Leonardo da Vinci

The History of Helicopters

1. Historical Background
2. Stepping Stones to the Helicopter
3. The Helicopter is Born
4. The Helicopter Comes of Age



While Edison was preparing the ground work for his helicopter experiments, two small boys in a midwestern home were having worlds of fun with a most unusual toy. It was a fragile affair, and the youths were careful to handle it gently. The toy would fly from their hands above their heads
and then travel with seemingly magical powers to the other side of the room they played in. Their father, Bishop Milton Wright, had just returned from a trip to France, where he had bought replicas of the Chinese top for Wilbur and Orville.

The youngsters were fascinated with their flying contrivances. It wasn't long before they were making duplicate models of their own, using bamboo sticks and tissue paper. Many of the models Wilbur and Orville built were changed somewhat from the ones their father had given them, containing features which the boys thought would make them fly even better. Even at their youthful age they were showing an aptitude for mechanics and inventiveness that some day would make them world famous.

In later years, when discussing this happy episode of their youth, the Wright brothers were asked why it was that during their serious experiments with aircraft they favored the fixed-wing type to that of the rotary model. They replied in effect that the helicopter presented far more complicated mechanical problems to solve. They felt they would more likely be successful by following the road already blazed by the fixed-wing glider experiments of Octave Chanute, Otto Lillienthal, and others, who had done much to help bring into existence the heavier-than-air flying machine with extraordinary pioneering glider flights.

Even though the Wright brothers gave the world its first practical heavier-than-air flying machine of the fixed-wing style in 1903, there still remained engineers and would-be inventors in other lands who felt that it was not the best approach to that long sought objective. The helicopter, to them, was still the better way. Thus, despite the magnificent forward strides made by the airplane as developed by the Wrights, rotary-wing aircraft experimenters continued to wrestle quietly with that craft's engineering and mechanical problems. Probably the foremost of this little band of helicopter experimenters during the early years of the twentieth century was M. Louis Breguet of France.

M. Louis Breguet came from a family that had long distinguished itself in the field of mechanics. His great-grandfather was a famous clock-maker during the rule of King Louis XVI; his grandfather was an expert in the field of electricity, while his father headed a factory that built delicate scientific instruments. Louis was educated as an electrical engineer, graduating with high honors from the l'Ecole Superieure d'Electricite. When only twenty-five, he was made chief engineer of the Breguet Electric Motor Plant, where he proved extremely capable.

But Louis Breguet soon became bored with dynamos and electrical switches. His thoughts and dreams lay in a radically new field of engineering—aeronautics. The Wright brothers had just startled and fascinated the world with their successful heavier-than-air flying machine, and Louis was caught in this great wave of interest. He attended lectures on the subject at the Academie des Sciences and became especially impressed with the studies of Colonel Charles Renard who was an enthusiastic supporter of rotary-wing aircraft. Unable to withstand the magnetism of flying machines any longer, Louis put aside his electrical work and plunged into the world of aviation. In view of his deep interest in the lectures of Col. Renard, it was inevitable that his thoughts about a flying machine should center on the helicopter. "My first conception in the aeronautical field was that of rotary wings," he tells us while writing of his early aviation experiences.

Up to the time of Breguet's experiments with rotor blades, knowledge concerning them was limited mostly to their rotating and lifting habits. Louis now advanced this study by finding out that slanting or tilting the rotor blades produced a forward pulling action. Most of his information on this, as well as the lifting properties of rotor blades, was obtained from a whirling-arm test stand which he built in 1905. Equipped with a storehouse full of newly acquired test data, Louis Breguet built his first helicopter in 1907.

This flying machine was distinctive for a number of reasons. On a test flight on August 24, the inventor managed to get the craft off the ground for a distance of a little more than three feet. The helicopter, together with pilot and fuel, weighed more than a half ton. Breguet claimed, "This was the first time such a machine ever lifted a person."

The French engineer's rotating-wing flying machine was equipped with four rotors, the blades of which were of the biplane type; that is, one blade was fixed above the other. Even though it established some history-making firsts in the helicopter field, the machine behaved in an erratic manner once off the ground and was difficult to control. The inventor decided that rather than try to eliminate the helicopter's troubles, it would be far easier to build another, which Breguet did shortly after. In the meantime, he patented his ideas on the forward propulsion ability of rotor blades which other aeronautical experimenters were to make use of in later years during their own helicopter investigations.

The French engineer's second helicopter came out the following year, without, he hoped, the unstable flying qualities of the first one. Again Breguet was doomed to disappointment. Although the pilot was able to make it rise a short distance above the ground, the machine resisted all his efforts to keep it steady. Breguet now had his fill with helicopters and temporarily abandoned them in favor of conventional airplanes. During the years that followed he gained considerable fame for himself by designing and building some very good fixed-wing aircraft. This was especially so during the First World War when he produced excellent fighter craft for the Allies.

M. Breguet was probably the first of the modern helicopter experimenters to meet with rotary-wing problems almost equal to those difficulties faced by earlier inventors in their lack of an adequate power plant. The French engineer discovered that while it was possible to lift a helicopter off the ground, other obstacles reared their heads—serious matters such as controlling and stabilizing the machine in the air. Until these knotty engineering problems were solved, the helicopter was to remain an elusive vehicle.

Paul Cornu, a countryman of Breguet, thought he had the answers with his helicopter, which also appeared in 1908. Cornu's rotary-wing flying machine had all the looks of an aerial bird cage, with its wires, cables and rods. The craft had large paddle-shaped two-bladed rotors, one fore and the other aft on a long, tubular frame. The engine, a 24-horsepower Antoinette, was placed in the center of the body directly above a four-wheel • landing gear. The pilot was in the most uncomfortable position —directly back of this noisy, smoky unit. The pitch or angle at which the rotor blades cut through the air could be adjusted to give them better lifting qualities. Cornu equipped his machine with a small horizontal wing which was moved by the action of the down-draft of air from the rear rotor. This tilted the helicopter forward slightly and helped it to fly better in a forward direction.

