II
The civil flying-machine, when it is examined in the light of contemporary aeronautical research-work, seems rich in possibilities.
Apart from electrical repulsion, there are five different ways of flying, of which only two are at present in general use, lighter-than-air flight and fixed-wing heavier-than-air flight. I think that a third method is about to be widely adopted, and that this third method will, in time, profoundly influence the whole future of aeronautics.
A comparison between the present system of artificial flight and natural flight will suggest what that third method is.
Let us go to Croydon, the airport of London, and examine a typical three-engined passenger-carrying aeroplane.
The three engines are running, for the machine is about to take off. The coffin-shaped thing whose sides flap in the wind from the airscrews is the fuselage. The machine shows signs of malnutrition, for its bones are prominent in the form of wires and struts. As the engines are run up, the tail shakes and sneezes and coughs until it seems that the fuselage will be ruptured. Now the machine taxis over the aerodrome, its engines open up with a roar, it labours over the ground, and then, looking a little fatigued, it rises into the air.
It passes overhead making a noise like a thunderstorm, shivering and quaking, barging its way along with a clumsy ineffectualness which gives it the appearance of flying through treacle.
When it is out of sight, go to Waterloo Bridge and watch the gulls.
A gull is a hopelessly uncommercial flying machine. It does not pay, it has no ground organization, it is not fitted with wireless, no control-tower informs it when it may land, no books are kept of its mileage or hours flown, no managers, assistant-managers, clerks, secretaries, typists, accountants, ministers, directors, officials, or meteorologists concern themselves in its safety. No offices, search-lights, flood-lights, neon-lights, leader-cables, or directional wireless stations are set aside for its control and supervision. No treatises are written about its future. A gull is not “a commercial proposition”. It is, however, a good machine for flying.
Neither the superficial nor the fundamental defects of the passenger-carrying aeroplane are present in the gull. The gull is a coherent, unified structure without exposed bracing-wires, struts, or engines. It gets off quickly, flies at a great pace (for its power-loading), is fairly silent and very manoeuvrable, can defeat fog, rain, hail, snow, and gale, and can alight anywhere.
As a flying-machine it owes its basic superiority over the aeroplane to a single, ingenious trick: a trick which looks easy, but which, for many years, the scientist found it impossible to reproduce in practical mechanics.
When flying was first thought about this trick engaged much attention. The mechanical difficulties in reproducing it, however, refused to be conquered, and about 1680, Borelli, having this trick in mind, wrote: “The Icarian invention is entirely mythical because impossible”, a view which, according to Mr J. E. Hodgson’s History of Aeronautics, was supported by Leibnitz. Afterwards and until just recently the trick has been almost entirely neglected. I think it probable that it will regain its old importance, and that it will become the pivot upon which the whole future of the heavier-than-air land-going flying-machine will turn.
What is this trick which for centuries baffled the mechanician, yet which the gull finds so simple? What is the one fundamental difference between the means employed by the gull for flying and the means employed by the aeroplane?—It is the difference between the fixed wing and the moving wing.
The gull has the trick of being able to move its wings relative to its body. The gull is a moving-wing flying-machine. The conventional aeroplane is a fixed-wing-flying-machine.
Almost every important advantage which the gull (and any other bird) has over the type of aeroplane which has so far been most popular may be traced to the gull’s ability to move its wings. For that reason alone it can get off without a long run, defeat fog and gale, and alight anywhere.
Since the time of the artificial “flying pigeon” of Archytas in the 5th. cent. b.c. the manner of whose flight seems obscure, attempts have been made to build machines which imitate the gull by flapping their wings. Several people, including Bladud, the legendary flying King of Britain, found out in an unpleasant manner that the muscles were not strong enough to actuate man-lifting wings. And in the construction of engine-driven ornithopters the mechanical difficulties invariably proved insuperable. The natural flapping wing has never been exactly imitated by mechanical means in a flying-machine, nor have the leg and foot been exactly imitated by mechanical means in a motor-car.
The motor-mechanician, in using the wheel in place of the leg and foot, imitated the principle employed by nature for land-locomotion but not the means. Will the aeroplane-mechanician imitate the principle employed by nature for flight but not the means?
The aeroplane-mechanician has already accomplished this feat in a rudimentary form in the Cierva Autogiro, which is commonly (and accurately) called the windmill aircraft.
The helicopter has never achieved much success and, for the present purpose, it may be classed with the ornithopter as obsolete. The autogiro, therefore, is the first practical moving-wing aircraft. It accomplishes that which generation after generation of mechanicians found it impossible to accomplish. It has seized on the bird-principle of flight and translated it into practical mechanics.