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  Partner: UNT Libraries Government Documents Department
 Decade: 1930-1939
 Year: 1938
 Serial/Series Title: NACA Technical Notes
 Collection: Technical Report Archive and Image Library
The aerodynamic drag of five models of side floats N.A.C.A. Models 51-E, 51-F, 51-G, 51-H, 51-J

The aerodynamic drag of five models of side floats N.A.C.A. Models 51-E, 51-F, 51-G, 51-H, 51-J

Date: December 1, 1938
Creator: House, R O
Description: The drag of five models of side floats was measured in the N.A.C.A. 7- by 10-foot wind tunnel. The most promising method of reducing the drag of floats indicated by these tests is lowering the angle at which the floats are rigged. The addition of a step to a float does not always increase the drag in the flying range, floats with steps sometimes having lower drag than similar floats without steps. Making the bow chine no higher than necessary might result in a reduction in air drag because of the lower angle of pitch of the chines. Since side floats are used formally to obtain lateral stability when the seaplane is operating on the water at slow speeds or at rest, greater consideration can be given to factors affecting aerodynamic drag than is possible for other types of floats and hulls.
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Discharge characteristics of a simulated unit injection system

Discharge characteristics of a simulated unit injection system

Date: November 1, 1938
Creator: Marsh, Edred T
Description: Rate-of-discharge curves that show the discharge characteristics of an injection system having a very short fuel passage are presented. The rate of discharge closely follows the rate of displacement of the injection-pump plunger for open nozzles in which the maximum calculated pressures at the orifice do not exceed a certain value, which is dependent on the particular injection pump. With small orifices and high pump speeds, the rate of discharge does not follow the rate of plunger displacement because the higher discharge pressure results in increased leakage with corresponding decrease in discharge rate. The rate of discharge is not directly related to the rate of plunger displacement with automatic injection valves having closed nozzles. The types of pump check valve tested did not control the rate of cut-off or the discharge rate but they did affect the injection lag. Use of the short fuel passage eliminated the formation of secondary discharges.
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The drag of inflatable rubber de-icers

The drag of inflatable rubber de-icers

Date: October 1, 1938
Creator: Robinson, Russell G
Description: Force tests on rubber de-icer models of several different profiles, at approximately one-third full scale, been carried out in the NACA 8-foot high speed wind tunnel. The conventional de-icer installation, deflated, added about 15 percent to the smooth-wing drag and, inflated, added about 100 percent. An improved installation with flash attaching strips added about 10 percent, deflated. The bulging, or ballooning, of de-icers from the wing surface is described and some remedies are discussed.
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The effect of air-passage length on the optimum fin spacing for maximum cooling

The effect of air-passage length on the optimum fin spacing for maximum cooling

Date: May 1, 1938
Creator: Brevoort, Maurice J
Description: The effect on cooling of baffle length with optimum cylinder finning is discussed. Results from tests of several streamlined cylinders are given. It is shown that by employing several baffles the cooling can be increased several times.
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Effect of spark-timing regularity on the knock of engine performance

Effect of spark-timing regularity on the knock of engine performance

Date: May 1, 1938
Creator: Biermann, Arnold E
Description: Tests on a high-speed single-cylinder engine are described. The regularity of the spark timing was varied by driving the timer from different engine shafts. A simple and reasonably accurate method of determining the spark timing is described. The results show that irregular spark timing may cause large errors in tests of the knocking properties of fuels. For the engine tested, it was found that a change of one crankshaft degree in spark restart was equivalent to an 0.85 inch Hg change in allowable inlet pressure.
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The effects of partial-span plain flaps on the aerodynamic characteristics of a rectangular and a tapered Clark Y wing

The effects of partial-span plain flaps on the aerodynamic characteristics of a rectangular and a tapered Clark Y wing

