Preliminary report published 2 September 2020
On 4 July 2020, at 1428 Western Standard Time, a Robinson Helicopter Company R44 Raven I, registered VH-NBY, was operated for a local scenic flight in Broome, Western Australia. The flight was conducted as a private operation under visual flight rules. On board were the pilot and three passengers.
The departure was from a confined, concreted area within an industrial property in Bilingurr, about 3 km north-north-east of Broome Airport. Nearby buildings, high fences, vehicles, and trees necessitated a vertical departure, and the pilot was familiar with the site.
The pilot started the helicopter, and it remained on the ground for 7 minutes, during which time the pilot arranged clearance for departure from air traffic control. Witnesses reported that the pilot then lifted the helicopter into a low hover for a few seconds before conducting a steep departure.
Three witnesses who were familiar with this departure process stated that nothing appeared out of the ordinary. None of the witnesses saw or heard the helicopter make contact with any obstacles or foreign objects.
As the helicopter reached a height of about 55 ft, witnesses heard a bang. One witness described the sound as similar to a metal bar hitting a metal pole. A recording from a fixed security camera nearby showed that the 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 ft while rotating rapidly to the right, before rolling and impacting the ground on its right side, about 30 m from the departure point (Figure 1).
The pilot and a passenger, both seated on the right side, were fatally injured. The front left seat and rear left seat passengers were seriously injured. The helicopter was destroyed.
Source: Google Earth, annotated by the ATSB
The pilot obtained a Private Pilot Licence (Helicopter) in May 2015. A family member estimated the pilot’s total flight hours to be between 1,200 to 1,500 hours, mostly on R44 helicopters. The pilot was also the owner of the aircraft.
The Robinson R44 is a four-place, single piston engine helicopter. The R44 was certified in December 1992 and the R44 Raven I was introduced in January 2000. As of the time of the accident, there were 558 R44s on the Australian civil aircraft register.
The R44 Raven I helicopter involved in the accident, serial number 2544, was built in May 2018 in the US. It was disassembled and shipped to Australia by the manufacturer.
The helicopter was first placed on the Australian register as VH-NBY on 28 August 2018. It was reassembled in Queensland in September 2018.
The helicopter was used privately for the first 52.5 flight hours, and spent time in Broome and Timor-Leste. In March 2019 it was transferred to an operator for tourism work at the Horizontal Falls area in Western Australia. During that time two warranty issues were resolved. A seatbelt reel tensioner was replaced in May 2019, and the helicopter’s battery was replaced in July 2019. Also in July 2019, the helicopter was provisioned with an external cargo hook, and it was used for occasional external load operations as well as tourism work after that time.
In October 2019, during a periodic inspection, the tips of the leading edge of the tail rotor blades were painted. This was to repair dust erosion and protect the blades from the sandy, coastal environment. After this inspection, the helicopter returned to private use.
At the time of the accident, the helicopter had 291.0 recorded hours in service.
Recent flights and maintenance
On 4 June 2020, with 286.9 recorded hours in service and 38.1 hours since the last periodic inspection, VH-NBY underwent a periodic inspection and an engine cylinder replacement. The inspection was conducted early because the owner planned to operate the aircraft in a remote location, and needed the maximum time available before the next scheduled maintenance visit. Following the maintenance, a pilot from the approved maintenance organisation conducted a maintenance check flight. This flight took 0.3 hours and the pilot found no anomalies.
The helicopter was collected by a pilot who flew from Broome to Horizontal Falls and then back to Broome. This trip took an estimated 3.0 hours.
On 29 June 2020, the same pilot made a short flight of around 0.1 hours from the industrial area in Bilingurr, where the helicopter was stored, to Broome Airport, where it was to be 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. After the flight, the pilot reported the vibration to the helicopter’s owner.
On 2 July 2020, the owner of the helicopter flew the helicopter with a passenger back to the industrial estate via Cable Beach. This flight took around 0.3 hours. After landing, the pilot who first felt the vibration approached the helicopter and discussed the problem with the owner who was still at the controls. The owner stated also having felt the vibration and requested the pilot to arrange engineers to look at it.
The two pilots thought the cause of the vibration was uneven application of paint on the tail rotor at the recent periodic inspection, not realising at the time that the tail rotor was not painted at that inspection, and advised the maintenance personnel of their opinion.
Maintenance activities on site
A licenced aircraft maintenance engineer (engineer), a helicopter pilot (maintenance pilot), and an aircraft maintenance engineering apprentice, all from the approved maintenance organisation, travelled to the industrial estate on the afternoon of 3 July 2020. The owner of the helicopter discussed the vibration problem, then departed the site. Neither of the pilots who had experienced the vibration were present during the inspection.
