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 Serial/Series Title: NACA Technical Notes
 Collection: National Advisory Committee for Aeronautics Collection
Empirical relation between induced velocity, thrust, and rate of descent of a helicopter rotor as determined by wind-tunnel tests on four model rotors

Empirical relation between induced velocity, thrust, and rate of descent of a helicopter rotor as determined by wind-tunnel tests on four model rotors

Date: October 1, 1951
Creator: Castles, Walter, Jr. & Gray, Robin B.
Description: The empirical relation between the induced velocity, thrust, and rate of vertical descent of a helicopter rotor was calculated from wind tunnel force tests on four model rotors by the application of blade-element theory to the measured values of the thrust, torque, blade angle, and equivalent free-stream rate of descent. The model tests covered the useful range of C(sub t)/sigma(sub e) (where C(sub t) is the thrust coefficient and sigma(sub e) is the effective solidity) and the range of vertical descent from hovering to descent velocities slightly greater than those for autorotation. The three bladed models, each of which had an effective solidity of 0.05 and NACA 0015 blade airfoil sections, were as follows: (1) constant-chord, untwisted blades of 3-ft radius; (2) untwisted blades of 3-ft radius having a 3/1 taper; (3) constant-chord blades of 3-ft radius having a linear twist of 12 degrees (washout) from axis of rotation to tip; and (4) constant-chord, untwisted blades of 2-ft radius. Because of the incorporation of a correction for blade dynamic twist and the use of a method of measuring the approximate equivalent free-stream velocity, it is believed that the data obtained from this program are more applicable to free-flight calculations than ...
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The factors that determine the minimum speed of an airplane

The factors that determine the minimum speed of an airplane

Date: March 1, 1921
Creator: Norton, F H
Description: The author argues that because of a general misunderstanding of the principles of flight at low speed, there are a large number of airplanes that could be made to fly several miles per hour slower than at present by making slight modifications. In order to show how greatly the wing section affects the minimum speed, curves are plotted against various loadings. The disposition of wings on the airplane slightly affects the lift coefficient, and a few such cases are discussed. Another factor that has an effect on minimum speed is the extra lift exerted by the slip stream on the wings. Also discussed are procedures to be followed by the pilot, especially with regard to stick movements during low speed flight. Also covered are stalling, yaw, rolling moments, lateral control, and the effectiveness of ailerons and rudders.
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The testing of aviation engines

The testing of aviation engines

Date: December 1, 1924
Creator: Dubois, R N
Description: None
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Droplet Impingement and Ingestion by Supersonic Nose Inlet in Subsonic Tunnel Conditions

Droplet Impingement and Ingestion by Supersonic Nose Inlet in Subsonic Tunnel Conditions

Date: May 1, 1958
Creator: Gelder, Thomas F.
Description: The amount of water in cloud droplet form ingested by a full-scale supersonic nose inlet with conical centerbody was measured in the NACA Lewis icing tunnel. Local and total water impingement rates on the cowl and centerbody surfaces were also obtained. All measurements were made with a dye-tracer technique. The range of operating and meteorological conditions studied was: angles of attack of 0 deg and 4.2 deg, volume-median droplet diameters from about 11 to 20 microns, and ratios of inlet to free-stream velocity from about 0.4 to 1.8. Although the inlet was designed for supersonic (Mach 2.0) operation of the aircraft, the tunnel measurements were confined to a free-stream velocity of 156 knots (Mach 0.237). The data are extendable to other subsonic speeds and droplet sizes by dimensionless impingement parameters. Impingement and ingestion efficiencies are functions of the ratio of inlet to free-stream velocity as well as droplet size. For the model and range of conditions studied, progressively increasing the inlet velocity ratio from less than to greater than 1.0 increased the centerbody impingement efficiency and shifted the cowl impingement region from the inner- to outer-cowl surfaces, respectively. The ratio of water ingested by the inlet plane to that contained ...
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A Dye-Tracer Technique for Experimentally Obtaining Impingement Characteristics of Arbitrary Bodies and a Method for Determining Droplet Size Distribution

A Dye-Tracer Technique for Experimentally Obtaining Impingement Characteristics of Arbitrary Bodies and a Method for Determining Droplet Size Distribution

