Missing.............Dyn Aero ZK-SML

From Stuff website updated at 1543 today (Sunday 10 April)

Rescuers searching for a missing former Olympian have narrowed their search to two areas after information was provided about aircraft dropping off the radar yesterday along his microlight's expected route.

The initial search was sparked when Auckland businessman Geoff Smale, 86, who represented New Zealand in yachting at the 1968 Mexico Olympic Games, left North Shore about 11am yesterday but failed to turn up in Ashburton by 3pm as planned.

Rescue Coordination Centre (RCC) spokesman Ross Henderson said Smale was an experienced and fit pilot and had made the more than 800-kilometre journey, expected to take up to four and half hours, a number of times.

The aircraft, a white microlight with red detailing, had a nine-hour flying range and was capable of 135 knots (250kph), so was able to complete the flight without refuelling stops.

The weather along the route yesterday was good overall, with a few cloudy patches, he said.

Earlier today four helicopters combed the area between Ashburton and Auckland looking for any sign of the microlight.

Henderson said rescuers had narrowed their search.

RCC search and rescue officer Neville Blakemore said radar tracking information provided by the Airways Corporation showed an aircraft leaving from Auckland at about the same time as Smale, then disappearing from radar about an hour later just South of Taharoa in the Waikato.

The information was roughly consistent with the estimated timing, speed and possible route of Smale's aircraft.

A helicopter from the Taranaki Rescue Helicopter Trust based in New Plymouth would carry out a thorough search of the area, Blakemore said.

As well, a fixed-wing plane from the Phillips Rescue Trust in Hamilton would fly a path between Auckland, Stratford and D'Urville Island in the Marlborough Sounds, after additional radar data provided by Airways showed an aircraft disappearing from radar about 1pm yesterday near D'Urville.

This was also roughly consistent with the estimated timing and possible route of Smale's aircraft.

Microlight pilot Mike Gray, of the Marlborough Aero Club, said flying conditions over Smale's route were good, except in Marlborough where a ''cyclonic gloom'' brought cloud cover down to about 250-400 metres.

''The higher you fly, the safer you are,'' Gray said. ''Once you get lower there are less options.''

If Smale had suffered a medical problem such as a heart attack, his plane could have continued unpiloted until it ran out of fuel or hit a mountain, Gray said.

A stricken plane ''does not drop like a stone or a brick'', he said. For every 12 metres a plane glided forward it would drop one metre.

Smale was carrying a personal locator beacon, radio, radar transponder and cellphone. The beacon has not been activated and attempts to contact Smale have been unsuccessful.

Dyn' Aero MCRO1 Club ZK-SML at its North Shore home in late January 2011, Mike Condon photo