ATTAINMENT of the full potentialities of airships as carriers is dependent upon and will be greatly expedited by the solution of mooring and ground-handling problems. It is felt that the fundamental solutions have been found, and trials of newly designed equipment are virtually at hand. Communities that desire to erect mooring masts and provide servicing facilities are advised to await patiently the further trial of experimental equipment designed by the engineers stationed at the Naval Air Station at Lakehurst, N. J. This equipment is now under construction on contract. Evolution of the mooring mast, a British post-war device, and the present methods of mooring an airship to the mast are described to show the trend of development.
COMPARISON by the author shows that the cost of aeronautic powerplants per horsepower is materially lower than that of ship powerplants, and that airplane reliability compares well with the safety of other modes of travel. Some of the advantages of radial air-cooled aeronautic engines are given, followed by a brief outline of their development, which was necessarily slow because of the novel mechanical problems involved in the connecting-rods, valve mechanism and lubrication. The supercharger drive and the recently developed propeller reduction-gears of the Wasp engine are described, and the paper concludes with an outline of procedure in developing a new model of engine. In the absence of Mr. Mead, the paper was presented by E. A. Rider, who answered the many questions propounded in the discussion. These have to do chiefly with supercharging, cooling problems, engine operation in flying upside down, and the use of a double ignition system.
NOTABLE developments in 1928 that have greatly increased interest in lighter-than-air craft were the transatlantic flight of the Graf Zeppelin as an experiment in commercial transoceanic air-service, the ordering by the United States Navy Department of the construction in this Country of two rigid airships larger than any yet built or under construction, the development and construction of two British airships for long-distance passenger and mail transportation, the starting of erection of the world's largest airship factory and dock at Akron, Ohio, and the construction and operation in this Country of a number of non-rigid airships to be used for commercial purposes. Each of these developments is dealt with in order. General dimensions, major characteristics, and unique features of the Graf Zeppelin, the new Navy airships, and the projected large transoceanic commercial airships are given.
ESSENTIALLY the Autogiro consists of a fuselage that is propelled more or less horizontally through the air by an ordinary engine and propeller combination and wings that possess at least one degree of freedom with respect to the fuselage and turn around a central axis of rotation that is approximately perpendicular to the longitudinal axis of the fuselage, being articulated to a central hub and free to flap within rather wide limits. The present machines also have two small low monoplane fixed wings, that act mainly as supports for the ailerons, a fixed tail, elevator, fin and rudder. Among the advantages claimed for the Autogiro are perfect stability, great flexibility, great adaptability, safety and the possibility of landing and taking off in a restricted area. The author claims that it is superior to the airplane for almost every purpose and is particularly adapted to civil aviation uses such as passenger transport, night mail service and especially for private flight.
WHAT can be done to increase safety, efficiency and comfort in flight of aircraft now in use? In answer, the author describes several devices designed to bring about this result and supplements this with the results of wind-tunnel research. Detailed descriptions of the particular devices mentioned are not included, the object of this paper being to show the great possibilities of their use and the resulting improvement in performance.
SPINS have been responsible for 40 per cent of fatal airplane accidents in the Army in 1927 and 45 per cent of those in the Navy during the last five years. These accidents happen to the most experienced pilots, as no airplane is fool-proof and every representative airplane manufacturer in this Country has had a recent model that has exhibited vicious peculiar spinning qualities. A majority of fatal accidents in the military service abroad result from spins, and it has been unofficially estimated that it costs $200,000 to kill a naval pilot. The spin is defined and the forces and couples involved are described. The physiological effects on the pilot, and the causes thereof, are explained. With the object of preventing accidents due to spin, the United States Navy effected negotiations for use of Handley Page wing slots on service airplanes of the Army and Navy and has conducted numerous tests of airplanes fitted with them.