Date: March 1, 1955
Creator: VonGlahn, Uwe H.; Gelder, Thomas F. & Smyers, William H., Jr.
Description: A dye-tracer technique has been developed whereby the quantity of dyed water collected on a blotter-wrapped body exposed to an air stream containing a dyed-water spray cloud can be colorimetrically determined in order to obtain local collection efficiencies, total collection efficiency, and rearward extent of impingement on the body. In addition, a method has been developed whereby the impingement characteristics obtained experimentally for a body can be related to theoretical impingement data for the same body in order to determine the droplet size distribution of the impinging cloud. Several cylinders, a ribbon, and an aspirating device to measure cloud liquid-water content were used in the studies presented herein for the purpose of evaluating the dye-tracer technique. Although the experimental techniques used in the dye-tracer technique require careful control, the methods presented herein should be applicable for any wind tunnel provided the humidity of the air stream can be maintained near saturation.
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Effect of Ice and Frost Formations on Drag of NACA 65(sub 1) -212 Airfoil for Various Modes of Thermal Ice Protection

Effect of Ice and Frost Formations on Drag of NACA 65(sub 1) -212 Airfoil for Various Modes of Thermal Ice Protection

Date: June 1, 1953
Creator: Gray, V. H. & Von Glahn, U. H.
Description: The effects of primary and. runback icing and frost formations on the drag of an 8-foot-chord NACA 651-212 airfoil section were investigated over a range of angles of attack from 20 to 80 and airspeeds up to 260 miles per hour for icing conditions with liquid-water contents ranging from 0.25 to 1.4 grams per cubic meter and datum air temperatures of -30 to 30 F. The results showed that glaze-ice formations, either primary or runback, on the upper surface near the leading edge of the airfoil caused large and rapid increases in drag, especially at datum air temperatures approaching 32 F and in the presence of high rates of water catch. Ice formations at lower temperatures (rime ice) did not appreciably increase the drag coefficient over the initial (standard roughness) drag coefficient. Cyclic de-icing of the primary Ice formations on the airfoil leading-edge section permitted the drag coefficient to return almost to the bare airfoil drag value. Runback icing on the lower surface did not present a serious drag problem except when heavy spanwise ridges of runback ice occurred aft of the heatable area. Frost formations caused rapid and large increases in drag with incipient stalling of the airfoil.
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Effects of Ice Formations on Airplane Performance in Level Cruising Flight

Effects of Ice Formations on Airplane Performance in Level Cruising Flight

Date: May 1, 1948
Creator: Preston, G. Merritt & Blackman, Calvin C.
Description: A flight investigation in natural icing conditions was conducted by the NACA to determine the effect of ice accretion on airplane performance. The maximum loss in propeller efficiency encountered due to ice formation on the propeller blades was 19 percent. During 87 percent of the propeller icing encounters, losses of 10 percent or less were observed. Ice formations on all of the components of the airplane except the propellers during one icing encounter resulted in an increase in parasite drag of the airplane of 81 percent. The control response of the airplane in this condition was marginal.
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Effects of extreme surface cooling on boundary-layer transition

Effects of extreme surface cooling on boundary-layer transition

Date: October 1, 1957
Creator: Jack, J. R.; Wisniewski, R. J. & Diaconis, N. S.
Description: None
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Correlations Among Ice Measurements, Impingement Rates Icing Conditions, and Drag Coefficients for Unswept NACA 65A004 Airfoil

Correlations Among Ice Measurements, Impingement Rates Icing Conditions, and Drag Coefficients for Unswept NACA 65A004 Airfoil

Date: February 1, 1958
Creator: Gray, Vernon H.
Description: An empirical relation has been obtained by which the change in drag coefficient caused by ice formations on an unswept NACA 65AO04 airfoil section can be determined from the following icing and operating conditions: icing time, airspeed, air total temperature, liquid-water content, cloud droplet impingement efficiencies, airfoil chord length, and angles of attack. The correlation was obtained by use of measured ice heights and ice angles. These measurements were obtained from a variety of ice formations, which were carefully photographed, cross-sectioned, and weighed. Ice weights increased at a constant rate with icing time in a rime icing condition and at progressively increasing rates in glaze icing conditions. Initial rates of ice collection agreed reasonably well with values predicted from droplet impingement data. Experimental droplet impingement rates obtained on this airfoil section agreed with previous theoretical calculations for angles of attack of 40 or less. Disagreement at higher angles of attack was attributed to flow separation from the upper surface of the experimental airfoil model.
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Wind tunnel force tests in wing systems through large angles of attack