During test flights with his machine, which was tethered to the ground, Cornu managed to raise it aloft for a distance of several feet. At one time it raised two men aloft for a distance of five feet and stayed there for 20 seconds. Despite these minor achievements, the inventor's airplane was no better as far as stability and control were concerned than Breguet's. Apparently more easily discouraged than the latter, Cornu abandoned his helicopter experiments shortly after.

Following the work of these Frenchmen, the spotlight on helicopter activity shifted temporarily to Denmark, where an aeronaut by the name of Ellehammer built a rotating-wing airplane in 1911. A year later he managed to fly with it a few feet off the ground before a number of witnesses in Copenhagen.

This pioneer helicopter was of the co-axial type, having two propellers one above the other. They were powered by a small gasoline engine and spun in opposite directions. The inventor achieved some control over his aircraft by means of tilting the rotors.

The First World War all but put an end to helicopter experimental work with one notable exception. This was the rotary-wing machine built by Lieutenant Petroczy and Dr. von Karman of the Austro-Hungary military forces in April of 1915.

The aerial contrivance was designed to do a job normally carried out at the time by gas-filled observation balloons. These were sent aloft to a certain altitude and then anchored to the ground. There, occupants would spy out the movements of the enemy and report their findings to headquarters. Dr. Theodore von Karman, a professor of aerodynamics, and his young military associate, Lieutenant Stefan Petroczy, felt that their helicopter observation craft would be an improvement over the balloons which were easily destroyed by gunfire. Receiving the approval of their superiors for the project, they began work in 1915. By April of that year the two inventors were ready to test-fly their brain-child.

The helicopter—perhaps the first to be designed strictly for military purposes—had two rotors which spun in opposite directions. Three engines were used to power the props, which were more than nineteen feet in diameter, and were connected to them by means of gears and shafts. Above the rotors was the crew's compartment. It was made of metal and was large enough to hold a pilot and an observer, plus a machine gun and fuel supply. The whole contrivance weighed 3,200 pounds.

Steel cables were used to hold the helicopter observation post to the ground and help keep it balanced aloft once the desired height was reached. The craft could not move in a horizontal path but only in an up and down direction. On one of its test flights the machine reached a height of a little more than a hundred feet. However, on a subsequent take-off, the engines suddenly stopped, causing the captive helicopter to topple over on its side and crash to the ground a complete wreck. Along with the physical remains of the helicopter there also died further plans to continue the experimental project.

The guns had hardly ceased to roar when a French engineer by the name of Etienne Oemichen made what was perhaps the most substantial progress that had yet been achieved with a helicopter. This inventor began his work shortly after the armistice and became so fascinated with helicopters that he built three machines. The first two were the most interesting.

The first machine Oemichen built was not a true helicopter, since he used a gas balloon to help his craft leave the ground. The engineer had not intended this originally, but after testing his aerial device and finding it impossible to rise into the air he quickly decided to seek the aid of a balloon. The latter helped a good deal. The inventor was not only able to get his craft off the ground, twenty feet up on some occasions, but he could also fly it for a good distance horizontally.

Oemichen apparently learned a lot from his combination balloon-helicopter because he soon began work on his second machine. This was a de luxe craft by comparison, equipped as it was with nine rotating propellers. Four of these were for lifting the craft off the ground, three to control it in the air, and two for driving it in a forward direction. The inventor decided that this would be sufficient to keep his helicopter aloft without any further assistance; therefore he did away with the balloon. His confidence was well justified. The French engineer's airplane flew with what, for that era, was remarkable success.

During the course of numerous test flights, Etienne guided his helicopter for the grand distance of one half mile! He also demonstrated the machine's ability to hover, a bit unsteadily to be sure, for periods of almost five minutes. The crowning achievement of the inventor's helicopter, however, took place in May, 1924, when he really taxed it to the limit of its flying ability. He jockeyed the craft over a circular course of almost one mile in extent and reached a top speed at times of fifteen miles per hour.

Although Oemichen's helicopter was undoubtedly one of the most promising to have been produced up to that time, it still fell far short of the capability of this type of flying machine. It was extremely limited in speed and climbing ability, and it could not perform all the functions of the true helicopter, such as flying backwards or sidewards. Besides all these factors, the machine was extremely difficult to control in flight. And so the experimental work continued, and inventors continued to pursue their elusive quarry both in Europe and the United States.

About five years after the Wright brothers achieved their winged victory, two successful American mechanical engineers with a strong interest in aviation matters decided to join forces and build a helicopter. The two gentlemen were Emile Berliner and J. Newton Williams. Both had done some experimental helicopter work before combining their activities. They had built rotor-lifting apparatus capable of raising several hundred pounds into the air. It was this accomplishment which encouraged them to try building a full-scale rotary-wing flying machine.

Their completed machine looked extremely crude, but was simple in construction. It had a small rectangular frame in the center of which the engine was fastened. Directly to the rear was the seat for the pilot. Rising straight up from the engine was a shaft on which the rotors were fastened. There were two of these, one above the other, and they rotated in opposite directions. Just below the rotors the inventors had an odd-looking unit made up of six rectangular panels placed in an upright position. These were intended to help steady the craft while in flight.

For landing purposes, the helicopter had two large landing wheels at the front end of the frame and a sort of tail skid beneath the pilot's seat. A large frame surrounded the units to which skid runners were attached.

Williams was the pilot on many of the craft's test flights, which sometimes actually left the ground. On these occasions the inventors felt that they were making promising headway, but suddenly all this activity ceased. The crash of the airplane, causing injury to one of their associates, was partly responsible for this. Another reason was a complete change in attitude by Berliner towards experimenting with helicopters.

Emile Berliner had become a wealthy man as a result of his achievements in the acoustical engineering field. He looked upon his helicopter experiments as one would a hobby—to be worked at or dropped whenever his mood urged him. For the moment he felt like giving the whole thing up. About five years later, however, the helicopter whim struck him once again, and he began thinking of new ideas for a workable whirligig airplane.

