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gliding-angle

Gliding competitions

Some of the pilots in the sport of gliding take part in gliding competitions. These are usually racing competitions, but there are also aerobatic contests and cross-country distance competitions. Many other pilots enjoy flying cross-country just for its own sake without racing.

History of competitions

In the early days, the main goal was to stay airborne for as long as possible. However flights lasted for days and pilots killed themselves by falling asleep. This type of contest was then abandoned.

From the earliest days of gliding there was also 'free distance' flying. Pilots launched themselves from a hill top, attempting to glide as far as possible. Once pilots learned to exploit ridge lift and thermals, flights could be extended further. Eventually they mastered flying from thermal to thermal, resulting in ever longer retrieves. As the pilots and gliders became better, the winner of a competition day might fly so far that he could not get back to the competition site for the next day. Turn-points were therefore used. Those pilots who managed to fly all the way to the turn-point and back would score the same distance as for free distance flights. When pilots and gliders became even better, most of the pilots would complete the task. Points were then awarded for speed.

Initially observers would be stationed at the turn-points to verify that the pilots rounded the them. Later on, pilots used cameras to photograph to prove they have rounded each turn-point. Today, pilots use GPS flight recorders to log their positions to prove that the task was correctly completed.

Present day

Modern gliding competitions now comprise closed tasks where everyone races on an aerial route around specified turn-points, plus start and finish points, that brings everybody back to base. The weather forecast and the performance of the gliders, as well as the experience level of the pilots, dictate the length of the task. Today, most of the points are speed points. Nowadays, the rule is to set the task so that all pilots have a fair chance of completing it.

With the advent of GPS, new types of tasks were introduced such as speed or distance tasks within assigned areas, and speed or distance tasks with pilot-selected turn-points. Despite the use of pilot-selected turn-points made possible by GPS, tasks over a fixed course are still used frequently. In the European Gliding Championships in 2005, a task of 1,011 km was set in the open class; the longest task in an international competition.

The FAI Sporting Code for gliders sets out the rules and procedures to be used to verify soaring performances in competitions and badge flights. The main objective of these rules is to ensure that a soaring performance is achieved to a level of proof that is consistent for all flights.

Levels of competition

Competitions are held at the local, regional, national and international level. Regional contests are typically the first contests that a pilot enters. Strong performance at the regional level allows pilots to gain a high enough ranking to enter national championships. Thereafter international competitions are available for the most ambitious pilots: the European Gliding Championships, and the World Gliding Championships. There is also the prestigious Barron Hilton Cup, which is an invitation event for the top pilots. There are now six classes open to both sexes, plus three classes just for women, and two junior classes (See Glider Competition Classes). Some competitive classes (Sports Class in the US, Club Class elsewhere) have scoring systems that are handicapped based on the type of glider each pilot is flying. This allows pilots to compete on a relatively equal basis even if their gliders have widely varying performance.

A competition day

Regional gliding contests generally last about a week, while international contests last two. Early in the day a weather forecaster will discuss the conditions with the 'task-setter'. Once the task has been decided, a briefing is held to describe the task, the forecast weather and any airspace restrictions. Before this, the pilots will have prepared their gliders and moved them onto the grid ready for launching. Launching takes place when the director believes that the gliders can easily stay airborne. Launching all the gliders usually takes less than an hour.

Water ballast

It may seem counter-intuitive, but pilots put water ballast into compartments in the wings to make their planes heavier. Modern gliders can take large quantities of water (a Nimbus-3, for example, can hold 272 kg). The objective is to increase the speed, while maintaining the same gliding angle. The downside is that the glider will climb more slowly in thermals.

If, for example, a glider's weight is increased by 50% by water ballast, then the forward speed together with its sink rate will also increase by about 50%. However the sink rate alone may only increase from 0.5m/s to 0.8m/s. The 0.3m/s increase in sink rate only results in a 10% loss in climb rate if the glider flies in a thermal that rises by a speed of 3m/s (which is common). The time lost in climbing more slowly is then more than recouped by the increased speed to the next thermal. However if the thermals are weaker, it may be better to fly without ballast.

The airframe of a glider is not designed to withstand the stresses of a hard landing while the glider is loaded with water. Consequently, pilots start emptying the ballast tanks shortly before the gliders cross the finish line so they are empty when they land. This results in spectacular images when competition pilots cross the finish line at low altitude.

