On September 12, 2007, a Robinson Helicopter R22 BETA (registration N993KC) operated by Smith Helicopters Inc was involved in an aviation accident near Fort Stockton, TX. Investigators recorded the probable cause as: The failure of the v-belt drive system to the main rotor for undetermined reasons. Contributing to the accident was insufficient altitude to perform a successful autorotation. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A single-engine helicopter experienced a hard landing following a belt drive system malfunction. The pilot heard a loud bang, observed abnormal RPM readings, and performed an autorotation. Investigation found a separated v-belt.
Incident Overview
A single-engine helicopter sustained a hard landing after a malfunction of the belt drive system for the main rotor. The pilot had just taken off from a trailer and transitioned to low-level cruise flight when a loud bang was heard. Cross-checking the engine instruments, the pilot observed that engine RPM was excessively high while rotor RPM was below 80 percent, accompanied by a low rotor RPM warning. An autorotation was initiated, and the helicopter landed hard with near zero forward speed. The aircraft bounced backwards after initial impact and came to rest in the upright position.
Investigation Findings
On-scene investigation revealed that one of the v-belts in the main rotor drive system had separated, which caused the other belt to slip off the upper spindle. The reason for the separation could not be determined.