Report presenting equations for calculating the stick-force characteristics obtained with a spring-tab type of elevator control. The main problems encountered in the design of the satisfactory elevator spring tab are to provide stick forces in the desired range, to maintain the force per g sufficiently constant throughout the speed range, to avoid undesirable "feel" of the control in ground handling, and to prevent flutter.

Report presenting a survey of the technical information contained in the literature on the subject of lubrication, friction, and wear of aircraft engine piston rings.

"An analysis is made to simplify pressure-drop calculations for nonadiabatic and adiabatic friction flow of air in smooth cylindrical tubes when the density changes due to heat transfer and pressure drop are appreciable. Solutions of the equation of motion are obtained by the use of Reynolds' analogy between heat transfer and skin friction. Charts of the solutions are presented for making pressure-drop calculations" (p. 1).

From Summary: "Local-instability tests of 24S-T aluminum-alloy formed Z- and channel-section columns were made in order to determine a length of test specimen that would avoid the increased strength associated with short lengths and also permit the occurrence of a convenient buckling pattern. The effect of column length on the critical compressive stress, on the average stress at maximum load, and on the number of half-waves of the buckling pattern is shown."

Report presenting testing to determine the best way to land the B-25 airplane in calm and rough water and to determine its probable ditching performance. By landing with flaps down in a tail-down attitude at as slow a speed as possible, smooth straight landing runs will probably result in calm water. Results regarding the effect of attitude, effect of flap setting, effect of simulated damage, effect of propellers, and effect of seaway are provided.

Report presenting the application of transient theory to the rational determination of dynamic loads on airplane structures during initial landing impact. Simplified procedures are described by which the distribution of the maximum attainable value of the dynamic stresses in the structure may be obtained.

Report discussing the knock-limited performance of blends of triptane and 28-R fuel in an F-4 engine at three sets of conditions and three compression ratios. The knock limits of the triptane blends were more sensitive to compression ratio than the 28-R fuel, and the sensitivities of the blends increased as the severity of other engine conditions increased.

Report presenting an investigation made on a supercharged CFR engine to determine a method for estimating lead susceptibilities of pure or blended paraffinic fuels. As a result of these studies, a chart consisting of a series of straight lines passing through the origin was developed to represent the lead susceptibilities of pure and blended paraffinic fuels in terms of knock-limited indicated mean effective pressures and octane numbers.

Report presenting an investigation of the relation between the knock limit and the blend composition of aviation fuels when tested under supercharged conditions in an air-cooled aircraft-engine cylinder. Results regarding the blending characteristics of two gasolines, paraffinic fuels, olefinic fuel, naphthenic fuel, aromatic fuels, when xylidines are present in the fuel components, and fuel components containing unequal concentrations of tetraethyl lead are provided.

Report presenting flight tests to determine the longitudinal stability characteristics of a pursuit airplane when flown with and without an experimental bellows-type bob weight. When the weight was installed, the stick-free static stability remained approximately constant irrespective of the shift in center of gravity resulting from a change in fuel quantity in the auxiliary fuselage fuel tank. Although the weight functioned satisfactorily, the performance could have been enhanced by the reduction of the friction in the mechanism.

Report presenting the use of the Ackeret iteration process to obtain higher approximations than that of Prandtl and Glauert for the flow of a compressible fluid past a circular arc profile. The procedure is to expand the velocity potential in a power series of the camber coefficient.

Report presenting an investigation of the icing and de-icing characteristics of a Pratt & Whitney R-1830 engine induction system. The current report covers a program to determine the most effective rate and method of injection of de-icing fluid to remove a heavy ice formation from the induction system. Results regarding the flow rates, recovery times, de-icing portions of the runs, and ice formation characteristics are provided.

Report presenting an investigation of underslung cooling-air ducts in various locations on a model of a typical single-engine tractor airplane in the full-scale tunnel. The report contains the results of tests of two forward underslung ducts. Results regarding pressure recoveries at the radiator, pressures behind the radiator, drag and duct efficiency, and critical speeds are provided.

