Jet engine

“ The evolution of the heavier-than-air flying-machine, like that of the lighter-than-air, covers a long period of time, and was fraught with many difficulties and dangers. For ages many scientific men played with the idea, but owing to the lack of motive power light enough to be mounted on a glider yet supplying sufficient strength to drive a set of planes through the air at 45 miles an hour, very little progress was made until the perfection of the steam-engine and the development of the gasoline motor. ”

“ About 0.55 pint per brake horse-power per hour was the usual fuel consumption necessary to full load running, and the engine was also economical as regards the consumption of lubricating oil, the lubricating system being ‘forced’ for all parts, including the cam-shaft. The shape of these engines was very well suited for work with aircraft, being narrow enough to admit of a stream-line form being obtained, while all the accessories could be so mounted as to produce little or no wind resistance, and very little obstruction to the pilot’s view. ”

“ This is all that need be said about why the air supports an airplane; all you have to remember is that as long as you have the forward sweeping movement, you will have the lift.
The forward movement is absolutely essential, however, and to maintain it requires a lot of horsepower and gasoline. For it is by means of the engine and propeller that this forward movement is maintained. The engine is a device for creating forward movement—the propeller drives the machine ahead in exactly the same way as is the case in a torpedo, or steamboat. ”

“ Also that is why the aviator has to be in his seat at the controls, and have some other person start his machine for him, by turning over the propeller, or propellers until the motor fires.
Lately however, especially since the talk of the flight across the Atlantic, a means has been found to allow the aviator, or some helper with him, to start the engine once it has stalled in midair. This is accomplished by means of a sprocket chain gear and a crank connected to the engine shaft. The turning handle is within reach of the aviator. ”

“ With regard to the flying-boat type of machine, a favourite practice is to mount the motor on the four struts supporting the centre section of the upper plane, which is braced by struts and wires from different points on the hull or body.
Although the modern aircraft engine is of greatly increased power, compared with the engine of the period 1912–1914, one does not find any great difference in the structural features of the mounting employed, and in view of the very diverse arrangements for mounting the same type of engine which now exist, there is need for greater uniformity. ”

“ The rear section, with separate leaves, like the feathers of a bird’s wing, likewise disappears, leaving only the long narrow wing which has always been the ideal speed machine.
“To drive this huge craft, whose body consists of two stories or decks with pilot house, staterooms, fuel chambers, engine room, bridges above and protective galleries, a much higher percentage of motor power than ever secured before had to be turned into propulsive energy. ”

“ Undoubtedly the engine problem has been the big one in the history of aviation. The coming of the internal combustion engine might be said to have placed practical aviation within the range of possibility, but at that it took a long time to evolve a motor especially suited to the needs of aircraft. There were three things needed in an airplane motor: Light weight, high power, and absolute reliability. How important the third factor is we can imagine if we stop to think that nothing keeps the heavier-than-air machine afloat but its own speed, creating an air pressure beneath its wings. ”

“ Subsequent developments have indicated that this type, with the further development from it of the double-Vee, or engine with three rows of cylinders, is likely to become the standard design of aero engine where high powers are required. The construction permits of placing every part so that it is easy of access, and the form of the engine implies very little head resistance, while it can be placed on the machine—supposing that machine to be of the single-engine type—in such a way that the view of the pilot is very little obstructed while in flight. ”

“ The idea of propelling a kite through the air, not by tying it to the earth, but by furnishing it with its own propeller and power plant, was conceived long [231] ago, but the problem was to find a power plant light enough. The honor of being the first man to rise off the ground in an aeroplane belongs to C. Ader, who made several short flights between 1890 and 1896 in a machine driven by a twenty-horsepower steam engine. ”

“ It showed a tendency to rise, but its lifting power was insufficient for the weight of the engine driving the propellers. It was evident, however, that if the power of the engine could be sufficiently increased, or, what amounts to the same thing, its weight sufficiently lightened, a machine built on the aeroplane principle could be made to fly. But at that time the lightest type of engine was a crude, heavy machine, and for the moment nothing more was attempted in producing a mechanical flying-machine propelled by steam. ”

“ The evolution of the motor-car led to the adoption of the vertical type of internal combustion engine in preference to any other, and it followed naturally that vertical engines should be first used for aeroplane propulsion, as by taking an engine that had been developed to some extent, and adapting it to its new work, the problem of mechanical flight was rendered easier than if a totally new type had had to be evolved. ”

“ But, in any case, the starting of the engine means the whirling of the propellers, for they are directly connected. This is why, when once the engine stops in mid-air, it can not be started again. Or at least if it is started it is mostly a matter of chance in getting it to go under compression or by the spark. There is no chance for the aviator to get out and whirl the propellers which are, in a measure, what a flywheel is to an automobile. ”

“ As we rise, the air becomes thinner. Finally a point is reached at which no propeller will ‘bite.’ The ceiling has been attained.
“With jet propulsion, exactly the opposite holds good. The less air there is, the more efficient is the motor. If the ejected gas has an expansion efficiency at rest of 40 feet in one-hundredth of a second—a rate of 4,000 feet a second—the same force exerted in motion would increase the speed up to a point where the maximum efficiency is reached at something like 10,000 miles an hour. Jet propulsion gets better and better as speed and height increase. ”

