Helicopter

“ The possibility of flight by this method is modified by a very definite disadvantage of which lovers of the helicopter seem to take little account. It is always claimed for a machine of this type that it possesses great advantages both in rising and in landing, since, if it were effective, it would obviously be able to rise from and alight on any ground capable of containing its own bulk; a further advantage claimed is that the helicopter would be able to remain stationary in the air, maintaining itself in any position by the vertical lift of its propeller. ”

“ In these respects the ability of man is limited. The wing ligatures of flying creatures is exceedingly strong, and flexible; the hollow bone formation and the feathers are extremely light, compared with their sustaining powers.
THE HELICOPTER MOTION.—The helicopter, or helix-wing, is a form of flying machine which depends on revolving screws to maintain it in the air. Many propellers are now made, six feet in length, which have a pull of from 400 to 500 pounds. If these are placed on vertically-disposed shafts they would exert a like power to raise a machine from the earth. ”

“ Helicopter is used to designate machines which are lifted vertically and sustained in the air by propellers revolving in a horizontal plane, as distinguished from the propellers of the aeroplane, which revolve in vertical planes. ”

“ Going still further in the same direction, we may find any day that one of the attempts in various countries to design and construct a successful helicopter has matured, producing a machine which, by reason of a very powerful propeller on a moveable shaft that can be inclined in any direction, will not only rise and descend vertically, but also may be made to travel forward at a great speed and to perform such acrobatic tricks as sudden halts, retreats and jumps. ”

“ The helicopter is a machine which theorists of that school believe can fly straight up into the sky because its air screw propeller works on a vertical axis. This type of aircraft has never been successful, for the reason that the propeller does not lift. It simply pulls a stream-lined surface through the air. The lifting must be done by planes.
The ornithopter is another heavier-than-air craft which seeks to fly by flapping wings like a bird. The effort to build this type of machine is as old as human desire to imitate the fowls of the air and it has been as unsuccessful as the helicopter. ”

“ If four men were standing fairly close together on the ground with running helicopters, they would tend to spread out as they left the ground, so as to not run into each other. Moreover, with a helicopter, it is not necessary to face the direction you intend to go. ”

“ The Helicopter, on the other hand, has no antecedent type, but is dependent for its raising powers on the pull of a propeller, or a plurality of them, constructed, as will be pointed out hereinafter.
AEROPLANES.—The only form which has met with any success is the aeroplane, which, in practice, is made in two distinct forms, one with a single set of supporting planes, in imitation of birds, and called a monoplane ”

“ With the aeroplanes, on the contrary, their running gear enables them to run forward on the ground almost with the first revolution of the propeller, and as they increase their speed the currents—technically called the “slip”—become less and less as the engine speed increases.
In the Cornu helicopter, which perhaps has come nearer to successful flight than any other, these downward currents are checked by interposing planes below, set at an angle determined by the operator. The glancing of the currents of air from the planes is expected to drive the helicopter horizontally through the air. ”

“ The result aimed at in the helicopter is the ability to rise vertically from the starting point, instead of 144 first running along the ground for from 100 to 300 feet before sufficient speed to rise is attained, as the aeroplanes do. The device employed to accomplish this result is a propeller, or propellers, revolving horizontally above the machine. After the desired altitude is gained it is proposed to travel in any direction by changing the plane in which the propellers revolve to one having a small angle with the horizon. ”

“ The helicopter is wasteful in power, but is stable and sure in ascending and descending, providing only that the motor power does not fail.
Why, then, not combine the types? An aeroplane-dirigible would be open to only one objection: on the ground of stability. The dirigible-helicopter would have as its only disadvantage a certain wastefulness of power, [Pg 180] while the aeroplane-helicopter would seem to have no drawback whatever. ”

“ Parachute.
Da Vinci’s second flyer was a helicopter, as shown in Fig. 26. An aërial screw 96 feet in diameter was to be turned by a strong and nimble artist who might, by prodigious effort, lift himself for a short time. Though various small paper screws were made to ascend in the air, the larger enterprise was never seriously undertaken. Many subsequent inventors developed the same project; but the fellow turning the screw always found it dreadful toil and a hopelessly futile task. Of late the man-driven helicopter has been abandoned, but the motor-driven one is very much cultivated. ”

“ Setting its regulator at “Half-speed,” he touched a button and began to ascend slowly. When the “Altitude Indicator” registered “1000 Feet,” he turned “full speed” into the helicopter device and finished with a rush. At “20,000 Feet” he shut the helicopter down to “Maintenance of Altitude” speed, pulled a lever which released a huge propeller from its underneath pocket, and set it going at full speed “In Reverse,” yanked the lever back at “21,500 Feet,” and came to a full stop at “22,000 Feet” with the underneath propeller roaring noisily but harmlessly in its enclosed pocket. ”

“ Garry looked a second time, carefully.
“Chick’s right,” he murmured to Don. “He says it’s a helicopter—it has the lifting blades that let it rise straight upward and then it has a ‘tractor’ propeller forward that sends it through the air horizontally. It can go higher by giving the horizontal blades more speed, stay almost stationary by adjusting speed, or settle lower by slowing the blades. The tractor prop gives it forward speed. Chick’s right.” ”

“ The larger project was obviously without merit; for no combination of springs can maintain flight for more than a few seconds even on the most favorable scale.
A more powerful toy helicopter was produced by Mr. Horatio Phillips in England in 1842. This was a single aërial screw emitting jets of steam which compelled it to spin, on the principle of a lawn sprinkler, or a Hero engine. The whole apparatus weighed two pounds, and had screw blades inclined 20° to the horizon. ”