Date: September 1, 1938
Creator: House, R O
Description: An investigation was made to determine the aerodynamic characteristics of tapered and rectangular wings with partial-span plain flaps. Two Clark Y airfoils equipped with center section and with tip-section flaps were tested. The results showed that the aerodynamic characteristics of partial-span plain flaps were, in general, similar to those of split flaps of the same span, but that the lift and the drag were less for the wing with plain flaps than for the wing with split flaps of comparable size. For the rectangular wing with center-section plain flaps, the maximum lift and the lift-drag ratio at maximum lift were greater and the drag at maximum lift was less than for the wing with tip-section plain flaps of the same size. The maximum lift of the tapered wing varied in the same manner as that of the rectangular wing but the drag and the lift-drag-ratio relationship were opposite.
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Engine performance and knock rating of fuels for high-output aircraft engines

Engine performance and knock rating of fuels for high-output aircraft engines

Date: April 1, 1938
Creator: Rothbrock, A M & Biermann, Arnold E
Description: Data are presented to show the effects of inlet-air pressure, inlet-air temperature, and compression ratio on the maximum permissible performance obtained on a single-cylinder test engine with aircraft-engine fuels varying from a fuel of 87 octane number to one 100 octane number plus 1 ml of tetraethyl lead per gallon. The data were obtained on a 5-inch by 5.75-inch liquid-cooled engine operating at 2,500 r.p.m. The compression ratio was varied from 6.50 to 8.75. The inlet-air temperature was varied from 120 to 280 F. and the inlet-air pressure from 30 inches of mercury absolute to the highest permissible. The limiting factors for the increase in compression ratio and in inlet-air pressure was the occurrence of either audible or incipient knock. The data are correlated to show that, for any one fuel,there is a definite relationship between the limiting conditions of inlet-air temperature and density at any compression ratio. This relationship is dependent on the combustion-gas temperature and density relationship that causes knock. The report presents a suggested method of rating aircraft-engine fuels based on this relationship. It is concluded that aircraft-engine fuels cannot be satisfactorily rated by any single factor, such as octane number, highest useful compression ratio, or allowable ...
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The estimation of the rate of change of yawing moment with sideslip

The estimation of the rate of change of yawing moment with sideslip

Date: February 1, 1938
Creator: Imlay, Frederick H
Description: Wind-tunnel data are presented on the rate of change of yawing moment with sideslip for tests of 9 complete airplane models, 20 fuselage shapes, and 3 wing models with various combinations of dihedral, sweepback, and twist. The data were collected during a survey of existing information, which was made to find a reliable method of computing the yawing moment due to sideslip. Important errors common to methods of computation used at present appear to be due to large interference effects, the investigation of which will undoubtedly require an extensive program of systematic wind-tunnel tests. At present it is necessary to place considerable reliance on past design experience in proportioning an airplane so as to obtain a reasonable degree of directional stability.
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Fatigue testing of wing beam by the resonance method

Fatigue testing of wing beam by the resonance method

Date: August 1, 1938
Creator: Bleakney, William M
Description: Preliminary fatigue tests on two aluminum-alloy wing-beam specimens subjected to reversed axial loading are described. The motion used consists in incorporating one or two reciprocating motors in a resonance system of which the specimen is the spring element. A description is given of the reciprocating motors, and of the method of assembling and adjusting the vibrating system. The results indicate that the method is well adapted to fatigue tests of not only uniform wing beams but also wing beams with asymmetrical local reinforcements.
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Flight and wind-tunnel tests of an XBM-1 dive bomber

Flight and wind-tunnel tests of an XBM-1 dive bomber

Date: April 1, 1938
Creator: Donely, Philip & Pearson, Henry A
Description: Results are given of pressure-distribution measurements made in flight over the right wing cellule and the right half of the horizontal tail surfaces of a dive-bombing biplane. Simultaneous measurements were also taken of the air speed, control-surface positions, control forces, and normal accelerations during various abrupt maneuvers in vertical plane. These maneuvers consisted of push-downs and pull-ups from level flight, dives and dive pull-ups from inverted flight. Besides the pressure measurements, flight tests were made to obtain (1) wing-fabric deflections during dives and (2) variation of the minimum drag coefficient with Reynolds Number. Supplementary tests were also done in the full-scale wind tunnel to obtain the characteristics of the airplane under various propeller conditions and with various tail settings. The results indicate that: (1) by increasing the fabric deflection between pressure ribs, the span load distribution was considerably modified near the center and the wing moment relations were changed; and (2) the minimum drag was less for the idling propeller than for the propeller locked in a vertical position. The value of C(sub D sub min) was equal to K(Reynolds Number)(exp -0.03) for a range from 2,800,000 to 13,100,000.
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A flight investigation of the reduction of aileron operating force by means of fixed tabs and differential linkage, with notes on linkage design

