Planes That Go Straight Up OPEN NEW FIELDS FOR AVIATION (Mar, 1935)
Planes That Go Straight Up OPEN NEW FIELDS FOR AVIATION
By Edwin Teale
AMONG the skyscrapers of lower New York City, a few weeks ago, a strange wingless craft drifted down in a vertical landing. Its wheels touched the concrete of a pier and rolled less than a dozen feet. With balancing wings eliminated, it represented the latest style in autogiros. The flying windmill has taken another step toward the goal of a thousand inventors, the helicopter.
An autogiro can descend vertically; but it can take off only after a run. A helicopter could get out of a field the size of its landing gear. It could climb straight into the sky, could hover like a humming bird, and could drop like an elevator descending its shaft. Entirely new realms of aerial travel await the perfection of such a craft.
Military observers could dart into the sky, sidestep diving pursuit planes, and plunge to a landing; private ships could be housed in rooftop hangars shaped like water towers; office buildings could be capped with honeycomb cells holding the helicopters of the workers, each craft dropping into its compartment in the morning and rising straight up from it at night; aerial shuttle lines could link centers of population with airports and suburbs. These are not fantastic visions. They lie entirely within the realm of possibility. And it is such possibilities that spur on the inventors of many lands.
As these words are being written, a cable from England tells of dramatic progress. Mechanics at the famous Blackburn airplane works are busy assembling a huge craft of revolutionary design. Invented by Oskar Asboth, former director of a government research laboratory in Austria, it is designed to climb vertically to 10,000 feet and to attain a cruising speed of 110 miles an hour.
A single-seated experimental model of similar design is said to have made 200 flights without a mishap. Secret tests were carried out by Capt. R. N. Liptrop, a technical official of the British Air Ministry.
He reports the ship climbed straight into the air at a surprising rate, that it maneuvered under perfect control, hovered over one spot, and landed gently at the end of each flight. On several occasions, he soared over the trial field with his hands off the controls. A mechanic, who had never piloted an airplane in his life, is reported to have taken the new craft up without the least difficulty.
All over the world, aeronautical experts are eagerly awaiting the tests of the new machine now nearing completion. Twin, motor-driven screws, cutting through the air in opposite directions, will lift the craft while a third propeller pulls it forward. This propeller is thrown in and out of gear by a clutch in the cockpit. Because the machine descends vertically, landing wheels are unneeded and the curious skycraft comes to rest upon four inflated pads which act as shock absorbers. In the event of engine failure, a self-spinning feature of the variable-pitch lifting screws is said to prevent a fall. Speed and load tests will soon reveal how far the new machines goes in rivaling the ability of orthodox planes. A second helicopter of like design is reported under construction in Austria.
To the average person, that item meant little. Political news crowded it from the front page. But to those who recall the long trail inventors have followed, searching for the goal of vertical flight, it was a thrilling story.
For five centuries, since the days of Leonardo da Vinci, the genius of the Renaissance, men have been striving by means of a host of mechanisms to lift themselves vertically into the sky with heavier-than-air machines.
It was a toy helicopter that first interested the Wright Brothers in aviation; it was the helicopter that Thomas A. Edison maintained throughout his life would be the ultimate craft of the sky; and it was the helicopter that such men as Peter Cooper Hewitt, inventor of the mercury arc lamp, Louis Brennan, inventor of the Brennan torpedo, Emile Berliner, father of the microphone, Edison, and others, spent years trying to perfect.
Among the papers left by Da Vinci at the time of his death in 1519, was the drawing of a proposed aerial craft which was to be lifted by “a great screw turning on a vertical axis.” Three centuries later, a Frenchman, named Pauceton, designed a machine for navigating the air. It was to have “two turning mills, one to support the apparatus, the other to drive it along. A few years afterwards, Launoy and Bienvenu, fellow-countrymen of his, exhibited a flying toy. Two screws, formed by four feathers and turned in opposite directions by rubber bands, carried it aloft.
In place of rubber bands, Enrico Forlanini, an Italian, used a midget steam engine which he designed about the time of the Civil War. His model helicopter, driven by its puffing power plant, actually rose from the ground and flew. But his design was never translated into a full-sized machine.
The gap between the model and the man-carrying craft is tremendous. Hundreds of patents have been granted to inventors for helicopters that appeared sound on paper. Models have pulled aloft weights that, increased proportionately for big machines, would have equalled 100 pounds lift per horsepower. But the complicated mass of tubing and guywires, engine braces and transmission shafts, balancing flaps and propeller braces, have piled up the weight and increased the danger of breakdown in the big machines.
