Soaring to the Stratosphere May 14]
These photographs were taken on 1st February this year (2014). The pilot is Klaus Ohlmann and clearly, he’s high because he’s using oxygen. But it’s where he is that is significant. The mountain peak in the pictures is Everest and Klaus is flying a glider. That makes Klaus the first person to soar over the highest point on earth. But, oddly enough, it didn’t earn him a height record.
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Soaring has come a long way since 1902 when Wilbur Wright stretched a glide to all of 26 seconds on the windward side of a sand dune. The next year flight times were extended further when an engine replaced slope lift.
Although there was astonishing progress in the development of aviation in WWI gliding re-appeared in several countries as a sport – a cheap way to get into the air. In the UK an international competition was held in 1922 at Itford Hill in Sussex. It was attended by Anthony Fokker, no less, who came along with two gliders. The first prize was won by a Frenchman with a slope-soaring flight of 3 hrs 21 mins. In 1923 the competitors were allowed to add engines and gliding was forgotten again. In Germany, however, they were still smarting under the restrictions imposed by the Versailles treaty and they weren’t allowed the luxury of engines. The sport flourished and soon escaped from the shackles of hill-soaring when the rising air under passing cumulus clouds was discovered. Then, in 1933, two pilots found a new kind of lift - an area of smooth strongly rising air downwind of a range of hills. It was the first encounter with a ‘lee wave’.
Other gliding enthusiasts began searching for this elusive lift. In 1939, three friends from Newcastle Gliding Club towed their trailer to Cumberland to explore the Helm Wind. The western edge of the Pennines ends in the Eden fault, a long westward-facing ridge. The locals knew well that, when there was a strong easterly wind it would sweep down the slope and bounce up into a roll of cloud, the Helm Bar. On the ground below it there could be damage to trees and buildings whilst in the countryside to the west the air was still. The glider was launched from a field under the bar. Two of the pilots were quickly forced down by the turbulence. Noel MacClean was luckier. He managed to contact the wave in front of the bar at 1000 ft and shot up to 11,140 ft, a British height record.
Even after the intensive flying activity of WWII there was little knowledge, and even less understanding of mountain lee waves. Two airline Dakotas crashed in North Wales and pilots told of mysterious rapid gains of height in calm air and, more seriously, of rapid height loss even when the engines were on full power. The standard practice became to avoid flying downwind of mountains in strong winds. Even so, in 1966 a BOAC Boeing 707 crashed in the severe turbulence downwind of MT Fuji in Japan after the pilot diverted to give his passengers a closer view of the mountain. And as late as 1993, a cargo Boeing 747 flying near Anchorage in Alaska encountered such rough air that one of its engines was wrenched off the wing.
Meanwhile, glider pilots deliberately sought out the magnificent lift that lee waves can provide and eastern California was a rich source. Downwind of the Rockies, high clouds marked waves and records were set at increasing heights. Every flight added to the knowledge and understanding of lee waves and Robert Harris soared to a record 49,009 ft in 1986.
Although there was astonishing progress in the development of aviation in WWI gliding re-appeared in several countries as a sport – a cheap way to get into the air. In the UK an international competition was held in 1922 at Itford Hill in Sussex. It was attended by Anthony Fokker, no less, who came along with two gliders. The first prize was won by a Frenchman with a slope-soaring flight of 3 hrs 21 mins. In 1923 the competitors were allowed to add engines and gliding was forgotten again. In Germany, however, they were still smarting under the restrictions imposed by the Versailles treaty and they weren’t allowed the luxury of engines. The sport flourished and soon escaped from the shackles of hill-soaring when the rising air under passing cumulus clouds was discovered. Then, in 1933, two pilots found a new kind of lift - an area of smooth strongly rising air downwind of a range of hills. It was the first encounter with a ‘lee wave’.
Other gliding enthusiasts began searching for this elusive lift. In 1939, three friends from Newcastle Gliding Club towed their trailer to Cumberland to explore the Helm Wind. The western edge of the Pennines ends in the Eden fault, a long westward-facing ridge. The locals knew well that, when there was a strong easterly wind it would sweep down the slope and bounce up into a roll of cloud, the Helm Bar. On the ground below it there could be damage to trees and buildings whilst in the countryside to the west the air was still. The glider was launched from a field under the bar. Two of the pilots were quickly forced down by the turbulence. Noel MacClean was luckier. He managed to contact the wave in front of the bar at 1000 ft and shot up to 11,140 ft, a British height record.
