*Editor’s Note.—This is but a portion of complete report.
THE PRESENT STATE OF TECHNICAL DEVELOPMENT
Aerodynamics.—Satisfactory progress has been made in the science of aerodynamics during the past year. It is gratifying to note that this progress not only includes the development of basic theories of air flow but also the practical applications of these theories. In the latter field the recent progress has been rapid and still further practical applications may confidently be expected. The most notable example of the recent adaptation of theory to practical problems is probably to be found in the Prandtl-Munk equations, which enable the drag of any system of wings to be calculated from monoplane-test data.
The progress which has been made in the technique and interpretation of wind-tunnel tests closely parallels that made in pure and applied theory. In particular, the limitations of the atmospheric wind tunnel, the corrections which must be applied for the interference between the model and the tunnel walls, the requirements which must be met in model construction, and the securing of full scale data are problems which appear to have been successfully solved, and the solutions will have an important influence on wind-tunnel investigations in the future. One important result of wind- tunnel investigation has been the development of a number of remarkably efficient wing sections of adequate thickness for economical structures. It is desirable that this development continue substantially along the present course.
There has recently been made available through the various research laboratories and organizations a large volume of airplane propeller data obtained from systematic tests in which all of the major elements of design are treated. These tests determine the effects not only of blade interference, blade shape, camber, pitch-diameter ratio, and so forth, but also of interference between the propeller and objects in its slip stream. The knowledge. of interference effects is of value to the propeller designer, since it enables him to obtain satisfactory results from a single design instead of following the cut-and-dry methods involving from three to six designs. While the progress in propeller design has been rapid, there is considerable information yet to be obtained. This information is of such nature that it is best obtained from full-scale tests either in free flight or in a suitable wind tunnel. Considerable free-flight work has already been done and arrangements have been made to supply facilities for full-scale wind-tunnel tests.
A careful study of the present state of knowledge in aerodynamics discloses a number of lines along which future investigations must be carried out. The most important of these will be described briefly.
More knowledge must be obtained on the forces on an airplane in various maneuvers in order that an efficient structure may be designed to carry these loads. The distribution of the loading is particularly important. For example, free flight, pressure distribution tests have shown the resultant forces to be substantially those used in design, but, owing to surprising irregularities in distribution, the local loadings sometimes are more than twice as great as the maximum values used in design. A large field for research lies along this line.
The subject of control of airplanes in flight is of primary importance, not only from the standpoint of adequate strength of the control surface, but also from the consideration of adequate control. Several cases of failure of control surfaces have occurred in flight during the past three years. Service operation and flight tests have revealed high local loadings in certain maneuvers on airplanes of the pursuit type. This knowledge is now being applied to current designs, hut more information is required.
In regard to the inadequacy of control, the limitations imposed by the inherently indefinite nature of the problem make its solution difficult. It is difficult to define adequate control just as it is difficult to define controllability or maneuverability. Every pilot and every engineer can perhaps find a definition which answers his own requirements, but universal agreement cannot be expected. However, the problem can be resolved into three general divisions, as follows:
(1) Control and design characteristics, that is, relations between control and the design characteristics such as the span, chord section, and arrangement of the wings, the location of the center of gravity, the size and location of tail surfaces, the size and shape of the fuselage, and so forth: Valuable work has been done along this line, but a thorough systematic research is needed.
(2) Controllability and maneuverability: Some airplanes are readily maneuvered into any desired position with very slight effort on the part of the pilot. Other airplanes differing but slightly in general appearance either cannot be so maneuvered, or else require considerable effort on the part of the pilot. A few of the factors which affect controllability and maneuverability are known, but more complete information is necessary unless the design of pursuit airplanes is to remain an art instead of developing into a science.
(3) Control at low speeds: This is a matter of vital importance for commercial aviation. The subject is now receiving concentrated attention abroad, and considerable work has been done in this country. Recent progress has been of such a nature that several solutions now appear available. The goal of the engineer is, of course, to free the airplane entirely from the danger of a crash due to loss of control following a stall at low altitudes. Two methods of attack are available—one to prevent the stall, the other to provide adequate control of the airplane in the stalled condition.
The problem of wing or control surface flutter seems to have been satisfactorily solved through wind tunnel tests, both as to causes and as to prevention. The primary cause appears to be one of relative stiffness or flexibility, and by a suitable proportion of stiffness in any particular case, flutter may be prevented. However, its complete elimination is not to be expected until an exhaustive treatment is made available to designers who will take the necessary precautions in design.
