By MATHEW DEARNALEY and NZPA
Investigators probing the country's worst air crash for 10 years believe weather conditions pushed the limit of navigational landing tools.
John Goddard, the man in charge of finding out what caused the Piper Chieftain to crash, killing eight people, near Christchurch on Friday night does not believe fog was to blame.
A blanket of fog descended later, severely hampering searchers as two injured survivors waited in a cold and desolate paddock to be found.
But Mr Goddard, head of the Transport Accident Investigation Commission inquiry, said last night that cloud cover was low and he could not categorically rule out fog.
Air Adventures pilot Michael Bannerman, who is among the dead, was likely to have been relying on navigational instruments rather than a visual approach to Christchurch International Airport.
Pilots operating on instrument flight rules must be able to see runway lights before they can land.
Christchurch International Airport chief executive George Bellew said a commercial aircraft had landed on the main runway five minutes before the crash.
"When fog hits here it comes in waves and bad - providing good visibility in some areas and restrictive in others," he said.
Mr Goddard said he did not know if the runway lights would have been visible to Mr Bannerman when his twin-engined aircraft disappeared from the traffic control tower's radar screen at 7.07pm, just 70 seconds flying time from the runway.
But he believed conditions would have been marginal. "Conditions at the time were towards the limit for that sort of approach," he said.
All possibilities were open for investigation, including whether any of the nine passengers - from the cream of the country's scientific community - were using cellphones.
Mr Goddard acknowledged that a cellphone call, or even a text message, could interfere with radio beams sent out from airports to aircraft navigational instruments.
This follows a comment by the partner of one of the dead passengers, Desma Hogg, that he knew something was wrong when she did not respond to a text message he sent her.
"I would imagine that if done by a cellphone it would have the potential," Mr Goddard said.
The biggest problem is the lack of research about the potential effects.
A UK Civil Aviation Authority-sponsored study in 1999 was the first to examine the potential for cellphone use to interfere with flight systems and instruments.nte
The plane's landing wheels were down and locked when it crashed 3km from the runway, and its approach was "closely on-line".
The aircraft should have been about 90m above ground at the distance it was from the runway, but the poplar trees it hit were under half of that height.
Survivor Tim Lindley, who was a front-seat passenger, told Mr Goddard from his hospital bed that it was a "fairly routine flight" and he didn't feel any anxiety about the approach.
Mr Goddard said: "His next recollection was sliding along on the ground and then waking up amid the wreckage".
Police believe all the dead on board the plane died on impact.
Emergency workers were forced to painstakingly cover a wide area north of the airport on foot after fog grounded rescue aircraft.
Mr Bellew said that although searchers wanted to mobilise helicopters, pilots refused to fly in the foggy conditions immediately after the tragedy.
"Conditions did deteriorate," he said. "People searching said the visibility was so bad even the Fire Service was only getting visual penetration of a few metres with their vehicles."
He defended the time it took to find the plane, citing the conditions, lack of crash reports, non-activation of the locator beacon which had broken off, and the sparsely populated area the plane went down in.
Rescuers who arrived at the scene off Greywacke Rd in Harewood about 9.30pm said it was a miracle the crash site was found so quickly.
St John Ambulance officer Glenn Cockburn, the first medic on the scene, was "99 per cent sure" none of those who died would have still been alive if they had been found within the "golden hour", one hour after the crash.
"I checked all of the deceased when I got there," he said.
"I would have been surprised if any of them would have survived from the way they were lying and their injuries."
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