Extended cross-country flights have been made in relatively low-performance gliders. However, on any given soaring day, a glider with a 40:1 glide ratio is able to fly farther and faster than one with 20:1, assuming the pilots in both have similar skill levels. Often, a glider pilot looks for more performance in a glider to achieve longer and faster cross-country flights.
Most high-performance gliders have a single seat. If a twoseat, high-performance glider is available, the pilot should obtain some instruction from an authorized flight instructor before attempting to fly a single seat high-performance glider for the first time. Before flying any single-seat glider, pilots should thoroughly familiarize themselves with the GFM/ POH, including important speeds, weight and balance issues, and all operating systems in the glider GFM/POH, such as landing gear, flaps, and wheel brake location.
High-performance gliders are usually more complex and somewhat more difficult to fly, but they vary considerably. Current Standard Class gliders (15 meter wingspan and no flaps) are easy to assemble, and newer types are comparatively easier to fly. On the other end of the spectrum, Open Class gliders (unlimited wingspan with flaps) can feature wingspans of 24 meters or more with wings in four sections. The experience required to fly a high-performance glider cannot be quantified simply in terms of a pilot’s total glider hours. Types of gliders flown (low and high performance) must be considered.
Almost all high-performance gliders have retractable landing gear, so pilots must make certain that “landing gear down” is on their prelanding checklist. Most landing gear handles are on the right side of the cockpit, but a few are on the left side, so caution is required when reaching for a handle to make sure it is not flaps or airbrakes. A common error is to neglect to retract the landing gear and then mistakenly retract it as part of the prelanding checklist. A gear-up landing in a glider usually causes only embarrassment and minor damage. The distance between the pilot and the runway with the landing gear up is minimal, providing no real “cushioning” protection for the pilot during a hard landing.
Many high-performance gliders have flaps. A few degrees of positive flap can be used when thermaling, and some gliders have 30° or more positive flap settings for lower landing speeds. Flaps can be set to 0° for relatively low-speed glides, while negative flap settings are available for glides at higher speeds. The GFM/POH and glider polar provide recommended flap settings for different speeds, as well as maximum speeds allowed for different flap settings. A few high-performance gliders have no air brakes and use only large positive flap settings for landing. This system allows steep approaches but can be uncomfortable for a pilot who has only used spoilers or dive brakes for landing. A thorough ground briefing is required.
Many high-performance gliders have greater wingspans that require special care to avoid ground loops on takeoff or landing. Runway lights and other obstructions near the runway can become a problem. If a wingtip strikes the ground before the glider has touched down, a cartwheel is a possibility, leading to extensive damage and serious injury. Gliders with long wings often have speed restrictions for dive brake use to avoid severe bending loads at the wingtips.
The feel of the controls on high-performance gliders is light, and pilot-induced oscillations (PIOs) occur easily with the sensitive elevator. Elevator movements using the wrist only, while the forearm rests on the thigh, can aid in avoiding PIOs.
Some high-performance gliders have only one center of gravity (CG) towhook either ahead of the landing gear or in 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.
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.
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.