The engineer visually inspected the flex plate, empennage, gearbox, pitch links, and tail rotor assembly, and found no defects. The engineer and apprentice then used electronic dynamic balancing equipment to measure the dynamic balance of the tail rotor. A sensor was fitted to the top right of the cap that covered the seal around the tail rotor drive shaft.
The maintenance pilot started the helicopter, and could not feel any vibration through their feet from the pedals. The engineer leant in and placed their hands on the pedals, and could not feel any vibration.
The system measured the total vibration level of the tail rotor in inches per second (IPS). The helicopter manufacturer’s balance limit was 0.20 IPS. The tail rotor assembly on VH-NBY measured 0.05 IPS, and therefore the engineer did not need to adjust the tail rotor balance.
The maintenance pilot, who ran the helicopter on the ground, assessed the confined area where the helicopter was stored. As access to the site could not be controlled and the security of objects around the site was uncertain, the pilot elected not to fly the helicopter within the confined area. This meant that tail rotor system could not be not assessed for vibration under load.
The engineer sanded a small amount of paint from the tips of the tail rotor and ran the test again, finding no significant change to the balance. The sensor was removed, the original bolt replaced, torqued to specification with a calibrated tool, lock wire applied, and its security independently inspected.
The engineer and apprentice moved the helicopter on ground handling wheels towards its hangar. This required the person steering the helicopter to handle the helicopter by the tail rotor gearbox, output shaft, and the stinger under the vertical fin (Figure 2). Force was required to lever the front of the skids from the ground, and steer the helicopter. Moving the helicopter did not reveal any movement in the tail rotor gearbox or any other unusual signs.
The maintenance pilot called the pilot who originally detected the vibration and the owner of the helicopter one after the other at about 1600 on 3 July 2020. The maintenance pilot stated that the pilot who originally detected the vibration and the owner were advised separately that the engineers had not detected a vibration, and the balance of the tail rotor was good. 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 relayed an instruction from the engineer to conduct a check flight.
Site and wreckage examination
On-site evidence indicated that the engine was producing power at the time of the occurrence, and there were no signs of contact with obstacles. The helicopter displayed no evidence of pre-existing damage to control linkages, and the tail rotor gearbox shafts could be rotated without resistance. All components from the helicopter were found at the accident site. There was no indication of any fire.
Numerous components were recovered for further examination (Figure 3 and Figure 4).
The ATSB developed a scope of work for examining the recovered components and determining factors associated with the in-flight failure. Representatives of the aircraft operator, maintenance organisation, Robinson Helicopter Company (the helicopter manufacturer), Civil Aviation Safety Authority, and Western Australia Coroner were invited to observe the disassembly of the tail rotor gearbox at the ATSB’s technical facilities in Canberra, Australian Capital Territory. Due to limitations associated with COVID-19 restrictions, attendance was through a remote video link.
Prior to its disassembly, the tail rotor gearbox was non-destructively X-rayed and exhibited no evidence of internal damage. No definitive results from other examinations are available at this stage.
In section 10 of the R44 pilot’s operating handbook (POH), the manufacturer included the following safety tip:
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. Hover the helicopter close to the ground to verify the problem is resolved, and then have aircraft reinspected before resuming flight.
It is not clear whether there were any vibrations present at the time of the accident flight. Nevertheless, the ATSB reiterates its strong endorsement of this advice, and urges any pilot that experiences unusual vibrations through the tail rotor pedals to land as soon as possible and follow the advice in the flight manual (POH).
At the time of the accident, the recorded weather conditions at Broome Airport were a light wind of 9 kt from the east, good visibility and a temperature of 33 °C.
The ATSB investigation is continuing. Further investigation will include consideration of:
- detailed technical examination of the retained components
- collection and examination of further components from the aircraft
- the helicopter’s construction, assembly, flight and maintenance history
- analysis of security and other video files
- policies and procedures for maintenance check flights
- related occurrences in Australia and overseas.
The ATSB will continue to consult the helicopter manufacturer, accredited representatives from the United States National Transport Safety Board (NTSB), and any other international agency who has encountered related occurrences.
Should a critical safety issue be identified during the course of the investigation, the ATSB will immediately notify relevant parties so appropriate and timely safety action can be taken.
A final report will be released at the conclusion of the investigation.
The ATSB would like to acknowledge the significant assistance provided during the initial investigation response by the Western Australia Police Force in recording, securing and maintaining the integrity of the accident site prior to the ATSB team’s arrival.
This preliminary report details factual information established in the investigation’s early evidence collection phase, and has been prepared to provide timely information to the industry and public. Preliminary reports contain no analysis or findings, which will be detailed in the investigation’s final report. The information contained in this preliminary report is released in accordance with section 25 of the Transport Safety Investigation Act 2003.
Update: 10 July 2020
Update: 10 July 2020
Based on closed-circuit television (CCTV) footage and an examination of the wreckage, the ATSB investigation into the fatal R44 helicopter accident near Broome Airport on 4 July 2020 has determined that the helicopter experienced an in-flight breakup. The tail rotor gearbox assembly, tail rotor and empennage assembly separated soon after the helicopter lifted off. The fuselage then fell to the ground out of control.