A flight investigation of the reduction of aileron operating force by means of fixed tabs and differential linkage, with notes on linkage design

Date: June 1, 1938
Creator: Soule, H A & Hootman, James A
Description: Flight tests were made to demonstrate the particularity of employing fixed tabs in conjunction with a suitably designed differential linkage to reduce the force required to operate ailerons. The tests showed the system to be practicable with tabs of the inset type. The relative ineffectiveness of attached tabs for changing the aileron floating angle rendered them unsuitable. Experience gained in the investigation has indicated that the use of the system is limited to maximum deflections of one aileron relative to the other of less than 30 degrees and that the differential linkage should always be designed on the basis of the highest probable floating angle.
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Flow observations with tufts and lampblack of the stalling of four typical airfoil sections in the NACA variable-density tunnel

Flow observations with tufts and lampblack of the stalling of four typical airfoil sections in the NACA variable-density tunnel

Date: October 1, 1938
Creator: Abbott, Ira H & Sherman, Albert
Description: A preliminary investigation of the stalling processes of four typical airfoil sections was made over the critical range of the Reynolds Number. Motion pictures were taken of the movements of small silk tufts on the airfoil surface as the angle of attack increased through a range of angles including the stall. The boundary-layer flow also at certain angles of attack was indicated by the patterns formed by a suspension of lampblack in oil brushed onto the airfoil surface. These observations were analyzed together with corresponding force-test measurements to derive a picture of the stalling processes of airfoils.
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Free-spinning wind-tunnel tests of a low-wing monoplane with systematic changes in wings and tails III : mass distributed along the wings

Free-spinning wind-tunnel tests of a low-wing monoplane with systematic changes in wings and tails III : mass distributed along the wings

Date: September 1, 1938
Creator: Seidman, Oscar & NEIHOUSE A I
Description: None
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Fuel consumption of a carburetor engine at various speeds and torques

Fuel consumption of a carburetor engine at various speeds and torques

Date: June 1, 1938
Creator: Schey, Oscar W & Clark, J Denny
Description: An investigation was conducted to obtain fuel-consumption curves for a single-cylinder engine with a Wright 1820-G and Pratt & Whitney 1340-H cylinder at varying speeds, manifold pressures, and air-fuel ratios. The 1340- H cylinder was tested at speeds from 1,200 to 2,400 r.p.m. and at manifold pressures from 21 to 38 inches of mercury absolute. Less than extensive tests were made of the 1820-G cylinder. The results of the tests showed that the minimum brake fuel consumption was obtained when the engines were operating at high torques and at speeds from 60 to 70 percent of the rated speed. The fuel consumption increased at an increasing rate as the torque was reduced; and, at 45 percent of maximum torque, the fuel consumption was 20 percent higher than at maximum torque when the engines were operating at 70 percent of rated speed. Minimum specific fuel consumption was obtained at the same air-fuel ratio regardless of compression ratio. No improvement in fuel consumption was obtained when mixtures leaner than an air-fuel ratio of 15.5 were used. The leanest mixture ratio on which the engine with the 1340-H cylinder would operate smoothly was 18.5 and the spark advance for maximum power with this ...
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A general tank test of a model of the hull of the Pem-1 flying boat including a special working chart for the determination of hull performance

A general tank test of a model of the hull of the Pem-1 flying boat including a special working chart for the determination of hull performance