Tactics

Races are won on the basis of speed over a specified course. Time on course is measured from when each pilot crosses the start line until they cross the finish line. Each competitor may elect to start any time after the start opens. To allow all competitors sufficient time to get into a good position to start, competition rules specify that no competitor may start until twenty minutes after the last competitor has launched. The start 'line' is generally a cylinder several miles in radius with a specified maximum altitude limit. Competitors will attempt to start as close to the maximum start height as possible and generally at the edge of the cylinder closest to the first turnpoint.

One of the more important decisions of a flight is when to start. This decision is based mostly on each pilot's desire to be on course during the strongest weather conditions of the day. There are also competitive considerations. Often competitors will try to start just after other pilots, using them as "markers" for favourable lift conditions ahead on course. Using this technique, a skilled pilot can make up several minutes on the earlier starters during the early portion of the flight. Skilled pilots who are being followed in this way may use a variety of tactics to shake off pursuers, such as doubling back after a start and starting again. Each pilot may start as many times as he or she chooses - only the last start counts. However, playing an endless game of "start gate roulette" can have disadvantages. Late starters can find themselves still out on course when the soaring weather becomes weak or wholly unsuitable. The best pilots are therefore also good weather forecasters.

The two most important factors influencing the overall speed at which glider can fly around a given course is the average strength of the lifting air and the altitude at which the rising air stops. Experienced pilots avoid circling in relatively weak lift and use only the strongest lift. However, being too selective runs the risk of getting too low to the ground and being forced to accept weaker sources of rising air in order to avoid landing "out". This can cost the competitor valuable time. The best pilots also expert at getting the most out of each source of lift by manoeuvring their glider quickly to the centre of the lift where the rate of climb is greatest.

It is often possible to fly efficiently by not stopping to circle in the areas of rising air but merely by slowing down in the rising air while flying straight ahead on course, then speeding up again when the air is no longer rising. This technique is known as 'dolphining'. If the conditions are favourable, the glider can gain enough energy from each source of lift and maintain its overall height for long distances without circling. Windy days are good for this, as the thermals often line up into cloud streets, enabling the pilot to race without having to turn. Choosing a straight course may be the best tactic if a slight diversion can keep the glider in rising air for longer, or at worst keep out of the strongly sinking air.

Another tactical decision has to do with the use of water ballast. Ballast allows a glider to cruise at a higher speed at the expense of some climb performance. On a strong day the glide performance matters more and carrying ballast is preferred. On a weak day the opposite is true. Competition pilots usually launch with ballast, even though they may elect to dump it on course. However it is possible that conditions may improve and so sometimes keeping the ballast throughout the task may be advantageous. Nevertheless heavier glider will be at a disadvantage if weak conditions persist and so sometimes dumping the water during the task may be the better choice.

One of the last critical decisions each competitor makes is determining when the glider is high enough to reach the finish. Taking on unnecessary altitude wastes time since there are no points gained for arriving high at the finish. However the higher glider will be able to cruise back faster and so if strong lift is available it may be better to take the final climb higher than the minimum height required to get home. Being higher also gives a safety margin if more sink than lift is encountered on the final glide.

Scoring

Each glider carries a device for recording its GPS position every few seconds. This provides evidence that the start, turn-points and finish have been legitimately reached. The winner on each competition day is the fastest and can have a maximum score of 1000 points. This can be devalued if very few gliders get around the task. (The reason being that if only a few gliders get round the task, then luck was probably a key factor.) The scores are then assigned according to the speed relative to the winner. A small proportion of the maximum score is given for the distance covered so that competitors who do not complete the task, will get a score. In some competitions, handicapping is used and so further factors are applied before determining each pilot's score for the day.

Grand Prix

In an attempt to widen the appeal of gliding contests, a new format contest, the Grand Prix, has been introduced. Innovations introduced in the Grand Prix format include simultaneous starts for a small number of gliders, tasks consisting of multiple circuits, and simplified scoring.

Online Contest

Also gaining popularity in recent years is an informal internet competition called the Online Contest (OLC) where pilots upload their GPS data files and are automatically scored based on distance flown. 10,209 pilots worldwide participated in this contest in 2007.

Aerobatics

Aerobatic competitions are held regularly. In this type of competition, the pilots fly a program of manoeuvres (such as inverted flight, loop, roll, and various combinations). Each manoeuvre has a rating called the "K-Factor". Maximum points are given for the manoeuvre if it is flown perfectly, otherwise points are deducted. Efficient manoeuvres also enable the whole program to be completed with the height available. The winner is the pilot with the most points.

See also

References

External links

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