by MikeMike

In an earlier article the “leeches”, “backpacks” or “caravans” were mentioned. What exactly are they?

In every gliding competition you have pilots that fly the competition and pilots that follow those that fly the competition. Imagine a group of pilots milling around in front of a start point waiting for the optimum start time. The group slowly circles up to the top of convection but nobody leaves the thermal yet. The thermal now peters out but still all gliders keep circling as if there is a thermal there. After a while the whole group starts to descend slowly but nobody breaks away from the now negative thermal. Sounds familiar? This is a very common sight in gliding competitions.

The group now slowly descending in their negative thermal is composed of a few top pilots, who are well up in the standings, and the rest are backpacks. They are waiting for their idol to lead out so they can follow him around the task and hopefully, when the leader scores well or even wins the day, they will have a good score as well. It is the responsibility of the “leader” to find good thermals around the track and make sure that “followers” arrive back with a minimum of delay and little or no stress. Naturally all the decisions are to be taken by the leaders and basically the leeches or backpacks are taking a chauffeur driven limousine around the course. Now, the leaders think of this behavior as profiteering, the backpacks call it contest tactics.

Every leader knows the feeling. You fly out in front the whole day and every time you pull up into a thermal you look over your shoulder to check the little ducks that have been following you all day, and you see them streaming into “your” thermal. This happens over and over again.

Sometimes things go wrong for the backpacks. In a competition in the Swiss Alps many years ago a group of backpacks were clinging like glue to a well-known (and very good) competition pilot, who was racing around the task. Whilst looking for a good thermal the leader made a mistake and one of the backpacks ended up quite a bit higher (like several hundred meters) above the leader in a thermal. Having arrived at cloud base the question was what to do now. If he would head out on course he could loose contact with “his leader” who would no doubt rocket past him and all his chances of the day would be lost. That thought proved to be too much for our friend so he opened his airbrakes and continued to circle in the thermal (with the airbrakes fully open!) until the leader had caught up with him and left the thermal to continue the task. The backpack sighed a sight of relief, closed his airbrakes and dutifully followed his leader out on track. Order had been restored!

Another (rare) example of things backfiring for the backpacks. A competition in France and a top Belgian pilot is racing his standard class glider to the first turn point of the task. He is followed by a backpack whom he has trouble to identify. Who is it?? Then, after a while it strikes him that his companion is a 15m class glider and not another standard class. No wonder he didn’t immediately recognize him but the plot now thickens; “why is he following me?” the Belgian pilot asks himself. They round the first turn point together and continue on the second leg. The mystery is not solved until some time after they finish the task. The other pilot was indeed from same contest, but from another class that had an entirely different task that day. Probably the poor soul had lost contact with his original “leader”, and was all by himself (the worst that can happen to backpacks). When he saw our Belgian friend rocket past he must have thought his fortunes had turned and he gratefully “hooked on”. It was only later that is was confirmed that the backpack had zero points for the day because he had flown the wrong task!

Now, what has all this got to do with Thermal tax? Thermal tax is a system to charge profiteers for their use of thermals found by others. For those who have followed the latest European and World Gliding Championships with the help of v-Pos you can actually see these little strings of gliders move across the computer screen (a little bit like a radar screen); the leader of the pack followed by the backpacks. As the leader finds a thermal they all bunch up for a while, their little wings rotating like they are being moved around on their wheel. Then one leaves and the others duly follow until the next thermal. The leader provides a service to them by eliminating the need for the others to actually find thermals. For this service he needs to be compensated and this is possible with the help of today’s GPS systems.

Imagine the following system. A glider in a contest finds a thermal. He is followed by for instance five more gliders who join him in the thermal. It seems no more than reasonable that the followers now pay the finder of the thermal a small compensation, lets say 2 points. At the end of the day, after the scores have been computed, these are adjusted by adding the thermal tax accumulated by those who found thermals to the score and deducting the thermal tax levied by the user of already detected thermals. So, let’s say a pilot has scored 850 points for the day and has found 9 thermals for others totaling 18 units of thermal tax @ 2 points each. His score for the day will now increase to 886 points. Another pilot who has followed our leader the entire day, and thus has the same performance, also scores 850 points, but he has used nine times the thermals found by others. So from his score the deduction is nine times two points, being 18 points, reducing his score to 832 points for the day. This system is great because now leaders don’t mind a group following them, the more backpacks the better in fact. The more taxpayers the better!! The backpacks will still have a better score than they would have had on their own, but some may see the light and go out on task alone and learn something!! Winners all around, so lets introduce this system. We have the technology, just needs someone to sit down and work out the definition of finding a thermal, when the tax flagfall is and to write a program that automatically allocates (thermal)tax paid and levied based on logger files (place and time info).

Just a final story on how backpacks can be a real nuisance. An open class contest in France, and the going is tough. A group of gliders, actually two leaders and six or seven backpacks, carefully progress along the task. The weather is deteriorating and the leaders are getting lower and lower. There is a very weak thermal at maybe 200 meters above the ground. The leaders must stop to circle if they do not want to land out. They are both dumping water to stay airborne, but close the taps when two backpacks arrive a little below them. Some more gliders join the pack including a notorious backpack who always manages to be in the way. He joins the group at the top of the gaggle. Backpacks sometimes do that because they do not need to think about centering the thermal. We are all still milling around without gaining much height when the aforementioned backpack, who is a little bit higher, decides there is no merit in carrying all this water and consequently opens all dump valves of his Nimbus, pouring water over a highly frustrated and muttering group of pilots who really don’t need this complication to stay airborne. This behavior of the man was not malicious by intent, just plain stupid and selfish, and from that perspective levying thermal tax is more than reasonable if that’s the sort of behavior one has to put up with in a contest.

Long live the (thermal)tax man!!