History of the Helicopter

In the last few years, a new dimension has been added to flying - vertical flight by helicopter. The very speed on which the aeroplane depends can sometimes be a handicap. Only a helicopter can hover. Only a helicopter could reach the stormbound Wolf Rock Lighthouse. Vertical movement was man's first vision of flight. For centuries, he tried to copy the free, controlled flight of birds and insects. He hadn't the eye of the slow-motion camera to follow the subtlety of wing movement of birds such as the hummingbird. But his attempts were brave enough. Not succeeding, he gave flight divinity and held it blasphemous to try to reach the stars. But men of vision, like Leonardo da Vinci, continued to search for means to fly. He experimented with flapping wings and whirling wings. It was also he who applied the word "helix", meaning "spiral", to whirling wings. "Helix" combined with "pteron", meaning "wing", becomes "helicopter". Leonardo da Vinci's whirling-wing design was similar to the Chinese top - a toy whose origin is lost in early Chinese history. The top consists of a pair of wings at the head of a stick. About two and a half centuries after Leonardo's death, the Englishman Sir George Cayley, one of the fathers of aeronautics, developed a more elaborate top on similar lines. His interest had been roused by a model made by Launoy and Bienvenu in France. The Launoy and Bienvenu top consisted of two sets of wings which rotated in opposite directions. Its unusual flight caused a sensation when demonstrated before the Academy of Sciences of Paris. By now, men had learned that if the blades of a wing or propeller are set level, they will only whirl when driven round. But if they are set at an angle and then driven round, the blades will produce lift. Cayley gave to the world the first plans for a man-carrying helicopter - the Aerial Carriage. His lead was followed by many others throughout the 19th century, but they all lacked a sufficiently light and powerful engine. At the end of the 19th century, men like Ponton d'Amécourt and Forlanini were trying to adapt steam engines to aircraft, but without success. Others, notably the Wright brothers, were working on fixed-wing aeroplanes. The petrol engine made possible man's first successful full-scale flight in 1903. Had the first successful flight been achieved with a rotary-wing helicopter, the history of flight might have been different. The achievement of the Wright brothers overshadowed all others and established the fixed-wing aircraft. But the moving wing still had its advocates. For the first 30 years of the century, they went on trying to make machines which would rise vertically into the air. In 1907, Bréguet produced the first helicopter to leave the ground with a pilot aboard. The machine was unstable, but it did at least prove that the rotating-wing aircraft was feasible. But all these early machines were unstable, and for safety, the aircraft had to be tethered to the ground. The stability of a rotary-wing aircraft is particularly difficult. First, the rotation of the blades tends to make the body of the machine turn round in the opposite direction. This can be counteracted either by a small vertical tail rotor driven by the same engine as the main rotor... or by two sets of main rotors revolving in opposite directions. Secondly, when the machine moves forward, one blade of the rotor is moving with the airflow, while another is moving against it. Therefore, when the aircraft is moving forward, the airspeed of a blade increases as it turns towards the nose. This produces unequal lift and, therefore, instability. The answer to this problem was to hinge the blades so that they could flap... and could also speed up or slow down relative to each other. Juan de la Cierva discovered this, and so managed to smooth out much of the irregularity of lift. This solves another problem. As the blades of the rotor are no longer rigidly fixed, they are held in position only by centrifugal force. The whole structure is therefore relieved of a great deal of strain. The Cierva aircraft, like this C.19, all used this principle of the flapping blade. But they were not helicopters. They were autogyros. In an autogyro, the machine is propelled by an airscrew, and the rotor is turned by the aerodynamic forces acting on it, and not by the engine. The autogyro was, in fact, an aeroplane in which the wings are replaced by a rotor. The ordinary autogyro could not take off vertically, although its takeoff run was very short. In later years, vertical takeoff was achieved in the autogyro by coupling the engine to the rotor. This principle could be used only for the takeoff. Meanwhile, work on helicopters went on. In 1930, Florine showed his machine with the new flapping blade to the public at the Brussels Exhibition. In the same year, D'Ascanio established the first world helicopter record, with a flight of eight and three-quarter minutes, covering 1,000 yards at a height of 59 feet. He reached a speed of about 15 miles an hour. Six years later, in 1936, the pioneer Bréguet came to the front with a much-improved design, in which the problems of control were tackled with considerable success. Records were established with this machine. Duration: 63 minutes. Altitude: 515 feet. Distance: 27.5 miles, at a speed of 62 miles an hour. Bréguet used what is today known as cyclic pitch control. This means that the angle at which a rotor blade meets the air is altered as the blade rotates with the hub. By photographing blades in slow motion, they can be seen to rise and fall with the influence of the airflow and centrifugal forces. When the aircraft is taking off, the pilot holds the stick roughly central, and the lift force is acting vertically. The pilot moves the stick