Even after the intensive flying activity of WWII there was little knowledge, and even less understanding of mountain lee waves. Two airline Dakotas crashed in North Wales and pilots told of mysterious rapid gains of height in calm air and, more seriously, of rapid height loss even when the engines were on full power. The standard practice became to avoid flying downwind of mountains in strong winds. Even so, in 1966 a BOAC Boeing 707 crashed in the severe turbulence downwind of MT Fuji in Japan after the pilot diverted to give his passengers a closer view of the mountain. And as late as 1993, a cargo Boeing 747 flying near Anchorage in Alaska encountered such rough air that one of its engines was wrenched off the wing.
Meanwhile, glider pilots deliberately sought out the magnificent lift that lee waves can provide and eastern California was a rich source. Downwind of the Rockies, high clouds marked waves and records were set at increasing heights. Every flight added to the knowledge and understanding of lee waves and Robert Harris soared to a record 49,009 ft in 1986.
Lee waves form when a stream of stable air passes over a mountain range. The trigger is the slope behind the ridge. The air is dragged down the slope and, being stable, tries to bounce back to its original height. Inevitably, it overshoots and launches into a series of oscillations. The layers of air above, usually travelling at increasingly greater speeds, are similarly affected and the resultant wave can extend to great heights. Any humid layers condense into cloud as they are forced upwards. On the descent, the cloud dissipates. These clouds appear to be stationary although the air is passing through them. In cross-section, they have a flat base and a hemispherical upper surface like a lens – hence their name, lenticulars (strictly, altocumulus lenticularis).
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A glider pilot entering a wave immediately notices how eerily smooth the air is. The glider slips silently through the air and the only thing moving is the rapidly rising needle of the altimeter. Of course, the areas of downdraft are equally smooth so careful positioning in the wave is the key to a successful climb. The other problem area is between the lowest wave and the ground where the chaotic airflow is extremely turbulent.
Not all waves are classically arranged in neat lines. They can vary in strength, creep up or downwind or be affected by a neighbouring wave system. The most fruitful hunting grounds are where a mountain range is aligned facing the prevailing wind. New Zealand is perfectly placed. The Maoris named it ‘the land of the
long white cloud’ and you can see why in the right hand picture (above) of Mt Cook and its waving skyscape.
These photographs show the pilot’s view. The leading edge of the cloud is an excellent indicator of the lift. A pilot wanting to move upwind to what could be a stronger wave has to negotiate the intervening downdraft. It’s a nice calculation to balance the speed he needs to fly to make progress against the strong wind, how far he has to travel and how much height he will lose in the process.
Not all waves are classically arranged in neat lines. They can vary in strength, creep up or downwind or be affected by a neighbouring wave system. The most fruitful hunting grounds are where a mountain range is aligned facing the prevailing wind. New Zealand is perfectly placed. The Maoris named it ‘the land of the
long white cloud’ and you can see why in the right hand picture (above) of Mt Cook and its waving skyscape.
These photographs show the pilot’s view. The leading edge of the cloud is an excellent indicator of the lift. A pilot wanting to move upwind to what could be a stronger wave has to negotiate the intervening downdraft. It’s a nice calculation to balance the speed he needs to fly to make progress against the strong wind, how far he has to travel and how much height he will lose in the process.
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In an effort to use waves purely for altitude the Perlan Project was conceived in 1999 by Einar Enevoldson, a former NASA test pilot. He planned to fly a sailplane at 90,000 ft. Much-needed funds were provided by Steve Fossett. In addition to his speed sailing records, Fossett had set 91 aviation records, including fastest airship and solo circumnavigations by balloon and powered aeroplane. Now he couldn’t resist another glider record. In 2005, after five years wave-hunting, he and Enevoldson, put on their full space suits, climbed into the stratosphere and reached 50,727 ft.
Fossett’s death in a light aeroplane accident in 2007 was a setback for the project but new funds have been found and Perlan II is alive and well. Here is the new pressurised fuselage of its sailplane ready for the next momentous step towards 90,000 ft.
And, just in case you get the impression that standing waves are found only in exotic and far-flung locations – this picture was taken in Yorkshire. |
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