Bigger and Stronger

Ever since the first reliable helicopters took to the air, these rotary-wing air­craft have been widely used all over the world for both military and commercial purposes. Helicopters are not cheap to operate, and they are noisy, but their flexibility has made them extremely useful that it is hard to imagine a world without them.

A disadvantage of a helicopter is that it is slower than a fixed-wing aircraft. Most helicopters travel at speeds of less than 200 miles per hour (320 kilometers
per hour). One way to make a helicopter go faster is to add jet-thrust engines or propellers for forward flight. This pro­duces a compound helicopter that can fly at more than 340 miles per hour (550 kilometers per hour).

The first helicopters had piston engines, but most modern helicopters are powered by a gas turbine jet engine called a turboshaft. Some helicopters, especially military craft, have short stubby wings that provide extra lift dur­ing forward flight. The wings also are used for attaching payloads and as mounts for missiles and other weapons.

The Soviet Union has built some of the world’s biggest helicopters, such as the Mil Mi-26, probably the heaviest helicopter ever flown. A rival U. S. heli­copter, the Sikorsky CH-53E Super Stallion (1974), used just one extra-large rotor with a diameter of 79 feet (24.08 meters). It could carry a crew of three and up to fifty-five troops.