forward. The advancing blade, furthest from the camera, decreases in pitch and flaps downwards. The retreating blade, nearest the camera, increases in pitch and flaps upwards. In effect, the rotor is tilted forward. It thus becomes the means of accelerating the aircraft forward, as well as the means of supporting it in the air. The nose tilts down in sympathy with the rotor. The pilot decides to turn to the right. Stick right. The blade on the left flaps up. The blade on the right flaps down. The aircraft goes into a right-hand turn. In 1937, the first really successful helicopter, the Focke-Achgelis, was announced. The flexibility and control of this machine were demonstrated when Hanna Reitsch flew it inside the Berlin sports stadium. Then another of the pioneers, Igor Sikorsky, who had been working on helicopter design from the beginning of the century, achieved success in America. All these discoveries helped to produce the helicopter as we know it today. It's still curious to look at, but it can fly in a way even surpassing the flight of birds. It takes off and lands vertically, hovers in the air, and even turns a full circle over the same spot. Helicopter design is constantly progressing. The precision of control is something of which D'Ascanio could only have dreamed. The British Bristol 171, a single-rotor type, carries three passengers, as well as the pilot. In contrast to the sleek lines of the Bristol is the angular body of the largest helicopter yet built - the Air Horse. It is produced by the pioneer company started by the late Juan de la Cierva. The engine used in this helicopter is so powerful that the three rotors can lift a total weight of just over eight tonnes. The Air Horse, with its enormous capacity, at last fills a gap between the usual helicopters, with their limited loads, and the aeroplane. At the other end of the scale, the Cierva Company has produced a small sister to the Air Horse - a neat-looking two-seater personal helicopter called the Skeeter. The Fairey Company holds the world's helicopter speed record with the Gyrodyne, and here we see it on its record-breaking run at 124.3 miles an hour. The Gyrodyne uses an offset propeller instead of a tail rotor to counteract the torque reaction of the main rotor. This has the added advantage that the propeller gives additional thrust to drive the aircraft. In France, Louis Bréguet is still one of the leaders of helicopter technique. He has been experimenting with a three-seater design using superimposed counterrotating rotors. A development of the pre-war German Focke-Achgelis, keeping the original rotor configuration, has been made by Sud-Est, and is designed to carry six people. Another French company, Sud-Ouest, have developed an experimental helicopter with a rotor driven by jets at the blade tips. These are fed with compressed air by an engine in the fuselage. One of the attractions of the jet-driven helicopter is that as the driving force is at the tips of the blades, there is no torque reaction to correct, and tail rotors and such devices aren't needed. Jet-driven rotors have also been developed in America. This experimental single-seater is built by the McDonnell Aircraft Corporation, and is called Little Henry. The helicopter's types and designs are unending. The Sikorsky, now being built in England by Westland, comes originally from America. It has been used for mail-service experiments, landing in small fields during the day to pick up the village post, and by night, flying blind, carrying mail between two large towns. The same type of aircraft showed the possibility of intercity transport by flying from the roof of a London garage to the Place des Invalides in Paris. The Westland Sikorsky was also used in the first regular scheduled passenger service, flying between Cardiff and Liverpool. The American Bell helicopter is being used on the land, with great success. Dusting orchards. Spraying crops and cattle. The downwash from the rotors directs the insecticide over and under the leaves. The rotor downwash is also used for a strange form of harvesting. It's a simple way of gathering walnuts, which can't be damaged by their forceful descent. The Piasecki, or "flying banana". An American military helicopter like something out of a story by Jules Verne or HG Wells. For emergency rescue from otherwise inaccessible places, the helicopter is unrivalled. It can transport the injured to a hospital, or the stranded to safety... whether the scene of the emergency is a jungle or a wrecked ship. In December 1946, Admiral Byrd took helicopters on his Antarctic expedition, and used them for surveys more detailed than could be undertaken by a normal aeroplane, and for getting to places no sledge could reach. The Hiller, with its Perspex bubble front, is a good example of a small helicopter with an all-round view. They can be useful for such things as police control of traffic and for surveying. The helicopter has provided new vantage points for the tourist. There is no better way of seeing the Grand Canyon, or of herding cattle or elk, than from the comfort of a helicopter, with its large field of vision and its ability to fly slowly. Yes, the helicopter has arrived. Slightly prehistoric to look at... but so versatile, that it fills an important gap in transport. Rotary-wing flight is now a reality. The helicopter was once part of a fantastic future in which you and I hoped to fly about in our own private aircraft. Indeed, an Oxford college dean has used it to visit a convention. The helicopter has been used to do work that seemed impossible, carrying heavy materials high up into the Welsh mountains to repair the Croesor Dam. The helicopter will not supplant the car or the aeroplane, but it will enable us to fly with a freedom that we've never had before.