Latest content added for UNT Digital Library Collection: Technical Report Archive and Image Libraryhttp://digital.library.unt.edu/explore/collections/TRAIL/browse/?fq=str_title_serial:NACA+Special+Report&start=10&fq=untl_institution:UNTGD2011-11-17T17:13:32-06:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Collection: Technical Report Archive and Image LibraryFlight Measurements of the Aileron Characteristics of a Grumman F4F-3 Airplane2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65202/<p><a href="/ark:/67531/metadc65202/"><img alt="Flight Measurements of the Aileron Characteristics of a Grumman F4F-3 Airplane" title="Flight Measurements of the Aileron Characteristics of a Grumman F4F-3 Airplane" src="/ark:/67531/metadc65202/thumbnail/"/></a></p><p>The aileron characteristics of a Grumman F4F-3 airplane were determined in flight by means of NACA recording and indicating instruments. The results show that the ailerons met NACA minimum requirements for satisfactory control throughout a limited speed range. A helix angle of approximately 0.07 radian was produced with flaps down at speeds from 90 to 115 miles per hour indicated airspeed and with flaps up from 115 to 200 miles per hour. With flaps up at 90 miles per hour, the helix angle dropped to 0.055 radian; above 200 miles per hour heavy aileron stick forces seriously restricted maneuverability in roll.</p>Tests of a Highly Cambered Low-Drag-Airfoil Section with a Lift-Control Flap, Special Report2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65162/<p><a href="/ark:/67531/metadc65162/"><img alt="Tests of a Highly Cambered Low-Drag-Airfoil Section with a Lift-Control Flap, Special Report" title="Tests of a Highly Cambered Low-Drag-Airfoil Section with a Lift-Control Flap, Special Report" src="/ark:/67531/metadc65162/thumbnail/"/></a></p><p>Tests were made in the NACA two-dimensional low turbulence pressure tunnel of a highly cambered low-drag airfoil (NACA 65,3-618) with a plain flap designed for lift control. The results indicate that such a combination offers attractive possibilities for obtaining low profile-drag coefficients over a wide range of lift coefficients without large reductions of critical speed.</p>Wind-Tunnel Investigation of an NACA Low-Drag Tapered Wing with Straight Trailing Edge and Simple Split Flaps, Special Report2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65192/<p><a href="/ark:/67531/metadc65192/"><img alt="Wind-Tunnel Investigation of an NACA Low-Drag Tapered Wing with Straight Trailing Edge and Simple Split Flaps, Special Report" title="Wind-Tunnel Investigation of an NACA Low-Drag Tapered Wing with Straight Trailing Edge and Simple Split Flaps, Special Report" src="/ark:/67531/metadc65192/thumbnail/"/></a></p><p>An investigation was conducted in the NACA 19-foot pressure wind tunnel of a tapered wing with straight railing edge having NACA 66 series low-drag airfoil sections and equipped with full-span and partial-span simple split flaps. The airfoil sections used were the NACA 66,2-116 at the root and the 66,2-216 at the tip. The primary purpose of the investigation was to determine the effect of the split flaps on the aerodynamic characteristics of the tapered wing. Complete lift, drag, and pitching-moment coefficients were determined for the plain wing and for each flap arrangement through a Reynold number range of 2,600,000 to 4,600,000. The results of this investigation indicate that values of maximum lift coefficient comparable to values obtained on tapered wings with conventional sections and similar flap installations can be obtained from wings with the NACA low-drag sections. The increment of maximum lift due to the split flap was found to vary somewhat with Reynold number over the range investigated. The C(sub L)max of the wing alone is 1.49 at a Reynolds number of 4,600,000; whereas with the partial-span simple split flap it is 2.22 and with the full-span arrangement, 2.80. Observations of wool tufts on the wing indicate that the addition of split flaps did not appreciable alter the pattern of the stall; even though the stall did occur more abruptly than with the wing alone.