The war interfered with Emile's plans to build his—so he hoped—improved helicopter. He had to wait until after the armistice to get back to his hobby. This time he persuaded his son Henry, an Army pilot during the war, to join with him in his experiments. Henry at first was not too enthusiastic about this sort of technical activity, but as the work progressed he became as deeply interested in the possibilities of rotary-wing flying machines as his father.

Late in the fall of 1919 their little helicopter was rolled out of its shed and made ready for its first test flight. This took place at College Park, Maryland, one of the Air Service's first flying fields. In appearance, the craft looked very much like other airplanes of that day except that it had two lift rotors which swirled above the pilot's head. Henry was the pilot, and pretty soon he discovered how well he and his dad had built their flying machine. The motor roared. The two lifting rotors spun at an ever faster rate, and the whole plane shook violently. Henry was wisely cautious at first until he was able to get the feel of the controls. Then, gently, he pushed the proper levers for lifting the craft off the ground. Slowly it rose into the air for a distance of several feet. After repeating this accomplishment several times, the young pilot-inventor then proceeded to fly the plane in a forward direction. For this maneuver his father had devised a special tilting device, and they were both anxious to see how well it worked. It did. Henry was able to fly the plane for a considerable distance forward.

Even though the father-son experimental team felt rather happy with the first flight of their helicopter they realized that it still required mountains of additional work before it could be called a finished vehicle. Accordingly the craft was rolled back into its shed, from which it was not to emerge until almost two years later. In fact, when it did, the helicopter was hardly recognizable. This time it sported three fixed wings, on the topmost of which were the two lift rotors. The additional wing was added at the strong insistence of Henry, who was very much disturbed by the great difficulty he had had landing their first machine. The fuselage was of the conventional type, and on its tail was another rotor to help control it better. Control was also added by an aileron device on the wings.

During test flights with this model, Henry was able to make it rise to a height of fifteen feet and to stay aloft for as long as one minute and thirty-five seconds. Aviation circles at the time considered this quite an accomplishment. Still another helicopter model followed this one, but equipped with only two fixed wings instead of three. However, the problems of control and stability seemed so difficult to solve that Henry was fast losing his interest in continuing the work, despite his father's persistent efforts to encourage him.

An incident in which Henry almost lost his life occurred in the spring of 1922 with one of the early models, and it undoubtedly had much to do with shaking the young man's confidence in the helicopter. He rose from the ground in the machine one morning in perfectly good style. Then he attempted to fly it horizontally, at which time trouble began. After traveling a considerable distance in this fashion, he saw that he was headed directly for the shed in which the helicopter was stored. He struggled desperately with the controls to try to change the machine's direction of flight. There was no response, and Henry saw that a crash was inevitable. In desperation he finally pushed the control stick forward, and this time he got a reaction. The helicopter nosed towards the earth in a graceful arc and crash-landed on its back just short of the shed. Henry wormed his way out of a tangled maze of wires and fabric, badly shaken but fortunately unharmed.

Reluctantly admitting defeat in their efforts to build a practical helicopter, Emile and Henry Berliner abandoned their experimental work in 1925. Frustrated in their efforts, this father-and-son team is nevertheless credited with adding a small measure of engineering knowledge to the age-long project of building such a flying machine. Better than any of the helicopter inventors before them, they knew how to steer their machine, once aloft, in a right or left direction, a result no doubt of Henry's near-fatal accident with one of the early machines which failed to respond to that kind of control.

On one occasion Emile and Henry put on a performance with their flying machine before an audience of Army, Navy, and Air Service officers. It was a stimulating experience for the military individuals. Many were impressed with the helicopter's promise of some day being especially valuable for war work. The Air Service visitors appeared to be more keenly interested than the others—and for a good reason. At that very moment their organization was also deeply engaged in a secret helicopter development project. For this work they had secured the services of an internationally known scientist and expert on helicopter flight theory, Dr. George de Bothezat.

Dr. Bothezat was a Russian scientist who had come to this country to escape the upheaval of the revolution in his own land. He was well known before his arrival on these shores, for his achievements in both the world of physical science and mathematics. One of his favorite studies was the theory behind the flying ability of the helicopter, and he was considered an authority on the subject. He developed a number of original ideas on rotary-wing flight and wrote a variety of deeply technical reports on these. "Aeroplane Stability" and "The General Theory of Blade Screws" were among some of the more important ones. It was largely due to his writings on helicopter designs that Air Service engineers were attracted to him. The next step, an easy one, was to persuade Dr. Bothezat to undertake the direction of their experimental rotary-wing airplane program. Of the officers chiefly responsible for this move, Major T. H. Bane was outstanding.

Major Bane was one of the real pioneer boosters of the helicopter for military purposes. Shortly after the end of World War I, he and a small group of fellow officers conducted an exhaustive study of the whole field of helicopter engineering as it existed at that time. This activity even included tests with a small model helicopter built by J. E. McWorter. But the one factor that stood out above all others was the well developed theoretical studies of Dr. Bothezat. These convinced the officers that the time was at hand when an experimental helicopter should be built. Thus, after the helicopter project was approved, Major Bane was given permission to acquire the services of the Russian scientist.

The Air Service officer wrote to the expert on rotary-wing airplanes, explaining what his organization had in mind and asking if he would care to direct the experimental work. In reply, Major Bane not only received a very willing "yes" to his invitation but also, in an extremely long letter, precise details for the design of a helicopter. Every syllable of the missive which follows seemed to breathe the scientist's great confidence in producing the desired flying machine. "Here will be found the complete disclosure of the helicopter invented by Professor Doctor George de Bothezat at the end of 1917 at that time in Petrograd. It is only the special conditions created by the outbreak of the Russian Revolution that have prevented the author to realize his invention until now. The helicopter here disclosed is to the best of the author's knowledge the first to possess all qualities of complete inherent stability and maneuverability which are essential for the navigation of any vehicle of locomotion."

