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Experiments with an airfoil model on which the boundary layers are controlled without the use of supplementary equipment

Description: This report describes test made in the Variable Density Wind Tunnel of the NACA to determine the possibility of controlling the boundary layer on the upper surface of an airfoil by use of the low pressure existing near the leading edge. The low pressure was used to induce flow through slots in the upper surface of the wing. The tests showed that the angle of attack for maximum lift was increased at the expense of a reduction in the maximum lift coefficient and an increase in the drag coefficient.
Date: April 1, 1931
Creator: Abbott, I H
Partner: UNT Libraries Government Documents Department

Fuselage-drag tests in the variable-density wind tunnel: streamline bodies of revolution, fineness ratio of 5

Description: Results are presented of the drag tests of six bodies of revolution with systematically varying shapes and with a fineness ratio of 5. The forms were derived from source-sink distributions, and formulas are presented for the calculation of the pressure distribution of the forms. The tests were made in the N.A.C.A. variable-density tunnel over a range of values of Reynolds number from about 1,500,000 to 25,000,000. The results show that the bodies with the sharper noses and tails have the lowest drag coefficients, even when the drag coefficients are based on the two-thirds power of the volume. The data shows the most important single characteristic of the body form to be the tail angle, which must be fine to obtain low drag.
Date: September 1, 1937
Creator: Abbott, Ira H
Partner: UNT Libraries Government Documents Department

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

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.
Date: October 1, 1938
Creator: Abbott, Ira H & Sherman, Albert
Partner: UNT Libraries Government Documents Department

A simplified method for the calculation of airfoil pressure distribution

Description: A method is presented for the rapid calculation of the pressure distribution over an airfoil section when the normal-force distribution and the pressure distribution over the "base profile" (i.e., the profile of the same airfoil were the camber line straight and the resulting airfoil at zero angle of attack) are known. This note is intended as a supplement to N.A.C.A. Report Nos. 631 and 634 wherein methods are presented for the calculation of the normal-force distribution over plain and flapped airfoils, respectively, but not of the pressures on the individual surfaces. Base-profile pressure-coefficient distributions for the usual N.A.C.A. family of airfoils, which are also suitable for several other commonly employed airfoils, are included in tabular form. With these tabulated base-profile pressures and the computed normal-force distributions, pressure distributions adequate for most engineering purposes can be obtained.
Date: May 1, 1939
Creator: Allen, H Julian
Partner: UNT Libraries Government Documents Department

Tank tests of Model 36 flying boat hull

Description: N.A.C.A. Model 36, a hull form with parallel middle body for half the length of the forebody and designed particularly for use with stub wings, was tested according to the general fixed-trim method over the range of practical loads, trims, and speeds. It was also tested free to trim with the center of gravity at two different positions. The results are given in the form of nondimensional coefficients. The resistance at the hump was exceptionally low but, at high planing speeds, afterbody interference made the performance only mediocre.
Date: March 1, 1938
Creator: Allison, John
Partner: UNT Libraries Government Documents Department

Tank tests of a model of one hull of the Savoia S-55-X flying boat -N.A.C.A. Model 46

Description: A model of one of the twin hulls of the Italian Savoia S-55-X flying boat (N.A.C.A. Model 46) was tested in the N.A.C.A. tank according to the general method. The data obtained from these tests cover a broad range of speeds, loads, and trims and are given in nondimensional form to facilitate their use in applying this form of hull to any other flying boat or comparing it's performance with the performance of any other hulls. The results show that the resistance characteristics at best trim of this model are excellent throughout the speed range. In order to compare the performance of the S-55-X hull with that of the 35, a pointed-step hull developed at the N.A.C.A. tank, the data are used in the computations of take-off example of a twin-hull, 23,500-pound flying boat. The calculations show that the S-55-X hull has better take-off performance.
Date: February 1, 1938
Creator: Allison, John M
Partner: UNT Libraries Government Documents Department

Tanks test of a model of the hull of the Navy PB-1 flying boat - N.A.C.A. Model 52