Date: December 1, 1938
Creator: Dawson, John R
Description: The results of a general tank test of a 1/6 full-size model of the hull of the Pem-1 flying boat (N.A.C.A. model 18) are given in non-dimensional form. In addition to the usual curves, the results are presented in a new form that makes it possible to apply them more conveniently than in the forms previously used. The resistance was compared with that of N.A.C.A. models 11-C and 26(Sikorsky S-40) and was found to be generally less than the resistance of either.
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Generalized analysis of experimental observations in problems of elastic stability

Generalized analysis of experimental observations in problems of elastic stability

Date: July 1, 1938
Creator: Lundquist, Eugene E
Description: A generalized method of analyzing experimental observations in problems of elastic stability is presented in which the initial readings of load and deflection may be taken at any load less the critical load. The analysis is an extension of a method published by Southwell in 1932, in which it was assumed that the initial readings are taken at zero load.
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Gyroscopic instruments for instrument flying

Gyroscopic instruments for instrument flying

Date: September 1, 1938
Creator: Brombacher, W G & Trent, W C
Description: The gyroscopic instruments commonly used in instrument flying in the United States are the turn indicator, the directional gyro, the gyromagnetic compass, the gyroscopic horizon, and the automatic pilot. These instruments are described. Performance data and the method of testing in the laboratory are given for the turn indicator, the directional gyro, and the gyroscopic horizon. Apparatus for driving the instruments is discussed.
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Hydrodynamic and aerodynamic tests of four models of outboard floats : (N.A.C.A. models 51-A, 51-B, 51-C, and 51-D)

Hydrodynamic and aerodynamic tests of four models of outboard floats : (N.A.C.A. models 51-A, 51-B, 51-C, and 51-D)

Date: December 1, 1938
Creator: Dawson, John R & Hartman, Edwin P
Description: Four models of outboard floats (N.A.C.A. models 51-A, 51-B, 51-C, and 51-D) were tested in the N.A.C.A. tank to determine their hydrodynamic characteristics and in the 20-foot wind tunnel to determine their aerodynamic drag. The results of the tests, together with comparisons of them, are presented in the form of charts. From the comparisons, the order of merit of the models is estimated for each factor considered. The best compromise between the various factors seems to be given by model 51-D. This model is the only one in the series with a transverse step.
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Hydrodynamic and aerodynamic tests of models of floats for single-float seaplanes NACA models 41-D, 41-E, 61-A, 73, and 73-A

Hydrodynamic and aerodynamic tests of models of floats for single-float seaplanes NACA models 41-D, 41-E, 61-A, 73, and 73-A

Date: July 1, 1938
Creator: Parkinson, J B & HOUSE R O
Description: Tests were made in the NACA tank and in the NACA 7 by 10 foot wind tunnel on two models of transverse step floats and three models of pointed step floats considered to be suitable for use with single float seaplanes. The object of the program was the reduction of water resistance and spray of single float seaplanes without reducing the angle of dead rise believed to be necessary for the satisfactory absorption of the shock loads. The results indicated that all the models have less resistance and spray than the model of the Mark V float and that the pointed step floats are somewhat superior to the transverse step floats in these respects. Models 41-D, 61-A, and 73 were tested by the general method over a wide range of loads and speeds. The results are presented in the form of curves and charts for use in design calculations.
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Hydrodynamic and aerodynamic tests of models of flying-boat hulls designed flow aerodynamic drag - NACA models 74, 74-A, and 75

Hydrodynamic and aerodynamic tests of models of flying-boat hulls designed flow aerodynamic drag - NACA models 74, 74-A, and 75

Date: October 1, 1938
Creator: Truscott, Starr; Parkinson, J B; Ebert, John W , Jr & Valentine, E Floyd
Description: The present tests illustrate how the aerodynamic drag of a flying boat hull may be reduced by following closely the form of a low drag aerodynamic body and the manner in which the extent of the aerodynamic refinement is limited by poorer hydrodynamic performance. This limit is not sharply defined but is first evidenced by an abnormal flow of water over certain parts of the form accompanied by a sharp increase in resistance. In the case of models 74-A and 75, the resistance (sticking) occurs only at certain combinations of speed, load, and trim and can be avoided by proper control of the trim at high water speeds. Model 75 has higher water resistance at very high speeds than does model 74-A. With constant speed propellers and high takeoff speeds, it appears that the form of model 75 would give slightly better takeoff performance. Model 74-A, however, has lower aerodynamic drag than does model 75 for the same volume of hull.
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Improvement of aileron effectiveness by the prevention of air leakage through the hinge gap as determined in flight

