KEY POINTS:
Two planes with passengers came within 50m of a mid-air collision over the Marlborough Sounds last summer.
The December 27 incident with a six-seater Piper Cherokee and a six- to eight-seater Patenavia was one of more than 30 near-collisions reported to the Civil Aviation Authority (CAA).
But one senior pilot and safety campaigner told the Herald on Sunday that figure was the "tip of the iceberg" and the real number could be at least 10 times higher.
Vincent Aviation managing director Peter Vincent said many pilots were not reporting near misses, despite a legal requirement to do so, possibly because they were unaware of how close they had come to a collision or didn't understand CAA definitions.
He said little had changed since the collision between a light plane and a helicopter over Paraparaumu in February that killed three. "There is going to be another mid-air accident."
The CAA report, released to the Herald on Sunday under the Official Information Act, details 34 near collisions around the country.
In the closest shave, a microlight came within 15m of a four-seater light aircraft about 900m above Eyrewell in Canterbury in March last year.
The report also reveals:
In August 2006, a Squirrel helicopter approaching Pukekohe came within 30m of a motorised hang-glider.
In March last year, a Cessna leaving Hamilton airport came within 30m of a Diamond DA20 training aircraft.
In September last year, a Cessna pilot descending to Paraparaumu airport glimpsed a helicopter passing less than 60m below him.
In April this year, a plane reported a near-collision with a weather balloon at Paraparaumu.
In March, again at Paraparaumu, a pilot reported he had to manoeuvre to avoid a head-on collision with another aircraft.
There were also several on-ground incidents involving passenger jets reported at Wellington and Auckland airports, including a 737 being pushed back from gates and coming "dangerously close" to smaller taxiing aircraft - in one case less than 9m.
The number of reported near-collisions has remained fairly steady over the past six years.
Ten were reported in 2002, rising to a high of 16 in 2005. Ten have been reported so far this year.
CAA spokesman Bill Sommer said the authority had done an "enormous" amount of work to raise awareness of safety and pilots' reporting responsibilities. "The number of accidents over the past 10 years has halved, that's well-known. The ideal would be to have none."
Sommer said near-collisions were "something we live with" and it was always a concern when aircraft came as close as a few metres.
"Obviously it's alarming to people to have that happen," he said. "But incidents like that are normally reported very quickly. Safety systems rely on the information flow.
"As to what the level of non-reporting is, how do we know it?
"The culture has changed quite noticeably in the past 10 years. People are becoming more aware of their responsibilities."
Vincent is unconvinced. "I don't think the CAA is being particularly pro-active in looking at this."
He said it was difficult for non-professional pilots to gauge how close aircraft were and he doubted whether all of them understood the CAA rules.
"Do you jump out and walk on air with a tape measure?" Vincent said his primary concern remained the lack of flight services to control aircraft at busy airports such as Paraparaumu, Ardmore and Taupo.
The decision to withdraw flight services from some airports was made by Airways New Zealand, a separate state-owned enterprise which looks after air traffic control.
Ardmore, which has up to 250,000 movements a year, lost its flight-tower presence in 1988, Taupo in 1996 and Paraparaumu in 1997.
Vincent said he had also heard worrying reports from Ashburton Airport. "I am sure there will be an accident there. I have heard many, many stories of close calls, too many for me to be comfortable."
Vincent said a near-miss of 15m was "very close. You don't see that coming. It's just a fluke that it's not a collision. It's like driving at 100km/h and a child stepping out from between two trees - it's all over before you realise what's happened. Two aircraft touching in the air is unthinkable. The chance of fatalities is very high."