Description: A model of the hull of the Navy PB-1 flying boat was tested in the N.A.C.A. tank as part of a program intended to provide information regarding the water performance of hulls of flying boats of earlier design for which hydrodynamic data have heretofore been unavailable. Tests were made according to the general method over the range of practical loadings with the model both fixed in trim and free to trim. A free-to-trim test according to the specific method was also made for the design load and take-off speed corresponding to those of the full-scale flying boat. The resistance obtained from the fixed-trim test was found to be about the same as that of the model of the NC flying-boat hull, and greater at the hump but smaller at high speeds than that of a model of the Sikorsky S-40 flying-boat hull.
Date: August 1, 1936
Creator: Allison, John M
Partner: UNT Libraries Government Documents Department

Tank tests of models of flying boat hulls having longitudinal steps

Description: Four models with longitudinal steps on the forebody were developed by modification of a model of a conventional hull and were tested in the National Advisory Committee for Aeronautics (NACA) tank. Models with longitudinal steps were found to have smaller resistance at high speed and greater resistance at low speed than the parent model that had the same afterbody but a conventional V-section forebody. The models with a single longitudinal step had better performance at hump speed and as low high-speed resistance except at very light loads. Spray strips at angles from 0 degrees to 45 degrees to the horizontal were fitted at the longitudinal steps and at the chine on one of the two step models having two longitudinal steps. The resistance and the height of the spray were less with each of the spray strips than without; the most favorable angle was found to lie between 15 degrees and 30 degrees.
Date: July 1, 1936
Creator: Allison, John M & Ward, Kenneth E
Partner: UNT Libraries Government Documents Department

The Effect of the Angle of Afterbody Keel on the Water Performance of a Flying-Boat Hull Model

Description: NACA model 11-C was tested according to the general method with the angle of afterbody keel set at five different angles from 2-1/2 degrees to 9 degrees, but without changing other features of the hull. The results of the tests are expressed in curves of test data and of non-dimensional coefficients. At the depth of step used in the tests, 3.3 percent beam, the smaller angles of afterbody keel give greater load-resistance ratios at the hump speed and smaller at high speed than the larger angles of afterbody keel. Comparisons are made of the load-resistance ratios at several other points in the speed range. The effect of variation of the angle of afterbody keel upon the take-off performance of a hypothetical flying boat of 15,000 pounds gross weight having a hull of model 11-C lines is calculated, and the calculations show that the craft with the largest of the angles of afterbody keel tested, 9 degrees, takes off in the least time and distance.
Date: September 1, 1935
Creator: Allison, John M.
Partner: UNT Libraries Government Documents Department

The aerodynamic characteristics of six commonly used Airfoils over a large range of positive and negative angles of attack

Description: From Summary: "This paper presents the results of tests of six commonly used airfoils: the CYH, the N-22, the C-72, the Boeing 106, and the Gottingen 398. The lifts, drags, and pitching moments of the airfoils were measured through a large range of positive and negative angles of attack. The tests were made in the variable density wind tunnel of the National Advisory Committee for Aeronautics at a large Boeing 106, and the Gottingen 398 airfoils, the negative maximum lift coefficients were found to be approximately half the positive; but for the M-6 and the CYH, which have less effective values were, respectively, 0.8 and 0.6 of the positive values."
Date: November 1931
Creator: Anderson, Raymond F
Partner: UNT Libraries Government Documents Department

The aerodynamic characteristics of three tapered airfoils tested in the variable density wind tunnel

Description: From Summary: "This report contains the lift, drag, and moment characteristics of tapered Clark Y, Gottingen 393, and USA 45 airfoils as obtained from tests made in the Variable Density Wind Tunnel of the NACA. The results are given at both low and high Reynolds Numbers to show scale effect and to provide data for use in airplane design."
Date: February 1931
Creator: Anderson, Raymond F
Partner: UNT Libraries Government Documents Department

Charts for determining the pitching moment of tapered wings with sweepback and twist

Description: This report presents a convenient method for calculating the pitching-moment characteristics of tapered wings with sweepback and twist. The method is based on the fact that the pitching-moment characteristics of a wing may be specified by giving the value of the pitching moment at zero lift and the location of the axis about which the axis is constant. Data for calculating these characteristics are presented by curves which apply to wings having a linear distribution of twist along the span and which cover a large range of aspect ratios. The curves are given for wings having straight taper and distorted elliptical plan forms. The characteristics of wings of other shapes may be determined by interpolation.
Date: December 1, 1933
Creator: Anderson, Raymond F
Partner: UNT Libraries Government Documents Department

