Description: The fundamental principles of fluid flow, pressure losses, and heat transfer have been presented and analyzed for the case of a smooth tube with fully developed turbulent flow. These equations apply to tubes with large length-diameter ratios where the f1ow is at a high Reynolds Number. The error introduced by using these equations increases as the magnitude of the tube length and the air-flow Reynolds Number approaches the values encountered in modern radiator designs. Accordingly, heat-transfer tests on radiator sections were made and the results are presented in nondimensional form to facilitate their use and for comparison with other heat-transfer data. In addition, pressure losses were measured along smooth tubes of circular, square, and rectangular cross section and the results were also correlated and are presented in nondimensional form. The problem of a radiator design for a particular installation is solved, the experimental heat-transfer and pressure-loss data being used, on a basis of power chargeable to the radiator for form drag, for propelling the weight, and for forcing the air through the radiator. The case of an installation within a wing or an engine nacelle is considered. An illustration of radiator design is carried through for an arbitrary set of ...

Description: A method that utilizes the Doppler effect on radio signals for determining the speed of an airplane and the distance traveled by the airplane has been developed and found to operate satisfactorily. In this method, called the NACA radio ground-speed system, standard readily available radio equipment is used almost exclusively and extreme frequency stability of the transmitters is not necessary. No complicated equipment need be carried in the airplane, as the standard radio transmitter is usually adequate. Actual flight tests were made in which the method was used and the results were consistent with calibrated air speed indications and stop-watch measurements. Inasmuch as the fundamental accuracy of the radio method is far better than either of the checking systems used, no check was made on the limitations of the accuracy.

Description: An investigation was made in the LWAL 7- by 10-foot tunnel of internally balanced, sealed ailerons for the Curtiss XP-60 airplane. Ailerons with tabs and. with various amounts of balance were tested. Stick forces were estimated for several aileron arrangements including an arrangement recommended for the airplane. Flight tests of the recommended arrangement are discussed briefly in an appendix, The results of the wind-tunnel and flight tests indicate that the ailerons of large or fast airplanes may be satisfactorily balanced by the method developed.

Description: As an aid to airplane designers interested in providing pursuit airplanes with decelerating devices intended to increase the firing time when overtaking another airplane, formulas are given relating the pertinent distances and speeds in horizontal flight to the drag increase required. Charts are given for a representative parasite-drag coefficient from which the drag increase, the time gained, and the closing distance may be found. The charts are made up for three values of the ratio of the final speed of the pursuing airplane to the speed of the pursued airplane and for several values of the ratio of the speed of the pursued airplane to the initial speed of the pursuing airplane. Charts are also given indicating the drag increases obtainable with double split flaps and with conventional propellers. The use of the charts is illustrated by an example in which it is indicated that either double split flaps or, under certain ideal conditions, reversible propellers should provide the speed reductions required.

Description: Wing ducts for liquid-cooled engine radiators have been investigated in the N.A.C.A. full-scale wind tunnel on a large model airplane. The tests were made to determine the relative merits of several types of duct and radiator installations for an airplane of a particular design. In the test program the principal duct dimensions were systematically varied, and the results are therefore somewhat applicable to the general problems of wing duct design, although they should be considered as preliminary and only indicative of the inherent possibilities.