What happened
On 24 January 2025, at about 1338 local time, the pilot of a Robinson R22 helicopter was conducting cattle‑mustering operations near Brunette Downs Station, Northern Territory. The pilot was the sole occupant onboard and the helicopter’s doors had been removed. Weather conditions were clear, with a temperature of about 38°C. During mustering, the pilot landed in the open flat ground behind the cattle to rehydrate. The collective[1] was in the full down position while the engine remained at 100% RPM and the pilot held the cyclic[2] between their legs with no flight control frictions engaged.
As the pilot took a sip from their water bottle, they felt the helicopter shake. They then put the bottle down, but the left skid was at this point already a few inches off the ground. They then tried to correct the tilt with left cyclic and reached for the collective, but the helicopter continued to roll to the right. When the helicopter rolled through about 45 degrees the pilot attempted to stop the roll by placing their right foot outside the helicopter and pushing against the ground. The main rotor then contacted the ground, followed by the engine stopping and the aircraft coming to rest on its right side (Figure 1), with the pilot’s right foot trapped underneath the fuselage.
Figure 1: The occurrence R22 helicopter
Source: Operator supplied
The pilot was able to extricate their foot out from underneath the helicopter, closed the fuel mixture control and switched off the battery master as they exited.
The helicopter was substantially damaged in the accident, with damage to the right skid, fuselage, main rotor assembly, drive belts, fuel tanks and gearbox.
Safety action
The operator has published a notice to its pilots reminding them to take the following precautions on each landing, no matter how short the time on the ground:
- Make sure all parts of the skids are firmly on the ground and the helicopter is stable.
- Collective set full down, governor off, engine RPM back to idle or 75%, cyclic neutral with friction on. Collective strap or friction always applied when the helicopter is on the ground and keep feet on the pedals.
- Be aware of possible dust devils[3] in the area, these may be hard to see in the wet season as there is no dust or grass present to indicate their location.
- Pilots are to report any cases where the collective rises on its own so any potential technical issues can be investigated and corrected.
Safety message
Helicopter pilots conducting mustering operations will be regularly landing for short periods of time for various reasons, including rehydration. Good airmanship requires that the helicopter is in a safe and stable condition before releasing the controls, including reducing RPM to idle and making sure the collective is in the full down position with the control frictions applied. This will reduce the risk of the helicopter inadvertently becoming airborne in case of disturbances from environmental conditions.
Once started, dynamic rollover will develop quickly and cannot be stopped by application of opposite cyclic control alone. Even with full opposite cyclic applied, there is insufficient control authority to arrest the roll once it is developed, as the main rotor thrust vector and its moment arm serves to accelerate the roll. Quickly reducing collective pitch is the most effective way to stop dynamic rollover from developing.
The R22 Pilot's Operating Handbook includes a safety notice (SN-9) which provides advice about how to avoid dynamic rollover situations.
About this report
Decisions regarding whether to conduct an investigation, and the scope of an investigation, are based on many factors, including the level of safety benefit likely to be obtained from an investigation. For this occurrence, no investigation has been conducted and the ATSB did not verify the accuracy of the information. A brief description has been written using information supplied in the notification and any follow-up information in order to produce a short summary report, and allow for greater industry awareness of potential safety issues and possible safety actions.
[1] Collective: a primary helicopter flight control that simultaneously affects the pitch of all blades of a lifting rotor. Collective input is the main control for vertical velocity.
[2] Cyclic: a primary helicopter flight control that is similar to an aircraft control column. Cyclic input tilts the main rotor disc, varying the attitude of the helicopter and hence the lateral direction.
[3] Dust devils are visible as wind vortices lifting dust from the surface with diameters usually less than one hundred metres but can extend up to a few thousand feet. They are a common occurrence throughout inland Australia, especially during the warmer months, and are dangerous to aircraft during take-off and landing (Source: Bureau of Meteorology)