Improvement of aileron effectiveness by the prevention of air leakage through the hinge gap as determined in flight

Date: January 1, 1938
Creator: Soule, H A & Gracey, W
Description: A flight investigation was made of the increase in effectiveness of ailerons that can be obtained by preventing flow of air through the wing at the hinges and of the possibility of reducing the aileron operating force by replacing ailerons having normal open hinge gaps with narrower but equally effective ailerons having sealed hinge gaps. Tests were made with a Fairchild 22 airplane with two sizes of plain unbalanced ailerons, one set having a chord equal to 0.18c, and the other chord equal to 0.09c. The results of the investigation show that improvement of the lateral-control effectiveness is obtained by completely preventing the flow of air through the wing at the hinge axis of conventional ailerons. The magnitude of the improvement depends on the aileron chord. For the 0.18c ailerons the gain in aileron effectiveness due to sealing the gap at the hinge axis was of the order of one-fifth and for the 0.09c ailerons the gain was about one-third. The importance of sealing the gap was demonstrated by the fact that the 0.09c ailerons with a slight increase in deflection range were made as effective as the 0.18c ailerons with an unsealed gap but required only about one-third as ...
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The increase in frictional resistance caused by various types of rivet heads as determined by tests of planing surfaces

The increase in frictional resistance caused by various types of rivet heads as determined by tests of planing surfaces

Date: May 1, 1938
Creator: Truscott, Starr & Parkinson, J B
Description: The increase in the frictional resistance of a surface caused by the presence of rivet heads was determined by towing four planing surfaces of the same dimensions. One surface was smooth and represented a surface without rivet heads or one with perfectly flush countersunk rivets. The other three surfaces were each fitted with the same number of full-size rivet heads but of a different type arranged in the same pattern on each surface. The surfaces were towed at speeds representative of the high water speeds encountered by seaplanes during take-off and the range of Reynolds Number covered by the test was from 4 x 10(exp 6) to 18 x 10(exp 6). The rivet heads investigated were oval countersunk, brazier, and round for rivets having shanks 5/32 inch in diameter. The oval countersunk heads were sunk below the surface by dimpling the plating around them. The results of the tests showed that, for the rivet heads investigated, the increase in the friction coefficient of the surface is directly proportional to the height of the rivet head. The order of merit in regard to low resistance is flush countersunk, oval countersunk (whether sunk below the surface or not), brazier, and round.
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Interference of wing and fuselage from tests of 17 combinations in the NACA variable-density tunnel combination with special junctures

Interference of wing and fuselage from tests of 17 combinations in the NACA variable-density tunnel combination with special junctures

Date: March 1, 1938
Creator: Sherman, Albert
Description: As part of the wing-fuselage interference program in progress in the NACA variable-density wind tunnel, a method of eliminating the interference bubble associated with critical mid wing combinations was investigated. The interference bubble of the critical mid wing combination was shown to respond to modification at the nose of the juncture and to be entirely suppressed with little or no adverse effect on the high-speed drag by special leading edge fillets.
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Interference of wing and fuselage from tests of eight combinations in the NACA variable-density tunnelcombinations with tapered fillets and straight-side junctures

Interference of wing and fuselage from tests of eight combinations in the NACA variable-density tunnelcombinations with tapered fillets and straight-side junctures

Date: March 1, 1938
Creator: Sherman, Albert
Description: The round fuselage of an unfilleted low-wing combination was modified to incorporate straight-side junctures. The resulting combination, with or without horizontal tail surfaces, had practically the same aerodynamic characteristics as the corresponding round-fuselage tapered-fillet combination.
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