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A Summary of Meteorological Conditions Associated With Aircraft Icing and a Proposed Method of Selecting Design Criterions for Ice-Protection Equipment

Description: Note presenting data from various sources on the observed values of meteorological variables, liquid-water content, mean-effective droplet size, and temperature, which are pertinent to aircraft icing. A method is proposed for the selection of design criterions for ice-protection equipment. The data are divided into two broad cloud types, stratiform and cumuliform clouds, because the icing conditions are very different for the two types.
Date: November 1951
Creator: Hacker, Paul T. & Dorsch, Robert G.
open access

Meteorological Analysis of Icing Conditions Encountered in Low-Altitude Stratiform Clouds

Description: "Liquid-water content, droplet size, and temperature data measured during 22 flights in predominately stratiform clouds through the 1948-49 and the 1949-50 winters are presented. Several icing encounters were of greater severity than those previously measured over the same geographical area, but were within the limits of similar measurements obtained over different terrain within the United States. An analysis of meteorological conditions existing during the 74 flights conducted for four winter… more
Date: March 1951
Creator: Kline, Dwight B. & Walker, Joseph A.
open access

Icing Properties of Noncyclonic Winter Stratus Clouds

Description: Note presenting measurements of the vertical distribution of liquid water concentration and drop size in winter stratus clouds in the absence of significant cyclonic or frontal activity. The observations indicate that the clouds are formed by turbulent mixing of the lower layers of the atmosphere, resulting in a region of constant specific humidity and adiabatic lapse rates. Calculations based on the observations were used to construct a graph that gives the liquid water concentration in terms … more
Date: September 1947
Creator: Lewis, William
open access

Observations of Icing Conditions Encountered in Flight During 1948

Description: Note presenting meteorological data from flight observations in icing conditions during the first 5 months of 1948. A total of 335 measurements of liquid-water content and mean-effective drop diameter were obtained by the multicylinder method in the course of 40 flights in icing conditions covering most of the northern United States. Information regarding the discontinuous character of icing clouds, variation of average liquid-water content with extent of icing conditions, and variation of drop… more
Date: June 1949
Creator: Lewis, William & Hoecker, Walter H., Jr.
open access

Icing Frequencies Experienced During Climb and Descent by Fighter-Interceptor Aircraft

Description: "Data and analyses are presented on the relative frequencies of occurrence and severity of icing cloud layers encountered by jet aircraft in the climb and descent phases of flights to high altitudes. Fighter-interceptor aircraft operated by the Air Defense Command (USAF) at bases in the Duluth and Seattle areas collected the data with icing meters installed for a 1-year period. The project was part of an extensive program conducted by the NACA to collect Icing cloud data for evaluating the icin… more
Date: July 1958
Creator: Perkins, Porter J.
open access

Statistical Study of Aircraft Icing Probabilities at the 700- and 500- Millibar Levels over Ocean Areas in the Northern Hemisphere

Description: From Summary: "A statistical study is made of icing data reported from weather reconnaissance aircraft flown by Air Weather Service (USAF). The weather missions studied were flown at fixed flight levels of 500 millibars (18,000 ft) and 700 millibars (10,000 ft) over wide areas of the Pacific, Atlantic, and Arctic Oceans. This report is presented as part of a program conducted by the NACA to obtain extensive icing statistics relevant to aircraft design and operation. The thousands of in-flight o… more
Date: May 1957
Creator: Perkins, Porter J.; Lewis, William & Mulholland, Donald R.
open access

Statistical Explanation of Spontaneous Freezing of Water Droplets

Description: Note presenting a statistical theory based on the presence of small crystallization nuclei suspended in water developed to explain experimental results showing that, on average, small droplets can be supercooled to lower temperatures than large ones. The average behavior of supercooled droplets is reproduced on the basis of probability theory with an assumed distribution of crystallization nuclei with respect to the temperatures at which the nuclei cause freezing.
Date: December 1950
Creator: Levine, Joseph
open access

Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets

Description: "A photomicrographic technique for investigating seupercooled water droplets has been devised and. used. to determine the spontaneous freezing temperatures of seupercooled water droplets of the size ordinarily found. in the atmosphere. The freezing temperatures of 4527 droplets ranging from 8.75 to 1000 microns in diameter supported on a platinum surface and 571 droplets supported on copper were obtained. The average spontaneous freezing temperature decreased with decrease in the size of the dr… more
Date: July 1950
Creator: Dorsch, Robert G. & Hacker, Paul T.
open access

Experimental Values of the Surface Tension of Supercooled Water

Description: "The results of surface-tension measurements for supercooled water are presented. A total of 702 individual measurements of surface tension of triple-distilled water were made in the temperature range, 27 to -22.2 C, with 404 of these measurements at temperatures below 0 C. The increase in magnitude of surface tension with decreasing temperature, as indicated by measurements above 0 C, continues to -22.2 C. The inflection point in the surface-tension - temperature relation in the vicinity of 0 … more
Date: October 1951
Creator: Hacker, Paul T.
open access

Tests on Stiffened Circular Cylinders

Description: "Compressive tests were made of two series of stiffened circular cylindrical shells under axial load. All the shells were 16 inches in diameter by 24 inches in length and were made of aluminum-alloy sheet curved to the proper radius and welded with one longitudinal weld. The ratios of diameter to thickness of shell wall in the two series of specimens were 258 and 572" (p. 1).
Date: March 1941
Creator: Holt, Marshall
open access

Tests of Round and Flat Spoilers on a Tapered Wing in the NACA 19-Foot Pressure Wind Tunnel

Description: "Several arrangements of round and flat spanwise spoilers attached to the upper surface of a tapered wing were tested in the NACA 19-foot pressure wind tunnel to determine the most effective type, location, and size of spoiler necessary to reduce greatly the lift on the wings of large flying boats when moored. The effect of the various spoilers on the lift, the drag, and the pitching-moment characteristics of the tapered wing was measured over a range of angles of attack from zero to maximum li… more
Date: March 1941
Creator: Wenzinger, Carl J. & Bowen, John D.
open access

Tests of a gust-alleviating wing in the gust tunnel

Description: "Tests were made in the NACA gust tunnel to determine the effectiveness of a torsionally flexible wing with the torsion axis ahead of the locus of the section aerodynamic centers in reducing airplane accelerations due to atmospheric gusts. For three gust shapes, a series of flights was made with the airplane model equipped with either a torsionally flexible or a rigid wing. The results indicated that the torsionally flexible wing reduced the maximum acceleration increment 5 percent for the shar… more
Date: April 1941
Creator: Shufflebarger, C. C.
open access

The Interference Effects of a Body on the Spanwise Load Distributions of Two 45 Degree Sweptback Wings of Aspect Ratio 8.02 from Low-Speed Tests

Description: From Summary: "Tests of two wing-body combinations have been conducted in the Langley 19-foot pressure tunnel at a Reynolds number of 4 x 10(exp 6) and a Mach number of 0.19 to determine the effects of the bodies on the wing span load distributions. The wings had 45 degrees sweepback of the quarter-chord line, aspect ratio 8.02, taper ratio 0.45, and incorporated 12-percent-thick airfoil sections streamwise. One wing was untwisted and uncambered whereas the second wing incorporated both twist a… more
Date: April 1956
Creator: Martina, Albert P.
open access

Study of Chromium-Frit-Type Coatings for High-Temperature Protection of Molybdenum

Description: "The achievement of more compact and efficient power plants for aircraft is dependent, among other factors, on the perfection of heat-resisting materials that are superior to those in current use. Molybdenum is one of the high-melting metals (melting point, 4750 F). It is fairly abundant and also can be worked into many of the shapes required in modern power plants. To permit its widespread use at elevated temperatures, however, some means must first be found to prevent its rapid oxidation" (p.… more
Date: July 1951
Creator: Moore, D. G.; Bolz, L. H.; Pitts, J. W. & Harrison, W. N.
open access