</p>Compressibility Effects in Aeronautical Engineering2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc64993/<p><a href="/ark:/67531/metadc64993/"><img alt="Compressibility Effects in Aeronautical Engineering" title="Compressibility Effects in Aeronautical Engineering" src="/ark:/67531/metadc64993/thumbnail/"/></a></p><p>Compressible-flow research, while a relatively new field in aeronautics, is very old, dating back almost to the development of the first firearm. Over the last hundred years, researches have been conducted in the ballistics field, but these results have been of practically no use in aeronautical engineering because the phenomena that have been studied have been the more or less steady supersonic condition of flow. Some work that has been done in connection with steam turbines, particularly nozzle studies, has been of value, In general, however, understanding of compressible-flow phenomena has been very incomplete and permitted no real basis for the solution of aeronautical engineering problems in which.the flow is likely to be unsteady because regions of both subsonic and supersonic speeds may occur. In the early phases of the development of the airplane, speeds were so low that the effects of compressibility could be justifiably ignored. During the last war and immediately after, however, propellers exhibited losses in efficiency as the tip speeds approached the speed of sound, and the first experiments of an aeronautical nature were therefore conducted with propellers. Results of these experiments indicated serious losses of efficiency, but aeronautical engineers were not seriously concerned at the time became it was generally possible. to design propellers with quite low tip. speeds. With the development of new engines having increased power and rotational speeds, however, the problems became of increasing importance.</p>Radiator Design and Installation - II, Special Report2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65172/<p><a href="/ark:/67531/metadc65172/"><img alt="Radiator Design and Installation - II, Special Report" title="Radiator Design and Installation - II, Special Report" src="/ark:/67531/metadc65172/thumbnail/"/></a></p><p>A mathematical analysis of radiator design has been made. The volume of the radiator using least total power has been expressed in a single formula which shows that the optimum radiator volume is independent of the shape of the radiator and which makes possible the construction of design tables that give the optimum radiator volume per 100-horsepower heat dissipation as a function of the speed, of the altitude, and of one parameter involving characteristics of the airplane. Although, for a given set of conditions, the radiator volume using the least total power is fixed, the frontal area, or the length of the radiator needs to be separately specified in order to satisfy certain other requirement such as the ability to cool with the pressure drop available while the airplane is climbing. In order to simplify the specification for the shape of the radiator and in order to reduce the labor involved in calculating the detailed performance of radiators, generalized design curves have been developed for determining the pressure drop, the mass flow of air, and the power expended in overcoming the cooling drag of a radiator from the physical dimensions of the radiator. In addition, a table is derived from these curves, which directly gives the square root of the pressure drop required for ground cooling as a function of the radiator dimensions, of the heat dissipation and of the available temperature difference. Typical calculations using the tables of optimum radiator volume and the design curves are given. The jet power that can be derived from the heated air is proportional to the heat dissipation and is approximately proportional to the square of the airplane speed and to the reciprocal of the absolute temperature of the atmosphere. A table of jet power, per 100 horsepower of heat dissipation at various airplane speeds and altitudes is presented.</p>A Brief Study of the Speed Reduction of Overtaking Airplanes by Means of Air Brakes, Special Report2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65165/<p><a href="/ark:/67531/metadc65165/"><img alt="A Brief Study of the Speed Reduction of Overtaking Airplanes by Means of Air Brakes, Special Report" title="A Brief Study of the Speed Reduction of Overtaking Airplanes by Means of Air Brakes, Special Report" src="/ark:/67531/metadc65165/thumbnail/"/></a></p><p>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.