Elevator (aeronautics)

“ The 1901 machine was, in consequence, nearly doubled in area—the lifting surface being increased from 165 to 308 square feet—the first trial taking place on July 27th, 1901, again at Kill Devil Hill. It immediately appeared that something was wrong, as the machine dived straight to the ground, and it was only after the operator's position had been moved nearly a foot back from what had been calculated as the correct position that the machine would glide—and even then the elevator had to be used far more strongly than in the previous year's glider. ”

“ The steering lever, working on a universally jointed shaft—forerunner of the modern joystick—controlled both the rudder and the wings, while a pedal actuated the elevator. The engine drove a two-bladed tractor screw of 6 feet 7 inches diameter, and the angle of incidence of the wings was 20 degrees. Timed at Issy, the speed of the machine was given as 36 miles an hour, and as Bleriot accomplished the Channel flight of 20 miles in 37 minutes, he probably had a slight following wind. ”

“ The engines and nose portion of the fuselage plowed into the ground to a depth of approximately six feet. The nose section of the right engine, propeller hub, and one blade of the propeller, still attached to the hub, and the nose section of the left engine, propeller hub, and two blades of the propeller, broken off at the shank, remained in the hole.
The right and left landing wheels and landing gear were about 50 feet beyond the point of impact. The left elevator and part of the left stabilizer were about 150 feet forward of the point of impact and about 30 degrees to the left. ”

“ To the pilot the aircraft responds the same, whether or not it was required to meet any stability criteria for the condition in which he finds himself. What would be of primary interest to the pilot and is of primary interest in this report is the fact that at lower speeds (220 knots) the airplane can under certain mistrim conditions exhibit low to neutral stick force per g and stick force versus elevator deflection, and at the higher climb speeds (310 knots) it can have very low speed-stability. ”

“ The Rheims Aviation Meeting, at which the Gordon-Bennett race was flown, also saw the first appearance of the Morane 'Parasol' monoplane. The Morane monoplane had been for some time an interesting machine as being the only type which had no fixed surface in rear to give automatic stability, the movable elevator being balanced through being hinged about one-third of the way back from the front edge. This made the machine difficult to fly except in the hands of experts, but it was very quick and handy on the controls and therefore useful for racing purposes. ”

“ The nosedown pitching moment encountered in high speed flight is offset in the DC-8 by the Pitch Trim Compensator (PTC) system which applies noseup control through the elevator system. Operation of the PTC is also required in the low altitude, high speed regime below mach effect to improve stick force characteristics as speed increases. This system consists of an electrical computer, an electrical actuator, spring loaded linkages, and a mechanical indicator. ”

“ It is nothing more, really, than overcontrolling. You don't see the airplane respond immediately so you have the tendency to put a little more elevator in, and by this time the airplane has started to respond and you suddenly find the response is more than you wanted. So the tendency is to reverse the process.... I can see this situation can be quite critical in turbulence or possibly under IFR conditions plus turbulence where, let's say, you do have some large gusts which change your attitude appreciably if the pilot attempts to... ”

“ One of these was that it eliminated all danger of a nose dive when the plane got into what is known as a “stall”—when the speed became too slow. The other reason was that the elevator in front, set at a positive angle with the pressure on its under side, not only produced inherent stability, but also carried part of the load, and so relieved the wings to that extent. (An elevator in the rear, set at a negative angle to provide inherent stability, carries a pressure on its upper side, which adds just that much to the load the wings must carry.) ”

“ The front edge of the elevator should be set about 3/8 inch higher than the back, and the model be tried first as a glider, with the rubber and propellers in position. If it glides satisfactorily, wind up the motor, say 500 turns, and launch by hand. When a good flight has been obtained, and the correct angle of the elevator has been determined, place the model on a strip of linoleum, wind up, and release the propellers. ”

“ At first the Wrights built the elevator in front of the planes so that they could see and study its effect. They soon discovered that the [20] control of the glider was much better with the elevator. This elevator has been incorporated as a standard fin on the tail of the fuselage of every aeroplane and is one of the chief factors in steering up or down. ”

“ It will soon be discovered that the elevator can be used as a brake to prevent pitching forward. The tail elevators on the Farman or Bleriot running gear are very effective owing to the blast of the propeller, even when the main planes are not moving forward at lifting speed. With the Curtiss type of running gear and a front elevator only, it is often possible at 18 to 20 miles per hour to raise the front wheel off the ground for a second or two—facts which indicate that at 25 to 28 miles per hour, the elevator is far more effective. ”

“ A typical control of the immensely popular “joy-stick” type is shown by Fig. 100. This consists of a vertical column pivoted through the medium of a fork-joint to a rocking shaft. The elevator wires are taken round pulleys mounted under the seat, and the aileron wires from a form of bell-crank, flanged and welded to the steel tube. A disadvantage with this system, in addition to the complication of the wires, is that lateral movement also affects the elevator, although the extent of this is of no great moment. ”

“ Upon his judgment of the time of first touching the earth depends the success of safely alighting. He may bank too high, and come down on the tail with disastrous results. If there is plenty of field room it is better to come down at a less angle, or even keep the machine at an even keel, and the elevator can then depress the tail while running over the ground, and thus bring the machine to rest. ”

