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## Sustainer Engines 

Some gliders are equipped with sustainer engines to assist in remaining aloft long enough to return to an airport. However, sustainer engines do not provide sufficient power to launch the glider from the ground without external assistance. These sailplanes are launched by either aerotow or ground launch. [Figure 2-17]  A more detailed explanation of engine operations can be found in Chapter 7, Launch and Recovery Procedures and Flight Maneuvers. 

## Landing Gear 

Glider landing gear usually includes a main wheel, a front skid or wheel and a tail wheel or skid, and often wing tip wheels or skid plates. Gliders designed for high speed and low drag often feature a fully retractable main landing gear and a small breakaway tailwheel or tail skid. Breakaway tail skids are found on high-performance gliders, and are designed to break off when placed under side loads. [Figure 2-18] 

For safety reasons, the main landing gear remains extended during the launch process. If there is a tow break or early release, the pilot needs to focus on a safe return. The pilot’s 

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normal landing checklist provides a landing gear check, but during a low-altitude emergency, important items could be skipped on any checklist. Therefore, it is good practice to leave the main gear extended until reaching a safe altitude. 

## Wheel Brakes 

The wheel brake, mounted on the main landing gear wheel, helps the glider slow down or stop after touchdown. The type of wheel brake used often depends on the design of the glider. Many early gliders relied on friction between the nose skid and the ground to come to a stop. Current glider models are fitted with drum brakes, disk brakes, and friction brakes. The most common type of wheel brake found in modern gliders is the disk brake, which is very similar to the disk brake on the front wheels of most cars. Most glider disk brakes are hydraulically operated to provide maximum braking capability. Wheel brake controls vary from one glider type to another. 

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