SCIENCE AIDS THE AIRMAN
Playing around with man-made typhoons, measuring sound that can’t be heard, testing flying boats that will never fly—of such are the duties of the men in the National Research Laboratories who are making the air safe for the aeronaut
IN THOSE dark years when the Old World was rent asunder by conflict, the winged men from Canada soared high overhead, establishing a record which was unsurpassed for determined daring and cool efficiency. Since then, they have established another record, equally inspiring. Both stories have been narrated and eagerly read because they are stories of accomplishment against great odds.
In the division of physics at the National Research Laboratories. Ottawa, special attention is being given to the problems peculiar to Canadian aviation. Some, at least, of the odds are to be removed. The urgency of their immediate removal is not generally recognized.
How would you, Mr. Citizen, care to take a battered old war bus, patch it up. brace it with bits of wire, and venture over the wilds of Canada's unconquered waste lands? Some of our pioneers of the air have done that and more.
How would you care to blaze trails for industry and settlement over those same uncharted, unmapped areas, where a forced landing means disaster, even though you have an up-to-date aircraft but not one that is designed to meet the special hazards you would encounter? For many of our airmen that is part of every day’s throw of the dice.
Even where an effort has been made to meet those special hazards, designers and manufacturers of aircraft have been handicapped by the lack of adequate testing facilities. You, as an ordinary citizen, may not contemplate an air voyage over unmapped lands. Your ambition may rise no higher than an air passage between Toronto and Montreal or Winnipeg and Calgary, and may be satisfied with a weekend “bus ride’’ just to say you have been up. Still, you are directly concerned with the aeronautic research work at Ottawa, for even on very short jaunts you encounter certain risks, some of them peculiar to Canada. And though you may not contemplate the least venturesome of these things and are perfectly content to remain on terra firma, you have an interest in what is being done at Ottawa.
AERONAUTICS has become an ■1 integral part of our national life. Over a quarter million of our fellow citizens have taken to the air in the last five years. To be exact, the number making flights increased from 9,090 in 1924 to 268,894 in 1929; the total number of flights increased from 3,776 to 144,143. In 1929, Canadians covered six-and-a-quarter million air miles in 445 aircraft. As compared with the record of 1924, the miles flown were multiplied by twenty, and the number of aircraft by over one hundred. The freight carried by aircraft increased fifty times, from 77,385 pounds to 3,903,908 pounds.
Airmen in the Making
This passenger and freight trans-
portation was handled by eighty-one firms operating aircraft in 1929. Five years earlier there were only eight. But more significant still is the fact that in one year, 1929, every item was doubled and a number were trebled.
All this is the forerunner of a stupendous transportation development, greater perhaps than any which has come to this young nation, even including our transcontinental railway systems. Our railway executives are aware of its importance, for they are getting into the air transport business with both feet.
But before we can develop fully as an air nation, we must have machines suited to our own special requirements and conditions. That the work is extremely urgent is shown by the enquiries continually pouring in to the National Research Council, both personally and by letter, regarding problems for which airplane manufacturers in Canada seek a solution.
Although aeronautical research embraces most branches of engineering and many other sciences, its three principal divisions are aerodynamics, hydrodynamics and power plant. At this writing a wind tunnel and a test tank are nearing completion at Ottawa, with provisions for trying out aircraft engines and other general airplane equipment.
Wind Tunnel Tests
TESTS in aerodynamics by means of a wind tunnel date as far back as 1893. when aeronautics was an infant science. Canada had its first wind tunnel, a small one,
five years later, built by W. R. Turnbull, of Rothesay, N.B., by which time there were others in England and the United States. Europe followed suit. But it was not until 1917 that Canada had one of any size, a four-foot tunnel at the University of Toronto, and until the National Research Council built the one at Ottawa this was the only wir d tunnel in the Dominion.
It is hardly necessary to wade through the intricacies of wind velocity, similitude of flow, geometric similarity of models, linear dimension and kinematic viscosity in order to deduce that the larger the tunnel the more accurate the tests which may be made. Having in mind the importance of aircraft development to Canada and the peculiar and difficult conditions under which our airmen are required to fly, the installation of one of the largest wind tunnels in the world is by no means over-ambitious.