“ In other words, to double the speed of a steamship (and the same is true of the balloon type of airship) eight times the engine and boiler capacity would be required, and four times the fuel consumption per mile of travel: while a flying machine would require engines of less than double the size, and there would be an actual decrease in the fuel consumption per mile of travel. But looking at the matter conversely, the great disadvantage of the flying machine is apparent; for in the latter no flight at all is possible unless the proportion of horse-power to flying capacity is very high ”

“ Owing to the great range of an airship a thoroughly reliable engine is a paramount necessity. The main requirements are--firstly, that it must be capable of running for long periods without a breakdown; secondly, that it must be so arranged that minor repairs can be effected in the air; and thirdly, that economy of oil and fuel is of far greater importance to an airship than the initial weight of the engine itself. ”

“ The machine was brought out with mechanics hanging to the wing-tips to steady her against the gusts, the engine started and given a trial run up; then the pilot eased her off, looked round, felt his controls, ran the engine up again until his machine was throbbing and quivering to the pull of the whirling propeller, and waved the signal to haul away the chocks that blocked his wheels. His machine began at once to taxi up into the wind, still swaying and swinging dangerously, and then, in answer to the pilot's touch, lifted clear of the ground, ducked a second, rose again and swooped upward. ”

“ They cannot possibly float horizontally in the air for any length of time, but to keep going must necessarily lose in elevation. They are excellent schooling machines, and that is all they are meant to be, until power, in the shape of an engine working a screw propeller, or an engine working wings to drive the machine forward, is added; then a person who is used to soaring down a hill with a simple soaring machine will be able to fly with comparative safety. ”

“ With this type of engine the breakage of air-screws was of frequent occurrence, and an engine having a more regular rotation was sought, both for this and to avoid the excessive vibration often experienced with the four-cylinder type. Another, point that forced itself on engine builders was that the increased power which was becoming necessary for the propulsion of aircraft made an increase in the number of cylinders essential, in order to obtain a light engine. ”

“ Upon going into a mathematical calculation of the whole subject, I found that it would be possible to make a machine on the aeroplane system, driven by a steam engine, which would be sufficiently strong to lift itself into the air. I first made drawings of a steam engine, and a pair of these engines was afterwards made. These engines are constructed, for the most part, of a very high grade of cast steel, the cylinders being only 3/32 of an inch thick, the crank shafts hollow, and every part as strong and light as possible. ”

“ With the flying machine, on the contrary, the same difficulty does not arise. Since it is at all times heavier than air, and is kept aloft simply by its motive power and mechanism, its weight is of no consequence, provided only its engine is sufficiently powerful. It may, therefore, be built as rigidly as need be, while, from its size—which is much smaller in proportion to its lifting power than in the case of the airship—and also from its construction, it is much less liable to be affected by the wind. ”

“ Then, there were double control wires, running from the levers to the rudder and the elevating planes, so that, if one wire broke (a thing that has caused many an aviator’s death) another would take its place.
For starting the machine from the seat—without having to have some one whirl the propeller till the engine was going—there was an electrical motor, which was a sort of boy of all work. For, when it was through its work as a motor, it became a dynamo, and filled up storage-batteries which worked the big electrical search-light, for use when the machine was flying at night. ”

“ In short distance, high-speed machines it works well, but in the larger planes the vertical or V-type motor has been found to give greater satisfaction.
When we read of the enormous trouble the pioneers of aviation went to, in order to find an engine suitable to drive the propeller of the airplane, we cannot help wondering just how the revolving of the propeller sends the whole machine flying forward through the air. ”

“ In the stoppage of its motor, when a craft is in flight, several factors need consideration; but one should clearly be understood: even if his engine does fail while he is passing through the air, a pilot is not helpless, nor does his machine fall to the ground. As he flies, of course, it is the thrust of his motor, acting through the medium of the propeller, that keeps his craft moving forward; and so long as this thrust is there, forcing his planes against the air and causing them to lift their load, the machine will fly ahead. ”

“ At the word “contact” the mechanics swing the propeller, and, sometimes only after several trials, the motor starts, with a roar and a rush of wind in the passenger's face. After a moment's slow running it is speeded up, the intermittent roar becomes a continuous note, the plane shakes and strains, while the mechanics hold down the tail to prevent a premature take-off. When the engine is properly 26warmed up it is throttled to a low speed, the chocks under the wheels are removed, the mechanics hold one end of the lower wing so that the plane swings around toward the field. ”

“ Most of us manufacturers, sold on our own doctrine, had now moved into the design and production of new transport aircraft intended to replace the war-weary war surplus. In United Aircraft, for instance, we had undertaken to expand the power output and increase the dependability of our current commercial engines and had at the same time inaugurated a wholly new engine, a twenty-eight-cylinder Wasp Major with a capacity of 4,360 cubic inches and an initial rating of 3,000 horsepower. ”

“ Raynor, who as advanced-flying pilot was for the present out of Hal’s school sector, sometimes of a night joined in these air battles fought out on the ground. All manner of past and modern experiments came under the fire of their discussions. Aeronautical engine builders seemed to have tried out many varieties of motors. There were the long ago experiments with steam engines for airplanes. The engine itself could be made much lighter than the gasoline engine, but the fuel and water added so much weight that the whole combination was far too heavy for air purposes. ”