Learning to Use Our Wings (Dec, 1928)
Learning to Use Our Wings
This Department Will Keep Our Readers Informed of the Latest Facts About Airplanes and Airships
CONDUCTED BY ALEXANDER KLEMIN
In charge, Daniel Guggenheim School of Aeronautics, New York City Aviation Safety Congress.
THE Daniel Guggenheim Fund for the Protection of Aeronautics has, since its inception, made safety in aviation the object of its main efforts. Recently the Fund organized a Congress on Safety in Aviation, arranged in co-operation with the National Safety Council, and held at the Hotel Pennsylvania in New York City. The program of the Congress is a proof of the fact that safety in flying is not a matter of one invention or method, but lies in the development of many divers aids. Thus the sessions of the Congress dealt with Structures and Materials in Relation to Aviation Safety; Airports and Airways; Aids to Navigation; Medical Aspects; Aerodynamics; Power Plants; Operation of Aircraft in Air Transport; Weather Service; The Public and Flying; and last but not least, Fire Prevention.
The sessions were attended largely by technical men, but the lay public was also well represented. In several of the sessions, members of the public would rise to ask how safe aviation really is.
Perhaps the best answer made to this question was that of Senator Hiram Bingham, the new president of the National Aeronautic Association. The Senator, who occupied an important position with the Army Air Service during the World War, and has since been a potent factor in aeronautical legislation, said that we could have any kind of safety that we wanted, just as we could have any kind of safety in going by water around Cape Cod. In a row boat, there would be considerable danger. A fishing sloop would be far from safe. An ocean liner would be perfectly safe. So in aviation, we could range from great hazard in the flying of unlicensed craft, manned by inexperienced personnel, to the safety approaching that of a railroad on the regular passenger lines operated by the great air transport companies.
The Congress achieved a great success in bringing the exact elements of aviation safety before the public and in placing squarely before the technicians the present status and the future needs of safe flying.
Experiments in Fog Flying.
FOG flying attracted due consideration at the Aviation Safety Congress. The Fund has made the conquest of fog one of its major projects. Lieutenant James H. Doolittle, of the Army Air Corps, one of the most experienced test and research pilots in the country, and winner of the Schneider Seaplane Cup in 1925, has been secured by the Fund for a series of systematic experiments in fog flying. A special plane with dual control will be placed at his disposal as well as every possible instrument or device likely to be of service in blind flying. The action of such devices will be tried out in fair weather, with one pilot closed in his cockpit. The “blind” pilot will attempt first to fly by instruments alone, then to land “blind” by the aid of special height indicators, based on electrical and acoustic principles. The experiments will then be repeated in an actual fog, under flying conditions. This work will certainly test even Doolittle’s iron nerves.
OUR photograph shows E. T, Allen, test pilot for the Boeing Company of Seattle, Washington, clad in leather and fur, with face mask, goggles, and oxygen tube glued to his lips, just as he would appear at an altitude of 30,000. feet or so above the ground.
In military or naval aviation, altitude gives the flier a great advantage. At very great heights, he is safe from observation and from anti-aircraft guns. Swooping down from altitude on an enemy pilot flying in a lower zone is a formidable maneuver.
The single seater pursuit built by the Boeing Company, not only attains a height of 30,000 feet, but it can fly at 180 miles per hour with full military equipment. The new pursuit ship has excellent lines and is very “clean.” After tests it is to be turned over to the Navy Department.
IT is interesting to read the classification of aviation hazards presented by Mr. Ted Wright, Chief Engineer of the Curtiss Company. Twenty percent of all accidents are caused by forced landings due to engine failure. This classification includes engine failures caused by breakage or non-functioning of the engine proper, or of the auxiliary systems such as fuel, ignition, cooling, or carburation. Approximately the same percentage of failures occurs in each of the above sub-items.
Mr. Wright advocated as remedies the use of multi-engined airplanes, capable of flying with one or more power units disabled; provision of a more dependable power plant; and provision of more landing fields throughout the country.