Shortly thereafter, June 1, 1921, Dr. Bothezat and the Air Service signed a contract for the production of an experimental helicopter. The scientist had to meet certain requirements with this machine which, if successful, would bring him generous financial rewards. In the first place he had to produce, "drawings and data to design, construct and supervise flight tests of a helicopter." In return, the government would give him all the necessary materials, equipment, assistants, and a working area to build the flying machine. When he turned over to the government the first complete set of engineering drawings and other data, he was to receive the initial sum of $5,000. An additional $4,800 would be paid to him after the helicopter's construction. If the airplane proved it could leave the ground, reach a height of three hundred feet, and return to its take-off point under a certain minimum speed, Dr. Bothezat would be given still further payments. In all, the scientist had the opportunity of making a total of $20,000 for conducting experimental work which he had long hoped to do. The arrangement was ideal, one which many inventors dream about but rarely achieve. Dr. Bothezat had to complete his work by January 1, 1922. But due to unexpected difficulties, he received an extension of time.

Work was begun in the summer of 1921 in a small metal-roofed hangar at McCook Field. This was the base where the Air Service carried out experimental and development activity on all types of airplanes. While Dr. Bothezat handled the technical matters, Major Bane was the military supervisor of the project. He saw to it that all the required supplies, equipment, and materials were at hand, as well as the workmen to assist the professor.

One feature of the undertaking which the inventor demanded with almost the urgency of a phobia was secrecy. Major Bane tried his best to see that the quick-tempered scientist had his wish, but he didn't succeed all the time. This was especially so when the helicopter reached a stage in its construction which required the work to be continued outdoors behind a canvas enclosure.

There was a great curiosity among those at the field not connected with the helicopter work as to what was going on behind the fenced-in area. This was greater among the pilots attached to the base than anyone else perhaps, and they had the ideal method of satisfying their inquisitiveness. When coming in for a landing, after a test flight, they would see to it that their low gliding plane would sail directly over the secret area. In this way they got a quick glimpse at the strange mechanical bird taking form below. The professor, fiery-tempered, suspected them of doing this deliberately because of the frequency of the visits. Every time it happened, Dr. Bothezat would dash outside the canvas fence and angrily shake his fist at the departing aircraft, shouting threats at the top of his voice.

At long last the machine was completed, months behind schedule. Many were the knitted brows of bewilderment when the helicopter was wheeled outside its protective fenec. It was a fantastic-looking structure having a skeleton framework entwined with a spidery network of wire. Four giant-sized rotors topped off the entire ensemble with a grand flourish. It was undoubtedly the weirdest looking flying machine ever to appear on McCook Field. The remarks of the onlookers were not very complimentary and almost all humorous. Had any of them reached Dr. Bothezat's ears—he was busily fussing about his brain-child in preparation for its first flight—it is doubtful if those uttering them would have been able to approach McCook Field again as long as the inventor was present.

December 18 was a sunny day with cool, crisp air. Those not busy with other affairs stood and watched with absorbed interest as Dr. Bothezat's beloved helicopter was slowly rolled to a quiet part of the field. Major Bane was going to attempt to fly this newborn aerial steed. For that task he had spent several days of preparation learning the controls from the inventor. The officer climbed through a network of wires toward the pilot seat, located in the center of the vehicle. He started the engine, warmed it thoroughly, and then signaled to his assistants that this was it—he was ready to take off.

The giant rotors began whirling ever faster. The machine shook and vibrated violently, and then, to the astonishment of the spectators, it rose from the ground! Major Bane was so busy with foot pedals and levers that he had little time to thrill to the experience of this novel flight. He raised the aircraft to a height of about five feet and kept it there for more than a minute and a half. Gently nudged along by air currents together with its own power, the helicopter moved slowly across the field for a distance of almost three hundred feet. Suddenly realizing that he was heading dangerously close to a fence, the test pilot brought the craft softly to earth under complete control. The landing was almost vertical. It rolled for a short distance of about three feet from the point where the wheels touched the ground. This was considered an achievement of some note since it was the first landing made by a helicopter under the complete control of the pilot. Other characteristics of the flying machine while aloft, such as stability, were also considered quite encouraging. The first Air Service helicopter at least had managed to climb into the air—even though it did not meet fully the expectations of the builders. Limitations or not, Dr. Bothezat was a happy man that day with his up-and-down-flying airplane.

Dr. Bothezat's helicopter was certainly a giant for its kind. It weighed very close to two tons and, shaped in the form of a cross, stretched sixty-two feet in length and sixty-five feet in width. Four large lifting rotors, twenty-two feet in diameter, were mounted at the ends of each of the crossed arms which formed the body of the machine. Four additional propellers were fixed to the helicopter and these were for controlling the craft after it was in the air. The controls operated by the pilot were very similar to those on conventional airplanes, a control stick and rudder pedals. There was an additional device in the form of a wheel which the pilot used to change the angles on the various rotor blades.

The Air Service's first helicopter made a number of brief flights following the historic ascension on December 18. Many of these were of record-breaking nature, such as the flight on January 23, 1923, when it left the ground with two people aboard, lifting a weight of 450 pounds to a height of four feet. The following month it established a helicopter endurance mark by staying aloft for two minutes and forty-five seconds. In April it added still further to its weight-lifting laurels by carrying four men clinging to the sides of the machine into the sky.

Despite its seemingly encouraging flying qualities, Dr. Bothezat's helicopter fell short of the desires of the Air Service. The scientist spent week after week of patient labor, stubbornly trying to improve his pet flying machine. All his efforts were fruitless. The helicopter was never able to surpass to any extent its first flying achievements. Besides its failings in the air, the airplane was thought to be too complicated in structure to care for properly. It was also far too difficult to fly. As a result, the Air Service stopped work on the project early in 1924.

Dr. Bothezat was bitterly disappointed over the abandonment of his helicopter. He felt certain that in time, with a few more refinements, the airplane would succeed in doing what the Air Service would like it to. Saddened though the scientist was, he could feel at least a measure of achievement with the knowledge that his helicopter was a big help towards the eventual creation of that aerial vehicle. The Air Service generously admitted as much in their final report on the project. "This development has contributed a definite forward step in helicopter progress . . . being a practical example of the proper method of design and . . . theoretically has provision for more desired performance properties than any other existing machine."

