Robinson Helicopter R44 N544SB accident near Miami Beach, Florida

Probable cause

A loss of engine power due to a stuck valve, which resulted in an autorotation and a hard landing in water.

NTSB analysis

The helicopter pilot was flying about 450 ft above ground level over water paralleling a coastline. The engine suddenly developed a violent shaking and vibration, and engine power was lost. The pilot entered an autorotation, flew toward shallow water, and impacted the water hard about 10 seconds after the onset of the vibration. Examination of the engine revealed no evidence of preimpact mechanical malfunction; however, the examination and teardown were significantly limited due to corrosion as a result of postaccident saltwater immersion.

Engine manufacturer guidance indicated that the helicopter was at an increased risk of stuck valves due to being operated in a region with high ambient temperatures, in addition to operating at lower altitudes and slower airspeeds. Within the year preceding the accident, a total of four engine cylinders had been overhauled and replaced due to stuck valves and low compression. The postaccident examination found no evidence of a stuck intake or exhaust valve. Given the engine’s repeated history of stuck valves and low compression, combined with the pilot’s reported sensations felt during the loss of power, and the lack of any evidence of catastrophic engine failure, it is likely the engine again experienced a stuck valve, which resulted in the loss of engine power and a forced landing in water.

At the time of the accident, the helicopter was 37 flight hours past its manufacturer-required 100-hour inspection interval. Had the inspection intervals been followed, it is possible evidence of valve sticking may have been identified, as it had been several instances within the year before the accident.

Text from the NTSB. Open the NTSB docket for ERA22LA131 for the full record.