A comparison of several tapered wings designed to avoid tip stalling

Description: Optimum proportions of tapered wings were investigated by a method that involved a comparison of wings designed to be aerodynamically equal. The conditions of aerodynamic equality were equality in stalling speed, in induced drag at a low speed, and in the total drag at cruising speed. After the wings were adjusted to aerodynamic equivalence, the weights of the wings were calculated as a convenient method of indicating the optimum wing. The aerodynamic characteristics were calculated from wing theory and test data for the airfoil sections. Various combinations of washout, camber increase in the airfoil sections from the center to the tips, and sharp leading edges at the center were used to bring about the desired equivalence of maximum lift and center-stalling characteristics. In the calculation of the weights of the wings, a simple type of spar structure was assumed that permitted an integration across the span to determine the web and the flange weights. The covering and the remaining weight were taken in proportion to the wing area. The total weights showed the wings with camber and washout to have the lowest weights and indicated the minimum for wings with a taper ratio between 1/2 and 1/3.
Date: June 1, 1939
Creator: Anderson, Raymond F
Partner: UNT Libraries Government Documents Department

Tests of three tapered airfoils based on the N.A.C.A. 2200, the N.A.C.A.-M6, and the Clark Y sections

Description: Three tapered airfoils based on the N.A.C.A. 2200, the N.A.C.A.-M6, and the Clark Y sections were tested in the variable-density wind tunnel at a Reynolds Number of approximately 3,100,000. The models, which were of aspect ratio 6, had constant core center sections and rounded tips, and tapered in thickness from 18 percent at the roots to 9 percent at the tips. The aerodynamic characteristics are given by the usual dimensionless coefficients plotted for both positive and negative angles of attack and by effective profile-drag coefficients plotted against lift coefficients.
Date: January 1, 1934
Creator: Anderson, Raymond F
Partner: UNT Libraries Government Documents Department

An investigation of cotton for parachute cloth

Description: This is a resume of the work of the Bureau of Standards on a cotton parachute cloth for use as a substitute for silk in the event of an emergency curtailing the supply. Cotton yarn of high strength in proportion to its weight and otherwise specially suitable for parachute cloth was developed. Cloth woven from this yarn in the bureau mill was equal or superior to parachute silk in strength and tear resistance, met the requirements with respect to air permeability, and weighed only a few tenths of an ounce per square yard more than the silk cloth. Practical trials of cotton parachutes carried out by the Navy Department clearly indicate that the cotton parachute closely approaches the silk parachute in performance as to rate of descent, opening time, strength and ability to function when stored in the pack for sixty days. The increase in weight of the equipment resulting from the use of cotton cloth instead of silk is considered to be well within practicable limits. A specification for cotton parachute cloth and the way in which the requirements of the specification have been met are given. Cotton yarns suitable for parachute cloth are now being woven commercially in the United States.
Date: September 1, 1931
Creator: Appel, Wm D & Worner, R K
Partner: UNT Libraries Government Documents Department

Resistance of transparent plastics to impact

Description: The problem of developing a windshield for aircraft which will withstand the effect of bird impacts during flight is a difficult one, as an estimate of the striking energy will indicate. If the average speed of the airplane is considered to be about 200 miles per hour and that of the bird about 70 miles per hour, the speed of the bird relative to the airplane may be as great as 400 feet per second. If a 4-pound bird is involved, a maximum impact energy of approximately 10,000 foot-pounds must be dissipated. To obtain this energy in a drop test in the Washington Monument, it would be necessary to drop a 20-pound weight down the 500-foot shaft. For both theoretical and practical reasons, it is necessary to keep the mass and speed more nearly like those to be encountered. However, to get an impact of about 10,000 foot-pounds with a 4-pound falling body, it would be necessary to drop it from a height of approximately one-half mile, neglecting air resistance. These facts will indicate some of the experimental obstacles in the way of simulating bird impacts against aircraft windshields.
Date: July 1, 1939
Creator: Axilrod, Benjamin M & Kline, Gordon M
Partner: UNT Libraries Government Documents Department

