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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 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.

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.

FOLLOWING a brief outline of the development of aircraft propellers and a statement of the most important fundamentals of propeller design, the authors discuss the problem of propellers for use on geared-down engines, this being the installation of reduction gearing between the crankshaft of the engine and the propeller hub when the increase of airplane-performance characteristics more than offsets the added complication of the installation. The advantages and the disadvantages of using reduction gearing are considered. Concerning the installation of reduction gears, the authors state that the decision whether to use gears or not must result from a compromise between the gains and the losses involved and the amount of net gain depends largely upon the particular engine and airplane combination and its designed performance.

A NUMBER of the more important commercial alloys having aluminum as their base are discussed by the author, who points out their main physical characteristics and outlines methods which can be used in their fabrication, indicating in a general way which alloys are best suited to various aircraft-engine requirements. Tables are given showing chemical compositions and physical properties, including a table of physical properties of various casting alloys at elevated temperatures. Special-purpose alloys are commented upon, and also a new aluminum alloy for pistons which is beginning to find commercial application and possesses properties particularly desirable in aircraft engines. Recent developments in magnesium alloys and their application to aircraft-engine design are specified, tables of physical properties are given, and comments are made on the characteristics of the material as compared with aluminum alloys.

ACHIEVEMENTS of the last ten years in increasing the power-weight ratio of aircraft engines are stated and contributing factors are analyzed. Aluminum alloys have replaced cast iron and steel for certain parts, not entirely because of their lower weight but because of a combination of properties which better fit them for the task. Similar considerations must govern the replacement of aluminum-base alloys by those of magnesium. The most promising immediate field for the magnesium alloys is said to lie in applications wherein strength and lightness are the main considerations and high-temperature properties are of secondary importance. Properties of magnesium castings and forgings are compared with those of castings and forgings of the aluminum alloys. Features of design are discussed which should receive special attention when changing a part from aluminum to magnesium. Machining practices for magnesium are covered in some detail.

THE PAPER urges united cooperation instead of the present division of responsibility between the engine designer and the airplane designer in the installation of aircraft engines. The tubular rings upon which engines are commonly mounted are usually supported by structural members that are welded to the ring and attached to the fuselage at the four longitudinals. Inaccuracy is common in these structures, and many of them lack sufficient stiffness. Gravity gasoline-feed is recommended for its simplicity, provided the pressure head required by the carbureter can be secured, but the author reports having seen an installation in which the engine would operate so long as the airplane had its tail on the ground, yet the engine would die as soon as the tail was raised during a take-off. The use of gasoline-resisting rubber-hose with metal liners and the avoidance of sharp bends are recommended for the gasoline connections.

CAUSES of troubles and expense to air-transport companies in their airplanes are dealt with comprehensively by the operations manager and a division superintendent of the National Air Transport. Commercial operation is asserted to be the proving ground for the products of both airplane and airplane-engine manufacturers, and four reasons given for this are (a) lack of understanding between the manufacturer and the purchaser as to precisely what is required of the airplane purchased, (b) inability of the manufacturer to deliver a product equal to his anticipation, (c) inability of the operator properly to use and care for the equipment furnished, and (d) the varied and opposed uses to which different operators must put their equipment. Detailed and valuable information is given regarding the parts that give trouble and what should be done to avoid it.

After indicating the line of development since November, 1918, toward making the internal-combustion engine better adapted to aircraft service, the successful application of the supercharger to improve engine performance at great altitude is described and the over-dimensioned and over-compressioned engine also is discussed as a means toward that end. The use of anti-knock compounds to permit the use of high compression-ratios at small altitudes without knocking is commented upon and engine size is considered for both airplane and dirigible service. Further review includes air-cooling experiments in reference to the air-cooled radial engine, refinement of aviation-engine details, and improvements in aircraft powerplant parts and fuel-supply systems. For commercial aviation, powerplant reliability and low cost are stated as essentials. Illustrations are presented of the supercharger and of the engines and sylphon fuel-pump mentioned.

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.

The personnel and the ground facilities that have produced such excellent results in the Air Mail Service are discussed apart from the flying equipment and its operation in the air. An airway is on the ground and the performance and safety of the pilots are dependent upon the ground facilities provided and the efficiency of the ground personnel. Pilots perform a highly important part in the operation of airlines and no matter how good the flying equipment may be, the desired results cannot be obtained without thoroughly trained and capable pilots. When selecting new pilots, the Air Mail Service looks for men who handle an airplane in a businesslike way and who are able, without taking unnecessary risks, to fly the ship without letting the ship fly them.

THE monocoque type of fuselage construction seems to promise satisfaction of the three requisites of prime importance; namely, high strength-weight ratio, “streamlined” form, and unobstructed interior, according to the author. The conventional method of building a fuselage consists, first, in the construction of a “form” of the required shape, upon which a layer of veneer is fastened. Other layers are applied, and thus a fuselage shell of two or three plies is completed. But the process is expensive and laborious, involving the handling and individual fitting of many small pieces. In the process described by the author, a wooden form of the exact shape of one half of the fuselage body, divided on a vertical plane passing through the center line, is built. This form, or pattern, is next suspended in a large box in which reinforcing bars previously have been woven, and concrete is poured in.

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.

Advances in airplane performance during the last few years may be ascribed mainly to advances in aerodynamics and to improvements in powerplants. The latter have resulted in producing more power for the same weight of engine and smaller over-all dimensions for engines of the same power-rating. The accompanying paper describes two engines of 500 and 800 hp. respectively that have been recently developed by the Packard Motor Car Co. for aircraft service. When these engines are compared with previous types they are found to be more compact and to produce more power per pound of weight. When each is operated at its rated speed, the Model 1500 engine develops 100 hp. more than the Liberty while weighing 140 lb. less, and the Model 2500 engine develops 250 hp. more than its predecessor, the Model 2025, with a decrease in weight of 75 lb.

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.

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.

A STUDY of possible economic advantages to the aircraft operator of utilizing the internal cooling potentialities of water to assist aircraft-engine cooling and increase detonation limited powers is presented here. Cost analysis is made of three methods of increasing airplane performance by water injection, namely: 1. By increasing cruising bmep's while maintaining engine cooling requirements at the value for conventional cruising bmep's. 2. By decreasing cruise power cooling requirements with the addition of water. 3. By increasing cruise powers up to meto at a constant F/A ratio while maintaining low cooling requirements and avoiding detonation with the use of water. It is concluded by the author that if the water to be used for cooling does not displace an equivalent weight of payload, a maximum saving of 7% at sea level and 18% at 25,000 ft can be realized in direct operating cost with water.

THEORETICAL principles of cargo pickup are outlined here by Mr. Schultz, who describes the design of pickup units, contact means, transfer equipment, and ground stations for both 200-lb and 60-lb units. He also outlines the basic features desirable in future pickup airplanes, as well as structural design requirements. The author then describes glider pickup, giving consideration to the basic theory behind this type of pickup, the design of pickup units, their installation in the airplane, the cable guide system, and contact means. He outlines the design features of glider pickup airplanes and structural design requirements to be used in the installation of the equipment. In closing the author points out that aircraft pickup has obvious military possibilities and that the peacetime potential is practically unlimited.