Cross-Country Flight Using Other Lift  Sources Water Ballast the landing gear well. If the CG hook is within the landing  gear well, retracting the gear on tow interferes with the  towline. Even if the glider has a nose hook, retracting the  gear on tow is not recommended, since the handle is usually  on the right cockpit side and switching hands to raise the gear  can lead to loss of control on tow. A CG hook, as compared  to a nose hook, makes a crosswind takeoff more difficult  since the glider can weathervane into the wind more easily.  In addition, a CG hook makes the glider more susceptible  to “kiting” on takeoff, especially if the flying CG is near the  aft limit. This can present a serious danger to the tow pilot. Many world distance and speed records have been broken  using ridge or wave lift. Under the right conditions, these  lift sources can extend for hundreds of miles from sunrise  to sunset. Ridge or wave lift is often more consistent than  thermals, allowing long, straight stretches at high speed. Cross-country flight on ridge lift poses some special problems  and considerations. Often, the best lift is very close to the  ridge crest where the air can be quite turbulent. Great pilot  concentration is needed over several hours close to terrain  in rough conditions for longer flights. On relatively low  ridges, (e.g., in the eastern United States) ridge lift may not  extend very high, so the pilot is never too far from a potential  off-field landing. These are not conditions for the beginning  cross-country pilot. In milder conditions, gaps in the ridge  may require thermaling to gain enough height to cross the  gap. Ridge lift can provide a place to temporarily wait for  thermals to generate. For instance, if cumulus have spread  out to form a stratus layer shading the ground and eliminating  thermals, a wind facing slope can be used to maintain soaring  flight until the sun returns to regenerate thermals. To maximize average cross-country speed on a day with  strong thermals, water ballast can be used. The gain in speed  between thermals outweighs the lost time due to slightly  slower climbs with water ballast. If thermals are weak,  ballast should not be used. If strong thermals become weak,  the water ballast can be dumped. In any case, water ballast  should be dumped before landing because heavy wings are  more difficult to keep level on the ground roll, and a hard  landing is more likely to lead to damage with a heavier  glider. Water dumping times vary but are typically between  2 and 5 minutes. Water ballast is carried in the wings in built-in tanks or water  bags. The latter works well but has been known to have  problems with leaks. Filling and dumping systems vary from  glider to glider, and it is vital to be familiar with the ballast  system as described in the GFM/POH. Filling without proper  venting can lead to structural damage. Care must be taken  to ensure that both wings are filled with the same amount of  water. If one wing has a few extra gallons, it can be lead to  ground loops and loss of control on takeoff, especially in the  presence of a crosswind. Wave lift can also provide opportunities for long and/or fast  cross-country flights. Most record flights have been along  mountain ranges; flights in excess of 2,000 kilometers having  been flown in New Zealand and along the Andes. In the United  States, speed records have been set using the wave in the lee  of the Sierra Nevada Mountains. In theory, long-distance  flights could also be made by climbing high in wave, then  gliding with a strong tailwind to the next range downwind  for another climb. Special consideration for pilot physiology  (cold, oxygen, etc.) and airspace restrictions are needed when  considering a cross-country flight using wave lift. Convergence zones can also be used to enhance cross-country  speed. Even if the convergence is not a consistent line but  merely acts as a focus for thermals, dolphin flight is often  possible, making glides over long distances possible without  thermaling. When flying low, awareness of local, small-scale  convergence can help the pilot find thermal triggers, enabling  climb back to a comfortable cruising height. Water expands when going from the liquid state to the solid  state. The force of the water ballast freezing can be enough  to split composite wing skins. If anticipating flying at levels  where the temperature might be below 0 °C, follow the GFM/ POH recommended additive to avoid freezing. Some gliders have a small ballast tank in the tail, as well  as ballast in the wings. Tail ballast is an effective means to  adjust for a CG that is too far forward. It should be used with  caution, however, since the position of the tail ballast tank  gives it a long arm aft of the empty CG. A careless calculation  can lead to too much water in the tail tank and a flying CG  that is aft of the limit. It is possible to find ridge, thermal, wave, and even  convergence lift during one cross-country flight. Optimum  use of the various lift sources requires mental agility but  makes for an exciting and rewarding flight. 11-17