“ It will not do to tip up the elevator to a large angle to make it rise quickly, because when once off the ground the angle of the elevator is wrong for actual flight and the model will probably turn a somersault and land on its back. I have often seen this happen. If the elevator be set at an increased angle to get it to rise quickly, then what is required is a little mechanical device which sets the elevator at its proper flight angle when it leaves the ground. ”

“ A few seconds later the two great propellers (or rather tractors) began to [3] flash around. With a snap and a roar the battle-plane started slowly forward, gained in speed till we were running along the big field like a racing automobile, then suddenly the people standing around dropped away from us as if on a gigantic express elevator leaving one standing on the upper floor of a skyscraper, and in a moment more the earth had become a strange and placid panorama with which we had no connection or concern. ”

“ Hawker had been proving the extraordinary stability of this machine. He used to take her up to 1,000 feet or so, switch off his engine, and let the machine glide. Then he would pull his elevator slowly back to stall her. With the elevator hard back she would neither tail-slide nor dive nor side-slip. She would simply descend on an even keel like a parachute, but moving gently forward and rolling slowly first on to one wing and then back to the other. Occasionally, in a gust, she would slide to one side, descending sideways at about 45 degrees, which is hardly a side-slip. ”

“ The wind proved to be not strong enough to sustain the weighted machine, and they were compelled to take to gliding. All their early glides were made as near the ground as possible. The machine had no vertical rudder, but they fitted it, in front, with what they called a horizontal rudder, that is, an elevator. By the use of this they could bring it to the ground at once when the wind was tricky and their balance was threatened. The lateral balance they attempted to control by warping the wings, but with no satisfactory results. ”

“ Fore and Aft Control.—After some preliminary trials the Wrights found that the fore and aft balance could be controlled by an elevator or horizontal rudder, supported on outriggers on the front of the airplane, and operated by a lever. If the pilot found the glider pitching too much downward, and tending toward a dive, he would tilt the elevator upward by moving the lever, thus turning the glider back into its proper attitude. ”

“ By the last quarter of the century, a continuous series of improvements in the valving, control systems, and safety features of the steam machine had made possible an elevator able to compete with the subsequently appearing hydraulic systems for freight and low-rise passenger service insofar as smoothness, control, and lifting power were concerned. However, steam machinery began to fail in this competition as the increasing height of buildings rapidly extended the demands of speed and length of rise. ”

“ If the engine is not throttled down, then the aeroplane may be expected to follow the course D, which results in a longer nose dive than in the case of the course C.
A steady, gentle movement of the elevator is necessary. A jerky movement may change the direction of motion so suddenly as to produce dangerous air stresses upon the surfaces, in which case there is a possibility of collapse. ”

“ The mechanical linkage was in a 5 degree left aileron down position. The power unit was separated from the mechanical unit and the broken ends of the cable strands were necked down in the area of separation. The aileron trim indicator cable drum was in the neutral position. The elevator centering spring assembly was in the center position and could be moved to contact both stops. While the elevator control linkage was damaged, there was no evidence of pre-impact distress or failure. The elevator feel computer and feel control units were functionally tested and met all test requirements. ”

“ Moreover, on the steam roads, at all the great terminals, and wherever there were tunnels to be passed through, the old giant steam engine in time yielded place to the electric motor.
The application of the electric motor to the "vertical railway," or elevator, made possible the steel skyscraper. The elevator, of course, is an old device. It was improved and developed in America by Elisha Graves Otis, an inventor who lived and died before the Civil War and whose sons afterward erected a great business on foundations laid by him. ”

“ The ordinary elevator is very useful in a large business or commercial house, where it saves the legs of people who, if they had to tramp up flight after flight of stairs, would probably not spend so much money as they would be ready to part with if their vertical travel from one floor to another was entirely free of effort. But the ordinary lift is, like a railway, intermittent. We all know what it means to stand at the grille and watch the cage slide downwards on its journey of, perhaps, four floors, when we want to go to a floor higher up. ”

“ The elevator is not exactly a new idea. Its pioneer form may be traced back to the Middle Ages, when heavy weights were lifted by aid of an apparatus worked by hand power. But it was not until well on into the nineteenth century that the steam-power elevator came into service. The first example is said to have been produced by Elisha Graves Otis, who applied steam power to an elevating machine in a little shop at Yonkers, on the banks of the Hudson, New York. ”

“ ELEVATING THE MACHINE.—Simply give the elevator lever the proper angle, sharp and quick and up you go. As the machine responds, and you can feel the cushioning motion, which follows, as it begins to ride the air, you are aware of a sensation as though the machine were about to turn over to one side; you think of the lateral control at once, but in doing so forget that the elevator must be changed, or you will go too high.
You forget about the earth; you are too busy thinking about several things which seem to need your attention. ”

“ Another kind of elevator, known as a lift or hoist, is used in mines and quarries and in serving blast furnaces. This is an elevator with one or two buckets. Essentially a heavy load lifter, it is intended for material of too large a bulk to be handled economically by ordinary elevators, and is employed for lifting in either a vertical or, more often, an inclined direction. ”

“ Such elevators may be constructed to carry either grain or minerals. The advantages are greater capacity than an ordinary elevator of the same dimensions and a more uniform delivery; moreover, smoother running is secured, since the buckets being close together need not plunge intermittently through the contents of the elevator-well. ”

“ Although this type of elevator is probably not so rapid as the vertical lift working in a straight line to the point it is desired to reach, its great advantage is that it does away with the waiting which often causes so much annoyance with ordinary lifts. ”