How tight do you circle?

October 28, 2020

A statistical analysis of thousands of flights shows: an average pilot needs around 25 seconds for a thermal circle. Experienced pilots often turn the crank closer. // Source: M. Morlet, Cross Country Magazine, edited The French XC driver Martin Morlet is the developer of the interesting XC Analytics app (Lu-Glidz reported). This can be used to statistically analyze many technical details of flights. For example: How closely do I actually circle in the thermal? With this question, Martin Morlet once examined around 100,000 flights from the database of the French XC online contest. The result was a graphic that shows the percentage distribution of the pilots: Which proportion closes its thermal circles rather quickly or does it take a lot of time? According to the results, a pilot needs an average of 25-26 seconds for a thermal circuit. But the average does not necessarily have to mean that the optimum is in this area. The interesting question is: How do the "better" pilots do it? Morlet wrote an article about his findings for the current issue 215 of Cross Country Magazine. Another graphic is included in the article: It shows that the typical thermal cycle duration of the evaluated flights decreases almost linearly with increasing XC distance. For flights of up to 50 km, the pilots still need an average of more than 25 seconds per thermal circle. For distances of 180 km and more, this value drops to under 23 seconds. Morlet sees the XC distance as a good indicator of the pilots' average experience. Morlet also points out that the most successful French XC pilots only need around 20 seconds or less to complete a circle. In other words: you crank a lot tighter than the average. Kelly Farina goes even further in his readable book Paragliding Like a Master. In it he recommends what he called the 4/90 rule. For each quarter of a thermal circle (i.e. 90 degrees) you should ideally only need 4 seconds. A full circle then lasts 16 seconds. If one takes Morlet's XC analyzes as representative, but only one percent of the pilots put Farina's recommendation into practice. In such thermal circle analyzes, it would also be interesting to look at the height of the thermal above ground. Typically, thermals start quite tight on the ground and then widen further upwards. To what extent is this taken into account by pilots in their crank behavior? Experienced pilots know that they often only have a chance to stay in a thermal near the ground or a slope if they "put the wing on the stabilo". Circles flown in this way then even take less than 16 seconds.

This article has been translated for your convenience and was originally written in alemán.