Wind tunnel force tests in wing systems through large angles of attack

Date: August 1, 1928
Creator: Wenzinger, Carl J & Harris, Thomas A
Description: Force tests on a systematic series of wing systems over a range of angle of attack from minus forty-five degrees to plus ninety degrees are covered in this report. The investigation was made on monoplane and biplane wing models to determine the effects of variations of tip shape, aspect ratio, flap setting, stagger, gap, decalage, sweepback, and airfoil profile.
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Notes on the N.A.C.A. control force recorder

Notes on the N.A.C.A. control force recorder

Date: July 1, 1923
Creator: Reeid, H J E
Description: Emphasized here is the desirability of using recording instruments in the investigation of the characteristics of airplanes with particular reference to the National Advisory Committee for Aeronautics (NACA) control force recorder. Given here are photographs, records, and a description of the instrument developed by NACA for investigations on different types of aircraft. Described here is an instrument for recording control forces. At present, this control force recorder registers only the forces exerted on the stick. However, attachments are being designed to enable the forces on the rudder bar also to be recorded. The instrument in its final form will consist of three parts, namely, the recorder, the controller for the stick, and the controller for the rudder. The first two are in use now. The theory of operation is simple. In the controller, which is slipped over and fastened to the stick, are small electrical resistances which vary with the force applied to the handle. The recording apparatus then consists of suitable variable resistances properly connected to galvanometers whose deflections are proportional to the forces applied to the stick.
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Notes on the theory of the accelerometer

Notes on the theory of the accelerometer

Date: May 1, 1920
Creator: Warner, E P
Description: None
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Comparison of Heat Transfer from Airfoil in Natural and Simulated Icing Conditions

Comparison of Heat Transfer from Airfoil in Natural and Simulated Icing Conditions

Date: September 1, 1951
Creator: Gelder, Thomas F. & Lewis, James P.
Description: An investigation of the heat transfer from an airfoil in clear air and in simulated icing conditions was conducted in the NACA Lewis 6- by 9-foot icing-research tunnel in order to determine the validity of heat-transfer data as obtained in the tunnel. This investiation was made on the same model NACA 65,2-016 airfoil section used in a previous flight study, under similar heating, icing, and operating conditions. The effect of tunnel turbulence, in clear air and in icingwas indicated by the forward movement of transition from laminar to turbulent heat transfer. An analysis of the flight results showed the convective heat transfer in icing to be considerably different from that measured in clear air and. only slightly different from that obtained in the icing-research tunnel during simulated icing.
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Analogy Between Mass and Heat Transfer with Turbulent Flow

Analogy Between Mass and Heat Transfer with Turbulent Flow

Date: October 1, 1953
Creator: Callaghan, Edmund E.
Description: An analysis of combined heat and mass transfer from a flat plate has been made in terms of Prandtl t s simplified physical concept of the turbulent boundary layer. The results of the analysis show that for conditions of reasonably small heat and mass transfer, the ratio of the mass-and heat-transfer coefficients is dependent on the Reynolds number of the boundary layer, the Prandtl number of the medium of diffusion, and the Schmidt number of the diffusing fluid in the medium of diffusion. For the particular case of water evaporating into air, the ratio of mass-transfer coefficient to heat-transfer coefficient is found to be slightly greater than unity.
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Analytical Investigation of Icing Limit for Diamond-Shaped Airfoil in Transonic and Supersonic Flow

Analytical Investigation of Icing Limit for Diamond-Shaped Airfoil in Transonic and Supersonic Flow

Date: January 1, 1953
Creator: Callaghan, Edmund E. & Serafini, John S.
Description: Calculations have been made for the icing limit of a diamond airfoil at zero angle of attack in terms of the stream Mach number, stream temperature, and pressure altitude. The icing limit is defined as a wetted-surface temperature of 320 F and is related to the stream conditions by the method of Hardy. The results show that the point most likely to ice on the airfoil lies immediately behind the shoulder and is subject to possible icing at Mach numbers as high as 1.4.
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The comparison of well-known and new wing sections tested in the variable density wind tunnel

