Accident Details
On 16 May 2022, a Robinson R44 helicopter, registered VH-KOV and operated by Wellspring Rural Services Pty Ltd, was conducting sightseeing flights over Limmen National Park, Northern Territory. The helicopter carried a pilot and three passengers. During cruise flight, the pilot detected vibrations and observed the engine RPM rise then drop to zero. Assessing an engine failure, the pilot initiated an autorotation, but the helicopter collided with terrain. Two passengers sustained serious injuries; the pilot and the remaining passenger sustained minor injuries. The helicopter was substantially damaged.
Investigation Findings
The Australian Transport Safety Bureau (ATSB) found that the clutch actuator lower bearing seized during flight, resulting in a total loss of drive from the engine to the rotor system. The bearing had not been maintained in accordance with the manufacturer's procedures, which likely caused its failure. Evidence showed dried grease on the lower sheave, indicating grease leakage or over-greasing for an extended period. The bearing was also nearing the end of its service life. The specific failure cause could not be determined due to damage extent, but inconsistent lubrication was probable.
The investigation also found that the passengers did not receive a pre-flight safety brief, leaving them unaware of emergency procedures and safety equipment. In December 2021, the Civil Aviation Safety Authority (CASA) released CASR Part 133, introducing changes to air transport passenger carrying operations in helicopters. Several changes were not effectively communicated to operators. The new regulations required passenger briefings on brace positions specific to aircraft type, but CASA did not provide guidance for helicopters like the R44 with three-point harnesses.
Additionally, the emergency locator transmitter (ELT) activated 10 hours after the accident. It was not being maintained, and the operator had not been advised. Robinson Helicopter maintenance procedures and CASA guidance lacked clear instructions for ELT maintenance in helicopters.
Safety Actions
In response, the maintainer contacted operators to ensure awareness of the ELT maintenance issue and advised carrying personal locator beacons. CASA updated Airworthiness Bulletin 02-002 to include ELT maintenance guidance. The ELT manufacturer corrected a discrepancy between the service letter and installation manual regarding self-test requirements. CASA also released revised advisory circulars including specific brace position guidance for helicopters with three-point harnesses.