Another subject of considerable importance is the limitations imposed on airplane performance by the design requirements. These limitations are not as widely known as they should be. Consequently, some designers may claim unreasonable performance for their designs because they have failed to take into consideration certain very important requirements, such as adequate structural strength and stiffness. A clear and complete statement of design requirements should be prepared for the information of all designers. Under the present arrangement most of the needed information is available but not in a convenient form.
Airplane Structures — Trend of design.—While neither the monoplane nor biplane has gained complete acceptance for any particular use during the past year, out of an increasingly clearer understanding of the relative advantages of the two types there has grown an increased tendency toward standardization. For high speed, either for racing or for pursuit airplanes, the biplane has steadily gained in favor until it dominates that field almost completely, notwithstanding the fact that a monoplane holds the world's record for straight-away speed. Structural difficulties with the monoplane, and particularly the danger of wing flutter, have been largely responsible for its decreased popularity where great speed range is desired. Experience seems to show that for general pursuit use, having regard to the importance of maneuverability and the minimum obstruction of the pilot's vision, a biplane with the lower wing considerably smaller than the upper has proven most successful.
The larger military airplanes are of the biplane type in most cases, partly because of the greater compactness of the biplane of a given area and weight. For naval service especially the last consideration is of vital importance.
For commercial service both monoplanes and biplanes are used, the latter having, in general, the advantage in maneuverability and in compactness of form, but suffering somewhat in aerodynamic efficiency by comparison with the single-wing type. Where speeds are low and efficiency is the primary requirement, as on the lines of central and western Europe, the monoplane controls the field. The monoplanes now in use are either of all-metal construction or fitted with winds covered with plywood.
In the light airplane the importance of efficiency is such that monoplanes and biplanes of very high aspect ratio have given the best results, the former being in the majority. Aspect ratios in this type of airplane, although well above the average for military machines, are, because of the importance of weight in the light airplane, much lower than had become common in glider construction. There is a general tendency to increase aspect ratios and use thicker airfoil sections in all types, and, except in England, the airfoil section having a maximum thickness of less than 0.09 of the chord has virtually disappeared.
Structural materials.—Metal construction of airplane wings has developed much less rapidly in America than in European countries. The practice of any nation in the design of military airplanes is largely governed by the nature of the materials readily available. In America, with large native spruce forests, wooden wing spars are used in most instances, although there is a steadily increasing interest in metal. In Great Britain steel is commonly employed, while in France, which has native resources for the production of aluminum, duralumin is almost universally employed for wings and fuselages. In Germany duralumin holds first place. Metal covering is little used outside of Germany, where it is universally used.
Fuselage construction is of metal in practically all cases because of its greater durability and better shock absorbing qualities in case of a crash.
In America, the Netherlands, and some of the smaller European countries, fuselages are commonly constructed of steel tubes assembled by welding.
British practice has also inclined toward steel tubes, but with assembly by pinned fittings, while most of the important continental manufacturers use duralumin, either in tubes or structural forms.
When metal is used in wing construction it may take the form of simple tubes, or, as is the common practice in Great Britain, the alloy steel of thin sheet may be rolled into somewhat complex forms and assembled into spars by riveting.
In landing-gear construction the outstanding development of the year in America has been the trial and rapid recognition of the value of the Oleo gear for shock absorption. Such gears reduce the liability to bouncing and at the same time increase the efficiency of shock absorption and the violence with which the airplane can be brought into contact with the ground without damage.
Small floats are still commonly made of wood, although duralumin is sometimes used. In flying-boat hulls, metal is steadily increasing in popularity, as it has been found that seaworthiness can be improved and the weight decreased. The PN-p flying boat which attempted the Hawaiian flight and had to cruise on the surface of the water for a number of days was fitted with a metal hull.
Aircraft Engines.—Progress in aircraft engines development in this country is reflected in the fact that we now have proved engines in horsepowers ranging from 60 to 800. In the 60-horsepower class there is the Lawrance 3-cylinder radial “L” type. In the 200-horsepower class there are available the Wright model “E” water-cooled and the Wright model “J” air-cooled engines.