Despite the heroic American failures just described, the ranks of helicopter experimenters remained unthinned. Just as soon as one had failed, another was ready to take his place. So it was that after Dr. Bothezat's whirligig airplane was given up, activity swung back to Europe—to the invention of Raul Pateras Pescara.

Pescara was an engineer long interested in aviation problems, particularly helicopters. He built his first machine in the very early twenties and demonstrated it in Barcelona, Spain. In fact, between 1920 and 1925, this industrious inventor constructed four rotary-wing aircraft. These helicopters were unusual in that they had bi-plane type rotors. One blade was fixed on top of the other and supported by small vertical struts. On the inventor's first machine each rotor had six biplane blades. Later models had four. These rotors whirled about in opposite directions.

Pescara's second helicopter built in 1924, was a startling performer. It made flights of almost one-half mile in length and could stay aloft for as long as twelve minutes. The secret of this inventor's success was in knowing how to twist the blades of the rotors for proper control. In addition, he knew how to extend the forward flying ability of a helicopter by tilting the rotor shaft. By a complicated mechanical hook-up he could put different pitch angles on the blades of the two rotors and as a result change the direction of the machine's flight. He is also said to have been among the first of helicopter experimenters to understand the principles of autorotation, an action whereby rotor blades keep spinning without mechanical energy and still produce lift for the airplane. A countryman of Pescara's was shortly to make this aerodynamic principle world famous.

Even though Pescara's helicopters were probably the best that had yet taken to the air, they still fell far short of the ultimate goal. Because of a constant succession of mechanical breakdowns with their rotor systems, and because the machines could never be fully trusted to stay aloft once off the ground, the inventor eventually abandoned his rotary-wing aircraft experiments.

During the years immediately after the First World War, helicopter experimenters had made perhaps as much progress in their field as had been made in the whole previous past century. Despite this encouraging picture, all with puzzling regularity seemed to arrive at the same dead-end avenue. They could build a helicopter with certain very limited flying qualities beyond which they were unable to advance. Some one vital element was needed that was beyond their grasp at the moment. If they had it, their pathway to success would at last be clear.

Like a ray of sunshine bursting through a cloud-filled sky, at last the missing piece of their aviation jig-saw puzzle made its appearance. The autogyro, the all-important key, was invented. This revolutionary flying machine was one of the most important stepping stones that led to the helicopter. Its inventor was one of aviation's most famous engineers, Juan de la Cierva.

A group of excited boys stood on the crest of a small hill just outside the city of Madrid. One, slightly taller than the rest, remained apart, talking and pointing in a rather serious manner. The object to which he was motioning was a rather crude-looking glider with a long, heavy rope fastened to the front end. Soon the boys broke up. Juan de la Cierva, for it was he giving directions, hung onto the lower wing of the man-carrying kite. At his signal, the boys each grabbed a portion of the rope and dashed down the hill.

Juan and his glider were jerked off their resting place and pulled skimming over the surface of the ground. Suddenly, with the help of a strong gust of wind, the glider and its passenger were off the ground and flying. The tow-gang were shouting and laughing now and ran still faster. Up, up sailed Juan until he was higher than the height of a man. When the boys became tired and stopped, the glider and its young pilot quickly returned to earth. Again and again the episode was repeated, each time with a different flyer. In this way all the boys were permitted to share the thrill of riding in the world of the birds.

Juan was only fourteen when he was building and flying these simple gliders. The airplane, invented in 1903, was only seven years old at the time. Like most boys of his age, he had a great curiosity about the world he lived in. But of all his boyhood interests, flying was the greatest. He read all the books he was able to obtain on the subject and long before reaching the glider stage he built "thousands of paper airplanes for practice." When he was sixteen, he together with several equally enthusiastic aviation friends built Spain's first airplane. This was in 1912, and the project cost them the gigantic sum of sixty dollars!

In reality their airplane was more in the nature of a rebuilt plane than an original. A French barn-storming pilot was putting his Sommer biplane through its paces one day at a race track near Madrid. The crowd was fascinated with his performance, and when the pilot attempted to bring his craft in for a landing, they dashed in front of his path, not realizing the danger. To avoid hitting them, the Frenchman was forced to crash-land his plane. It was this tangled mess of splintered wood and torn fabric which Cierva and his friends bought from the grief-stricken French flyer.

With only the engine and landing wheels of any use, the youths worked feverishly for many weeks, and then, before their own amazed eyes, an airplane appeared. They painted it a bright red and called it the Red Crab. By the time it was ready to fly, it so completely contained Cierva's ideas and workmanship that it was truly his airplane.

Since none of the boys could pilot a flying machine, they persuaded the French pilot to try it for them. He was amazed at the machine the boys had built. First carefully testing it on the ground, he nosed it into the air one day and thrilled the young airplane builders with simple flying maneuvers. The Red Crab was a success. Cierva was probably the happiest of all and was further encouraged, if that was necessary, to make aviation his career.

Juan's parents were well off financially and gave the young man a good schooling in engineering. During his university training he revealed a remarkable talent for mathematics, which was destined to be one of his most valuable tools when he was ready to make his lasting contribution to the aviation world. The engineering taught young Cierva was not aeronautical. All his knowledge in that field was self-obtained, gained either from building aircraft like the Red Crab and others or through study and experiment.

Another crashed airplane provided the inspiration for Juan in constructing the autogyro. Shortly after the close of the First World War, the Spanish government offered a prize of ten thousand dollars to the inventor able to build a bombing plane according to certain specifications. The youthful aviation expert leaped at the opportunity, and with the financial help of some friends, began building his entry, a three-motored giant.

When finally completed, his huge flying machine had room for fourteen passengers, with a wing span of eighty feet. Concentrating on the airplane to the exclusion of everything else, Juan paid little attention to the question of whether it would fit through the doorway of the shed. It didn't. To get the machine onto the flying field, the builders had to remove the walls of the work shed. This was a minor problem, however. The inventor was more interested in knowing whether his machine would fly, which it soon proved capable of doing. But only for a short time.