Errors of judgment by the pilot are responsible for 53 percent of accidents. We believe that this estimate is far too high. It is sometimes very difficult to determine the causes of an accident. There is a temptation for investigating boards to blame the pilot, particularly when the pilot is dead and not able to defend his reputation. The accident may really have been due to instability, insufficient control, too high a landing speed or other deficiency in design. It may be argued that the pilot should realize these deficiencies and fly his ship so as to take account of them. That is asking perhaps too much from even skilled flyers. The remedy lies partly in better training, partly in better design of our airplanes.
Weather conditions were estimated by Mr. Wright as being responsible for 19 percent of all accidents. These include chiefly accidents due to severe storms, lightning, fog, ice formation, et cetera. More metereological stations and better weather service, particularly by the use of radio communication, will do much to remove these hazards.
Finally, 8 percent of accidents are due to structural failure. The structural design of the airplane is very advanced, which accounts for the low percentage. The worst of structural failures is that they are apt to involve fatal results, and also that they cause the greatest blow to morale. Accidents due to weather are taken somewhat for granted in all human activities. There is, on the other hand, something particularly disquieting in the report of a fatal accident due to the loosening of a wing in the air. The remedy here is in still more careful structural analysis of the airplane, in rigid inspection during manufacture, and in better maintenance.
While Mr. Wright’s paper dealt especially with structural analysis and design, it really gave a bird’s eye view of the entire problem of aircraft safety, and was all the more valuable on that account.
World’s Smallest Airship.
THE Meadowcraft Balloon and Airship Company have recently built what is the smallest airship of to-day. It is 65 feet long and 30 feet in diameter, and has a gas capacity of only 22,000 cubic feet. With a 22 horsepower Henderson motorcycle engine it attained a speed of 20 miles per hour. It has a weight empty of 800 pounds and can carry 500 pounds of useful load.
The airship is non-rigid of course, and consists of two lobes. The front lobe is the main lifting unit; the rear lobe is jointed and serves to give both directional and horizontal control. This is an entirely novel idea, and the control obtained is very powerful; according to Air Travel News, the ship can be turned completely around in a space no wider than a city street, or held almost stationary in the air.
The airship has always been regarded as a naval or military weapon and as a medium of long distance transportation. It has never been considered as of possible usefulness in aerial service, while the airplane has been put to work in dozens of industrial applications. The Meadowcraft airship with its small size and extreme maneuver- ability has possibilities for such work as aerial advertising, aerial photography and insect control. With its ability to hover over one spot, it has, for certain phases of such work, an obvious superiority over the airplane. Its employment for such purposes may mark a new phase of airship utility.
A New Type of Silencer.
THE new Loening cabin amphibian, Wasp engine powered, is a remarkable plane, whose many excellent features we hope to describe in detail at a later date. The muffler is particularly interesting. It consists of three concentric cylinders, the inner two perforated. The exhaust gases enter on one side, and therefore whirl as they expand. The innermost cylinder consists of two truncated cones, producing a Venturi effect.
The gases pass from the chamber between the outer two cylinders to the one between the inner two cylinders and then inside the inner cylinder. In the process the flame and noise of the exhaust is reduced. At the same time the Venturi effect gives suction instead of the back pressure which is customary with mufflers. As a result the Wasp engine actually turns up more revolutions with the muffler than without it. • Runways for Airports.
THERE is now a special publication devoted to the construction and operation of airports and appropriately termed Airports. A most interesting series of articles starting in a recent number is that dealing with runways.
Where the soil is such that dry weather does not make it dusty, if there is sufficient drainage to keep it from getting muddy or wet, and until the traffic gets heavy, the natural soil scraped clear of vegetation serves all purposes. But where these desirable conditions are not available and air traffic is heavy, artificial runways become necessary. Asphalt, brick and concrete each have their advocates. For each of these, firmness and uniformity, smoothness, good visibility, and durability are claimed. Experience alone will decide their relative merits. In the meantime, civil and highway engineers and manufacturers of these three materials will have many arguments about their respective merits.
A Rubber-Hydraulic Landing Gear THE design of an airplane landing gear is quite a difficult matter. An axle between the two landing wheels may get caught by an obstacle on rough ground and tend to nose the airplane over. Therefore, the transverse axle has disappeared in most modern designs. It has evolved to a short, stub-like affair to the end of which are connected three struts, as shown in our photograph of the Stearman landing gear.