</p>Estimated Effect of Ring Cowl on the Climb and Ceiling of an Airplane, Special Report2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65147/<p><a href="/ark:/67531/metadc65147/"><img alt="Estimated Effect of Ring Cowl on the Climb and Ceiling of an Airplane, Special Report" title="Estimated Effect of Ring Cowl on the Climb and Ceiling of an Airplane, Special Report" src="/ark:/67531/metadc65147/thumbnail/"/></a></p><p>Although the application of a ring cowl to an airplane with an air-cooled engine increases the maximum L/D and the high speed to an appreciable extent, the performance in climb and ceiling is not increased as much as one would expect without analyzing the conditions. When a ring cowl is installed on an airplane, the propeller is set at a higher pitch to allow the engine to turn its rated r.p.m. at the increased high speed. V/nD is increased and the propeller efficiency at high speed is increased slightly. The ratio of r.p.m. at climbing speed, V(sub c) , to the r.p.m. at maximum speed, V (sub m) is dependent upon the ratio of V(sub c) to V(sub m). The increase in V(sub c) for all airplane with ring cowl i s not as great as the increase in V(sub m), so that the ratio V(sub c)/V(sub m) is less than for the airplane without ring. Consequently the r.p.m. and full throttle thrust power available are less at V(sub c) for the airplane with ring cowl and in spite of the increase in L/D due to the installation of the ring, the excess thrust power available for climbing is not appreciably changed. The same method of reasoning accounts for the small increase in absolute ceiling in spite of a large increase in L/D maximum.</p>Definition of Method of Measurement of Supporting and Control Surface Areas, Special Report2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65140/<p><a href="/ark:/67531/metadc65140/"><img alt="Definition of Method of Measurement of Supporting and Control Surface Areas, Special Report" title="Definition of Method of Measurement of Supporting and Control Surface Areas, Special Report" src="/ark:/67531/metadc65140/thumbnail/"/></a></p><p>Definitions of methods of measurements of supporting and control surface areas are presented. Methods for measuring the supporting surface, i.e., the wing area, and the control surfaces, i.e., the horizontal tail area, the vertical tail area, and the trailing control surface areas are defined. Illustrations of each of the areas are included.</p>The Effect of Surface Irregularities on Wing Drag. I. Rivets and Spot Welds, 1, Rivets and Spot Welds2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65149/<p><a href="/ark:/67531/metadc65149/"><img alt="The Effect of Surface Irregularities on Wing Drag. I. Rivets and Spot Welds, 1, Rivets and Spot Welds" title="The Effect of Surface Irregularities on Wing Drag. I. Rivets and Spot Welds, 1, Rivets and Spot Welds" src="/ark:/67531/metadc65149/thumbnail/"/></a></p><p>Tests have been conducted in the NACA 8-foot high-speed wind tunnel to determine the effect of exposed rivet heads and spot welds on wing drag. Most of the tests were made with an airfoil of 5-foot chord. The air speed was varied from 80 to 500 miles per hour and the lift coefficient from 0 to 0.30. The increases in the drag of the 5-foot airfoil varied from 6%, due to countersunk rivets, to 27%, due to 3/32-inch brazier-head rivets, with the rivets in a representative arrangement. The drag increases caused by protruding rivet heads were roughly proportional to the height of the heads. With the front row of rivets well forward, changes in spanwise pitch had negligible effects on drag unless the pitch was more than 2.5% of the chord. Data are presented for evaluating the drag reduction attained by removing rivets from the forward part of the wing surface; for example, it is shown that over 70% of the rivet drag is caused by the rivets on the forward 30% of the airfoil in a typical case.</p>Method of Determining the Weights of the Most Important Simple Girders2011-11-17T17:13:32-06:00http://digital.library.unt.edu/ark:/67531/metadc65146/<p><a href="/ark:/67531/metadc65146/"><img alt="Method of Determining the Weights of the Most Important Simple Girders" title="Method of Determining the Weights of the Most Important Simple Girders" src="/ark:/67531/metadc65146/thumbnail/"/></a></p><p>This paper presents a series of tables for the simple and more common types of girders, similar to the tables given in handbooks under the heading "Strength of Materials," for determining the moments, deflections, etc., of simple beams. Instead of the uniform cross section there assumed, the formulas given here apply only to girders of "uniform strength," i.e., it is assumed that a girder is so dimensioned that a given load subjects it to a uniform stress throughout its whole length. This principle is particularly applicable to very strong structures. Girders of uniform strength are the lightest girders conceivable, because any girder, all of whose members are stressed to the limit, can not be surpassed by a lighter girder, if the two girders have the same form. The weight G of a member of length l, cross section F and specific gravity gamma is: G = Flgamma.</p>