To test-fly his bomber, Cierva had obtained the services of one of the Spanish Army's "hottest" flyers. He had a great deal of experience with small planes but hardly any with the giant multi-engined size. When he took the inventor's three-motored craft aloft, he flew it as he would a small pursuit plane. This was a mistake that almost cost the airman his life. One day, while circling above the flying field, he brought the giant plane around in a sharp turn dangerously close to the ground. It seemed to flutter for an instant, halt in its flight, and then nose into the ground before the horrified eyes of Cierva.

Fortunately for the pilot, he was only slightly injured, but the experimental bomber was a complete wreck. Juan's hopes for winning the competition were now gone as well as $32,000 which the engineer and his friends had spent on the project. He stood strangely quiet before the unsightly jumble of broken wood and torn fabric. He was bitterly disappointed that careless flying had crushed a lifelong dream, but other thoughts soon began crowding through his mind. Most of these centered on why his airplane had fallen to earth. Slowly walking back to his workshop, head bowed, Cierva began analyzing the situation.

He knew why his bomber had crashed. Fixed-wing aircraft such as his need a steady strong flow of air over the wings to stay safely airborne. If the forward speed of a plane falls below a certain minimum rate, the air stream over the wings becomes weak, loses its lifting power and the airplane is forced to land. This hazardous flight condition is commonly known as "stalling." If it occurs when the plane is close to earth, it almost always means a crack-up. The youthful engineer came to the conclusion then and there that since the airplane invented by the Wright brothers would always have that dangerous characteristic, there must be another way to build a better, safer heavier-than-air flying machine.

For weeks the young engineer walked about in a fog, thinking about the problem. Then one day a possible solution came to him. Why not an arrangement of movable wings that would provide a constant and proper flow of air over their surfaces regardless of the forward speed of the aircraft? What better way to do this than to spin them around a central shaft? Cierva's eyes began to sparkle with interest the more he thought of this idea.

In his early approach to the question of rotating-wing aircraft, the engineer thought of the helicopter as an answer. But after investigating the background of the many unsuccessful attempts to build such a flying machine, he dismissed the notion. "Mechanical difficulties have been insuperable and even when they are solved very much greater power is needed to drag a weight vertically as compared to pulling it horizontally," he stated. He even thought of the ornithopter with its flapping wings, but this thought was even more quickly brushed aside.

Cierva finally decided that rotating wings were what he actually wanted. If these could be designed so they were kept spinning solely by air pressure acting against them and without any mechanical energy to drive them, the "stalling" habit of conventional airplanes would be eliminated. An airplane so equipped would be capable of a forward speed far lower than those with rigid wings and therefore would be safer. Juan was soon embarked on the road of a lifetime career with rotary-winged aircraft.

Juan de la Cierva began his actual work on the autogyro in the early months of the 1920's. He was fortunate during his experimental work to receive help from his government in the form of money and the use of testing facilities—especially a wind tunnel. Days and weeks of study and testing dozens of tiny models preceded the building of his first full-scale machine. Questions arose to challenge his rotating-wing theories, and these first had to be answered. "Would a freely revolving wing, built like a windmill of blades or vanes, actually turn as the machine went through the air?" "Would the machine fly on it— that is, would it have 'lift' enough to raise the craft and hold it in the air?" "Would the resultant flying machine be stable, manageable and useful?" These were only a few of the problems, and the wind tunnel with its mechanically produced air currents helped mightily to provide some of the answers.

One day, after a series of disappointing tests with models having various rotor arrangements, the inventor received his first major encouragement. He tilted the blades forward on a model that had previously show little desire to remain airborne in the man-made air-stream. With pleasant surprise he noticed that it wanted to rise and stay aloft. Writing in his autobiography, he tells us, "This was highly important, for it proved that I was on the right track. The lifting force of the kind I now knew acted on the rotating windmill much as it does on the slightly inclined fixed wings of an ordinary airplane." Soon the first full-size autogyro was on its way.

Cierva's pioneer autogyro came out in October of 1921 and sported a double system of rotors, one above the other. This machine quickly proved that it was incapable of flight. The twin rotors disturbed the air between them so badly that their lifting ability was destroyed. Back to the workshop went the airplane, and the inventor returned to his drafting board to find the cure for the difficulty. Several months later in 1922, autogyro number two was ready for test-flying. This craft was drastically changed from the first one, having only one rotor of three blades. These blades were fastened rigidly to a vertical shaft that rose up from the top of the aircraft. It was little more successful than the first machine. The autogyro would taxi a few feet along the field, then tip over on its side despite every effort of the pilot to keep it upright.

Again the experimental airplane was rolled back to the shop, and Cierva once more re-examined his theoretical and test data to find the cause of this difficulty. Almost a year later, after he thought he had the solution, his third autogyro appeared. It turned over on its side, just as the previous two had, without ever leaving the ground. The inventor was really perplexed now, and he came to the unhappy conclusion that a workable autogyro "would not be found in such a design" as he adopted for these first experimental types.

Disappointed but undaunted, Cierva went back to making tiny models to find the reason why his autogyros rolled over. He knew the explanation, but at the moment he could think of no way to overcome the difficulty. As the rotor blades whirled around the shaft, they were causing unequal lift forces. Thus, as the blades spun to the front of the airplane, they gave more lift than when they reached the rear of the craft. Consequently, the stronger lift action on one side toppled the machine over. The engineer knew that if he could overcome this condition, he would have a successful rotary-wing airplane.

One day Cierva built a miniature model autogyro out of rattan, including the rotor blades, and powered it with a rubber-band motor. He was amazed to see how wonderfully it flew. It was steady, beautifully balanced in flight, and showed no desire to fall over on its side. Why couldn't he do the same with a full-size flying machine? The question haunted him for weeks. Then one evening, while he was attending an opera performance with his wife, the answer struck him like a bolt of lightning. The wings of his toy autogyro were made of rattan and therefore very flexible. It was this flexibility that gave the model its wonderful flying qualities. The more he thought about it, the more certain he was that it was the solution. For the remainder of the performance only Cierva's body was present—his mind was in his workshop designing and building his number four autogyro.