The landing loads may come on the chassis from any direction. There is always a vertical load as the wings lose lift and the plane settles on the ground. There may be a side load, if the landing is made with one wheel lower than the other, or if there is a side wind. There may be a force in a backward direction if the plane meets an obstacle of any kind on the ground. The struts, therefore, are so arranged that they can take loads in any direction.
In the Stearman landing gear, the two inclined struts are hinged at the center of the fuselage, and take up the side and backward loads. The outer strut is a shock absorbing member which compresses through several inches so as to lessen the shock. A study of the photograph will show that the wheels will swing up and out as the compression strut is shortened. The design of these compression struts has passed through many stages of evolution, and they are now generally a combination of a hydraulic system and a spring or rubber system.
For a given weight, rubber is the material which will take up the greatest energy of shock. It is so elastic that it has far better shock absorbing properties than the best of steel springs. Up to two or three years ago, rubber was used as the sole shock absorbing element. The rubber, in the form of cord or disks, took up the initial shock admirably. Unfortunately, the energy stored in the rubber is only partially destroyed during its absorption; therefore after a severe landing the airplane tends to rebound. Hydraulic shock absorption does away with this rebounding tendency.
In the Stearman “rubber-draulic” gear, the hydraulic unit consists of a piston with a small orifice operating in a cylinder full of oil. As the strut compresses and the piston travels upwards in the cylinder, the oil is forced through the narrow orifice, energy is dissipated thereby, and converted into heat without the possibility of reconversion into energy of rebound.
After the landing shock has been absorbed by the hydraulic system, taxiing loads are taken up by rubber shock absorber cord in tension. This cord is a continuous piece wound around a series of pins welded to the frame of the gear, and extended as one part of the compression strut. The part fixed to the wheel moves upward relatively to the part which is fixed to the rest of the airplane. The greater the travel in compression, the less the load actually transmitted to the fuselage of the airplane, and in this particular gear the total travel is eight inches, of which six inches is taken by the hydraulic portion. An average grade of lubricating oil is used in the cylinder, but in winter a zero oil is employed.
Aerology at the Airport.
NOTHING is more important for air transport operation than efficient weather service for the pilot. We are glad to see therefore how seriously the matter is treated at the Brook Park Airport, of Cleveland, Ohio. One of our photographs shows L. E. Pierce, in charge of the aerological office at this airport, on top of one of the hangars, about to launch a meteorological balloon. This is similar in appearance to a toy balloon, but larger, inflated with hydrogen, and far more buoyant. Such a balloon when properly inflated will rise at a predetermined rate, which is 550 feet a minute as a rule.
With a telescope and sextant, Pierce observes the course of the balloon in flight and by plotting its course in all three dimensions, can determine both the velocity and direction of the wind at various altitudes. Temperature, barometric pressure, condition of weather, ceiling, and visibility are other meteorological data recorded at frequent intervals at this and other stations. The data from all stations along a given route are recorded on a large board in the hangar and serve to give a pilot invaluable information before his flight.
The Goodyear “Puritan”.
IT is possible that small airships will really be the first air-borne craft to land consistently and in safety on the roofs of our cities, a feat recently accomplished by the Goodyear Pilgrim. A sister ship of the Pilgrim, the Goodyear Puritan, has a gas capacity of 86,000 cubic feet of helium, and is powered with two Ryan-Siemens five-cylinder radial engines, which can drive the ship at a maximum speed of 55 miles per hour. The engines are mounted on outriggers, so that the cabin is insulated as much as possible from their noise and vibration. The framework of the car and keel are built of duralumin girders, almost exactly like those to be incorporated in the 6,000,000 cubic foot airships now on order. The passenger cabin is built of sheet duralumin over the girder framework, and is shaped very much like a flat iron. The keel is contained inside the envelope, making the cabin an integral part of the bag.
