The Parts of A Dirigible
The framework of a rigid dirigible consists of lengthwise metal girders held together by encircling metal rings. The girders, usually made of strong aluminum alloy material, are shaped to meet at the nose and tail of the framework. Fixed surfaces, known as fins, are attached to the tail section of the framework. To the vertical fins are hinged the rudders that steer the dirigible, and to the horizontal fins are attached the elevators that control the angle at which the airship rises or descends.
The framework has an outer cover of cloth stretched and weatherproofed by several applications of aircraft dope. Inside the framework are several gas cells. These cells hold the lighter-than-air hydrogen or helium gas that make the dirigible buoyant, or able to float in the air. (Further information on the principles that explain why a dirigible remains aloft is found in the article Balloon.) The passenger cabins of dirigibles are suspended beneath the frame or placed inside it. The internal-combustion engines that turn the propellers are rigidly attached to the frame. (As on a ship, the propellers face rearward and push the dirigible forward.) The top speed of a dirigible is about 80 miles per hour (130 km/h), but it can travel 5,000 miles (8,000 km) without landing.