Cierva lost himself in feverish activity following that evening at the opera. He spent countless hours with intricate calculations, designing, making, and assembling parts until at last his newest autogyro was ready for a test flight. It was brought to the Getafe Airdrome just outside of Madrid, and the skilled services of Lieutenant Alejandro Gomez Spencer were obtained to fly the machine.

The inventor and a small group of his associates who aided with the work huddled quietly around the flying machine as the engine was warmed up. The pilot then signaled that he was ready to move, and the little group of men walked to one side. Slowly the airplane began moving; the rotor above the Lieutenant's head started to rotate. Several times the craft was taken around the field as the whirling fan spun faster. At this point the inventor could sense victory; the machine showed no tendency to roll over. Lieutenant Spencer was now ready for the great test. With the rotor spinning faster than ever, the autogyro gently rose into the air. The take-off run had been very short, and soon the pilot leveled out a few feet above the ground. He flew in this manner to the far end of the field and then brought the flying machine back to earth. He hit the turf with a soft jounce; the autogyro rolled a few feet and then stopped. A historic air flight had just been accomplished. The autogyro, the world's first practical rotating-wing airplane, was a success.

Cierva was breathless but jubilant when he ran up to the pilot. He aimed a torrent of questions at the airman, who smilingly tried to assure him that the airplane handled beautifully. There was only one minor weakness, and that was poor lateral or side-to-side balance. The inventor let out a sigh of relief. That could be fixed with a pair of ailerons, which were subsequently added.

The secret of the Spanish engineer's success was the flexibility which he had built into his rotor system. He did this by hinging the rotor blades to the vertical shaft. Now when the blades spun on their circular journey, there was an equal lifting force throughout the disc area. When they approached the front of the machine, they rose slightly in an up and down direction while losing some of their lifting power. As the blades spun to the rear, they dropped down a bit, picking up an extra amount of lifting power. This equalizing action took place very rapidly throughout the 360° of the blades' travel and was the secret of keeping Cierva's whirling airplane in perfect balance. Of course, this wasn't the only reason why the Spanish inventor's autogyro was able to make successful flights. As a result of his long hours of study and experiment with rotor blades, he found out how these should be properly twisted to give them the best possible lifting power. This was very important both while the engine was pulling the craft through the skies and in the event it stopped. In an emergency the blades would keep rotating automatically and with their great lifting power ease the machine gently to earth.

The autogyro, during the early years of its existence, looked very much like ordinary aircraft of that time. The fuselage and tail were the same, and it had an engine in the nose to pull the craft through the skies. Cierva's first models had small winglike panels on long booms extending from the sides of the fuselage to replace the wings. These panels, or ailerons, were movable and helped the pilot balance the craft better, especially around turns. Later types were fitted with very short wings to further increase stability. The pilot's controls were almost identical with those of the ordinary aircraft. There was a stick for moving the tail elevators for up and down flight and also the ailerons at the ends of the booms. Rudder pedals were provided to move the tail rudder for flying in a right or left direction.

The one feature that made the autogyro different from all other airplanes was a tripod structure rising from the top of the fuselage. Fixed to its upper end was the rotor with its series of long narrow wings that whirled above the pilot's head. These wings or blades acted in almost the same way as the fixed wings of conventional airplanes. On the latter the lifting surfaces are directly dependent on the operation and speed of the engine to enable them to keep the airplane in the air. Once the power plant stops or falls below a minimum necessary forward rate, the flow of air over the wings will be reduced so drastically as to destroy its lifting power, and the airplane will be forced down. Rotating wings, however, provide their own means of keeping the vital stream of air over their surfaces for lifting purposes, with little if any dependence on the engine. Once the rotor blades are spun, air begins streaming upward past them causing each of these to want to move in a forward or circular direction. Thus, the faster they spin about, the more they want to rotate. This action is known as "autorotation" or "self-turning" and inspired the inventor to call his airplane an "autogyro." At the same time, lift is being created on each blade, which enables the autogyro to become a flying vehicle.

The rotor blades of the autogyro are not connected to the engine. The latter is merely used to give the craft forward flying action. Even though the engine might fail, the autogyro could still be landed safely because of the self-spinning wings. The danger of flying far below a minimum forward speed was much less than with the conventional airplane.

On the very early autogyros, rotors were started on their spinning path by means of a rope wound around the shaft and then pulled off by several men. More often, however, the pilot would get them rotating by taxiing around the field several times and, when the proper speed was reached, would raise his craft into the sky.

Several weeks after Lieutenant Gomez Spencer had taken the autogyro on its historic flight, Cierva put his airplane through its startling flying maneuvers before an audience of high government officials and military leaders. Their astonishment and enthusiasm over this most unusual flying machine was no less than that of observers throughout the world. For indeed, it wasn't too long after the autogyro's flying performances in Spain that the inventor was invited to bring his revolutionary flying machine to other countries.

Cierva built a brand new airplane, his number six, before leaving Spain for England where the world was given its first glimpse of this unique aircraft. The inventor exhibited the autogyro at the Hendon Air Pageant in 1926 and created an immense amount of interest. Indeed, several enterprising Britishers were so impressed with this rotating-wing airplane that they persuaded the Spanish engineer to establish a factory in their land to build them. The Cierva Autogyro Company, Ltd., was soon in operation.

The Spanish inventor meanwhile did much to popularize the autogyro on his own account. In 1928 he made the first windmill airplane cross-Channel flight from England to France. Shortly thereafter he embarked on a three-thousand-mile tour that took him throughout Great Britain and Western Europe. Great enthusiasm was created wherever he appeared with his odd-looking airplane. In many of these lands, notably France and Germany, aircraft companies obtained patent privileges from the inventor to build similar models. Even the United States became interested in the autogyro when a young engineer by the name of Harold Pitcairn saw the autogyro perform in England in 1928. He was fascinated by the craft's performance and shortly thereafter obtained the licensing privileges to build the machine in the United States and also the authority to license others in that country who might want to do the same thing.