To visualize the wind tunnel at Ottawa, take a length of pipe and at either end place a funnel. In one funnel, if you are to have wind, you will need a fan or propeller to suck the wind into the funnel at the opposite end, through the inside and out past your propeller. Your aircraft model, if you get that far, will be suspended for observation in the Continued on page 24
Continued from page 16
pipe or jet. The length of the jet at Ottawa is twelve feet and its diameter nine feet. The funnel through which the air is sucked graduates from a seventeen-foot square to a nine-foot circle. A wind speed of 125 miles per hour is developed by a fan with thirteenfoot blades driven by a 600 horsepower motor in which are embodied a number of new features.
But the construction of a wind tunnel, so 1 discovered at Ottawa, is not so simple a matter as that brief description might seem to indicate. If you have been in a cyclone or a heavy windstorm you will know that “unconfined” wind can play some queer and dangerous pranks. It has its vagaries in a wind tunnel also. In order to observe those before constructing the tunnel proper, a model tunnel was built at Ottawa. Some very remarkable things regarding “burbling," turbulence, velocity, distribution and other peculiarities of wind were detected.
An ordinary fortyto sixty-mile-an-hour wind rages, tears, rips, and, most dangerous of all, forms vacuum pockets. If an ordinary gale will play such dangerous pranks in the open when unconfined, can you imagine what tricks a 125-mile-an-hour wind, about the highest typhoon velocity yet measured, would play inside a building unless controlled? Can you imagine what it would do when asked to turn comers?
In the tunnel at Ottawa the wind has to turn eight right-angle comers. The comers are necessary in order to maintain control, for. after having been sucked through the tunnel, the wind is returned to the entry funnel by means of two passages, one on either side of the tunnel proper. To keep the wind behaving properly it is expanded in a cone, disciplined by banks of vanes which look not unlike immense Venetian blinds, and passed through sieves—the nomenclature is my own—that remind one of a honeycomb automobile radiator.
The aim of the engineer when constructing a wind tunnel is to produce conditions as nearly ideal as possible. Once he attains ideal conditions for flight, it is relatively easy by means of the controls to render them otherwise, to turn the wind into a cyclone or merely an ordinary storm.
With his windstorm under control, the engineer may then observe what is happening to the model suspended in the jet. A notable feature of the Ottawa wind tunnel is that the recording instruments for this purpose are installed on an observation and control platform in experimental room over the tunnel, so that direct wind interference either with the instruments or the operator is reduced to a minimum. As the purpose in this writing is not scientific I shall attempt no further details. If desired, those may be obtained from Ottawa.
A Four-Hundred-Foot Tank
' I 'HERE is perhaps a greater percentage 4 of aircraft of the flying-boat type in Canada than in any other country. In most provinces there are large water areas. Flying boats and aircraft equipped with floats are becoming increasingly popular. Approximately twenty-five per cent of the air miles flown are in seaplanes.
No naval architect would consider building an important vessel without first making model trials in a test tank, and as long as they were without adequate experimental and testing facilities the manufacturers of marine aircraft in Canada were severely handicapped.
The ship test tank, which has been used to test models of flying-boat hulls and aircraft floats, offers an unsatisfactory substitute. A marine-craft hull and an aircraft float do not cleave or skim the water in the same attitude. Still more important is the matter of speed. Racing craft strike the water in a smother of spray at 125 miles an hour and over; ordinary “freighters” at between fifty and seventy-five miles an
To some extent, speed may be reduced for testing purposes by reducing the size of the model. But with a very small model, the forces to be measured are so reduced that exact measurement is difficult. Dust on the surface of the water has serious enough effects to make such experiments of doubtful value. The points to be watched in building a test tank are almost as numerous as these which crop up in the erection of an air tunnel.
