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Soaring: Difference between revisions
Adding obvious unit conversions to make the topic understandable for metric audience
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In a broader sense, this article covers how to enjoy flights with gliders, motorgliders, hanggliders and paragliders by understanding how to plan unpowered flights, how to set up weather conditions for reasonable lift, how to launch gliders and how to make use of lifting airmasses. | In a broader sense, this article covers how to enjoy flights with gliders, motorgliders, hanggliders and paragliders by understanding how to plan unpowered flights, how to set up weather conditions for reasonable lift, how to launch gliders and how to make use of lifting airmasses. | ||
''Note on units: In many areas of the world, glider pilots use metric units and instruments show altitude in meters and | ''Note on units: In many areas of the world, glider pilots use metric units and instruments show altitude in meters (m), airspeed in kilometers per hour (km/h) and climb/sink rate in meters per second (m/s) - we will in this article follow this convention.'' | ||
== Basics of glider flight == | == Basics of glider flight == | ||
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=== Ridge lift === | === Ridge lift === | ||
When a sufficiently strong wind meets rising terrain, the airstream is forced upward and thus a lift component is created at the windward slopes of a range. However, behind the ridge, the airstream turns down into the valley, and thus at the leeward side of a range a strong sink appears. For sufficient ridge lift conditions, winds stronger than 10 kt need to be perpendicular to a slope. Stronger winds create stronger lift, but make flight planning in general more difficult (see above). | When a sufficiently strong wind meets rising terrain, the airstream is forced upward and thus a lift component is created at the windward slopes of a range. However, behind the ridge, the airstream turns down into the valley, and thus at the leeward side of a range a strong sink appears. For sufficient ridge lift conditions, winds stronger than 5 m/s (10 kt; 18.5 km/h) need to be perpendicular to a slope. Stronger winds create stronger lift, but make flight planning in general more difficult (see above). | ||
The region of lift is usually very close to the ground, so one has to stay dangerously close to possibly rugged terrain in order to get good ridge lift conditions. | The region of lift is usually very close to the ground, so one has to stay dangerously close to possibly rugged terrain in order to get good ridge lift conditions. | ||
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When, in strong winds, the air descends behind a mountain range, it can 'bounce back' from the ground and form a pattern of rising and falling waves in the lee of a mountain range. These waves provide lift with almost no turbulence which can reach very high - more than 10 km altitude have been reached in waves. | When, in strong winds, the air descends behind a mountain range, it can 'bounce back' from the ground and form a pattern of rising and falling waves in the lee of a mountain range. These waves provide lift with almost no turbulence which can reach very high - more than 10 km altitude have been reached in waves. | ||
Typically waves form well behind a significant mountain range in winds of 30 kt and above when the wind is roughly perpendicular to the mountain range. At the leading edge of the wave is a very turbulent 'rotor' region, and lense-shaped Lenticularis clouds indicate often the top region of the wave (the region of maximum lift is found before the Lenticularis). | Typically waves form well behind a significant mountain range in winds of 15 m/s (30 kt; 55 km/h) and above when the wind is roughly perpendicular to the mountain range. At the leading edge of the wave is a very turbulent 'rotor' region, and lense-shaped Lenticularis clouds indicate often the top region of the wave (the region of maximum lift is found before the Lenticularis). | ||
Wave lift is difficult to find, but easy to fly - the region of lift is huge, there is no turbulence and one can simply hold the glider almost stationary against the wind while rising far above terrain and clouds. | Wave lift is difficult to find, but easy to fly - the region of lift is huge, there is no turbulence and one can simply hold the glider almost stationary against the wind while rising far above terrain and clouds. | ||
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--altitude=3000 --vc=70 --heading=180 | --altitude=3000 --vc=70 --heading=180 | ||
to the commandline (this will initialize the glider at 3000 ft with a velocity of 70 kt with a heading of 180 degrees - note that the altitude is absolute altitude rather than above ground level and adjust as needed!). | to the commandline (this will initialize the glider at 3000 ft (914 m) with a velocity of 70 kt (36 m/s; 129 km/h) with a heading of 180 degrees - note that the altitude is absolute altitude rather than above ground level and adjust as needed!). | ||
Hanggliders and paragliders launch from mountains by running down a steep mountain slope till enough lift is generated. This means that you need to scout the terrain before and find a good loaction. A typical starting position may then be defined like | Hanggliders and paragliders launch from mountains by running down a steep mountain slope till enough lift is generated. This means that you need to scout the terrain before and find a good loaction. A typical starting position may then be defined like | ||
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If you'd like to discover the Austrian alpine region with AI thermals, you might want to read [[Pinzgauer Spaziergang]]. | If you'd like to discover the Austrian alpine region with AI thermals, you might want to read [[Pinzgauer Spaziergang]]. | ||
Ridge lift works well with Basic Weather. Typically winds should be chosen to be perpendicular to a slope between | Ridge lift works well with Basic Weather. Typically winds should be chosen to be perpendicular to a slope between 10–20 kt (5–10 m/s; 18–37 km/h) for good ridge lift conditions. When using the wind layer interface, it is important to set not only the aloft winds but also the boundary layer winds to this value. This makes for a nasty landing, as the winds even close to touchdown in the valleys blow at full strength, but since ridge lift is only strong close to the terrain, a glider using ridge lift is almost always in the boundary layer zone, and if the boundary layer winds are reduced to get the landing conditions in the valleys right, ridge lift on the slopes collapses as well. | ||
=== Advanced Weather === | === Advanced Weather === | ||
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As a result, you will almost never find good soaring conditions early in the morning or strong thermals over the sea. Any 'high pressure' weather situation will generate at least some amount of convective clouds, low pressure situations usually do not. | As a result, you will almost never find good soaring conditions early in the morning or strong thermals over the sea. Any 'high pressure' weather situation will generate at least some amount of convective clouds, low pressure situations usually do not. | ||
In order to set up ridge lift, select wind model 'constant' and set the wind perpendicular to the slope with | In order to set up ridge lift, select wind model 'constant' and set the wind perpendicular to the slope with 10–20 kt (5–10 m/s; 18–37 km/h). Advanced Weather computes the boundary layer dynamically dependent on terrain, as a result there will be a realistic reduction of windspeed for a landing in the valley but not at mountain slopes. | ||
Advanced Weather has a working model for wave lift, but so far no way of automatically detecting the conditions which lead to a lee wave, thus in order to use it, some Nasal coding is required. | Advanced Weather has a working model for wave lift, but so far no way of automatically detecting the conditions which lead to a lee wave, thus in order to use it, some Nasal coding is required. | ||