the windscreen. The two observers in the helicopter, sitting in the left front and rear, had no obstruction preventing them seeing the approaching Archer. The Commission found the Airwork (NZ) Operations Manual specifically addressed collision avoidance between these two aircraft: Discussions with other pilots of the aircraft and police crew found they were familiar with the normal operating altitudes of 1,500 feet for the Police Traffic Patrol and 1,000 feet for the Police Eagle. The Commission found the accident occurred because neither pilot saw the other aircraft. Contributing factors were the helicopter not levelling at the agreed altitude, the helicopter did not establish mutual position by radio, and the helicopter crew did not see the traffic in time. It also cited the inherent limitations with the "see and avoid" method as a causal factor. The Commission recommended the Director of Civil Aviation promulgate a single advisory radio frequency for aircraft in the uncontrolled airspace between Auckland and Whenuapai Control Zones, which he did. References Sources 1993 in New Zealand Aviation accidents and incidents in 1993 Aviation accidents and incidents in New Zealand 1990s in Auckland Mid-air collisions Mid-air collisions involving general aviation aircraft Mid-air collisions involving helicopters November 1993 events in New Zealand