Observations in flight of the region of stalled flow over the blades of an autogiro rotor

Description: The flow over the inner halves of the rotor blades on a Kellet YG-1B autogiro was investigated in flight by making camera records of the motion of silk streamers attached to the upper surfaces of the blades. These records were analyzed to determine the boundaries of the region within which the flow over the blade sections was stalled for various tip-speed ratios. For the sake of comparison, corresponding theoretical boundaries were obtained. Both the size of the stalled area and its rate of growth with increasing tip-speed ratio were found to be larger than the theory predicted, although experiment agreed with theory with regard to shape and general location of the stalled area. The stalled region may be an important factor in both the rotor lift-drag ratio and the blade flapping motion at the higher tip-speed ratios. The method of study used in this paper should be useful in further studies of the problem, including the reduction of the size of the region.
Date: December 1, 1939
Creator: Bailey, F J , Jr & Gustafon, F B
Partner: UNT Libraries Government Documents Department

Aerodynamic effects of a split flap on the spinning characteristics of a monoplane model

Description: From Summary: "The investigation described in this report was made to determine the change in aerodynamic forces and moments produced by split flaps in a steady spin. The test were made with the spinning balance in the NACA 5-foot vertical wind tunnel. A low-wing monoplane model was tested with and without the split flaps in 12 spinning attitudes chosen to cover the probable spinning range. The results obtained indicate that the use of split flaps on an airplane is unlikely, in any case, to have much beneficial effect on a spin, and it might make the spin dangerous."
Date: December 1934
Creator: Bamber, M J
Partner: UNT Libraries Government Documents Department

Spinning characteristics of wings II : rectangular Clark Y biplane cellule: 25 percent stagger; 0 degree decalage; gap/chord 1.0

Description: General methods of theoretical analysis of airplane spinning characteristics have been available for some time. Some of these methods of analysis might be used by designers to predict the spinning characteristics of proposed airplane designs if the necessary aerodynamic data were known. The present investigation, to determine the spinning characteristics of wings, is planned to include variations in airfoil sections, plan forms, and tip shapes of monoplane wings and variations in stagger, gap, and decalage for biplane cellules. The first series of tests, made on a rectangular Clark Y monoplane wing, are reported in reference 1. That report also gives an analysis of the data for predicting the probable effects of various important parameters on the spin for normal airplanes using such a wing. The present report is the second of the series. It gives the aerodynamic characteristics of a rectangular Clark Y biplane cellule in spinning attitudes and includes a discussion of the data, using the method of analysis given in reference 1.
Date: April 1, 1935
Creator: Bamber, M J
Partner: UNT Libraries Government Documents Department

Spinning Characteristics of Wings III : A Rectangular and Tapered Clark Y Monoplane Wing with Rounded Tips

Description: An investigation was made to determine the spinning characteristics of Clark Y monoplane wings with different plan forms. A rectangular wing and a wing tapered 5:2, both with rounded tips, were tested on the N.A.C.A. spinning balance in the 5-foot vertical wind tunnel. The aerodynamic characteristics of the models and a prediction of the angles of sideslip for steady spins are given. Also included is an estimate of the yawning moment that must be furnished by the parts of the airplane to balance the inertia couples and wing yawing moment for spinning equilibrium. The effects on the spin of changes in plan form and of variations of some of the important parameters are discussed and the results are compared with those for a rectangular wing with square tips. It is concluded that for a conventional monoplane using Clark Y wing the sideslip will be algebraically larger for the wing with the rounded tip than for the wing with the square tip and will be largest for the tapered wing. The effect of plan form on the spin will vary with the type of airplane; and the provision of a yawing-moment coefficient of -0.025 (i.e., opposing the spin) by the tail, fuselage, and interference effects will insure against the attainment of equilibrium on a steady spin for any of the plan forms tested and for any of the parameters used in the analysis.
Date: September 1, 1937
Creator: Bamber, M J & House, R O
Partner: UNT Libraries Government Documents Department