In the 300-400 horsepower field the Curtiss D-12, a 12-cylinder water- cooled engine, is in production and has given excellent performance, particularly in pursuit type airplanes. In the 400-500 horsepower field we have the Liberty, Packard 1A-1500, and Curtiss V-1400 engines. The two Packard 1-1500 engines, with a gear ratio of 2 to I, formed the power plants for the two PN-9’s on the west-coast-Hawaiian flight project. The Curtiss V-1400 engine was installed in the Pulitzer and Schneider cup racers. It gives every indication of being an extremely light and rugged engine.
The Wright model P-2 is now undergoing its dynamometer trials and is giving very satisfactory results. This is a 9 cylinder radial air-cooled engine of 450 horsepower at 1,800 revolutions per minute.
In the 500-600 horsepower class the 12-cylinder T-3 water-cooled engine meets the present requirements. This engine in the past year has been extensively used by the Navy in the three-purpose scout-torpedo-bombing airplane.
In the 600-800 horsepower class the Packard 1A-2500, a 12-cylinder water-cooled engine, has been flown in the PB-1, the Navy’s west coast- Hawaiian airplane built by the Boeing Airplane Company, and in the latest Army and Navy bombers.
The Curtiss radial 400-horsepower 9-cylinder air-cooled engine is undergoing its tests at McCook Field. It gives great promise as a light-weight engine.
In the past year strides have been made in the matter of reliability and increased service between overhauls. A life between overhauls from two to four times as great as has been had in previous engines is now being obtained by the Wright model “J” and T-3 engines.
The aeromarine inertia starter has solved the starting problem and is in wide use in the Navy.
Airships.—During the past year there has been no new airship construction started in the United States. The technical development of airships has necessarily been confined to experimental investigations and research looking toward the improvement of existing airships.
With the completion of the RS-1 semi-rigid airship, constructed for the Army Air Service by the Goodyear Tire and Rubber Company, the Army Air Service now has in its possession the largest semi-rigid airship in the world. A special subcommittee on the RS-l appointed by the National Advisory Committee for Aeronautics to report on the design and construction of semi-rigid type airships has made its report.
The technical development of airships lags considerably behind that of airplanes. There appear to be two reasons for this—the higher cost of airships, and the longer time taken for construction of airships.
The arrival in the United State of the ZR 3, now the U.S.S. Los Angeles, on October 15, 1924, after an epoch-making non-stop voyage of 5,600 miles in 81 hours, made the United States the possessor of two rigid type airships. The Los Angeles is a splendid example of modern airship design and construction.
In October, 1924, the U.S.S. Shenandoah successfully completed a 9,000- mile voyage from Lakehurst to Seattle and return. The airship remained away from her shed almost 20 days, basing on mooring masts, and during the period encountered unfavorable weather. The successful completion of the voyage proved the efficiency of the mooring masts, the soundness of construction of the Shenandoah, and the skill of her operators.
The loss of the Shenandoah on September 3, 1925, while on a voyage to the middle west, was a severe blow to airship development. At this time the cause of the accident has not been determined, and it is hoped that the naval court of inquiry, after sifting all the evidence, will be able to determine the cause of the accident.
The past few years the United States has led the world in experimental research with reference to improved design and operation of airships. The United States has now lost its position to Great Britain, which during the past year has actively pursued research and experimental problems and started the construction of two 5,000,000-cubic-feet rigid airships, one being built by the government and one by a private manufacturer.
During the past year, however, progress has been made in determining the magnitude of stresses which may be encountered by airships in flight, in June, 1925, preliminary strain-gauge measurements were made on the Los Angeles in conjunction with the use of a rate-of-turn indicator. It is proposed to extend this work and in addition to conduct simultaneous pressure-distribution measurements in an effort to fix some relation between aerodynamic loads, magnitude of stress in important structural members, and acceleration in a horizontal or vertical plane as shown by a rate-of- turn indicator or sensitive accelerometer mounted in the airship’s control cabin.
Further confirmation of existing design theories has been found through the extended, tests carried out on a photo-elastic model of the structure of a rigid airship at the Massachusetts Institute of Technology.
The behavior of duralumin and other light alloys under conditions likely to be encountered in airship practice has been investigated. Special study has been given to corrosion or deterioration of these alloys from various causes and possible means for preventing such corrosion or deterioration.
Water recovery apparatus has been improved in type, and with this improvement has come a considerable reduction in weight.
Study has been continued on substitute materials for the expensive goldbeater’s skin heretofore considered necessary in gas-cell construction. One type of substitute fabric gave so much promise of success that the Navy Department constructed an experimental full-sized cell for test.
