Introduction
On the afternoon of 13 February 2017, wildfires broke out on the Port Hills between Lyttelton Harbour and the south-eastern suburbs of Christchurch, New Zealand. The National Rural Fire Authority coordinated the response, contracting helicopter companies for firefighting support. Way To Go Heliservices Limited provided a Eurocopter AS350 BA ‘Squirrel’, registration ZK-HKW. The pilot flew back to base at Rangiora Airfield at dusk.
Narrative
At about 0540 on 14 February, the same pilot flew from Rangiora to rejoin the firefighting operation. The air attack supervisor briefed pilots on weather, hazards, and procedures. The supervisor allocated aircraft to sectors and appointed the accident pilot as lead pilot for his sector. The pilot briefed his group on circuit patterns and radio procedures.
During the morning, the group operated at several locations. After a lunch and refuelling break, they were directed to drop water near the ‘Sign of the Kiwi’ building. The dipping pond was about two kilometres northeast of the fires. Pilots flew a left-hand pattern in clear conditions around Sugarloaf peak. A circuit took approximately four minutes.
At about 1405, an abbreviated ‘Mayday’ call was heard. A roll call revealed the accident pilot did not respond. Another pilot found the wreckage near a gully east of Sugarloaf. The pilot was fatally injured and the helicopter destroyed.
Findings
The Transport Accident Investigation Commission determined that the monsoon bucket suspension line contacted the tail rotor. The video recording from an external camera showed the bucket rising toward the tail rotor. An object, virtually certain to be the window dislodged from the left rear sliding door, fell from the helicopter shortly beforehand. The pilot had experienced a similar window loss on a 2015 firefighting mission.
The door configuration was prohibited in the flight manual; the helicopter was flown outside approved limits. The bucket likely rose due to forward airspeed and turbulence, and the pilot’s slowing in response to the window loss caused the tail rotor to dip and contact the line.
The Commission noted that the hazard of an underslung load striking a tail rotor is a known risk. Although not directly contributing, three deficiencies indicated the operator’s quality assurance system should be reviewed. Toxicology testing found it very unlikely the pilot was impaired by recent cannabis use.
Safety Issues
Two safety issues were identified: (1) insufficient industry awareness of risks with underslung load operations, especially monsoon buckets during firefighting; (2) the operator lacked adequate systems to determine weight and balance or to ensure incidents like the window loss were recorded, notified to the CAA, and investigated.
The Commission made a new recommendation to address the operator’s procedural safety issues, building on previous recommendations about substance impairment and industry awareness.