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AFTER outlining the history of development of the Packard X engine, the author states the legitimate position in aviation deserved by the water-cooled aviation-engine of this type and predicts large increases in the size, speed and carrying capacity of airplanes within the near future. Passing then to a discussion of the important features of the X-type engine, various illustrations of its parts are commented upon. The cylinders are built-up from steel forgings, with all welds arranged so as to be subjected to no excessive alternating stresses. The novel features of this cylinder design lie in the fact that the valve seats are entirely surrounded by water and that water space is provided above the combustion-chamber and below the top plate of the cylinder. The cylinder-head is extremely rigid, resisting deflection and assuring the maximum integrity of valve seats. The valve ports are machined integrally with the cylinder-head and are not welded thereto as in the Liberty engine.

USEFUL load-carrying capacity is a measure of the comparative value of two airplanes of the same size, having identical powerplants, speed, rate of climb and other flying characteristics. It seems to be feasible to combine in the same airplane both the greatest ability to carry useful load and the least cost of construction. Blanked and pressed metal work offers substantial advantage to the extent that parts, particularly sub-assemblies, can be made directly by machine in complete units ready to set in the final assembly. The author shows and describes the methods followed by his organization in forming the members, building the frames and assembling the units of metal aircraft. Trusses are blanked and the web members pressed to ¾-circle form. Dies for long members are variable in length by being made in pieces that can be removed or inserted as desired. Flanged-tube sections are employed for truss chords.

AFTER pointing out that the rivalry between the monoplane and the biplane is of long standing, and that each must therefore have some advantages, the author proceeds to the consideration of the question at issue by comparing structural efficiency, aerodynamic characteristics, performance, and certain other features. In structural efficiency the biplane is considered superior both in strength-weight ratio and in rigidity, but the monoplane has the advantage of being better adapted to metal construction. In aerodynamic characteristics the monoplane has the advantage on the basis of wings of the same area and profile, but the lower lift-drag ratio and greater unit weight of the monoplane wing tend to reduce its superiority. World's records in performance are divided between the two types, and in speed the recent Schneider Cup races show the monoplane and the biplane to be about equal.

MORE and more is being demanded of Navy airplanes beyond the requirements of commercial planes. Catapulting and deck landings are required of some planes and corrosion must be guarded against. Bombers and fighting planes each have their special requirements, and planes must be able to land safely on either land or water. The most important developments in aerodynamics now going on are to restrict the travel of the center of pressure of the wings as the angle of attack changes; but widespread adoption of slotted wings and other results of experimental development may be expected. Metal is being used more than formerly in structural work but there are as yet no all-metal service-types in the Navy. Chrome-molybdenum steel is replacing mild carbon-steel in the tubular frames of fuselages, and there is a tendency to seek substitutes for welded joints. Duralumin is slowly replacing steel where welding is not required, but its adoption is retarded because of corrosion.

Several years ago some of the most prominent leaders in automotive industries cooperated to form a purely engineering group that had as its primary purpose developing a type of rigid-airship construction in which the public would have confidence. It was conceived that such an airship should be (1) Fireproof (2) Weatherproof (3) Durable and permanent in structure (4) Navigable in practically all kinds of weather (5) Economical in the use of buoyant gas and ballast To meet all of these requirements it was decided, after mature consideration, that a substantially all-metal construction was imperative.

Reduction of cost and of the time required to construct airplanes and seaplanes by applying so-called shipbuilding practice to their fabrication, embodying late types of production methods, are discussed by the author, who says that the company he represents adheres to a number of technical principles to reduce to the minimum the risk of designing and constructing new types. The technical principles refer to general arrangement and to layout, as well as to the detail design of many parts of the planes. They include also very careful and minute preparation for the actual workshop construction by the supplying of perfect workshop-drawings and by proper organization of the technical departments. The paper outlines the technical principles, including reasons for their adoption, and then describes the organization of the work of construction. Wing-loading and power-loading are discussed, and the statement is made that the company builds monoplanes only.

