II.

Craft

The first gliders, made of wood and fiber, were developed by the German inventor Otto Lilienthal in the 1890s, and were subsequently improved upon by the American inventors Orville and Wilbur Wright. Later design modifications have produced the highly streamlined modern craft, made of fiberglass, with slender wings spanning 15 to 20 m (50 to 65 ft). Gliders are equipped with spoilers, dive brakes, or flaps to increase descent rate. Flight controls and instruments are similar to those of powered aircraft: a control stick to operate the ailerons and elevators; rudder pedals for rudder control; an airspeed indicator; an altimeter; a turn-and-bank indicator; a compass; and a variometer to register changes of altitude. A two-way radio and oxygen equipment may also be carried.