Straight Up: The Helicopter

^{National Archives from Navy}

^{Marine infantry attack from a helicopter in Korea, September 20, 1951, one of the first times a helicopter was used as an offensive weapon.}

“The helicopter,” said the famous pioneer, “does with great labor only what a balloon does without labor.” He concluded: “The helicopter is much easier to design than the aeroplane but it is worthless when done.” That was Wilbur Wright in 1906.

Mr. Wright had a point. People had been trying to build helicopters for centuries, and their efforts had produced hardly any results. In 1935, airplanes had reached the altitude of 47,352 feet, attained the speed of 440 miles per hour and had flown non‑stop for 5,657 miles. At the same time, the helicopter altitude record was 518 feet, a chopper had reached the speed of 60 miles per hour and another had flown 27 miles.

This was in spite of the fact that Europeans had been making toy helicopters since the 12th century, and the Chinese had been making them even earlier. The toy helicopter was a stick with rotor blades. The stick fitted into a cylinder that was wound up with a string. The operator pulled the string, and the little ’copter flew straight up. Powering the rotor was an early problem. One bright soul in renaissance times suggested that the helicopter pilot pull a rope wound around the rotor the way a child pulled the string of the toy. Aside from the fact that Superman, or his ancestors, was still on the planet Krypton and rope‑pulling propulsion awaited his coming, the author of this idea could not explain how the pilot would rewind the rope to continue his flight. Leonardo da Vinci, who did so much futurist thinking, took a shot at helicopter design. His machine had two counter‑rotating rotors and was powered by clockwork. Clockwork appeared in many inventions of the 15th and 16th centuries – everything from clocks to wheel lock rifles.

About the only power source available in the 18th and most of the 19th centuries, other than muscle power, was steam. And nobody was able to design a steam engine with a high enough power‑to‑weight ratio. In 1842, an Englishman named W.H. Phillips flew a jet‑powered helicopter, perhaps the first man‑carrying jet aircraft in history. Phillips’s machine had jet nozzles on the tips of his rotors. The fuel he burned was an alarming mixture of potassium nitrate, charcoal, and gypsum. Substitute sulfur for gypsum, change the proportions a bit, and you have gunpowder. That early jet carried Phillips several hundred yards, but it was a technological dead end.

Until the internal combustion engine appeared, powered flight in either helicopter or airplane appeared hopeless. But, after the Wright brothers showed the way, the development of airplanes was phenomenally fast, although helicopters were barely able to get off the ground. The trouble was that helicopters had some problems that never occur in airplanes.

One was torque. The huge rotor blades spinning above the helicopter had a tendency to twist the whole ship and drive it off course. If this tendency could not be cured, the helicopter could only fly in a giant circle. The chopper pioneers tried two methods to neutralize torque. One method was to have counter‑rotating rotors (like Leonardo’s plan), another was to put a small propeller on the tale. The rotors could also cause another type of twisting – one considerably more dangerous.

Each rotor blade is a kind of wing, generating lift the same way a wing does.

The faster air passes over a wing, the greater the lift it generates. On a helicopter, the blades moving forward generate more lift, because the speed of the air over the blade equals the speed of the blade plus the speed of the craft’s forward motion. The speed of the air over the retreating blade equals the speed of the blade minus the speed of the helicopter’s forward motion. As a result, the helicopter without compensation would roll over. So helicopter progress depended on finding a way to vary the pitch of the rotor blades depending on their direction of motion.

While engineers were working on that problem, a Spaniard named Juan de Cierva invented a new type of rotor plane: the autogyro. The rotors were attached with flapping hinges that let them automatically change their pitch. The rotors were unpowered. The autogyro was propelled by an ordinary aircraft engine and propeller. As the plane gained speed, the rotors turned freely and provided the lift. Some autogyros had a clutch that let the engine supply power to the rotors for a brief time, making possible a straight‑up takeoff. Autogyro air mail planes were actually flown from the roofs of large post offices. Several air forces adopted them, and the Soviet Union’s autogyros strafed the German invaders during World War II.

While de Cierva was working on his autogyro, an Argentine, Marquis de Petraras Pescara, invented cyclic pitch control on a helicopter with powered rotors spinning around a tilting rotor head, which made possible a practical helicopter. That was in 1924 – 21 years after the Wright brothers’ flight, which made possible a practical airplane. From there, progress was rapid. In 1936, Heinrich Focke of Germany produced a twin rotor helicopter that flew successfully. Two years later, it traveled 143 miles, reached a speed of 76 miles per hour and climbed to 11,243 feet.

Also in 1938, a Russian immigrant, Igor Sikorsky, who had earlier designed and flown groundbreaking large passenger and military planes in Russia, settled in the United States and started designing helicopters. In 1941, his single rotor ’copter smashed all records and became the basis of all modern helicopters.

The Germans had a few helicopters in World War II, but too few to accomplish anything noteworthy. In the Korean War, the small helicopters of the time were used extensively for reconnaissance, transporting generals, and, especially, evacuating wounded. Almost 80 percent of all the wounded airlifted to field hospitals got there by helicopter. Helicopters grew in size during that war, and in the next war, Vietnam, they were big enough to carry significant numbers of troops and artillery. They were used for reconnaissance; directing battles from the air; and taking part in battles with machine guns, automatic cannons, and rockets. They were still used for medical evacuation, and were the basis for all the tactics of the First Cavalry Division, the U.S. Army’s first “air mobile” division.

A deal between the U.S. Army and the U.S. Air Force gave all fixed‑wing planes to the Air Force and all helicopters to the Army. Today, every U.S.

Army division includes helicopters. Helicopters have replaced all airborne divisions’ gliders and usurped most of the functions of their parachutes. Equipped with the wire‑guided TOW rockets, they fight tanks; with the six‑barreled modern Gatling guns, they mow down infantry; with other special equipment, they lay mines. In Iraq, they have taken part in street fighting. In Israel, and to a lesser extent in Iraq, they have been used to assassinate suspected terrorists.

Most helicopter successes have been against foes lacking effective antiaircraft fire. Even in Vietnam, where neither the Viet Cong nor the North Vietnamese Army was strong in antiaircraft weapons, helicopter losses were heavy.

A weapon like the Carl Gustaf recoilless gun (see Chapter 44) would be deadly against a hovering helicopter. A shell from a recoilless gun has far more velocity than a rocket, especially one of the guided rockets now used for antitank work. The chances of the helicopter evading the shot after it’s been fired are virtually nil.

Nevertheless, the “chopper’s” ability to take off and land on a postage stamp, to hover at will, to hide behind hills and other terrain features, to climb beyond the range of most ground fire, and to travel faster than any other vehicle except an airplane insures that it will continue to influence warfare for a long time.