The marked advance that has been made in the last 10 years in constructional details and in performance of airplane engines and in airplane performance is reviewed, beginning with the year 1916 when the Curtiss OX-5 eight-cylinder water-cooled engine was brought to its final stage of development. The author describes briefly each type of engine produced successively by the company he represents and tells of the changes that were made to improve the performance. From the 8-cylinder V-type the constructors changed to the 6 and 12-cylinder water-cooled type and are now developing a 9-cylinder air-cooled radial engine that was built in 1925. An important field of usefulness is foreseen for the air-cooled engine.

Confining his subject matter strictly to a discussion of the Wright Whirlwind engine and its bearing on the present status of the air-cooled aircraft-engine, the author says that the type of engine specified embodies in its development two distinct forms of cylinder construction, the first having been developed by Charles L. Lawrance and the second by S. D. Heron. The application of these cylinders to the engine under discussion is outlined and the subsequent development is traced. The development of the J-5 type of engine was undertaken in an effort to place the air-cooled engine fully on a par with the water-cooled type as regards fuel consumption. The cylinder is characterized by a hemispherical combustion-chamber employing two valves with axes inclined at 70 deg. The valve-seats are of aluminum-bronze shrunk into the cast-aluminum head. The cylinder-barrel with integral cooling-fins and hold-down flange is screwed and shrunk into the aluminum-head casting.

Following a description of airplane structure, the author discusses structural requirements and outlines the main features of properly coordinating the engineering and the manufacturing activities. He says that each of the three subdivisions of airplane design has its own series of calculations, these being related to predictions of performance before the machine is built, to stability determinations and to the design of a self-contained structure of sufficient strength to withstand any stresses developed in flight or in landing. He states also that no inspection is worth the name or the money spent on it that does not include constructive work and a knowledge at all times that the intentions of the designers are being carried out in detail so that the safety of the craft is assured. Materials used in aircraft should be light and easily workable and should possess the desired physical and chemical properties; they must have the specified cross-section and be free from defects.

Trouble with the exhaust-valves of the Type-J air-cooled cylinder caused an investigation to be made of valve-cooling and of valve and guide wear. A temperature of 1300 deg. fahr. invariably caused fractures of the exhaust-valve stem at the junction of the stem and the neck. A file-hard tungsten-steel valve with a shallow hole and no filling eliminated breakage but scaling was apparent. The same valve, using a hard tungsten-steel guide, when tested with salt filling, gave improved cooling; the area of the hot zone was reduced in size and the stem remained dead-black. Scaling was reduced and the wear of the valve-stem and guide that appeared was overcome by substituting a roller tappet for the solid tappet previously used. Tests showed that extreme hardness is of advantage even for inlet-valves. Experiments with a Type-K air-cooled cylinder gave excellent results with a salt-cooled valve in spite of a very high head-temperature; with an unfilled valve the results were not so good.

Principal developments along the lines of the HS, H-16 and F-5-L types of seaplane, which were used during the war for convoy work, submarine patrol and scouting, are represented by present types PN-7, equipped with Wright T-2 engines, and PN-8, having Wright T-3 engines, a metal hull and metal tail-surfaces. Brief statements about their construction and performance are made and the subject of metal floats for seaplanes is discussed. “Training,” scouting and other types of seaplane are mentioned, and outlines given of their characteristics and performance. Launching airplanes from a catapult is described, some details of the development of the apparatus being given, and reference is made to a late development in which the catapult is actuated by the explosion of a powder charge instead of being operated by compressed air.

This paper is illuminative and affords an opportunity for better comprehension of the remarkable progress and accomplishment made in Europe along the lines of commercial aviation. Reviewing the present European routes now in regular or partial operation, the author stresses the essentialness of the attitude of the press in general being favorable if commercial aviation is to become wholly successful. The airship appears most practical for long-distance service, to the author, and he mentions the possibility of towns and cities growing up around “air ports.” The cost of airship travel is specified, although it is difficult to figure costs and necessary charges because so few data on the depreciation of equipment are available. Regarding successful operation, much depends upon the efficiency of the ground personnel and organization.