THE causes and nature of the spinning of an airplane, and measures for the prevention of and recovery from a spin, are discussed. Tests and analysis are said to have shown that spinning is a stable motion of rotation, and that the real dangers are in its instability. Recovery from a spin is held to be more important than prevention, as complete knowledge of means of recovery will lead to mastery of the whole phenomenon. The spinning motion is a combination and balance of aerodynamic and purely dynamic forces and couples, asserts the author. Full-scale experiments prove beyond doubt that side-slip may be very pronounced in a spin, which changes considerably the rate of roll of the simple autorotational kind. The rolling of the wings leads to the establishing of a yawning couple which may become dangerous, tending to keep the craft in a spin because of the increased shielding of the tail surfaces.
A TABULAR statement in which comparisons are made between acceleration and deceleration is presented by the author as proof of the need of frequent and scientific maintenance practices with regard to brakes. From the viewpoint of service, the author believes that the engineer's findings as to what constitutes the best lining for the particular brake he has designed for his particular car must be adhered to strictly. No one brake-lining will work equally well on all cars. In reconditioning used cars of any make, he has purchased the lining supplied by the manufacturer of the particular make of car when possible. Although water affects brakes equipped with molded linings, the trouble is only momentary, according to the author, because the heat quickly dries off the surface moisture. Squeaks are seldom caused by the molded lining itself, but mostly by protruding rivets, out-of-round brake-bands or brake-shoes, foreign matter on the linings, or eccentric adjustments.
IF brake-lining manufacturers would insist on holding the values of friction coefficients to 0.3 or 0.4, many of their troubles would cease, in the opinion of the author, who asserts that the main objections to high friction-coefficients are rapid wear, greater liability to cause scoring, and instability. The first results of tests on molded brake-lining materials were so superior to tests on woven material that further development of molded materials was carried on. Regardless of the type or make of molded material tested, it was found that the friction-coefficient value remained much more uniform than did that of woven material and that, without exception, the friction value and general characteristics of molded material were not changed by wear conditions. Molded material shows longer life than woven material, according to tests, and the author thinks that possibly this is because of the completeness of the saturation of the molded material.
FIRST reviewing briefly the history of molded brake-lining, the author states that the introduction of molded lining has, until recently, met with considerable opposition. After the first volume-production adoption in 1924, there were no further adoptions of the strictly molded types in production until 1927, when the trend in brake design seemed to change suddenly from the external type to the internal type of brake. The present movement toward the use of molded brake-lining was brought about through the inability of woven lining to meet the exacting demands of some of the newer types of internal brake. In the author's opinion, the molded type of lining has more nearly fulfilled the present requirement of internal brakes than has any other type. He states that at least seven different brands of molded lining are now on the market, and that three of them are in large-volume production.
STATING that the performance of rear-axle gears depends on both satisfactory gears and suitable mountings, the author describes three laboratory tests for axles. The first is a deflection test to determine the displacement of the gears and deflections of the differential carrier under load applied by a 20-hp. motor through changeable gear-reduction giving a propeller-shaft speed of approximately 12 r.p.m. Load is applied by means of a prony brake, and deflections are registered on indicators applied at various points. The second is called the four-square test. In it four axles are set up in a closed circuit, so that the gears and shafts are subject to static torque, and driven by a motor. This gives a high loading with a small expenditure of power. It is a severe wearing test. The third test is known as the laboratory road-test. In it an axle with heavy flywheels in place of the road-wheels is driven by an automobile engine under conditions simulating road tests.
STATING that improvements can be made in the smoothness, flexibility and economy of motor-cars by the provision of axle ratios and transmission steps that will make high road-speeds possible with lower engine-speeds than at present, and without increasing the size of the engine, the author presents arguments for the provision of two quiet and efficient gear-ratios. He asserts that the desired result can be obtained with either a two-speed rear-axle or a four-speed transmission having a quiet geared third speed, and a discussion is given of the considerations that determined the ratios actually selected in an experimental car fitted with a four-speed transmission having an internal-gear train for obtaining the third speed. Charts are included which show the car speeds at various engine-speeds and the grades that can be climbed with the several gear-ratios. The beginning of a tendency toward the use of transmissions of this type in Europe is reported at the conclusion of the paper.
