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Design Considerations and Guidance for Helicopter Hoists

2020-05-05
WIP
ARP6836
The Aerospace Recommended Practice will focus on the areas of helicopter hoist design that require more detailed guidance than is required in the Aerospace Standard, to keep the AS from being too prescriptive and explicit. The ARP will expand on areas such as fatigue substantiation, damage tolerance evaluation, functional hazard assessment and analysis, cable-specific requirements such as cable abrasion, sharp edge, and design criteria.
Technical Paper

Variable-Pitch Propellers

1929-01-01
290060
WHILE much experimental work has been done on the controllable-pitch propeller, complexity of existing devices has prevented their being placed on the market. After reviewing briefly the difficulties encountered, due to propeller and engine characteristics, the author discusses the effect of camber ratio and of angle of attack on the speed at which burble occurs, following this with comments on the efficiency of propellers as static-thrust producers, the use of the method of momentum to compute thrust and the application of adjustable-pitch propellers to supercharged engines. The causes of the forces required to operate the control adjustments are given as (a) friction, (b) twisting moments produced by centrifugal force and (c) twisting moments produced by air pressure.
Technical Paper

Aircraft Propellers

1929-01-01
290059
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.
Technical Paper

Gearing of Aircraft Propellers

1929-01-01
290062
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.
Technical Paper

Modern Naval Aircraft

1927-01-01
270072
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.
Technical Paper

Correlation of Propeller and Engine Power with Supercharging

1933-01-01
330005
THE primary purpose of this paper is to discuss some of the most pressing problems involved in choosing the propeller that is most suitable for use on a particular airplane. Propeller design is not dealt with, the discussion being limited to the selection of metal propellers of established design. Questions of noise, efficiency and diameter limitation are merely mentioned, and the emphasis is placed upon the choosing of propellers which will transmit the most engine power for the most needed condition of airplane performance; maximum and cruising speeds at altitude, or take-off and climb. Airplane performance enters only inasmuch as it is used to illustrate a case of power absorption. The proper choice of a propeller is becoming increasingly difficult to determine because of the current design trends of both airplanes and engines. Especially important is the fact that many of the supercharged engines now in use cannot be operated at full throttle below their critical altitudes.
Technical Paper

Commercial Flight Tests Improved by New Equipment and Methods

1933-01-01
330003
THE purpose of this paper is to show that the value of commercial flight-testing depends largely upon the utility, reliability and accuracy of the equipment and instruments employed. In general, it is found that improvements in these three factors depend largely on the simplicity of the apparatus used. Special engine-tests have led to the development of instruments and apparatus not commonly available commercially, and the use of these has made it possible to employ the aircraft engine as an instrument for the measurement of power in flight. This ability to measure power has led to the development of a method of making comparative engine-temperature and other tests which eliminates or corrects for a number of the major variables ordinarily affecting such tests. Because of the increasing popularity of the controllable-angle propeller, tests are also described which enable one to determine the value of such a propeller when only an adjustable-angle propeller is available.
Technical Paper

Engineering Aspects of the Modern Autogiro

1932-01-01
320055
HEREIN is presented for the first time a technical analysis of many of the fundamental engineering features of the development of the Autogiro by the engineering departments of the parent American company and its licensees. Intensive study is still being given to both the aerodynamic and the structural improvement of the rotor and also to other component elements. Attention is given in the paper to many of the developments that have contributed to the present engineering status of the machine in this Country. Phases of the subject discussed and analyzed are the aerodynamic relationships existing in the three or four widely different combinations of rotor and fixed wing and the longitudinal balance and stability of these several types of Autogiro to determine the extent of displacement of the center of gravity that is possible without impairing the behavior of the machine in slow forward speed or nearly vertical descent, while still maintaining longitudinal stability at high speed.
Technical Paper

Controllable and Automatic Aircraft Propellers

1932-01-01
320036
THE DEMAND for a successful controllable or automatic propeller is greater today than ever. Such a propeller will enable commercial aircraft to take off safely with greater loads, and it may enable multi-engine airplanes that cannot now maintain altitude with one engine dead to do so with a safe margin of power. For military aircraft it means increased rate of climb and increased speed at altitude, especially with supercharged engines. To obviate confusion in nomenclature, the authors give definitions of adjustable, controllable and automatic propellers. Distinction is drawn between the needs of different classes of airplane for different types of changeable-pitch propellers. Many propellers falling within the several classes have been designed but few are in use. Cost, weight and complication are obstacles to their commercial success. Several problems still confront the designer in this field, the chief one being that of obtaining material that is sufficiently light and strong.
Technical Paper