Non-rigid airships used to have their cars suspended by a net work of cables which increased head resistance. This is avoided in semi-rigid airships, and we believe that the Puritan really belongs to the class of semi-rigid airships. One of the innovations in design is a single landing wheel projecting below the center of the cabin. This wheel, mounted on a duralumin frame, acts as a support for the ship when it is on the ground, and permits easy rolling from one place to another. Because the airship is lighter-than-air, the wheel receives very little load on the ground.
It is quite possible that airships of this type may have a future as a new kind of air-yachts. The record of the Puritan from August 6 of this year to September 15, was a series of flights on 33 days out of 45, covering 5635 miles and carrying 450 passengers, which is highly creditable. An objection to airships has been so far in the difficulties of handling. An interesting and new development in this regard is the use of a motor car specially equipped for airship service. A feature of this motorized machine shop is a portable mooring mast to assist in landing.
Elements of Aviation.
COLONEL V. E. CLARK is a rare combination of pilot, airplane designer and aerodynamicist, and his recently published book “Elements of Aviation” (Roland Press, New York City) gives proof of his breadth of view. The author knows aerodynamics, but presents the subject not as an abstract science but as a real introduction to the study of airplane design. The treatment is remarkably clear, and mathematical expressions are reduced to a minimum.
The author modestly disclaims original thought in his treatise, but his methods of presentation are both original and striking. Even an experienced designer will find much to interest him in this elementary book.
Throughout the book we find apt definitions and illustrations. We shall look forward to the companion volume on design which is to follow.
THE industrial applications of the airplane constantly are being increased. While sky writing has apparently suffered a temporary eclipse, aerial advertising at night is to be undertaken vigorously by Aerial Advertising, Inc., a New York City company.
A huge biplane, built by the Keystone Aircraft Corporation, with the lower wing of 15 feet greater span than the upper one, so that its total spread is 90 feet, is being equipped with an illuminated sign, 90 :feet in length and six feet, six inches in width. Small strips of bass wood, measuring two and a half inches in width are mounted on the underside of the lower wing. The illuminated letters of the advertising sign are secured to these strips.
Six wind-driven electric generators mounted on the wing provide the current for the sign. For extra reliability there are two independent lighting circuits. The tests made on Long Island have shown that these signs can easily be read from an altitude of 3000 feet.
Inventions Needed for Safety.
WHILE aviation safety is not solely a matter of invention, depending as much on training of personnel, ground organization, et cetera, still many inventions are needed. We can only list a few typical suggestions.
In the structure of the airplane, there is inevitable vibration due to the engine, which cannot be avoided, particularly when only a few cylinders are employed. Perhaps it may be possible to avoid the transmission of vibration from the engine to the rest of the plane, by the employment of rubber as a shock absorber between the engine mount and the rest of the plane.
Radio, lighting, and weather service as aids to navigation, are progressing rapidly. We have still to see a dependable altimeter which will warn the pilot of dangerous proximity to the ground in case of fog. A field localizer which will guide the pilot to the center of a field still remains to be made practical. The danger of collision will increase as the number of planes aloft increases, and some form of collision signal is needed. Television through the fog has been often suggested.
In the aerodynamic design of the plane, as we have often discussed, there is need of devices which will decrease its landing speed without affecting other desirable characteristics.
In the prevention of fire, the production of a light weight engine on the Diesel or semi-Diesel principle, burning heavy, non-inflammable fuel, will be a great boon.
There are many opportunities for engineers and inventors.
Popularizing the Science of Flight.
THE properties of the wheel, the pulley, the lever are instinctive with us through many generations of use. While the air is all pervading, it is invisible and very much of a mystery. The science of aerodynamics or air flow as applied to the airplane therefore needs popularization, and a number of authors have undertaken to write simple accounts of the theory and construction of the airplane. Such works will do a great deal of good to the cause of aviation.
They are very much harder to write than technical treatises in which mathematical language can be freely used. We have recently received an excellent book of this type, “The ABC of Flight” by W. Laurence Le Page, published by John Wiley and Sons. In simple language with clear diagrams Mr. Le Page explains the fundamental principles of flight, how stability and control are achieved, how an airplane is built, and the elements of flying instruction.