Competition Ballooning – Elbow
The rule (or information) for this task is set out in Chapter 15 of the Event Rules
As it says on the tin, the simple aim of this task is to make as great a change of direction as possible. The remaining information just relates to how far you have to fly each leg to score; usually 2-3 km but in light winds can be 1km. At the briefing you need to draw circles indicating the minimum and maximum distances of the first leg. The length of that first leg will depend on whether, once you have achieved the minimum distance, that direction can be improved by flying further or you start to deviate towards the intended direction of your second leg.
It is almost always set during the morning flight when the change in wind with height is maximal. The overnight inversion often produces very light winds near the ground that are over 90o from those aloft. Where this task fails is if everyone achieves the maximum 180o i.e. flies back in the exact opposite direction of the first leg. Results are then reliant on the accuracy of measurement. In the 1989 World Championships in Saga, Japan, well before GPS and electronic loggers it was a case of flying back across your previous track and dropping a marker in the middle of a field. Then trying to measure the exact location with tape measures and compass bearings ended up a bit of a lottery. It was no better in the World Championships in Hungary in 2010 when we did have electronic loggers. Results of the top 30 pilots were all within 1 degree; accuracy was measured to two decimal places and a pilot achieving 179.85o received about 750 points. 179.85o rather than the perfect 180o would occur if the position of your logger point was recorded as 4 metres before or after crossing the exact line of your previous outward track, well within the accuracy of the GPS measurement. As you may imagine competition pilots are not exactly enthused at losing a potential 250 points because of measurement inaccuracy; this situation has not been fully resolved yet. This is why the competition director should be assured that 180o is not attainable when setting the task and that the greatest change of direction is due to skill and not due to the accuracy of measurement. The ideal situation is where there is most change in direction at an intermediate height and not between ground and the highest altitude you are allowed to fly; all competitions have a maximum altitude e.g. 10,000ft for the competition area and any flight above that incurs penalties. This situation occurred in the World Championships in Battle Creek in 2012 where the greatest change was between the wind at 1,420ft and one at a height of 5,000ft. The skill then was to fly for 2km at exactly 1,420ft with change of direction lost at altitudes only 20-30ft above or below that and then to repeat it at 5,000ft.
The next strategic decision to consider is whether to do the high leg first or low leg. As mentioned, the overnight inversion produces the greatest change of direction and as the sun comes up the left on the ground will disappear so, usually, the greatest change in direction occurs at the beginning of the flight. However ground features are important to consider. There is no point doing the low leg first if the flight path takes you straight towards a sensitive area with a height restriction of 2,000ft. The situation may arise where by flying the high leg first the wind takes you towards a deep valley where the valley wind offers an even greater change in direction than the ground wind at the take off site. The other factor to take into account is the speed of the wind. I remember dropping down into a valley in Luxembourg expecting a wind at right angles to my present track to find that there was no wind at all, or what there was would take me nowhere fast; each task usually has a scoring period meaning you have to complete it within a certain time.
Finally you have to take the speed of the wind into account during the transition from the first leg to the second leg. If the greatest directional change is between ground level and a wind at height and there is a fair wind at both altitudes then the balloon will take time to turn as it ascends or descends. This can take up to 1km and you have to predict when you are halfway through your turn as that will be the best position to drop your marker of mark your logger point. The balloon always appears to take longer to turn ascending than descending and this can be exacerbated by the balloon ‘tracking’ i.e. distorting in shape such that its momentum takes it straight on rather than in the direction of the wind. Having said that the balloon does not track if it starts out at nil velocity so if the wind near the ground is calm or you climb from take off to do the high leg first, then the turn onto the higher wind direction tends to be tighter. Most importantly, as you drop your marker or record your logger point, mark it on your map. You can then draw circles centred on that mark indicating minimum and maximum distances you can fly the second leg for your next scoring point. As the turning point reduces the difference in change of direction between the legs it is best to fly the maximal distance allowed before achieving your scoring point to minimise that effect.
With all that theory I have flown an elbow with a score of close to 0o i.e. I ended up flying straight on. I did my low leg first and then went up in search of a change in wind direction. I found the greatest change was with a wind only 20o to the left of my first track at 4,000ft but after 10minutes found the wind had changed slowly towards my previous track. I change height again and found a wind direction 30o to the right so headed out on that. This wind then changed to the left so by the time I had reached my maximum distance I was back on the same track I had had during the first leg. You might think you cannot get worst than 0o but you can also end up infringing distance limits and receiving penalties for flying through PZs etc.!
Elbow. British Nationals, Ludlow. High leg first to use valley effect from Brimfield to Burford. Black circles to show minimum distance of legs.
The low leg. World Championships , Battle Creek, USA. 2012 Karin Bareford
The High leg. World Championships, Debrecen, Hungary 2010. David Bareford
Written by David Bareford