EARLY innovators like Edison and Emile Berliner were handicapped by heavy engines. Edison’s weighed almost fifty pounds per horsepower. If, he said, motors could be built weighing only three or four pounds per horsepower, vertical flight would be simple. Today, we have air-cooled aircraft engines that develop a horsepower for every pound and a half of weight.
By 1907, motors had been improved greatly and that year stands as a landmark in helicopter history. In France, two machines carried their pilots into the air. One was designed by Paul Cornu, the other by Louis Breguet, later famous as a designer and builder of airplanes. It was one of his
ships that, in 1930, carried Capt. Dieudonne Coste and Maurice Bellonte 4,030 miles on the first westward transatlantic flight linking Paris and New York.
Cornu’s machine had cloth-covered, paddle-shaped blades. The power was transmitted to them by leather belts running from the engine. This fact, during one of the early trials, gave the inventor an exciting few minutes. Only the quick wit of his brother saved him from disaster.
As the craft nosed from the ground, the belt to the rear lifting blades began to slip. The blades slowed down. The front of the machine reared higher and higher into the air. A moment later the whole apparatus would have crashed over in a backward somersault had not Cornu’s brother leaped up, caught the forward framework and, dangling from it, restored balance until the machine could settle to a landing.
FOUR biplane blades lifted the huge machine constructed by Breguet. On August 24, 1907, with the motor volleying like a machine gun and the blades threshing the air, the awkward craft lifted its inventors several feet from the ground, then dropped back to earth. About this time, inventors all over Europe were tinkering with helicopters. One was a young Russian, now world-famous as a designer of huge multi-motored flying boats. In 1908, Igor Sikorsky finished a machine near Moscow. It had a fifteen horsepower engine and twin lifting propellers whirling on a concentric shaft. The engine was too weak. At the trial, the machine buzzed like an infuriated bumblebee, but hugged the ground.
Undiscouraged, young Sikorsky persuaded his father, a professor of psychology at Moscow, to venture more rubles on a second machine. It had a stronger motor and on several occasions rose into the air carrying ballast instead of a pilot. Controlling it by long strings, young Sikorsky ran alongside as the helicopter made flea like hops over a level field. Shortly afterwards, he turned his attention to airplanes and these early adventures with helicopters are little known.
The World War saw a curious adaptation of the helicopter idea, a “flying tin can” which carried observers aloft over the Austrian trenches. Three motors, reenforcing each other, delivered power to twin lifting screws. Above the framework was a cylindrical turret, suggesting a tin can, which housed the observers. The whole craft was operated like a captive balloon, rising at the end of a cable and being pulled down from the sky by means of a winch. Known after its designers as the Petroczy-Karman helicopter, it rose on a number of occasions to heights of a hundred feet and more.
HOWEVER, the men who rode it never attempted to bring it to earth by throttle control. They always let the cable pull them back to earth. Thus, the machine contributed little to one of the biggest problems of the helicopter, the problem of landing safely, especially if the engine fails. As a matter of fact, designers have found it easy to get off the ground. The hard nuts to crack have been maintaining balance in the air and descending safely.
To keep on a level keel, some machines have had the opposing propellers tilted toward each other. Others have had the whole mast upon which the air screws revolved designed so it could be tilted in any direction. Still others have had small auxiliary blades spinning at the far corners of the apparatus to lift or depress as the pilot wished. Variable-pitch lifting screws, which can be changed to regulate the “bite” they take out of the air, and consequently their lift, form a fourth solution which has been advanced by innovators. Nearly all the helicopters which have been produced have had the engines and pilots placed low to provide a pendulum effect that would aid in maintaining balance in the air.
So far, no helicopter has flown on a gusty day and no helicopter has landed safely from any height with its engine dead. Unless the machine can come to earth without crashing in event of engine failure, such craft never will be widely used.
The suggestions for attaining this end have been many. They range from having a collapsible balloon, which can be filled from a tank of compressed hydrogen in an emergency, to folding window-blind wings that the pilot can open by means of a lever. Most inventors, at present, are working along the line of variable-pitch propellers. These lifting screws could be shifted from a positive to a slightly negative angle during the descent. Thus the wind would turn them like the blades of a windmill and check the drop. In addition, just before reaching the ground, the pilot could shift the. blades back to their most effective lifting angle and their momentum would produce an upward thrust that would slow the machine down before landing.
A VARIATION of this scheme is proposed by a young American inventor. He plans to have a gyroscope in the machine to keep it level in the air. In a descent, the heavy wheel of the gyroscope would be spun by the whirling blades and when the variable-angle screws were shifted back to their lifting position, the gyroscope would give them added momentum.
