Diversion on a soaring cross-country flight is the norm rather than the exception. Some soaring days supply fair weather cumulus evenly spaced across all quadrants, and it is still beneficial to deviate toward stronger lift. Deviations of 10° or less add little to the total distance and should be used without hesitation to fly toward better lift. Even deviations up to 30° are well worthwhile if they lead toward better lift and/or avoid suspected sink ahead. The sooner the deviation is started, the less total distance is covered during the deviation. [Figure 11-16]
Deviations of 45° or even 90° may be needed to avoid poor conditions ahead. An example might be a large cloudless area or a shaded area where cumulus have spread out into stratus clouds. Sometimes deviations in excess of 90° are needed to return to active thermals after venturing into potentially stable air.
Deviations due to poor weather ahead should be undertaken before the flight becomes unsafe. For instance, if cloud bases are lowering and showers developing, always have the option for a safe, clear landing area before conditions deteriorate too much. Generally, glider pilots will encounter stable air or sinking air which will put them on the ground before VFR conditions disappear. If the sky becomes cloudy, thermaling will cease. Ridge lift might remain but will be in the clouds so either way the glider pilot must get on the ground. It is better to land on your terms rather than be forced down by total lack of lift. Thunderstorms along the course are a special hazard, since storm outflow can affect surface winds for many miles surrounding the storm. Do not count on landing at a site within 10 miles of a strong thunderstorm—sites farther removed are safer. Thunderstorms ahead often warrant large course deviations of up to 180° (i.e., retreat to safety).
NOTE: Cloud development can and does shade the earth, decreasing the heating, and hence decreasing lift. Be aware of cloud shadowing.
Navigation has become far easier with the advent of GPS. Since GPS systems are not 100 percent free from failure, pilots must still be able use the sectional chart and compass for navigation. It is important to have an alternate plan in the event of becoming lost. As discussed earlier, preflight preparation can help avoid becoming lost. Spend some time studying the sectional chart for airports or other notable landmarks along the route.
If you are still lost after some initial searching, try to remain calm. The first priority is to make sure there is a suitable landing area within gliding distance. Then, if possible, try to find lift, even if it is weak, and climb. This buys time and gives a wider view of the area. Next, try to estimate the last known position, the course flown, and any possible differences in wind at altitude. For instance, maybe the headwind is stronger than anticipated and not as far along the course as expected. Try to pinpoint the present position from an estimate of the distance traveled for a given period of time and confirm it with visible landmarks by reference to the sectional chart. For instance, if at point X, averaging about 50 knots, heading north for about 30 minutes should put the glider at point Y. Look again at the sectional chart for landmarks that should be nearby point Y, then search the ground for these landmarks. Thermaling while searching has the added advantage of allowing a wider area of scan while circling.
Once a landmark is located on the sectional and on the ground, confirm the location by finding a few other nearby landmarks. For instance, if that is a town below, then the highway should curve like the one shown on the chart. Does it? If you are lost and near a suitable landing area, stay in the area until certain of location. Airports and airport runways provide valuable clues, like runway orientation and markings or the location of town or a city relative to the airport.
If all efforts fail, attempt a radio call to other soaring pilots in the area. A description of what is below and nearby may bring help from a fellow pilot more familiar with the area.