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Commander Le Prieur, whose flight experience in a low-speed seaplane we related in our number of September 27, 1924, invented, four years ago, an instrument destined to render very great service to aviators, namely, the "navigraph", designed to correct errors of orientation due to the effect of the winds during flight.
The Avro Avian, designed by Mr. Chadwick of A.V. Roe & Co., Ltd. has a very low structural weight (estimated at 750 lbs. empty) but with sufficient structural integrity to be eligible of an "Aerobatics" certificate from the British Air Ministry. It can be configured as a monoplane, or a biplane with seaplane floats. It is designed for economical production.
In the present article, several suggestions will be made for shortening the otherwise long take-off distance. For the numerical verification of the process, I will use a graphic method for determining the take-off distance of seaplanes.
This is the third in a series of investigations of the water pressures on seaplane floats and hulls, and completes the present program. It consisted of determining the water pressures and accelerations on a Curtiss H-16 flying boat during landing and taxiing maneuvers in smooth and rough water.
The NACA model 40 series of flying-boat hull models consists of 2 forebodies and 3 afterbodies combined to provide several forms suitable for use in small marine aircraft. One forebody is the usual form with hollow bow sections and the other has a bottom surface that is completely developable from bow to step. The afterbodies include a short pointed afterbody with an extension for the tail surfaces, a long afterbody similar to that of a seaplane float but long enough to carry the tail surfaces, and a third obtained by fitting a second step in the latter afterbody. The various combinations were tested in the NACA Tank by the general method over a suitable range of loadings. Fixed-trim tests were made for all speeds likely to be used and free-to-trim tests were made at low speeds to slightly beyond the hump speed. The characteristics of the hulls at best trim angles have been deduced from the data of the tests at fixed trim angles and are given in the form of nondimensional coefficients applicable to any size hull.
Flight tests were conducted on the OS2U-2 seaplane with simple circular-arc-type ailerons directly connected to the actuating torque tube. Two aileron test installations were made, differing only in the inclination of the projecting surface with the wing's upper surface. The lateral-control characteristics of the airplane were determined from data obtained in stalls and rudder-fixed aileron rolls. The revised ailerons were deficient in maximum rolling effectiveness, but were capable of controlling the rolling tendencies of the airplane near the stall.
Tests were conducted on hydrofoil assemblies approximating an arrangement for use under seaplanes or surface boats. A series of hydrofoils, each supported by two struts, was towed at various depths ranging from partial submersions to a depth of 5-chord lengths. At depths greater than 4 or 5 chords, the influence of the surface of the water is small; hydrofoils operating at low speed will have characteristics similar to those of airfoils of the same section.
Experiments with planing surfaces are fundamental, hydrodynamic researches for the purpose of obtaining the most favorable forms for planing boats, flying boats, and seaplane floats, with respect to water resistance and seaworthiness.
The present report deals with the processes accompanying the planing of a planing boat or a seaplane on water . The study is largely based upon theoretical investigations; mathematical problems and proofs are not discussed. To analyze theoreticaly actual planing processes, giving due consideration to all aspects of the problem, is probably not possible. The theories therefore treat various simple limiting cases, which in their entirety give a picture of the planing processes and enable the interpretation of the experimental results. The discussion is concerned with the stationary planing attitude: the boat planes at a constant speed V on an originally smooth surface.
The hydrodynamic characteristics of an aerodynamically refined planing-tail hull were determined from dynamic model tests in Langley tank no. 2. Stable take-off could be made for a wide range of locations of the center of gravity. The lower porpoising limit peak was high, but no upper limit was encountered. Resistance was high, being about the same as that of float seaplanes. A reasonable range of trims for stable landings was available only in the aft range of center-of-gravity locations.
This preliminary investigation was made to study the hydrodynamic properties and general behavior of simple hydrofoils. Six 5- by 30-inch plain, rectangular hydrofoils were tested in the NACA tank at various speeds, angles of attack and depths below the water surface. Two of the hydrofoils had sections representing the sections of commonly used airfoils, one had a section similar to one developed Guidoni for use with hydrofoil-equipped seaplane floats, and three had sections designed to have constant chordwise pressure distributions at given values of the lift coefficient for the purpose of delaying the speed at which cavitation begins. The experimental results are presented as curves of the lift and drag coefficients plotted against speed for the various angles of attack and depths for which the hydrofoils were tested. A number of derived curves are included for the purpose of better comparing the characteristics of the hydrofoils and to show the effects of depth. Several representative photographs show the development of cavitation on the the upper surface of the hydrofoils. The results indicate that properly designed hydrofoil sections will have excellent characteristics and that the speed at which cavitation occurs may be delayed to an appreciable extent by the use of suitable sections.
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A summary is given of the background and present status of pure-planing theory. Data for models having sharp chines have been obtained for a rectangular flat plate and two V-bottom surfaces having constant angles of dead rise of 20 degrees and 40 degrees and also for rectangular-flat-plate surfaces having very slightly rounded chines. The theory presented in NACA Technical Note 3233 for a rectangular flat plate is revised and extended to include triangular flat plates planing with base forward and V-shaped prismatic surfaces having a constant angle of dead rise, horizontal chine flare, or vertical chine strips. The agreement between the results calculated by the proposed theory and the experimental data is satisfactory for engineering calculations of lift and center-of-pressure location.
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Tank tests were made of a hull model of the Hughes-Kaiser cargo airplane for estimates of take-off performance and maximum gross load for take-off. At hump speeds, with the model free to trim, the trim and resistance were high, which resulted in a load-resistance ratio of approximately 4.0 for a gross load coefficient of 0.75. With a 4000,000-lb load, the full size craft may take off in 69 sec over a distance of 5600 ft.