Impingement of Water Droplets on NACA 65A004 Airfoil at 8 Degree Angle of Attack

Description: The trajectories of droplets in the air flowing past an NACA 65AO04 airfoil at an angle of attack of 8 deg were determined. The amount of water in droplet form impinging on the airfoil, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and presented to cover a large range of flight and atmospheric conditions. These impingement characteristics are compared briefly with those previously reported for the … more
Date: July 1954
Creator: Brun, Rinaldo J.; Gallagher, Helen M. & Vogt, Dorothea E.
open access

Variation of Local Liquid-Water Concentration About an Ellipsoid of Fineness Ratio 10 Moving in a Droplet Field

Description: From Summary: "Trajectories of water droplets about an ellipsoid of revolution with a fineness ratio of 10 (10 percent thick) in flight through a droplet field were computed with the aid of a differential analyzer. Analyses of these trajectories indicate that the local concentration of liquid water at various points about an ellipsoid varies considerably and under some conditions may be several times the free-stream concentration. Curves of the local concentration factor as a function of spatia… more
Date: April 1955
Creator: Brun, Rinaldo J. & Dorsch, Robert G.
open access

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

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… more
Date: March 1955
Creator: von Glahn, Uwe H.; Gelder, Thomas F. & Smyers, William H., Jr.
open access

Impingement of Water Droplets on a Sphere

Description: Droplet trajectories about a sphere in ideal fluid flow were calculated. From the calculated droplet trajectories the droplet impingement characteristics of the sphere were determined. Impingement data and equations for determining the collection efficiency, the area, and the distribution of impingement are presented in terms of dimensionless parameters. The range of flight and atmospheric conditions covered in the calculations was extended considerably beyond the range covered by previously re… more
Date: November 1955
Creator: Dorsch, Robert G.; Saper, Paul G. & Kadow, Charles F.
open access

Impingement of Water Droplets on a Rectangular Half Body in a Two-Dimensional Incompressible Flow Field

Description: "Trajectories of water droplets moving in the ideal two-dimensional flow field ahead of a body of rectangular cross section and infinite extent in the downstream direction have been calculated by means of a differential analyzer. Data on collection efficiency and distribution of water impingement are presented" (p. 1).
Date: February 1956
Creator: Lewis, William & Brun, Rinaldo J.
open access

Impingement of water droplets on NACA 65A004 airfoil at 0 degrees angle of attack

Description: From Summary: "The trajectories of water droplets in the air flowing past an NACA 6511004 airfoil at a n angle of attack of 0 deg were determined. The amount of water in droplet form impinging on the airfoil, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface were calculated from the trajectories and presented t o cover a large range of flight and atmospheric conditions. These impingement characteristics are compared briefly with those pre… more
Date: November 1955
Creator: Brun, Rinaldo J. & Vogt, Dorothea E.
open access

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

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" (p. 1).
Date: May 1958
Creator: Gelder, Thomas F.
open access

Experimental Droplet Impingement on Several Two-Dimensional Airfoils with Thickness Ratios of 6 to 16 Percent

Description: "The rate and area of cloud droplet impingement on several two-dimensional swept and unswept airfoils were obtained experimentally in the NACA Lewis icing tunnel with a dye-tracer technique. Airfoil thickness ratios of 6 to 16 percent; angles of attack from 0 deg to 12 deg, and chord sizes from 13 to 96 inches were included in the study. The data were obtained at 152 knots and are extended to other conditions by dimensionless impingement parameters" (p. 1).
Date: December 1956
Creator: Gelder, Thomas F.; Smyers, William H., Jr. & von Glahn, Uwe
open access

Impingement of Droplets in 60 Degree Elbows with Potential Flow

Description: Trajectories were determined for water droplets or other aerosol particles in air flowing through 600 elbows especially designed for two-dimensional potential motion. The elbows were established by selecting as walls of each elbow two streamlines of a flow field produced by a complex potential function that establishes a two-dimensional flow around. a 600 bend. An unlimited number of elbows with slightly different shapes can be established by selecting different pairs of streamlines as walls. S… more
Date: October 1956
Creator: Hacker, Paul T.; Saper, Paul G. & Kadow, Charles F.
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