In accordance with legislation recently enacted, the Bureau of Mines, Department of Commerce, on July 1, 1925, took over the control of all matters affecting the conservation and production of helium, including operation of the helium production plant at Fort Worth, Texas, heretofore operated by the Navy Department. Attention has been given to lowering the cost of helium transportation and the Army Air Service and the Navy Department have each purchased a tank car for transporting helium. Each car will carry about 215,000 cubic feet of helium, and the saving in freight charges for a period of about two years will practically pay the cost of the tank car.
Experimental work has been continued toward the development of better means of handling large airships in and out of their sheds and while near the ground. The progress made promises the further development of methods which will materially reduce the number of men required for a handling crew. The success obtained with mooring airships both to stationary masts and to the floating mast on the U.S.S. Patoka has been gratifying.
AERONAUTICAL RESEARCH IN THE UNITED STATES
The National Advisory Committee for Aeronautics is charged by law with the supervision and direction of the scientific study of the problems of flight, with a view to their practical solution. The committee is authorized by law to direct and conduct research and experiment in aeronautics in such laboratories as may be placed under the direction of the committee. The membership of the committee and of its technical subcommittees is drawn from the governmental agencies concerned and from private life. The members of the main committee and of all subcommittees serve as such without compensation. It is a matter of gratification that since the creation of the committee no person has ever declined an invitation to serve as a member of either the main committee or one of its subcommittees. The committee has therefore been able to draw upon the best talent in America for the study of the fundamental problems of aeronautics, and in this way it has wielded an influence for the advancement of the science of aeronautics that could not have been secured in any other way. This has been done at the direct cost to the government that involved only the traveling expenses of the members and the maintenance of a place for meetings.
The way the influence of the National Advisory Committee for Aeronautics is exerted is through discussion by each subcommittee of the new technical problems that are constantly arising in aeronautics, and the preparation of research programs from time to time, which programs invariably indicate the particular laboratory where each investigation recommended can be conducted to the best advantage of the government. Investigations are assigned both to public and private laboratories in a way that makes for the most effective utilization of existing facilities and the most effective study of the problems. After approval by the main committee, estimates for the prosecution of the research programs are submitted to the Bureau of the Budget, and after the appropriations are made by Congress the investigations are pursued under the general cognizance of the executive committee. The more fundamental investigations, for which facilities do not exist elsewhere, are undertaken in the committee's own laboratory, known as the Langley Memorial Aeronautical Laboratory, located at Langley Field, Virginia, on a plot of ground set aside for the purpose by the Secretary of War, and on which the necessary buildings have been erected by the committee with appropriations provided for the purpose by the Congress. Other investigations are assigned, for example, to the Bureau of Standards, to the Forest Products Laboratory, to the Weather Bureau, to the Engineering Division of the Army Air Service, to the Navy, and to various universities having the requisite facilities for the proper study of the particular problems so assigned. This method has proved practical and successful in operation, and has led to the accomplishment of substantial results with a maximum of economy and efficiency.
The committee was created by Congress with the status of an independent government establishment. It is a service organization, ministering to the needs of the Army, Navy, and Air Mail Service, as well as to the needs of commercial aviation. By virtue of its status, it has been able to initiate and conduct fundamental scientific investigations while at the same time responding to numerous requests from the War and Navy Departments for special investigations in aeronautics.
The committee enjoys many advantages which have contributed to its success. Chief among these may be mentioned the following:
1. The members of the National Advisory Committee and of its standing subcommittees serve without compensation, thus enabling the government to obtain the services of men who would not otherwise be available for government service.
2. The committee has the status of an independent government establishment, and by virtue of such status reports directly to the President, receives its appropriations direct from Congress, and is enabled to initiate and conduct investigations of a truly scientific character, limited only by the funds available.
3. The research laboratories of the committee are located on a flying field, where all phases of the work, including flight operations, are controlled and actually performed by the committee’s own technical staff, thus bringing theory and practice together under ideal conditions.
4. The committee has the confidence and support of the Army and Navy Air Services, and is able at all times to obtain any cooperation desired.
The committee has just completed its tenth full year of activity. While the satisfaction of useful service rendered is ample reward, the committee feels especially grateful to the President for his recognition of its services, expressed in his message to Congress transmitting the tenth annual report of the committee on December 8. 1924. It is therefore with pardonable pride that the committee quotes the following extract from that letter of President Coolidge, addressed to the Congress of the United States:
I concur in the committee’s general recommendations, and agree that in the last analysis substantial progress in aviation is dependent upon the continuous prosecution of scientific research.