Of course, such proposals do not answer the problem of engine failure close to the ground. They are applicable only during a considerable descent to become effective. However, improvement in the landing gear, so it will absorb greater shocks, may take care of this problem. The experimental work with the autogiro has accomplished much in this direction. The modern machine of this type can touch earth without damage when it is dropping twelve feet a second. And, it is the shock of impact and not the fall that does the damage.
In the early nineteen-twenties, there was another burst of activity in the helicopter world. In 1921, the Marquis de Pescara, an Argentine of Italian descent, rode a twin-propeller craft into the air at Barcelona. It was equipped with a small body like a racing car, the engine and radiator being in front and the two screws, revolving at 200 revolutions a minute, overhead. Two years later, at Issy-les-Moulineaux, France, he set a world’s record with a flight of approximately half a mile. On July 21 of that year, he achieved the first circle ever flown with a helicopter.
DURING that same year, Etienne Oehmichen, in France, and Dr. George de Bothezat, in America, also made helicopter history. Oehmichen, in a machine with four lifting air screws and a number of auxiliary propellers, won a prize of 90,000 francs by flying over a circular course of nearly a mile.
In America, the U. S. Army financed the experiments of De Bothezat. His giant apparatus, measuring sixty-five feet from tip to tip, was shaped like a huge Maltese cross. It had a six-bladed lifting screw, twenty-six and a half feet across, at each of the four outer points. The framework, formed by a maze of tubing and wire, brought the weight of the craft up to 3,400 pounds. Yet, when it was tested at McCook Field, Dayton, Ohio, the apparatus not only lifted its own weight but 1,000 pounds besides. Its balance in the air was so steady that in one flight it lifted three men hanging from three of the four points of the frame. A hundred times, it ascended from the field and landed again without accident. The craft, on one occasion, was clocked at thirty miles an hour in a flight across the field.
Although De Bothezat’s helicopter was one of the most successful tested, it flew only in perfect calms, and its provision for changing the pitch of the blades to provide for safe descents in case of engine failure was not tried. The progress made in vertical flight during 1923 encouraged the British Air Ministry to offer a $250,000 prize for a helicopter that could pass four tests. The winning craft must rise vertically to 2,000 feet and descend, landing without damage. It must climb to 2,000 feet, hover over a given area for half an hour, descend and land without damage. The third test was a flight at 2,000 feet over a twenty-mile course at a speed of sixty miles an hour. For the final test, it had to descend from 500 feet with the engine dead and land in a circle of 100-foot radius.
ALL over the world, a weird array of “flying turtles,” “sky windmills” and “aerial tunnels” were reported as being groomed to carry off the prize. But the time limit of the competition came and went without anyone fulfilling the requirements.
However, the Air Ministry has maintained its interest in developing a machine capable of vertical flight. In 1925, Louis Brennan, noted English naval inventor, was subsidized by the government in experiments with an original design. The machine is reported to have lifted 1,000 pounds and to have hovered over one spot for fifteen minutes.
Four years later, in 1929, another machine, the Isacco Helicogyre, was built experimentally under the auspices of the Air Ministry. It had a single huge lifting screw with air-cooled motors at each end equipped with smaller propellers that pulled around the lifting blades. A somewhat similar idea is incorporated in the Curtis-Bleecker helicopter, a $250,000 experimental craft produced a couple of years ago in America. Each of its four lifting blades has a propeller in front to keep the aerial windmill turning.
Two other machines, one in Italy, the other in Belgium, have marked further advances recently.
With twin blades spinning in opposite directions on a central mast, the D’Ascanio helicopter hovered and circled about over an air-field near Rome for more than eight minutes, early in 1931. Lighter than most machines of the kind, it weighs only 1,750 pounds and has a ninety-five horsepower motor. Smaller propellers at the outer edges of the framework aid in directing the craft and in maintaining balance.
The Belgian craft, designed by a mechanic named Florian, is lifted by a pair of twenty-four-foot screws, with a stubby auxiliary propeller spinning between them. Its curious landing gear consists of four shock-absorbing bumpers shaped like elephant hoofs. Rising higher than the surround buildings, the machine hovered aloft for almost ten minutes.
At the present time, a number of inventors are reported working upon the idea of combining a helicopter and a rocket. One plan is to have the lifting screws propelled by rockets, another, and more daring one, is to have the craft shot upward to a desired height as a projectile. Then, when forward momentum ceases, vanes, folded into the side of the projectile, open out and, propelled by an internal motor, carry the machine along as a helicopter.
In the search for the goal of vertical flight, noblemen, mechanics, famous inventors, unknown tinkerers, and noted scientists all have grappled with the problem. They have spent millions of dollars and patents innumerable record their ideas. Yet, so far, only tantalizing, partial success has been their reward.
It is no wonder, then, that men all over the world are awaiting eagerly the forthcoming trials of the English machine.