THE PAPER is a preliminary report on a study of engine oil-filters made at the University of California Agricultural Experiment Station in connection with research on the effect of character and condition of lubricant on bearing wear. It is similar in its general character to the papers, presented at the 1924 Semi-Annual and the 1925 Annual Meetings, giving data on air-cleaner tests made under the direction of the author. To determine what the engine-crankcase oil-filter removes, a number of used filters were obtained, principally from vehicles used by the California Highway Commission, the dirt and filter material removed and incinerated, and the ashes weighed and chemically analyzed. The results of this work are tabulated and the quantity of ash remaining after incineration serves as a measure of the solid foreign matter removed from the oil.
SELECTION of the proper crude is an important consideration in the manufacture of aviation-engine oils. The authors class petroleum into asphalt-base, paraffin-base and mixed-base crudes, stating that scientific research and actual-performance tests have demonstrated the advantages of paraffin-base oils over asphalt-base oils for aviation engines, and that their superiority is now conceded by most authorities. Much attention has been given recently to the dewaxing and fractionating of lubricating oils, and this has resulted in an improvement in their quality and in their unrestricted use as “all-weather aero oils.” After quoting statements from several authorities who agree that an oil which will meet both summer and winter requirements is desirable, the authors give the definitions of viscosity, fluidity, consistency and plasticity determined by the American Society for Testing Materials and then discuss the fluidity or consistency of aviation-engine oils below their A. S. T.
ALTHOUGH the author and his associates have designed, built and tested a Diesel airplane-engine, a description of the mechanical details is omitted because the engine is still in the experimental stage. The general subject of Diesel engines for aircraft is therefore presented in its broader aspects. Typical indicator-diagrams of a gasoline engine and of a Deisel engine are compared as a means of ascertaining whether the pessimistic attitude that the Diesel engine cannot be made light enough for aircraft-propulsion purposes is justified. These considerations lead to the statement that, since a practicable Diesel aircraft-engine must run at speeds five or six times as fast as the stationary or marine-type of Diesel powerplants, whereas the ignition time-lag is substantially the same, it can be seen that the high-speed engine demands a different type of combustion than does the low-speed Diesel.
QUOTING a comparison of the radial engine with a star fish, the author compares the frontal areas of radial and V-type engines and shows how air can be applied to the cylinders of in-line engines to secure efficient cooling with minimum parasite drag. Advantages of upright and inverted engines are contrasted in various respects; and engine-mountings, cylinder design and valve gears are discussed. Difficulties that have been encountered in gearing in-line engines having less than 12 cylinders are mentioned, and a simple method of gearing is proposed in which the elasticity of a relatively long propellershaft is utilized. The paper concludes with a comparison of the production problems of radial and in-line aircraft engines.
NEARLY all the aircraft propellers used by both the Army and the Navy are of the detachable-blade type. The Navy has found it necessary to make its own designs and to furnish the propeller manufacturers with finished detail drawings. The author lists the sources from which data can be obtained and shows a chart from which can be found a diameter and setting of a pair of detachable blades that will give reasonably good performance for nearly any horsepower, revolutions per minute and airspeed commonly used with the direct-drive type of propeller. Discrepancies between model tests and wind-tunnel tests are cited, and the author then considers the subject theoretically. Substitute propellers are next considered, and also the strength of propellers.
BEGINNING with a statement of the requirements of a high-temperature cooling-liquid and a short history of what had been previously done in this field, the author gives a description of the liquid used in the investigation which was conducted by the Materiel Division at Wright Field. The investigation is divided into five parts which includes dynamometer test of Curtiss V-1570 and D-12 engines, endurance test and flight tests of D-12 engine and a dynamometer test of a high compression-ratio D-12 engine. The engines and cooling systems used, the results obtained and troubles experienced are given in detail, with curves, sketches and views of the airplanes. Extremely low fuel-consumption was obtained, and the results show that the ratio of installed weight to power of a liquid-cooled airplane-engine is considerably reduced by using this system of cooling.