“ Later, however, Leonardo did design another model on this principle which has been called the forerunner of the modern helicopter. It was to be operated by four men standing on a platform. Each man would hold a bar which wound a spring-driven mechanism, much as in a modern clockworks. The air-screw was a broad blade spiraling about a vertical shaft—the ancestor of the modern propeller. ”

“ But, in applying such a propelling force to the air, most of the force is utilised in maintaining aerodynamic support—as a matter of fact, more force is needed to maintain this support than the muscle of man could possibly furnish to a lifting screw, and even if the helicopter were applied to a full-sized, engine-driven air vehicle, the rate of ascent would depend on the amount of surplus power that could be carried. ”

“ The enemy does not have air and naval superiority. Heavily populated hostile areas obstruct exfiltration. The team cannot be resupplied. Casualties must be extracted. b. Techniques. Several techniques may be used to extract the LRS teams:
(1) Helicopter landing. This is the best method. It lets the team board the helicopter with their equipment in the least time. (2) Troop ladder. The troop ladder allows the team members to board the helicopter. But, if necessary, the helicopter can lift off while soldiers are still on the ladder. (3) SPIES or FRIES extraction systems. ”

“ A still more ambitious helicopter was that shown in Fig. 37 invented by Professor Forlanini, an Italian Civil Engineer, and launched in 1878. The lower screw was fastened to the frame of a steam engine, the upper screw was attached to the crank shaft. Steam was supplied from the globe shown beneath, which was two thirds filled with water, and well heated over a separate fire just before an ascension. As the globe was merely a reservoir of hot water and steam, carrying neither fuel nor furnace, its power waned rapidly. ”

“ Another difficulty is that the helicopter screws, in running at the start before they can attain speed sufficient to lift their load, have established downward currents of air with great velocity, in which the screws must run with much less efficiency. ”

“ In high-speed racing craft such inclined screws were of necessity often used, but it was at a sacrifice of their efficiency. In any case the efficiency of the inclined-screw helicopter could not compare with that of an aeroplane, and that type might be dismissed from consideration so soon as efficiency became the ruling factor of the design. ”

“ Although, in model form, there is nothing quite so strikingly successful as the helicopter in the range of flying machines, yet the essential weight increases so disproportionately to the effective area that it is necessary to go but very little beyond model dimensions for the helicopter to become quite ineffective. ”

“ The helicopter may be regarded as the limiting type of aeroplane, the sail area being reduced nearly to zero; the wings becoming mere fins, the smaller the better. It therefore requires maximum motor power and is particularly dependent upon the development of an excessively light motor. It is launched and descends under perfect control, without regard to horizontal velocity. It has very little exposed surface and is therefore both easy to steer and independent of wind conditions. By properly arranging the screws it can be amply balanced: but it must have a particularly stout and strong frame. ”

“ Its quadruple floats, each the size of a tugboat and each capable of being exhausted of air, constituted a potential lifting-force of enclosed vacuums that very largely offset the weight of the mechanism. It was still a heavier-than-air machine, but the balance could be made nearly perfect. And the six helicopters, whose cylindrical, turbine-like drums gleamed with metallic glitters—three on each side along the fuselage—could at will produce an absolutely static condition of lift or even make the plane hover and soar quite vertically. ”

“ They assigned two general missions to Marine Helicopter Experimental Squadron 1 (HMX-1) , organized late in 1947 before the first rotary-wing aircraft had been delivered. These missions were:
(1) Develop techniques and tactics in connection with the movement of assault troops by helicopter in amphibious operations;
(2) Evaluate a small helicopter as a replacement for the present OY type188 aircraft to be used for gunfire spotting, observation, and liaison missions in connection with amphibious operation.282
282 CMC ltr to CO MCAS, Quantico, 3 Dec 47. ”

“ The best flight lasted about twenty 201seconds, attaining a height of 42 feet. The apparatus weighed 77 pounds, spread 21.5 square feet of screw surface, and lifted about 26.4 pounds per horse power.
Many other helicopter models have been tried from time to time, with various sources of power, without, however, yielding any important results beyond those already given. But these were sufficiently encouraging. If a large machine could be made to lift as many pounds per horse power, it would be easy to build one competent to carry a man. ”

“ But it is based on the airplane and the motor of to-day without allowance for the development and improvement which are proceeding apace. It contemplates a craft which has but one motor, but the more modern machines have sufficient lifting power to carry two motors, and can be navigated successfully with one of these out of service. Experiments furthermore are being made with a device after the type of the helicopter which with the steady lightening of the aircraft motor, may be installed on airplanes with a special motor for its operation. ”

“ Then I'd bind those two criminals hand and foot or surround them with live wires, so that, should they awake unexpectedly, they would not dare to stir."
"There is certainly something in what you suggest about bringing the aeroplanes over, though we should have a deuce of a job to land them in this place; they're by no means possessed of the powers of a helicopter. However, I'll get into touch with Colonel Tempest and ask for immediate assistance, and also ask him to bring over Professor Verne to investigate these mysterious engineering and chemical appliances." ”

“ He knew them all: the pleasure craft, the big, red-bellied freighters, the sleek liners, whose multiple helicopters spun dazzlingly above as they sank down through the shaft of pale-green light that marked a descending area. ”

“ On their last mission, the two young men had been absorbed in mapping an interesting valley in the north polar regions—a pursuit which they had no intention of giving up. A few days after they had finished the work, therefore, they announced their intention of taking the helicopter out again. ”

“ Of the various inventors who have built man-lifting helicopters M. Cornu and M. Bréguet, in France, seem to have been first to attain a measure of success. While their machines have raised a passenger directly from the ground, they have not yet maneuvered in horizontal flight with sufficient speed to be of practical service. However, a few helicoptrists in various countries are still industriously at work, and hope eventually to rival the aëroplanists in the mastery of flight. ”