When the National Advisory Committee for Aeronautics was established by Congress in 1915, there was a deplorable lack of technical information on aeronautics in this country. In submitting this, the tenth annual report of the committee, I feel that it is appropriate to say a word of appreciation of the high-minded and patriotic services of the men who have faithfully served their country without compensation as members of this committee and of its subcommittees. Through this committee the talent of America has been marshaled in the scientific study of the problems of flight, with the result that today America occupies a position in the forefront of progressive nations in the technical development of aeronautics. The status of the committee as an independent government establishment has largely made possible its success.
Calvin Coolidge
RELATION OF AERONAUTICAL RESEARCH TO NATIONAL DEFENSE
The relation of aeronautical research to national defense is direct, and its relative importance is increasing. This is necessarily so, because every improvement in the performance of aircraft makes the probable role of aviation in warfare greater. As the relative importance of aviation increases, it becomes more and more desirable for America to achieve and maintain leadership. As leadership cannot be attained in all respects, it becomes of the greatest importance for America to lead in technical development. For ultimate leadership in time of emergency the United States must depend on the results of continuous research and development.
The National Advisory Committee for Aeronautics therefore believes it to be its duty to emphasize the importance of scientific research as the most fundamental activity of the government in connection with the development of aeronautics. Closely associated with this is the problem of engineering development of aircraft to meet the special needs of the military and naval services.
While the committee is of the opinion that there should be no monopoly of engineering development, either by the government or by the industry, it believes that it is desirable, in order to secure the best results, that the actual users of military and naval aircraft should be in close touch with competent aeronautical engineers. As a practical proposition, this can be done only if there are such "engineers in the Army and Navy Air Services who are in such close touch with the operators that the latter are able to offer them constructive criticisms in regard to engineering problems. This would enable the aeronautical engineers of the industry to thoroughly understand the problems presented to them and would prevent them from wasting their energies in attempting to develop military types of airplanes which would not meet the requirements of the services.
Without attempting to be specific, the committee is of the opinion that the military and naval services should maintain aeronautical engineering divisions which should be charged primarily with the formulation of specifications of military aircraft, their characteristics and performance; with the critical examination and testing of designs and of aircraft offered by the industry; and with such experimental and development work as can be carried on by them most effectively and most economically.
THE GENERAL PROBLEM OF AERONAUTICAL ORGANIZATION
In its tenth annual report, for the year 1924, the National Advisory Committee for Aeronautics presented an outline of the organization and functions of the four governmental agencies directly concerned with the use or development of aeronautics—namely, the Army Air Service, the Naval Bureau of Aeronautics, the Air Mail Service, and the National Advisory Committee for Aeronautics.
During the past year, there have been two major investigations of the aeronautical situation—the first by the Congressional Select Committee of Inquiry into Operations of the United States Air Services, created by Resolution Number 192 of the House of Representatives (Sixty-eighth Congress, first session), of which Representative Florian Lampert, of Wisconsin, is chairman; the second by the special board appointed by President Coolidge on September 12, 1925, known as “The President’s Aircraft Board,” of which Mr. Dwight W. Morrow is chairman. The investigations of the two bodies referred to have gone deeply into all phases of aeronautical activity and governmental organization in aeronautics, including the major problems of the relation of aircraft to national defense; the organization, morale, and sufficiency of air personnel; the maintenance of the aircraft industry; the regulation, and encouragement of commercial aviation; the development of airways, and so forth.
It is to be hoped that the recommendations of these two investigating bodies will receive careful consideration and lead to a settlement of the controversies in aeronautics that have existed since the war. The continued unrest in aeronautical circles has served to focus attention primarily on organization and administrative matters, but has also indirectly brought about a broader recognition of the increasing relative importance of aircraft for purposes of war and of commerce.
In the judgment of the National Advisory Committee for Aeronautics, however, the people of the United States are not so much concerned with the form and administration of the government’s activities in aeronautics as they are with the question as to whether practical and efficient results are being secured. It is only fair to say that the best results have not been obtained and will not be obtained as long as the personnel are disturbed and their attention distracted from their real duties. It is most desirable, therefore, that measures to improve the situation be formulated and carried into effect without delay. This will enable all who have the best interests of aeronautics at heart to cooperate and settle down to work in harmony with that full measure of devotion to duty which is necessary to bring about the greatest practicable development of aeronautics in America, for both military and commercial purposes.