"The theory of heat.transfer from a solid body to a liquid stream could he presented previously only with limiting assumptions about the movement of the fluid (potential flow, laminar frictional flow). (See references 1, 2, and 3). For turbulent flow, the most important practical case, the previous theoretical considerations did not go beyond dimensionless formulas and certain conclusions as to the analogy between the friction factor and the unit thermal conductance, (See references 4, 5, 6, and 7,) In order to obtain numerical results, an experimental treatment of the problem was resorted to, which gave rise to numerous investigations because of the importance of this problem in many branches of technology" (p. 1).

"The lubrication of a piston ring is treated as though the ring were a rigid slider of finite width. An expression is obtained for pressure distribution which takes into account the effect of oil leakage from the ends of the ring and which has the convenient form of an end correction to the pressure-distribution formula for an infinite slider. The important formulas are summarized for convenience and two examples are included of their use in finding the pressure pattern over wide sliders" (p. 1).

Report presenting problems relating to the stability and control of tailless airplanes in consideration of contemporary experience and practice. Some observations in regards to small and large airplanes are provided.

"In the present part I of a series of reports on the inward bulge type buckling of monocoque cylinders the buckling load in combined bending and compression is first derived. Next the reduction in the buckling load because of a nonlinear direct stress distribution is determined. In experiments nonlinearity may result from an inadequate stiffness of the end attachments in actual airplanes from the existence of concentrated loads or cut-outs" (p. 1).

This paper is the second part of a series of reports on the inward bulge type buckling of monocoque cylinders. It presents the results of an experimental investigation of buckling in combined bending and compression. In the investigation it was found that the theory developed in part I of the present series predicts the buckling load in combined bending and compression with the same degree of accuracy as the older theory does in pure bending.

Report presenting knock-limited small-scale-engine tests of tulene, ethylbenzene, p-xylene blended individually in various concentrations with selected base fuels. Data was obtained for the aromatics to determine the blending sensitivity, the lead susceptibility, and the sensitivity of blends to inlet-air temperature.

Report presenting testing on a Chandler-Evans 1900 CPB-3 carburetor mounted on a Pratt & Whitney R-1830-C4 intermediate rear engine section to find the limiting conditions for no icing, icing that would not affect engine operation (visible icing), and icing that would affect engine operation. Results regarding classification and location of ice formations, effect of icing on fuel-air ratio, and ways to limit icing conditions are provided.

Report presenting icing tests on a Bendix-Stromberg PD-12F5 carburetor mounted on a Pratt & Whitney R-1830-C4 intermediate rear engine section. Limiting icing conditions were established for simulated cruising power and simulated rated power over a range of carburetor-air temperatures, and relative humidities are provided.

"Measurements have been made, in flight, of the concentration of free water present in clouds under conditions of icing. These show the beneficial effect of kinetic heating in reducing the severity of those conditions, and permit the functioning of the thermal system for protecting airplanes against ice to be analyzed. The concentration of free water is deduced from measurements of the humidity of the air after the water had been vaporized" (p. 1).

Report presenting charts and formulas in convenient form for use in the computation of the effects of propellers on stability. Formulas are given for the contributions of the direct propeller forces to the airplane pitching moment, yawing moment, and shift in neutral point due to power.

Preignition-limited performance data were obtained on a supercharged CFR engine at two sets of operating conditions over a wide range of fuel-air ratios to determine the preignition characteristics for the following five fuels: s-3 reference fuel, s-3 plus 4 ml. tel per gallon, afd-33(140-p), benzene, and diisobutylene. Maximum thermal-plug temperatures at constant intake-air pressures were also determined to correlate the preignition characteristics of each fuel with its ability to increase general engine-temperature levels. Additional runs were made to compare the preignition-limited performance of triptane, triptane plus 4 ml. tel per gallon, and an-f-28r fuel.