Radar problems at Chch too

Press, 30 June 1982, Page 6

Radar problems at Chch too

With the exception of approaches from the west, aircraft approaching Christchurch Airport will normally fade from the screens of air traffic controllers for 32 kilometres at a time, according to the national president of the Air Traffic Controllers’ Association, Mr L. J. Taylor. Mr Taylor said that the effective range of the radar has declined from 177 kilometres to up to 64 kilometres. and is unreliable outside that range. These distances vary according to the altitude the aircraft is flying at.

The aircraft may paint, or show; on the controller’s screen for 32km, come back for 16km to 24km and then fade for another 24km. Mr Taylor said. These distances mean that the aircraft could disappear from the. screen for about three minutes at a time.

“We know of about, four big holes mainly north and south of Christchurch." Mr Taylor said. “From the west

they seem to paint very well." Mr Taylor said that it was not so bad when a controller was expecting an aircraft to fade, as he could then build in some other form of separation between aircraft. The problem arose, with controllers wanting to believe what, was on the screen in front of them, Mr Taylor said. “Under normal circumstances there is no. danger of a mid-air collision, but there is a, degree of loss of time, and' valuable fuel to the company.” Mr .Taylor said. This would be caused by an aircraft’s having to be allocated a much greater "step-through” distance to move through the altitude of an aircraft on a similar flight path if the controller could not rely on the radar, and had to employ distancemeasuring equipment to control the manoeuvre. This could .triple the separation distance between the aircraft, Mr Taylor said, and might mean one aircraft

would have :to spend longer in the air or even circle. “Under more abnormal circumstances it is not impossible at Christchurch for a loss of separation to occur." Mr Taylor said. “The reason is that the equipment that we have does have holes, and does place a lot more responsibility on the controller than there should be. It is unfair to ask a controller to work with unreliable equipment,” he said. The equipment at Christchurch Airport had been in use for about 17 or 18 years, Mr Taylor said. The problems with holes were “something that people are aware of, and have another try at every now and then,” he said. Technicians were sent to Christchurch from the Civil Aviation head office to examine the problem. Theories relating to causes of the holes had ranged from the new Air New Zealand hangar to trees at the Harewood golf course. Mr Taylor said that New Zealand was the only country

with a highly developed, air traffic control system which did not employ secondary radar. Fiji and a lot of Third World countries also relied on primary radar. Primary radar was like a searchlight emitting a narrow’ beam which swept the countryside and was reflected back after hitting aircraft. Secondary radar relied on a radar beam from the airfield triggering equipment in the aircraft, which fired a very strong signal back to the airfield. “The problem is that when you consider the vast steps that have been taken in the last 20 years since we have had DC3s, when nothing moved much faster than 200 knots, we have not kept up with the aviation age,” Mr Taylor said. . , “Now we have jets moving .very quickly. In order to be safe in most cases triplicate systems are used. Everything _■ is designed to be ultra failsafe but that technique, has not been -reflected on the

ground.” Mr Taylor said. He believed the problem was largely a result of insufficient communication between the air traffic controllers and Ministry management. something he would point out to the Minister of Aviation when he met him.

In Wellington, the Minister of Transport (Mr Gair) said last evening that there were two reasons which might explain why the head office of the Civil Aviation Division of the Ministry of Transport had no knowledge of the alleged further two "near misses" at the Auckland Airport. One was that the incidents did not warrant reporting. The second was that someone had made an error in not reporting them. Mr Gair said that he would discuss the situation with the Chief Inspector of Air Accidents. Mr Ron Chippindale, later this week when the latter presented a draft of his report on the second of the two incidents under investigation.