Story and pictures by CHRISTOPHER TAN
When I was growing up, I remember being enthralled with the way eagles flew high in the air, circling and gliding, often without even flapping their wings. Now I was actually soaring like an eagle!
We were riding the winds in New Zealand, flying back and forth along the face of a ridge, pulling tight turns of figure eights whenever we flew into a thermal to gain altitude. Once we reached top of that ridge, we would cruise to a higher ridge nearby to repeat the process and gain more altitude.
Earlier, we had taken off from Omarama airfield in South Island, about an hour’s drive from Mount Cook National Park. A tow-plane had pulled us 600m high before we disconnected the tow rope and went flying free on our own, without any onboard engine to keep us airborne!
We slid to the nearby hills and Mike Till, my instructor, demonstrated the methods of using rising warm air along the face of the ridges to climb further.
When we entered an updraft, an instrument called a variometer would start chirping excitedly. The stronger the updraft, the more it chirped.
To stay within the updraft, we needed to immediately execute a tight turn. The idea was to go back and forth within the rising column of warm air to climb higher. If we lost the rising air, we would continue along the ridge looking for another thermal.
It was thrilling to cruise along so close to the ridge. I could clearly see tussocks of grass bending in the wind. At times we must have been only a few dozen metres away from the hillside. Normal passenger aircraft are required to stay at least 600m above hills, whereas here we were doing the opposite, staying close to high terrain to be able to stay airborne!
When we had gained some 600m with our thermal acrobatics, we headed out over the plains to a higher set of hills. Enroute, we performed some exercises to experience the stall characteristics of the glider.
It was amazing how slow the Grob 103 glider could go before commencing a very mild stall, with a loss of only about 30m.
After that, we did more ridge soaring along the hills before deciding to return to the airfield.
A glider hardly descends in the normal flight configuration. So to go down gradually, the air brakes needed to be partially extended to make the wings less efficient. The only other option was to dive down at a high speed!
It was amazing: we had just spent two hours in the air in an unpowered aircraft, just gliding around. The only effort required was to find the currents of rising air to stay aloft.
It was my wife’s turn next and Till briefed her on the flight controls, instruments and safety gear. This was our first day of a two-day introductory glider course. No flight experience was required, just a sense of adventure!
Gliding needs certain weather conditions to be successful and generally the summer period is better for gliding. We had turned up at the airfield the day before, but the winds were at gale force strength, making it unsafe to go gliding.
The next day, we took off in the Duo Discus, a high performance cross-country glider. After gaining altitude by ridge soaring, we headed cross-country towards the Southern Alps; we were now about 2,500m high.
As we approached, we flew into a “mountain wave” – the air downwind of a mountain range moves up and down in waves, just like sea waves.
Surfing on air
Fly the glider into the area where the wave is rising and it will climb – as long as you keep cruising in this area of the wave (which parallels the mountain range). My instructor gave me pointers throughout the flight on where to look for such rising air and the best ways to operate the glider in various conditions.
It did not take long for us to climb past 3,000m. It was time to put on our oxygen supply so that we would not get hypoxia (oxygen deficiency). The cruise along the mountain wave was very smooth and calm compared to the bumpy and turbulent ride when ridge soaring.
Prior to this, we had been flying at speeds of 100km/h – 150km/h. Now that we were steadily cruising in the mountain wave, I was told to put the glider’s nose down and gain speed. We began cruising at over 220km/h and yet we were still gaining altitude!
We were flying over scenic Lake Pukaki, nestled among the snow-capped mountains, when the variometer started singing a dismal tone. We had entered the descending part of the mountain wave and we were rapidly sinking.
I turned downwind and tried to find rising air but we continued to lose altitude. This was not good. We then turned back into the wind and had to fly through more descending air, losing more valuable altitude. Thankfully, we eventually entered a rising wave of air and were able to continue flying to our objective!
There was another glider that was not so fortunate. We heard them radio the base that they had to land at a small airstrip below us. They requested the tow-plane to fly out to the airstrip and give them a, well, “lift”.
We continued flying all the way to Mount Cook, the highest mountain in New Zealand. Then, we turned back, using another mountain wave to soar back to Omarama.
During the cruise, we reached an altitude over 5,000m or 5km! We could have gone even higher but we would have had to get permission from New Zealand air traffic control to do so, as airspace above us was reserved for commercial passenger flight aircraft.
The flight back to Omarama was just as exhilarating, with both coasts of New Zealand’s South Island in view – the Pacific Ocean to the east and the Tasman Sea to the west.
I was airborne on this flight for four hours and covered over 400km with just natural “air power”! It was a flight I will never forget.