Increasing the Thrust Horsepower from Radial Air-Cooled Engines

1931-01-01
310037
MANUFACTURERS of radial air-cooled engines have centered their attention upon low specific weight for their product. This is accomplished by compact design, using the best of materials and the highest grade of workmanship and finish, with the production of the maximum possible horsepower per cubic inch of engine displacement. High output can be accomplished by a combination of high rotative speed and high brake mean effective pressure with low friction losses. Many considerations of design and operation must be correctly proportioned to approach the ultimate in horsepower. Important advances have been made in improving engine output by cooling air-cooled cylinders with well designed fins supplied with air from directing baffles, thus increasing the brake mean effective pressure which can be produced on a given fuel without detonation.
Technical Paper

DEVELOPMENT IN NAVAL AERONAUTICS

1924-01-01
240057
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.
Technical Paper

ENGINES OF THE AIR

1916-01-01
160039
After a brief consideration of airplane-engine practice in France, England and Germany, the author outlines the problems encountered in designing a twelve-cylinder aviation engine. He explains at some length the difficulties in determining the connection between propeller and engine and shows why valve-in-head location was chosen. Such features of engine design as the mounting of carbureter and exhaust pipes, methods of fuel and lubricant supply and details involved in selecting the lighting, starting and ignition equipment are considered.
Technical Paper

SOME PROBLEMS IN AIRPLANE CONSTRUCTION

1917-01-01
170001
The authors advance for discussion some important problems in the construction of airplanes for military use in this country. The functions of military airplanes designed for strategical and tactical reconnaissance, control of artillery fire and for pursuit are outlined. Problems in construction with reference to the two-propeller system, methods of reducing vibration, application of starting motors, details of the gasoline supply-system, metal construction for airplanes, flexible piping, desirable characteristics of mufflers, shock absorbers, landing gear, fire safety-devices, control of cooling-water temperature, variable camber wings, variable pitch propellers and propeller stresses, are all given consideration. The paper is concluded with suggestions for improvement in design relating to the use of bearing shims, the rigidity of crankcase castings, interchangeability of parts and better detail construction in the oiling, ignition, fuel supply and cooling systems.
Technical Paper

RECENT AEROPLANE-ENGINE DEVELOPMENTS

1916-01-01
160025
The author gives a brief review of developments during the past year in the construction of aeroplanes, particularly as affected by the European War. He takes as an example the Renault twelve-cylinder engine, citing the respects in which the present differs from previous models. Such factors as the changes in cooling systems, method of drive, valve construction and starting devices are considered. The requirements of aeroplane engines, such as constant service, high speeds (of aeroplanes) and stream-line form of engines and radiators, are outlined. Propeller requirements are dealt with at length, curves being given by which the efficiency and diameter of the propeller can be obtained. In conclusion a number of different engine installations are illustrated and compared.
Technical Paper

The Design and Construction of Highway Systems

1927-01-01
270051
AN impetus to more scientific highway-construction was given by the World War, and, while it is necessary to limit the weight and size of motor-vehicles to safeguard the existing investment in highways, these limitations are being made as liberal as conditions permit. It is necessary for highway engineers to obtain a clear understanding of the interrelation of the highway and the vehicle. The author explains briefly the effects each has on the other and discusses these in connection with the problems of road location, grades, safety of users, cross-section of concrete slabs, the design of non-rigid road-surfaces, classes of highway and their cost to the public, and the economics of highway improvement and transportation. It is believed to be possible, the author states, to show that, under certain conditions, road improvement creates wealth, either in the form of lowered transportation costs or as improved social and educational conditions, or both.
Technical Paper

The Synchrometer for Brake Testing

1928-01-01
280071
PROPER brake testing is stated to involve the measuring and recording of vehicle deceleration and rate of speed for every foot of individual wheel travel during the period from the initial application of the brakes up to the moment the car comes to a standstill. The brake synchrometer, designed to duplicate the conditions under which a vehicle is tested on the road, embodies the principle of traction between each tire of the vehicle, on one hand, and a rotor on the other hand. The kinetic enegery of the four testing rotors must be equal to the energy of a vehicle of a certain weight at a given testing speed. The author describes a brake synchrometer designed for testing vehicles of 3500-lb. weight, which machine, however, is adjustable to compensate for greater or lesser car weight, so as to include heavier or lighter vehicles in its test range.
Technical Paper

The Development of Fixed Radial Air-Cooled Engines

1929-01-01
290055
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.
Technical Paper

The Autogiro

1929-01-01
290052
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.
Technical Paper

Possible Improvement of Present-Day Aircraft

1929-01-01
290051
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.
Technical Paper

Developments in Lighter-than-Air Craft

1929-01-01
290053
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.
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