THE AIRWAY

Sun (Auckland), Volume III, Issue 716, 16 July 1929, Page 16

THE AIRWAY

Solving the First Problems By "THE ROO” THE airplane is as much a part of our life in Auckland now that when a machine passes overhead it certainly does not attract that keen attention from persons below which it did some months ago when the Auckland Aero Club first got under way. And yet, it is surprising how little is known by the average person about airplanes, and how little he understands the fundamental principles of flight.

One hears many amusing pronouncements of why an airplane flies, the most common apparently being the belief that the wind stream from the propeller blows the plane up in the air. Many of the principles of flight were known for a long time before airplanes first took to the air. Some of the first models of airplanes made nearly 100 years ago had many of the characteristics of the planes of today, with the exception of the method of lateral control first used by the Wrights. Lateral control is a means of preventing the plane from slipping off its longitudinal axis. Maxim built, a plane in 1890 that lifted a ton, although it was fastened to the tracks so that it could not get far from the ground. It had no controls to keep it from tipping to one side or the other. One day it tore loose, toppled over and was smashed. So it can be seen that, although when 1 he lifting power of curved surfaces liad been discovered, one of the great problems of flight had been solved, the problem of control still remained. Eiffel’s Discovery A plane lifts from the ground because of the vacuum created on top of the wing when it is forced through the air. Seventy-five per cent, of the lift of an airplane comes from this negative pressure on top of the wing, and the rest from the pressure of air on the under surface of the wing. Very little was known about the exact aerodynamic qualities* of wings until Eiffel made public in 1911 his famous wind tunnel experiments, on which the science of aeronautics is founded. The wings before that time were curved, but very thin, having only the thickness of the ribs which held the fabric in place. But it was found by calculation and experiment

that a wing that was thick on the forward edge and tapered in a gradual curve to a thin edge behind possessed greater lifting qualities and less resistance. The air flowed smoothly over such a surface and did not set up eddies. What Stabiliser Does The wing, however, is unstable, and so in the first Wright machine a horizontal rudder was used in front to correct the tendency to pitch. It was not entirely satisfactory and this surface and the vertical rudder were later placed in the rear, and the supporting structure later became the inclosed fuselage or cabin of the present airplane. As aeronautics progressed a staballsing surface . was added at the tail of the plane, just in front of the horizontal rudder, or elevator, as it is now called, to maintain the plane in horizontal position. The stabiliser automatically counteracts a tendency of the plane to dive or climb in rough air. When the nose of the plane goes above a normal position the angle of attack of the stabiliser to the air stream is increased, producing a greater lift on the tail of the machine, thus tending to bring the nose back to a normal position. A similar effect is obtained if the plane noses downward under sudden air pressure. In front of the vertical rudder for steering to right or left is now placed a vertical fin, which automatically keeps the plane’s nose into the air stream when the tail veers to one side, acting exactly like a windvane on a barn. Perhaps the most important device for securing stability was that for maintaining lateral balance, and this was one of the most valuable improvements by the Wright brothers. It enabled them to fly where others had

failed. It was originally a method of warping the wings, but later balancing planes were placed between the wing tips, and in a short time they became fixed at the rear edge of the wing toward the ends, where they are now known as ailerons. When one of these flaps is depressed it exerts a greater pressure and lifts that side of the wing, and at the same time the aileron on the other side is raised, bringing that side of the wing down. Until some such method of securing balance was evolved it was obvious that the airplane could not well be flown in rough air. Langley and a few others depended upon a dihedral angle of the wings to obtain balance, that is, the wings were tipped up on each side of the body at a slight angle. This is still used and gives some degree of automatic stability, as it is obvious that when a tipped-up wing drops and nears the. horizontal position it will lift more than the sharply tilted wing on the other side and so tend to pull up the wing. But this in itself, although very valuable, is not enough for the rough conditions of actual flight. These paragraphs may serve to explain the fundamental principles of the airplane. Getting Off the Ground The remaining factor in flight is the propeller, which, driven by the engine, pulls the plane forward through the air. It is an odd fact that the tips of the propellers do most of the work. So it can be seen now that when the motor of the airplane is opened and the propeller begins to revolve rapidly, the plane is pulled forward. The tail is lifted from the ground as the plane gathers speed, and when the speed reaches a point at which the suction on the upper side of the wing plus the pressure on the bottom overcomes the weight of the plane, it begins to rise. The careful pilot, however, does not then point his plane’s nose toward the sky, but levels off and gathers flying speed before manoeuvring very much. With certain types of planes with powerful motors, of course, a pilot can climb very rapidly with safety and turn almost as soon as he is off the ground, but an attempt by a beginner to do this in an ordinary plane eventually ends in the hospital. Once in the air, the plane is easily controlled because of the natural stability of the modern machine. It has achieved in the hands of engineers a stability such that many planes will actually fly themselves indefinitely, even in bad weather. What a great advance this is over the first few crude planes! The planes of today are so safe that in competent hands a -well-built and well-designed ship is safe. Their inherent stability in some respects is actually greater than that of the birds, although an entirely different method of flight has been attained.