Administration inspector revealed that the tail boom was separated about 3 ft forward of the tail rotor gearbox. The tail rotor blades remained intact and attached, with one blade bent about 8 inches from the tip. The tail rotor gearbox rotated smoothly; the chip detector was debris-free, and the drive shaft and controls were intact. Main rotor blades were slightly bent but mostly undamaged, with no delamination. The main gearbox rotation showed slight binding; its chip detector was free of debris. The main rotor blade pitch change links were fractured, with ends attached to attach points. Flight controls were intact from cockpit to the fractured links. Upper and lower drive sheaves and belts appeared undamaged.
Examination of the engine showed secure mounts, normal magneto operation, and normal valve movement. Cylinder compression ranged from 68 psi (#5) to 79 psi (#3, #4). A borescope examination revealed normal wear and carbon buildup. The engine was test run successfully with a slight vibration. Fuel samples from main and auxiliary tanks were unremarkable.
A subsequent examination by the National Transportation Safety Board and manufacturer representatives found no preimpact anomalies or malfunctions that would have precluded normal operation. No airframe anomalies were noted. A postaccident engine test run for about 20 minutes showed slight roughness until warm-up. Exhaust pipe temperatures ranged from 650°F to 750°F. An investigator in the pilot seat felt roughness and observed small tachometer needle oscillations. Occasional "chuff" sounds from the exhaust at high power were noted. A magneto check showed an rpm drop of about 12% from each magneto. After heat-soak cycles, the engine ran smoother. Compression checks after testing showed values from 62 psi (#4) to 78 psi (#1).
Maintenance Records
At the time of the accident, the engine had accrued 3,318 total hours and 1,118 hours since overhaul. Since overhaul, three maintenance entries indicated valve inspections per Lycoming mandatory service bulletin SB-338C (preventive maintenance to reduce stuck/broken valves due to carbon buildup). All were performed within the 400-hour interval; the last occurred about 5 weeks and 85 flight hours before the accident.