Hughes 369 N105JL accident near Riverside, California

Probable cause

The instructor’s delayed remedial action to an excessive descent rate during a simulated autorotation, which resulted in a hard landing.

NTSB analysis

The pilot receiving instruction was performing a full-touchdown, 180° autorotation when the instructor noted that the helicopter was going to be short of the intended landing zone and advanced the throttle to initiate a power recovery. The helicopter continued to descend and landed hard and rolled over, resulting in substantial damage. The instructor reported no mechanical malfunctions with the helicopter or engine that would have precluded normal operation. It is likely that the instructor’s delayed response to the helicopter’s excessive rate of descent resulted in the hard landing.

After egressing the helicopter, the instructor noted that the pilot receiving instruction had been ejected from the helicopter during the accident sequence. Examination of the restraint systems revealed that the cotter pins for the hook-end fitting that attached to the airframe seat belt fittings had not been installed. The centrifugal force generated by the rotation of the helicopter during the accident sequence was likely sufficient for the hook-end fitting, void of the cotter pin, to separate from the seat belt fitting, which then resulted in the student being ejected from the helicopter. As a result of the accident, the manufacturer issued a mandatory service bulletin requiring the installation of cotter pins in the seat belt assemblies.

Text from the NTSB. Open the NTSB docket for WPR18LA226 for the full record.