Although the necessity for larger models allowing increased speed had been explained, I was impressed with the size of the Ottawa tank. After all, 400 feet of tank is a lot. Even though it is only nine feet wide and six feet deep, that means 19,000 cubic feet of water; and the question might be asked, if an air tunnel can be housed in a building 142 feet long, why is a building 410 feet in length necessary for a testing tank?
In the case of an air tunnel the wind passes a “stationary” model, but in a test tank the model passes over and through the water. It has to gather speed, maintain it for observation, and slow down, so 100 feet is used for acceleration, 200 feet for the speed run, and 100 ieet for deceleration. With this arrangement models up to four feet in length may be tested and a speed of twelve knots attained. The motive power is supplied by a seventy-five horsepower shunt motor driving a structural steel carriage mounted on four steel wheels which run on steel rails laid at either side of the tank at water level. To this is attached a dynamometer which tows the model.
An Accommodating Instrument
A GREAT deal oí ingenuity has been used in order th3t speed and other controls shall be accurate, such as the mounting of the carriage, braking devices, guide rollers, etc. But to me it seemed that the dynamometer, designed at the laboratories and which I prefer to think of as the towing and recording balance, is the most interesting of all the various instruments and machinery used on the test tank. It has so much to do and so little time in which to do it—just seven and a half seconds with the model travelling at twelve
The four things which scientists and designers of flying-boat hulls or floats for airplanes particularly wish to leam in that flash of time are:
Resistance to the water at different speeds, attitudes and drafts.
Attitude and behavior under different conditions.
Cleanness and wave formation; and influence of air control surfaces on behavior.
Wave formation and cleanness are taken care of by an observer armed with a camera who travels with the carriage, and the dynamometer has to record almost everything else that is happening to the bobbing, plunging model.
And what an accommodating, sensitive instrument is the dynamometer! It has a hand on the reins which the finest horseman might envy. The model must not be restrained; it must be allowed to assume its natural position in the water. Then the engineer demands of this child of his brain that it allow him to apply forces to the model representing the dead weight of the machine and the lift of the wings. Not satisfied with that, he needs must adjust the centre of gravity and make the model wiggle as its fullgrown brother does when subjected to propeller thrusts and controls. And when the run is finished, he asks the dynamometer how far the model has travelled and the time occupied. The dynamometer tells him. The whole record is on a
I left that test-tank building with the conviction that Canadian designers of marine aircraft are fortunate in having such accurate information at their disposal.
From the tank room I was piloted to an underground cavem. “This,” explained J. H. Parkin, who is in charge of aeronautical research at Ottawa, “was an old boiler room. It makes an admirable testing department for airplane engines.”
VW'ITH the expansion of aircraft transW portation in Canada there is a growing domestic demand for engines of the air type. Three firms are engaged in their manufacture, and already Canadian assembled engines are finding a market abroad. But there has been no equipment in Canada for adequately carrying out tests, although under Air Regulations 1920 the Dominion Government is required to test engines for export. Very properly, this has become a function of the National Research Council.
As in other tests in aerodynamics, air conditions are a chief consideration. For instance, air-cooled engines for aircraft are tested under conditions duplicating an airship travelling at up to 130 miles an hour. A large centrifugal fan, driven by a 250 horsepower motor, discharges a shrieking wind through a cylindrical duct and adjustable nozzle past the cylinders of the engine being tested.
A unique part of the tests is the application to the crankshaft of thrusts corresponding to propeller thrusts. These run all the way up to 6,000 pounds. The enginetesting plant at Ottawa is very complete. It will handle engines of any type, air or water cooled, tractor or pusher, right or left rotation, with power up to 1,000 horsepower at speeds up to 2,500 revolutions per minute, being the only equipment of its size and type in Canada.
Airplane Landings by Sound?
TN THIS article the point has been made
that Canada has its own special hazards for winged men. Landing hazard is by no means peculiar to Canada, but in this country, with its vast and rough terrain, the risks are multiplied in darkness, fogs and hazy weather.
Altitude instruments, except perhaps some still in the experimental stage, do not record height under 500 feet from the ground. Any closer than that, just when an airman landing in the dark needs their guidance most, they go dead, and he is left with a terrible problem, out of which sheer nerve, luck or instinct may or may not extricate him.