PROGRESS IN COMMERCIAL AVIATION
The past year was notable as witnessing what may prove to be a real, substantial beginning of commercial aviation in America. The most encouraging factors were the initiative shown by private companies in establishing air lines and the relatively large number of responsible bidders for the carrying of air mail by contract with the Post Office Department. When it is realized that commercial aviation exists in European countries at this time only by virtue of the support of the various governments given through various plans of direct and indirect subsidies, it should be especially gratifying to all concerned with the advancement of aeronautics in this country to feel that the era of commercial aviation on a sound basis is about to dawn in America.
Although the National Advisory Committee for Aeronautics has long been of the opinion that commercial aviation must largely make its way in America, it believes at the same time that the government should aid commercial aviation in certain respects where government aid is practicable and necessary. If, in recognition of this principle, commercial aviation can be successfully developed in America on a firm basis, its development will not be limited, whereas the development of European commercial aviation on a direct subsidy basis is necessarily limited by the nature and extent of the subsidies given. The committee believes that the American policy is sound and in the long run will be more effective in stimulating the substantial development of commercial aviation than will the European policy of direct subsidy.
In spite of this optimistic note, the facts of the situation that must be faced show a number and variety of problems requiring study and solution before commercial aviation can take its proper place in America. The most pressing needs requiring attention at this time are, first, legislation establishing the fundamental right of flight, creating a bureau of air navigation in the Department of Commerce for the regulation and licensing of aircraft, airports, and aviators, and for the establishment, maintenance, and lighting of adequate national airways, and providing for the necessary meteorological information; and, second, the improvement of airplane design and structure with a view primarily to making airplanes safer, more reliable, more controllable at low speeds incident to taking off and landing, and less expensive in initial cost, as well as in the cost of maintenance and operation. There should also be assistance from the other governmental agencies concerned, such as the Hydrographic Office, the Coast and Geodetic Survey, the Weather Bureau, the Lighthouse Service, and the Army and Navy Air Services.
To accomplish the first purpose, legislation is necessary. This has been repeatedly recommended by the National Advisory Committee for Aeronautics and has been indorsed in principle by all agencies of the government concerned. This question is discussed at length in the report of the committee on civil aviation of the Department of Commerce and American Engineering Council. To accomplish the second purpose requires continuous prosecution of scientific research on the more fundamental problems of flight. This is the definite prescribed function of the National Advisory Committee for Aeronautics, and in the last analysis is necessarily the most fundamental activity in the whole field of aeronautics.
In the past the committee has devoted its attention primarily to the solution of problems arising from the development and use of military and naval types of airplanes and, to a lesser extent, airships. While the basic problems of aerodynamics and of design are the same for military and commercial airplanes, the service requirements as to performance, efficiency, and safety differ. Up to the present time airplanes used for commercial purposes in America have been largely adaptations of military types. This is best evidenced by the fact that the Air Mail Service is still using up war-time DH-4 airplanes with certain modifications.
The committee is of the opinion that with the advent of commercial aviation, a new series of problems peculiar to commercial aircraft will be presented. The committee has therefore decided to hold one or more meetings annually with the engineering representatives of aircraft manufacturing and operating industries, with a view to ascertaining definitely the problems deemed of most vital importance and to incorporating the same, as far as practicable, into the general research programs prepared by the committee.
THE PROBLEM OF THE AIRCRAFT INDUSTRY
In its tenth annual report, the committee outlined the relation of the aircraft industry to national defense, and emphasized the need of maintaining a satisfactory nucleus of an industry. This was defined as “a number of aircraft manufacturers distributed over the country, operating on a sound financial basis, and capable of rapid expansion to meet the government's needs in an emergency.” The committee presented certain definite suggestions of steps to be taken by the government and by the industry to meet the situation that existed at that time. There has been substantial progress during the past year along the lines outlined by the committee, and it is believed that the condition of the industry and the relations of the government to the industry have been much improved. The greatest single factor in bringing about this improved condition has been the increased volume of government orders for aircraft, made possible by increased appropriations and contract authorizations for the purchase of aircraft. The present situation, on the whole, may be regarded as more satisfactory at this time, and as offering promise of further improvement.
