What's known about the Gold Coast helicopter tragedy
Key findings from the preliminary investigation into the mid-air helicopter collision that killed four people on the Gold Coast on January 2.
* Two helicopters were operating five-minute scenic flights from separate helipads about 220m apart near Sea World.
* At 1:52pm, helicopter XH9 pilot Michael James makes an inbound radio call to alert that he is landing.
* Ground crew do not see any other aircraft and signal for XKQ helicopter pilot Ashley Jenkinson to take off.
THE SECOND HELICOPTER
* Mr James sees passengers being loaded into XKQ and the doors closing, thinking it will pass behind his aircraft.
* He doesn't hear any outbound taxi radio call from Mr Jenkinson or see XKQ approaching.
* Mr James focuses on avoiding creating downwash for a boat passing below as he makes a final approach to the helipad.
* At 1:56pm, two passengers notice Mr Jenkinson's helicopter approaching and one tries to tell Mr James. After he doesn't respond, one passenger starts tapping his shoulder.
* Mr James later remembers being alerted by passengers but still doesn't see the other chopper.
* About 23 seconds after Mr Jenkinson takes off, the helicopters collide 40 metres off the ground.
*The main rotor blades of Mr Jenkinson's helicopter XKQ strike the windscreen and forward cabin of XH9.
* XKQ breaks apart in the air and crashes into shallow water next to a sandbar.
* Mr Jenkinson and three passengers are killed with three other passengers seriously injured. The helicopter is destroyed.
* The cabin, instrument console and main rotor blades of helicopter XH9 are significantly damaged, but Mr James is able to land on the sand bar.
* Mr James and two passengers are seriously injured, while other passengers sustain minor injuries.
* The helicopters were too low for air traffic control to guide them so they were relying on radio calls and sight.
* The surviving pilot didn't hear the other pilot make a standard outbound taxi call before he took off.
* A third pilot heard the surviving pilot make an inbound call, but did not hear the second pilot.
* The surviving pilot didn't see the other helicopter before the collision.
* Both helicopters were fitted with a traffic collision avoidance system, but they could only issue audio alerts. The surviving pilot said he did not hear one before the collision.
* XH9 was not transmitting secondary surveillance radar responses at the time of the flight.
DEATHS AND INJURIES:
* Pilot Ashley Jenkinson, 40, British couple Ron and Diane Hughes, and Sydney mother Vanessa Tadros, 36, were killed.
* Vanessa's son Nicholas, 10, is recovering in hospital after having his leg partially amputated, while Victorian mother Winnie de Silva, 33, and her nine-year-old son Leon were also seriously injured.
* Pilot Michael James, and Zealand women Marle Swart and Elmarie Steenberg suffer shrapnel injuries, while their husbands Edward Swart, Riaan Steenberg, and an unnamed 27-year-old West Australian woman were not physically injured.
(Source: Australian Transport Safety Bureau)