It is possible a solution may be found in a special study of sound vibrations which Dr. R. W. Boyle is making at Ottawa. Already quite new phenomena have been disclosed. Let me explain the possibilities from a simple, everyday viewpoint.
When we step forth from our holiday camp on one of those rare still mornings when Nature is hushed and even the air has ceased whispering, you and I say it is a “profound silence.” But we are wrong. Sound is still there, it is ever present. There is sound in the nearest approach to a vacuum that science knows, for sound is produced by the collision of molecules, and science will teach us that in ordinary air each molecule collides with another about 3,000 times each second.
But as we stand there considering all this we hear the first murmur of a distant airplane. It is borne to us by waves or zigzags of colliding molecules, which by the time they reach us have lost momentum, thus the gentle murmur. Presently the airplane comes closer; the molecule collisions in our vicinity are accelerated; we hear them hum. Then the birdman swoops, roars past in thunderous noise. We are almost deafened, so violent are the billions upon billions of molecule collisions. There is sound in the jug of water on a table, and the ginger ale bottle also, though the mole-
cules move so slowly the collisions are not sufficiently violent for us to hear. Pour the water, shake the ginger ale bottle and we hear a pleasant gurgle and fizz because we agitate the molecules, send them clashing against each other.
Now consider that at Ottawa there are instruments which record “silent” sound, record the amount of agitation in a body of molecules, and it is not so difficult to understand what the scientist is driving at when he says that the study of sound reflections and other phenomena—sound rebounds from a surface such as the earth—may provide a solution for airplane landings.
THE amateur photographer who imagines he has more than his share of failures should go picture shooting along with the winged argonauts who sail the skies. At the research laboratories there are numbers of aerial photographs which look like pictures of the star-spangled heavens. Others look as though the airman had flown through an electrical storm and photographed lightning flashes. Those “pictures" should be landscapes, and the exposures were made on clear, sunny days. Light refractions? A faulty camera? Not at all. There had been electrical “storms,” but those storms were inside the camera itself. Their elimination is urgent, for the problem of faulty aerial photographs is one which concerns closely our national defense.
Research work at Ottawa shows that the “stars” and “lightning flashes” are caused by static electric sparks which, under certain atmospheric conditions, generate as the film passes between the glass and felt at the back of the camera. Having discovered the “storm,” the next step was to find its origin, determine the particular atmospheric conditions producing it.
In this research, as in others, the scientist becomes an inventor. I was shown a set of instruments designed and made at Ottawa. These instruments were taken on flights and they record the conditions, such as the amount of ionization and humidity of the atmosphere under which static may occur. Back comes the scientist to his laboratory. There he reproduces the conditions causing the “camera storms,” and gets busy on the serious problems of their elimination.
Even the fuel which airmen use is watched at Ottawa. Should his engine stall he has a long way to fall. And if you are inclined to dismiss with scorn those advertisements which claim less knock for certain gasolines, you may visit Ottawa and have your scepticism dispelled. Some motor fuels do cause less motor knock than others. There is a machine at Ottawa which makes that clear, both by sound and record.
In commencing this article I quoted figures showing Canada’s remarkable development as an air nation, but figures give no idea as to the completeness with which the aircraft is entering our national life. In protecting our timber wealth by the detection and suppression of bush fires, in timber cruising and forest sketching, for prospecting, geological exploration and development work in the great North country, the aircraft has no equal. Against the pests and blights which Nature sends to attack our crops and forests, war is waged by the airplane. In commerce it serves the nation by clipping days off the transCanada mail service and by carrying business executives and freight. Our customs and fisheries officials soar high overhead on the lookout for smugglers and poachers. And when there is an. urgent call for medical aid from an isolated community, it is the aircraft that goes to the rescue. In the words of Mr. Parkin, “Aircraft are being put to a variety of useful and practical tasks known in no other country.”
As a nation, then, we should be ready to back Mr. Parkin and his staff in their task of assisting the nation’s air development.