The comparison of well-known and new wing sections tested in the variable density wind tunnel

Date: May 1, 1925
Creator: Higgins, George J
Description: Three groups of airfoils have been tested in the variable density wind tunnel. The first group contains three airfoils. The second group is a systematic series of twenty-seven airfoils. The third group consists of several frequently used wing sections.
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De-icing Effectiveness of External Electric Heaters for Propeller Blades

De-icing Effectiveness of External Electric Heaters for Propeller Blades

Date: February 1, 1948
Creator: Lewis, J. P.
Description: None
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Experimental investigation of an NACA 64A010 airfoil section with 41 suction slots on each surface for control of laminar boundary layer

Experimental investigation of an NACA 64A010 airfoil section with 41 suction slots on each surface for control of laminar boundary layer

Date: April 1, 1952
Creator: Burrows, D. L. & Schwartzberg, M. A.
Description: None
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The formation of ice upon exposed parts of an airplane in flight

The formation of ice upon exposed parts of an airplane in flight

Date: July 1, 1928
Creator: Carroll, Thomas & Mcavoy, Wm H
Description: In order to experimentally study the conditions leading to ice formation on aircraft surfaces, an aircraft was equipped with small auxiliary surfaces and aerodynamic shapes similar to struts, wires, Pitot heads, etc. This airplane was flown at an altitude where a temperature of 32 F was encountered, at such times as cloud formations could be found at the coincident altitude. Here it was discovered that ice formed rapidly in regard to quantity,character, shape, and rapidity of formation. An examination of this data, which confirms observations of pilots, indicates that the weight of ice collected can very possibly be sufficient to force the airplane to rapidly lose altitude on account of the increased loads. However, it is more evident that the malformation of the aerodynamic shapes may so increase the drag and reduce the lift so as to produce a loss of altitude even greater in consequence, the combination of the two working in the same direction having a double effect. Other adverse consequences are noted. The recommendation for the guidance of those who must encounter these conditions appears to lie entirely along the lines of avoidance.
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Investigations relating to the extension of laminar flow by means of boundary-layer suction through slots

Investigations relating to the extension of laminar flow by means of boundary-layer suction through slots

Date: October 1, 1949
Creator: Loftin, L. K., Jr. & Burrows, D. L.
Description: None
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Langley Field wind tunnel apparatus

Langley Field wind tunnel apparatus

Date: January 1, 1922
Creator: Bacon, D L
Description: None
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Langley Field wind tunnel apparatus

Langley Field wind tunnel apparatus

Date: October 1, 1921
Creator: Bacon, D L
Description: The difficulties experienced in properly holding thin tipped or tapered airfoils while testing on an N.P.L. type aerodynamic balance even at low air speeds, and the impossibility of holding even solid metal models at the high speeds attainable at the National Advisory Committee's wind tunnel, necessitated the design of a balance which would hold model airfoils of any thickness and at speeds up to 150 m.p.h. In addition to mechanical strength and rigidity, it was highly desirable that the balance readings should require a minimum amount of correction and mathematical manipulation in order to obtain the lift and drag coefficients and the center of pressure. The balance described herein is similar to one in use at the University of Gottingen, the main difference lying in the addition of a device for reading the center of pressure directly, without the necessity of any correction whatsoever. Details of the design and operation of the device are given.
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Similitude tests on wind sections

Similitude tests on wind sections

Date: March 1, 1921
Creator: Bacon, D L
Description: None
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Some effects of rainfall on flight of airplanes and on instrument indications

Some effects of rainfall on flight of airplanes and on instrument indications

Date: April 1, 1941
Creator: Rhode, Richard V
Description: Several possible effects of heavy rain on the aerodynamic performance of an airplane and of heavy rain and associated atmospheric phenomena on the indications of flight instruments are briefly considered. It is concluded that the effects of heavy rain on the performance of an airplane are not so great as to force the airplane down from moderate altitudes. Serious malfunctioning of the air-speed indicator may occur, however, as a result of flooding of the pitot-static head and subsequent accumulation of water in the air-speed pressure line. In strong convective situations, like thunderstorms, the rate-of-climb indicator may also be seriously in error owing to rapid variations of atmospheric pressure when entering and emerging from the convection currents.
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