An ATSB preliminary investigation into an R44 that crashed on 4 July, killing two on board, has revealed its tail rotor and gearbox broke off within a second of witnesses hearing a bang.
The components, since recovered, are still being analysed but early X-rays found no evidence of internal damage. The early findings appear to corroborate CCTV footage obtained within days of the accident, that the ATSB have refused to release due to the “distressing nature” of the accident.
The tragic incident in the Kimberley region of WA killed the founder of a West Australian seaplane tour company, Troy Thomas, and a 12-year-old girl. The pilot’s daughter survived and a 24-year-old woman was airlifted to hospital in a critical condition.
“The ATSB will continue to extensively examine and analyse the recovered components as it seeks to determine the contributing factors behind the in-flight break-up,” said the ATSB’s director of transport safety, Dr Mike Walker.
The report details how the R44 departed a yard in the Broome industrial suburb of Bilingurr for a private local scenic flight.
As the helicopter reached a height of about 55 feet, witnesses heard a bang, which one described as sounding similar to a metal bar striking a metal pole.
Footage from a nearby CCTV camera showed that the R44’s aft tail cone bulkhead, empennage, tail rotor gearbox and tail rotor assembly all “separated” from the helicopter in about one second.
The helicopter climbed to around 75 feet while rotating rapidly to the right, before spinning and crashing to the ground on its right side, about 30 metres from the departure point.
The pilot, who owned the helicopter, and a passenger, both seated on the right side of the helicopter, were killed, while the front left seat and rear left seat passengers were seriously injured. The helicopter was destroyed.
The preliminary report details that on 29 June the R44 was ferried from Bilingurr to Broome Airport, where it was fitted with a tracking system.
“That pilot reported feeling a vibration in the tail rotor pedals that felt like someone tapping the pilot’s feet with spoons. The sensation was noticeable yet not strong enough to cause significant alarm,” said Dr Walker.
Three days later the helicopter’s owner, accompanied by a passenger, returned the helicopter to Bilingurr, where on landing the owner also reported feeling vibrations in the pedals, and requested maintenance engineers inspect the helicopter.
Subsequently, on 3 July, a maintenance engineer visually inspected the R44’s flex plate, empennage, gearbox, pitch links and tail rotor assembly, and found no defects.
In addition, the maintenance engineer and an apprentice used electronic dynamic balancing equipment to measure the dynamic balance of the tail rotor, which was found to be within limits.
A maintenance pilot started the helicopter, and while ground running the R44 could not feel any vibration through the pedals. In addition, the maintenance engineer leant into the cabin and placed their hands on the pedals, and also could not feel any vibration.
Due to the confined nature of the yard, and concerns over securing the site, the maintenance pilot elected not to test fly the helicopter, and so the tail rotor system was not assessed under load.
The maintenance pilot stated separately advising the pilot who originally detected the vibration and the owner that the engineers had not detected a vibration, and that the tail rotor was in balance.
The maintenance pilot also stated that the owner was told that no changes were made to the balance weights, that the helicopter had not been flown, and that an instruction from the engineer to conduct a check flight was relayed.
The accident flight was conducted the following day, with the helicopter owner as the pilot.
“It is not clear whether the pilot experienced any vibrations through the pedals at the time of the accident flight,” Dr Walker said. “Nevertheless, the ATSB urges any R44 pilot who experiences unusual vibrations through the tail rotor pedals to land as soon as possible and follow the advice in the pilot’s operating handbook.”
The R44 pilot’s operating handbook advises that a “change in the sound or vibration of the helicopter may indicate an impending failure of a critical component. If unusual sound or vibration begins in flight, make a safe landing and have the aircraft thoroughly inspected before flight is resumed”.
The ATSB said it will review policies and procedures for maintenance check flights, and examine related occurrences involving the R44.
“While the investigation is continuing, should a critical safety issue be identified at any time, the ATSB will immediately notify relevant parties so appropriate and timely safety action can be taken,” said Dr Walker.
Australian Aviation earlier reported that pilot Thomas, 40, set up Horizontal Falls Seaplane Adventures in 2006 before selling it last year to tourism group Journey Beyond. However, he was retained for one year as a manager.
The group had been on their way to a family holiday when the helicopter crashed shortly after take-off.
Thomas’ friend Karl Langdon, a sports commentator, had breakfast with the pilot hours before his death.
In a tribute on Sunday, he wrote, “To Sophie, the kids and whole Thomas clan I’m mourning with you today. I still cannot believe what has happened. We lost an inspiring father, brother, son and friend yesterday.”