Aviation safety investigations & reports

Main rotor speed decay and forced landing involving Robinson R44, VH-HGX, 5 km south Ayers Rock Airport, Northern Territory, on 17 January 2018

Investigation number:
Status: Active
Investigation in progress


Updated: 17 January 2020

The investigation into the main rotor speed decay and collision with terrain involving Robinson R44, VH-HGX, 5 km south Ayers Rock Airport, Northern Territory, on 17 January 2018 is continuing.

The investigation report is currently in the ‘Final report: External review’ phase. During this phase, to check factual accuracy and ensure natural justice, Directly Involved Parties (DIPs) are given the opportunity to comment on the final report before it is approved to ensure their input has been accurately reflected.

DIPs are individuals or organisations outside the ATSB who possess direct knowledge of the circumstances surrounding the incident or accident. DIPs can only comment on the factual accuracy of an investigation, not its analysis and findings.

Following the DIPs process, the report is approved by management before being sent to the ATSB Commission for final approval. Once approved, the final report is prepared for publication and dissemination and released to DIPs prior to its public release.

Updated: 9 May 2018

Factual information

On 17 January 2018, at about 1821 Central Standard Time,[1] a Robinson R44 helicopter, registered VH-HGX, departed from the Yulara Town helipad, Northern Territory, for a 15-minute scenic flight with one pilot and three passengers on board. This was the third scenic flight for the pilot in VH-HGX since the last refuel that afternoon.[2] Shortly after take-off, and while flying over trees, the helicopter’s engine speed and main rotor speed began to decay. The low rotor speed warning horn activated.[3] In response, the pilot advanced the throttle, but was unable to recover the rotor speed, which continued to decay. About 30 seconds after departing, the pilot broadcast a MAYDAY[4] call and conducted an emergency landing. The pilot in the front right seat and passenger in the rear right seat sustained serious injuries in the landing. The two passengers seated in the front and rear left seats sustained minor injuries. The helicopter was substantially damaged.

Video footage review

A rear seat passenger provided video footage for the first 17 seconds of the flight. A review of that footage found that:

  • The engine speed and rotor speed decayed simultaneously.
  • The low rotor speed warning horn activated at about 22.5 inches manifold pressure at a height of about 30 ft and airspeed of about 26 kt. At this time, both airspeed and power were increasing.
  • About 3–4 seconds after the warning horn activated, engine power reached about 24 inches manifold pressure.
  • About 12 seconds after the warning horn activated, the engine power can be seen at 25–26 inches manifold pressure. At this time, the helicopter had an airspeed of about 33 kt and about 80 per cent engine and rotor speed (matched).

Helicopter performance

Ayers Rock Airport is at 1,626 ft elevation. At 1830, the airport weather data recorded a temperature of 38 °C, QNH 1007[5] and wind of 9 kt from 080°. According to the Robinson R44 pilot operating handbook the maximum continuous power limit was about 24.2 inches manifold pressure. A further 1.6 inches manifold pressure can be added to maximum continuous power for a 5 minute maximum take-off power of about 25.8 inches manifold pressure for the environmental conditions at the time of the accident.

Maintenance and inspections

A scheduled 100-hourly inspection was completed on the helicopter on 15 January 2018. Following the accident, an independent inspection and test of the right magneto and associated wiring was conducted by the insurance surveyor (the signal source for the throttle governor is the engine right magneto secondary points). The right magneto secondary points were about 1/1000th of an inch below the lower limit, but otherwise no fault was found and the magneto tested serviceable to a multi-meter check. No fault was found with the associated wiring.

Ongoing investigation

The ATSB will continue to work with the helicopter operator, insurance surveyor and manufacturer (via the accredited representative) for possible further inspection and testing of the governor control unit.



The information contained in this update is released in accordance with section 25 of the Transport Safety Investigation Act 2003 and is derived from the initial investigation of the occurrence. Readers are cautioned that new evidence will become available as the investigation progresses that will enhance the ATSB's understanding of the accident as outlined in this web update. As such, no analysis or findings are included in this update.



  1. Central Standard Time (CST): Coordinated Universal Time (UTC) + 9.5 hours.
  2. Three passengers were taken on each flight.
  3. The low rotor speed warning horn activates at 97 per cent rotor speed.
  4. MAYDAY: an internationally recognised radio call announcing a distress condition where an aircraft or its occupants are being threatened by serious and/or imminent danger and the flight crew require immediate assistance.
  5. QNH: the altimeter barometric pressure subscale setting used to indicate the height above mean sea level.
General details
Date: 17 January 2018   Investigation status: Active  
Time: 18:00 CST   Investigation level: Defined - click for an explanation of investigation levels  
Location   (show map): Ayers Rock Airport, 5 km South   Investigation phase: Final report: Approval  
State: Northern Territory   Occurrence type: Engine failure or malfunction  
Release date: 09 May 2018   Occurrence category: Accident  
Report status: Pending   Highest injury level: Serious  
Anticipated completion: 3rd Quarter 2020    

Aircraft details

Aircraft details
Aircraft manufacturer Robinson Helicopter Co  
Aircraft model R44  
Aircraft registration VH-HGX  
Serial number 0762  
Operator Professional Helicopter Services  
Type of operation Charter  
Sector Helicopter  
Damage to aircraft Substantial  
Departure point Ayres Rock, Northern Territory  
Destination Ayres Rock, Northern Territory  
Last update 07 August 2020