THE AIRSHIP PROBLEM
Airships are of three types: Rigid, semi-rigid, and non-rigid. The value of airships for military or commercial purposes has not as yet been conclusively demonstrated. It cannot be said, however, that they are without value, nor that they have no further possibilities than have already been demonstrated. The fact of the matter is that all types of airships are in the experimental stage of development. The recent regrettable loss of the rigid airship Shenandoah has been urged as a reason for the government’s abandoning airship development, or at least rigid airship development, on the theory that rigid airships will never be practicable.
The committee fully appreciates the seriousness of the airship situation and believes that despite all that has been done in many countries to develop airships, they are still rather delicate structures. The conclusions of the naval court of inquiry as to the causes for the destruction of the Shenandoah have not yet been made public. Regardless, however, of the actual technical causes, the committee is of the opinion tiiat it would be a serious error at this time to adopt a policy of merely marking time in the development of airships. In the judgment of the committee, the time has come to decide to do one of two things, viz., either to carry on with the development of airships or to stop altogether.
The development of rigid airships in America for military and naval purposes has, by joint agreement between the War and Navy Departments, been entrusted to the Navy. The question of continuing their development, however, is not altogether a war problem, for airships of all types have probable applications also for commercial purposes. The question, therefore, whether the Navy should continue with the development of rigid airships at this time should not be determined solely upon considerations of their probable naval usefulness. The Army is directly concerned and the commercial development of airships in America may be said to be also at stake. The problem is therefore a national one. Viewed as such, the Navy becomes, in a peculiar sense, the agent of the whole people in the development of rigid airships. In the last analysis, however, it is for the Congress to determine America’s policy with regard to continuing the development of airships. As between the two alternatives of carrying on or stopping altogether, the National Advisory Committee for Aeronautics, after careful consideration of the matter, is of the opinion that the development of airships should be continued.
SUMMARY
There has been continued gratifying progress in the technical development of aircraft. Performance and reliability have increased. The committee’s program of research for the coming year promises to add substantially to the store of technical knowledge. There is nothing in sight at this time to indicate the probability of the discovery of a revolutionary principle contributing any great or sudden improvement in aircraft. While progress must be gradual, there is every reason to believe that there will be steady improvement in the performance, efficiency, reliability, and safety of aircraft.
Aviation has become more generally recognized as a weapon indispensable to war operations and as an instrument that gives promise of taking its place in the immediate future in the commercial life of the nation.
During the past year alone there were three investigations of the aircraft situation. A special committee of the House of Representatives known as the “Lampert .Committee,” and a special board appointed by President Coolidge known as “The President’s Aircraft Board,” inquired into all details of the aircraft situation and the aeronautical organization of the government. A third investigation, limited to civil and commercial aviation, was made by a special committee on civil aviation of the Department of Commerce and American Engineering Council. The recommendations of these bodies should serve to clarify the public mind and to focus attention on the major problems requiring immediate solution. Measures to meet the situation should be formulated and carried into effect without delay. In this connection the National Advisory Committee for Aeronautics reiterates its recommendations of previous years for the creation of a bureau of air navigation in the Department of Commerce to regulate and encourage commercial aviation.
The state of the aircraft industry is gradually improving. The most substantial factors in improving the situation during the past year were the increase in appropriations and contract authorizations for the purchase of aircraft by the War and Navy Departments and the increasingly close liaison between the industry and the government engineers. With sustained government patronage on a continuous production basis and with the prospect of a growing commercial demand for aircraft, the condition of the aircraft industry will steadily improve.
Air mail service is no longer a novelty. It is passing out of the experimental stage and becoming a necessity in the daily business life of the nation. It has reached the point where it has become practicable for private firms to carry air mail under contracts with the Post Office Department. Air transportation of the mails should therefore be extended gradually to meet the requirements of the people in all parts of the country.
CONCLUSION
The committee is of the opinion that America is at least abreast of other progressive nations in the technical development of aircraft for military purposes. The committee is grateful to the President and to the Congress for the support that has been given to scientific research in aeronautics. The committee feels that the continuous and systematic study and investigation of the basic problems of flight is the most fundamental activity of the government in connection with the development of aeronautics and that the continuance of this work will serve to keep America at least abreast of other progressive nations in the technical development of aircraft for all purposes.
Respectfully submitted,
National Advisory Committee for Aeronautics, Joseph S. Ames, Chairman, Executive Committee