Accurate polar data is very difficult to measure. Although we have made many attempts over the years to measure actual glider performance, we have found that even with the best instruments and the most careful measurement methods, the level of scatter in the measured data is very high, and in fact eclipses the differences in performance between one model of glider and another, or even between one class of glider and another.
It has been our policy for 20 years not to publish claims of specific L/D performance, because of the problems cited above with measuring the data accurately and because the use of published performance claims by pilots to compare one glider to another inevitably leads to performance “inflation.”
However, due to the large number of pilots now using advanced instrumentation incorporating speed to fly calculations, we are receiving more and more requests for polar data. As a result, we have generated estimated polars for each of our gliders. The data is based on a large number of measurements of both relative and absolute performance of a large number of different gliders over many years. This data is not a claim of performance, and is not intended to be used to compare one glider’s performance against another’s. (While we feel that this data gives an accurate relative comparison among the models named, it would be useless to compare one of these models with a model not on this list, using data for that model obtained from another source.) We have tried to state realistic data so that the data will be useful for speed to fly calculations. The data represents what we expect for a pilot hooking in at 130% of the minimum recommended pilot weight (as listed in the owner’s manual or operating limitations placard). Theoretically, to a first approximation, L/D will not change with changing pilot weight, and the true airspeed and descent rate for a given L/D / airspeed data point shown, at any pilot weight other than 130% minimum recommended, will be equal to the square root of the ratio of total weight (pilot plus glider) times the speed and descent shown. (In other words, if the placarded minimum pilot weight is 140 lbs, the polar data is for an assumed pilot weight of 140 * 1.3 = 182 lbs. If the glider weight is 65 lbs, the total weight for which the polar is assumed is 247 lbs. If you are using a pilot weight of 210 lbs, then the total weight is 275 lbs. At each L/D / airspeed data point indicated, to compute the new speed and descent for that new pilot weight, multiply the speed and descent rate shown by the square root of the ratio of 275 divided by 247, or 1.055.)
For a very clear explanation and discussion of glider polar theory, the webpage “Glider Performance for Dummies” by Jim D. Burch is hard to beat. The examples are all based on sailplanes, but the theory applies to hang gliders (and paragliders, for that matter).
Brauniger Polar Input
Nominal values for use with Brauniger flight instruments, for recreational pilot and harness configurations. Increase V2 mph by 6% for performance tuning and harness configurations.
|Model||V1 (fpm@mph)||V2 (fpm@mph)|
|Ultra / Super||196@22||530@40|
|U2 / Fusion||176@23||530@44|