On Pitcairn's return to America, he brought with him an English-built autogyro, which, when it arrived at his airplane factory in Willow Grove, Pennsylvania, was equipped with an American airplane engine. On December 17, 1928, at Bryn Athyn, outside of Philadelphia, after all the necessary adjustments had been made, the first autogyro flights in this country took place. American aviation authorities were no less impressed than their European associates, calling the autogyro a truly remarkable advance for mechanical flight.

The following year Harold Pitcairn organized the Autogyro Company of America, which was actually a licensing company rather than one that did any manufacturing. From this there eventually were established three companies that engaged in autogyro activities in this country, The Pitcairn Company of America, Kellett Autogyro Company, and the Buhl Manufacturing Company. The first two were the most active, introducing many improvements in autogyro structure and operation. They were also the largest sellers of these unique aircraft to commercial, sporting, and military interests.

By the early thirties, the autogyro had completely captured the fancy of the professional aviation circles as well as the public. All had the feeling that here at last was the answer to the long-held dream of a near-perfect flying machine, an aerial vehicle that was within the reach of the man in the street with its unique and seemingly foolproof flying features. The military and commercial airplane people were equally excited about it.

The Army and Air Force saw the autogyros as excellent aerial vehicles for artillery spotting, reconnaissance, and communication work because they were able to take off from and land in places not possible with conventional planes. The Navy thought they would be especially valuable for doing anti-submarine patrol work while escorting merchant convoys. It was thought their ability to use very small areas for take-offs and landings would make it possible for them to operate from special platforms on the decks of warships or merchantmen. Many commercial airline operators looked on the autogyro as the missing element in their stable of aerial steeds that would bring aviation right into the heart of big cities. Landings could be made on the rooftops of large buildings, carrying passengers, cargo, and mail. During the mid-thirties, Eastern Airlines tried this very thing with an experimental autogyro mail delivery service between Philadelphia's downtown post office and the Camden airport. The roof of the post office was used for landing and take-off purposes. Others saw it as an excellent aerial taxi, ferrying passengers between airports or airports and hotels. There were still others with a really serious gleam in their eyes who thought it might rival trains and buses in commuting services—transporting workers from their outlying residences to places of employment in cities and vice versa.

Alas, for all these grand expectations, none came to pass. As rapidly as its fame spread throughout the world when first introduced by Cierva, so the autogiro slid into oblivion.

They could never be owned, like automobiles, by masses of people because they were much too expensive to buy and maintain. Their cost was far greater than conventional sport planes of that era. Besides this very important fact, the autogyros required a great deal of skill to fly, something which could be obtained only after lengthy and costly training.

The military lost interest in the autogyros when they discovered that small, lightweight ordinary airplanes were being made that could do practically the same things as the autogyros. They were much more economical to fly and easier to keep in repair, assets during military operations.

The autogyros never attained any worthwhile commercial uses. The airmail test route was discontinued by Eastern Airlines after a few months when the service was found too costly —even though the windmill airplane had shown it could speed up mail delivery between the airport and the post office. Actually, the only really large scale commercial use to which the autogyro was put was for advertising purposes. Because of their odd appearance, some wide-awake advertising individual saw them as a happy device to help his trade. Often they were used to tow large banners across the sky advertising some popular brand of cigarette, food, or gasoline. Advertising was also printed on the sides of the machine. Throughout the thirties they were a common sight in the skies above large cities and over resort areas throughout the country.

A strange feature of the period of dwindling interest in the life of the autogyro was the fact that the flying machine underwent a steady improvement, both in its appearance and flying efficiency. These technical advancements took place both in Europe and the United States. Among the more important of these perhaps was the shedding of wing surfaces and basing almost all flight maneuvers on improved rotor systems. The new autogyros were known as direct control gyros as compared to the early fixed-wing types. This meant that the pilot now guided his craft by simply tilting the rotor head. Thus, by using the control stick, the pilot flew upward by pulling back on the stick, tilting the rotor backward. Downward flight was accomplished by pushing the stick forward. Banking for either a right or left turn was achieved by pushing the stick to the right or left as desired, moving the rotor head in those directions. The tail rudder, as well as the changing of the pitch of the rotor blades, also played a part in these movements.

These direct-control autogyros had still another improvement in the form of a shaft and gears which connected the rotor to the engine. With this arrangement, the rotor could now be started mechanically and lengthy taxi runs were eliminated as well as the laborious cable-pulling method. Once the rotor head began to spin, the pilot disengaged the engine connection by means of a clutch.

"Jump take-off" was one of the last refinements made with the autogyro before it passed into eclipse. Essentially, the pilot spun the rotor at a greater than normal speed with the angle of the blades set almost at zero pitch or with very little lifting force. With the whirling wings spinning furiously, and ready for take-off, he suddenly changed the pitch of the blades to a strong lifting angle, and the gyro would shoot upward at a near-vertical angle. Little or no take-off run was necessary when this method was used.

More direct landings could also be accomplished by following a nearly similar procedure. The rotor blades were twisted to an excess pitch angle, giving them far greater lifting power than normally, and the autogyro would float gently to earth in a very steep inclined path.

By the late thirties, the first practical helicopter was born and far outshone the autogyro in flying performance. It was the last strange turn in aerial technical developments that made the autogyro a museum piece rather than a valued flying machine. Despite its failure to become a permanent part of the aviation world, the autogyro will long hold a special place of importance in the history of aeronautics. It was mainly responsible for bringing into being the world's most nearly perfect aircraft, the helicopter.

Juan de la Cierva did not live to see the passing of his beloved aerial invention. He died in an airplane accident at Croydon Airport in 1936. Ironically, it was in the type of flying machine of whose airworthiness he had considerable doubt and led him to invent the autogyro. Although he long questioned the possibility of the helicopter's ever becoming a practical flying machine, Cierva almost certainly would have been among its most ardent supporters had he lived to see that craft's amazing flying ability today.

From "Flying Windmills" by Frank Ross, 1953

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