Robinson Helicopter R22 BETA N74603 accident near West Melbourne, Florida

Probable cause

Separation of the main rotor drive belts due to maintenance personnel’s failure to adequately inspect the upper drive sheave prior to installing the belts.

NTSB analysis

During takeoff, while the helicopter was about 80 to 100 feet above the ground, the clutch caution light illuminated. The light stayed lit only long enough for the pilot to notice it, and then it turned off. The clutch light illuminated once again, and the pilot felt the helicopter vibrate. The pilot initiated a descent and heard a loud “pop and grinding noise” from the rear of the helicopter as he lowered the collective. The pilot autorotated and impacted the ground in a nose-low attitude. A postaccident examination of the drive system found that the grooves in the upper sheave were worn beyond serviceable limits. The helicopter’s maintenance manual requires inspection of the sheaves prior to installation of the drive belts. An entry in the logbook states that the drive belts were removed and replaced 22.9 hours prior to the accident. Given the level of wear in the upper sheave grooves, it is unlikely that maintenance personnel inspected the sheave prior to drive belt installation.

Text from the NTSB. Open the NTSB docket for ERA10LA361 for the full record.