The ATSB has conducted a detailed examination of the entire aircraft at Broome, and is transporting relevant components back to Canberra for more detailed examination. These components include the tail rotor gearbox, tail rotor, empennage, tail cone, tail rotor drive shaft, and flight controls. During this process, the ATSB has been consulting with the Robinson Helicopter Company (the helicopter manufacturer), the US National Transportation Safety Board and the Australian Civil Aviation Safety Authority.
Images of the components that separated are provided at the end of this update. The ATSB will not be releasing the CCTV footage due to its potentially distressing nature. The ATSB is providing access to the footage to relevant experts to assist with the investigation.
The ATSB has interviewed a pilot who recently flew the helicopter and maintenance personnel who conducted maintenance on the helicopter. It has also obtained copies of the helicopter’s maintenance records and reviewed other documentation. Based on this information:
- The R44 Raven I helicopter involved in the accident (serial number 2544) was manufactured in 2018. It was imported new into Australia and was first registered on the Australian civil aircraft register in August 2018.
- The helicopter underwent its last periodic (100 hourly) inspection on 4 June 2020, with 286.9 hours total time in service.
- A pilot who flew the helicopter on 2 July 2020 to Broome Airport reported feeling unusual vibrations through the tail rotor pedals. He described it as if something was repetitively tapping through the pedals. The pilot of the accident flight also conducted a short flight in the helicopter and confirmed the unusual vibrations.
- Maintenance personnel conducted a dynamic tail rotor balance on 3 July 2020 (the day before the accident). The dynamic tail rotor balance was found to be within limits, and the maintenance personnel could not detect any unusual vibration on the ground.
- The accident flight was the first flight since the maintenance was conducted. Overall, the helicopter had 291 recorded hours in service.
- The Robinson R44 was certified in December 1992 and the R44 Raven I was introduced in January 2000. There are currently 558 R44s on the Australian civil aircraft register.
In the initial phase of its investigation, the ATSB is focussed on examining the wreckage, reviewing the CCTV footage and reviewing potentially related occurrences.
At this stage the reasons for the in-flight breakup are not known. The ATSB will provide further advice when relevant information is available.
Pilot advisory information
The R44 Pilot’s Operating Handbook (POH) includes the following 'safety tip':
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. Hover helicopter close to the ground to verify problem is resolved, and then have aircraft reinspected before resuming free flight.
The ATSB strongly endorses this advice, and urges any R44 pilot that experiences unusual vibrations through the tail rotor pedals to land as soon as possible and follow the advice in the POH safety tip.
Images of the separated components
The following images show the empennage (Figure 1), the tail rotor gearbox (Figure 2), the tail cone (Figure 3), and the tail rotor (Figure 4).
This update details factual information established in the investigation’s early evidence collection phase, and has been prepared to provide timely information to the industry and public. It contains no analysis or findings, which will be detailed in the investigation’s final report. The information contained in this update is released in accordance with section 25 of the Transport Safety Investigation Act 2003.
The ATSB is investigating a collision with terrain involving a Robinson R44 helicopter, registered VH-NBY, near Broome Airport, Western Australia, on 4 July 2020.
The helicopter was departing from Bilingurr, about 2 km north of Broome Airport, with the pilot and three passengers on board. Soon after lifting off, the helicopter collided with terrain. The pilot and one passenger were fatally injured and the other two passengers were seriously injured.
Transport safety investigators with experience in helicopter operations, helicopter maintenance and aircraft systems from the ATSB’s Perth and Brisbane offices will examine the wreckage and the accident site.
The ATSB will also analyse any available recorded data and interview witnesses. In addition, the ATSB will review aircraft maintenance and operational records, pilot records and weather information.
A preliminary report will be released within about 30 days of the accident. A final report will be published at the conclusion of the investigation.
Should any safety critical information be discovered at any time during the investigation, the ATSB will immediately notify operators and regulators so appropriate and timely safety action can be taken.
|Date:||04 July 2020||Investigation status:||Active|
|Time:||1436 WST||Investigation level:||Defined - click for an explanation of investigation levels|
|Location:||Bilingurr, 3 km NNE of Broome Airport||Investigation phase:||Examination and analysis|
|State:||Western Australia||Occurrence type:||In-flight break-up|
|Release date:||02 September 2020||Occurrence category:||Accident|
|Report status:||Preliminary||Highest injury level:||Fatal|
|Anticipated completion:||3rd Quarter 2021|
|Aircraft manufacturer||Robinson Helicopter Co|
|Type of operation||Private|
|Damage to aircraft||Destroyed|
|Departure point||Bilingurr, Western Australia|
|Destination||Bilingurr, Western Australia|