The Squirrel helicopter was being used to carry an underslung load of operating fireworks during the Perth Australia Day fireworks display. The helicopter's flight path followed the Swan River, remaining clear of spectators. After the fireworks were ignited, some projectiles from the fireworks appeared to pass through or close to the left side of the helicopter's main rotor disc. The helicopter was not damaged.
The helicopter operator had approached the local District Office of the Civil Aviation Safety Authority (CASA) for an approval to conduct the display. The operator was of the understanding that the fireworks were non-projectile and advised this to the local CASA officers. Although the company fitting the fireworks had advised the event promoter that the fireworks included eight-shot Roman Candles, eight-shot Crosette Candles, Flares and Silver Fountains, the event promoter, the local CASA officers, and the operator expected a cascading type display with nothing ejecting from the helicopter's underslung load.
Because it was the first display of its type in Australia, the local CASA officers sought advice from CASA officers in Canberra. Although the Canberra based officers advised against approving the display, the local CASA officers considered that because the fireworks were non-projectile, the display could be conducted safely if the operator met certain guidelines. The helicopter operator was also required to demonstrate that the rig, on which the fireworks were mounted, could be safely flown as an underslung load. The local officers reported that CASA officers in Canberra advised that because the fireworks were being flown as an underslung load, they were not regarded as dangerous goods.
The rig on which the fireworks were mounted, was a large circular metal frame attached to the helicopter by web-type slings. When flown, the rig demonstrated good flying qualities and the local CASA officers reported that the mechanisms securing the fireworks to the rig appeared sound. However, the assessment flight was done without the fireworks attached or a test firing of the fireworks. A Flying Operations Inspector from the local CASA district office granted conditional approval for the flight. The conditions included requirements to remain a minimum distance of 300 m from the shoreline and that the display was not to be flown over any person or boat.
The helicopter lifted the load from a pad near the Swan River and while it was flying along the river, the fireworks were ignited electrically from a control box operated by a pyro-technician sitting in the cabin. The pilot reported that he was surprised when the first fireworks ignited, that they were red flares that ejected from the rig. However, they operated without incident. The cascading-type fireworks also operated without incident but when the Roman Candles fired, some of the shots fired upwards towards the helicopter. The pilot reported that he had felt the rig moving in response to the igniting fireworks but this movement did not affect the controllability of the helicopter. He was unaware that any of the shots had come close to the helicopter until the copilot later reported that some had appeared to do so.
After the helicopter landed, it was found that eight rounds of the Roman Candles had dislodged during the flight and fallen from the rig. The recoil generated by the shots ejecting from the rounds appeared to have caused the rounds to move up and out of the securing straps. As the rounds fell from the rig, they tumbled and the shots continued, some of which passed close to the helicopter. The company that fitted the fireworks reported that the strength of the recoil generated by the Roman Candle had been underestimated.
During the investigation, it became apparent that there were differing opinions as to whether an underslung load was considered to be part of the helicopter with respect to dangerous goods requirements. CASA subsequently informed the investigation that anything attached to an aircraft is considered to be part of the aircraft and that dangerous goods carried as an underslung load must be treated no differently from dangerous goods carried inside the aircraft. CASA also advised that dangerous goods carried differently to that which is required by the Civil Aviation Regulations must be subject to written permission issued by CASA.
There was a misunderstanding among the pyro-technicians, event organiser, helicopter operator and local CASA officers in relation to the types of firework being carried by, and fired from, the helicopter. As a result, the approval given by CASA for the display was based on incorrect information. The mechanisms that secured the Roman Candle rounds to the rig did not prevent the rounds from dislodging from the airframe and were therefore inadequate for the purpose.