What happened
On 30 August 2018, an Airbus Helicopters AS 350, registration VP-CIH, was conducting a 20-minute commercial sightseeing tour around Grand Cayman. The aircraft was carrying one pilot and four passengers. While descending through 500 feet and preparing for the final approach to George Town Aerodrome, the pilot noticed that the tail rotor pedals were failing to produce the expected yaw response.
In response to the control issue, the pilot aborted the initial approach and notified Air Traffic Control of his intention to return to Owen Roberts International Airport. During the subsequent approach, the pilot confirmed that directional control remained unresponsive. He requested fire service attendance and initially planned a run-on landing. After determining that the grass surface was too soft for a safe run-on, the pilot performed another circuit and successfully completed a run-on landing on Runway 26. There were no injuries to the crew or passengers.
The investigation
An examination of the helicopter revealed that the tail rotor gearbox (TGB) actuating rod had suffered a rupture at its aft end. Detailed inspections of the airframe and flight controls, conducted according to manufacturer guidelines, showed no other damage to the aircraft. The manufacturer noted that they had no prior record of such an occurrence on the AS 350 type.
The failed component was sent to the manufacturer for a detailed defect investigation, which was overseen by an investigator from the BEA. The investigation determined that the rupture was linked to the steel sleeve inside the external aluminium alloy tube becoming uncoupled. Investigators identified an anomaly within the internal material structure of the rod, as well as cracks located in a cold worked area.
Findings
- The loss of tail rotor control was caused by the rupture of the tail rotor gearbox actuating rod.
- The failure was associated with the uncoupling of the internal steel sleeve from the external aluminium alloy tube.
- Structural anomalies and cracks in a cold worked section of the rod were present.