In a lecture I once attended, Peter Harvey pointed out that the one thing all top pilots had in common was keen eyesight. Pilots should ensure that if necessary their distance vision is adequately corrected not only for safety reasons, but also to be able to spot visual clues to the presence of lift. Astigmatism, in particular, will make power lines difficult to spot. Most pilots are aware of 'direct' clues such as clouds, birds thermalling, smoke rising, gliders climbing and grass or other debris at altitude but sometimes less obvious 'indirect' clues can make the difference between staying up or bombing out.

Sometimes the direction of smoke may not only mislead us about the general wind direction but also give away the presence of a nearby thermal. Usually smoke travels more or less horizontally from the fire for some distance before rising. Air feeding a thermal is often drawn towards the source across flat ground so that a smoke source in the 'cachment' area of the thermal will 'point' towards the source. Occasionally we might be lucky enough to find a two fires whose smoke trails seem to converge at an oddly wide angle. Go for it! The smoke is nicely triangulating the source for us. A more common situation is that we may be soaring part of a broken ridge and wondering if the next hump along is working well. A smoke source in the valley may point towards the part of the ridge which is working best.

Although not as easily seen as smoke, flags can be a great help. The Hope valley provides us with a good example. If we are flying on the south east face of Mam Tor wondering whether Treak Cliff is soarable we can try gliding across until we see the flag at the Treak cavern. If it was soarable on Mam Tor and the flag points towards Treak cliff there is a good chance Treak will be soarable. If the flag points along the cliff or droops forget it and go back to Mam. This exercise also classically demonstrates the advantage of good eyesight.

Anything which is visibly influenced by the wind can give us clues. Washing on a line, trees, grass, water surfaces, sailing boats and peoples clothing are all good examples. Remember that the type of clothing people wear can give us an idea of conditions on the ground.

These are nasty pieces of work. As well as being one of the most frightening things to get low over, located in really awkward places, eyesores, needing backup for when the wind drops and paid for by a levy on our electricity bills, (you can tell I'm a great supporter of them) most of the ones currently in service are designed to run at a constant RPM. This means that as long as there is enough wind to turn them you can't tell by looking at them how strong the wind is.