It is of course impossible to consider propeller design very much in detail in a paper of this nature. It can be said, however, that the airfoil theory, in connection with the inflow theory, has given very good results and proved exceedingly valuable for the aerodynamic design of propellers. Both theories, however, in the present state of knowledge, must be applied with a number of empirical factors. Propeller-design theories and the subject of aerodynamics are discussed mathematically, as well as the elements governing the best propeller diameter for obtaining the highest thrust. Consideration is given in detail to steel, adjustable-pitch and reversible propellers as well as to those made of laminated construction consisting of sheets of paper fabric impregnated with bakelite as a binder. The mathematical considerations that apply to propellers when reversed in flight, the time and distance required to stop when landing and the propeller stresses are enumerated and commented upon.

A tendency exists in most shops to assume that brazed joints cannot be successfully heat-treated. As a consequence, many fittings used in aircraft work and assembled by brazing smaller parts together are finished and installed without being heat-treated after the brazing operation. This practice causes parts to be used that not only do not develop the available strength of the material, but which are in some cases, under internal stress due to the heating in the brazing operation. Recent experiments made at the Naval Aircraft Factory show that the assumption mentioned is entirely erroneous. The author considers this matter with a view to specifying the use of steels and brazing spelters which will permit the subsequent or perhaps the simultaneous heat-treatment of the parts.

THE Navy Department established the Naval Aircraft Factory (a) to assure a part, at least, of its aircraft supply; (b) to obtain cost data for the Department's guidance in dealing with private manufacturers, and (c) to have under its own control a factory capable of producing experimental work. The history of this development is given in some detail, including statistics of size, valuations and output.

Naval aircraft are distinctively American types. Only one foreign seaplane was copied by the United States during the war, and when finally put into production it resembled the British prototype in externals only. While the Navy does a large part of its own designing and building through a corps of naval constructors, its theory of manufacture is to assemble parts procured from separate makers, and private design and construction are encouraged by contracting with builders. Available talent both in and out of the service and the facilities of parts makers, the new materials developed during the war and organized engineering which drove the entire process toward speedy results were appropriated by the Navy. The NC flying boat is typical of U. S. Navy practice. In the same way the dirigible C-5 is a purely American type. The development of really large flying craft before 1917 was held back because no suitable engine had been designed. When the 350-hp.

THE impression that recent aircraft experience should have taught engineers how to revolutionize automobile construction and performance, is not warranted by the facts involved. Aircraft and automobiles both embody powerplants, transmission mechanisms, running gear, bodies and controls, but their functions are entirely different. The controls of an airplane, except in work on the ground, act upon a gas, whereas with an automobile the resistant medium is a relatively solid surface. Similarly, the prime function of the fuselage is strength, weight considerations resulting in paying scant attention to comfort and convenience, which are the first requirements of an automobile body. Aircraft running-gear is designed for landing on special fields, and is not in use the major portion of the time. The running-gear is the backbone of an automobile, in use continuously for support, propulsion and steering; hence its utterly different design.

Starting with the statement that command of the air in warfare rests largely with the side that produces the best single-seater fighter, the author proceeds to outline some of the problems confronting the designer of fighting airplanes, and particularly the smaller ones. Considering better performance and better fighting qualities as the main desiderata, the author discusses means of obtaining them by: (1) increasing the horsepower-weight ratio; (2) decreasing the wing or structure resistances; (3) devising a new arrangement of the supporting planes, with regard to the position of pilot or crew, or by a combination of the above. Considerable space is devoted to methods of decreasing wing resistance, principally by employing low-resistance aerofoils, and the shaping of wing tips is also referred to.