"THIS DOCUMENT ... IS BEING RELEASED IN THE INTEREST OF MAKING AVAILABLE AS MUCH INFORMATION AS POSSIBLE"

An example of the abstracts listing.

Introduction

The 1981 reprint of "Selected Bibliography of NACA-NASA Aircraft Icing Publications" ¹ included abstracts of the 132 references in 17 categories.

Unfortunately, the online version available has rather poor image quality. A note is included:

THIS DOCUMENT HAS BEEN REPRODUCED FROM
MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT
CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED
IN THE INTEREST OF MAKING AVAILABLE AS MUCH
INFORMATION AS POSSIBLE

In some areas, the text is barely legible. I believe that this has hampered awareness about and use of this important publication.

Here, the text is reformatted and presented here in html format, which is both human- and machine-readable.

The formats vary in the original text. Some match what is in the publications, and others are briefer summaries typically found on library reference cards. No effort was made here to make them more uniform in style (for example, some titles are in ALL CAPS, and others are not). The abstracts may differ from those that you may find in listings at ntrs.nasa.gov.

The numbering from the 1981 publication is used here. A later republication (in AC 20-73) used consecutive numbering within a category, but not for the entire list.

Several text extractions techniques were used, but all of them had some errors. Errors found were corrected manually, but there still may be errors.

The 17 categories:

Meteorology of Icing Clouds
Fundamental Properties of Water
Meteorological Instruments
Impingement of Cloud Droplets
Propeller Ice Protection
Induction System Ice Protection
Turbine-Type Engine and Inlet Icing Studies
Wing Icing Protection
Performance Penalties
Windshield Icing Protection
Cooling Fan Icing Protection
Radome Icing Protection
Antenna Icing
Inlet and Vent Icing Protection
Jet Penetration
Heat Transfer
Miscellaneous

SUMMARIES/ABSTRACTS OF DOCUMENTS LISTED IN BIBLIOGRAPHY

Meteorology of Icing Clouds

1
NACA TN 2738 National Advisory Committee for Aeronautics.
A PROBABILITY ANALYSIS OF THE METEOROLOGICAL FACTORS CONDUCTIVE TO AIRCRAFT ICING IN THE UNITED STATES.
William Lewis and Norman R. Bergrun. June 1952. 93p. diagrs., 11 tabs. (NACA TN 2738)
Meteorological icing data obtained in flight in the United States are analyzed statistically and methods are developed for the determination of (1) the various simultaneous combinations of the three basic icing parameters (liquid-water content, drop diameter, and temperature) which would have equal probability of being exceeded in flight in any random icing encounter, and (2) the probability of exceeding any specified group of values of liquid-water content associated simultaneously with temperature and drop-diameter values lying within specified ranges. method provides a convenient means of calculating the percentage of icing encounters in which the water collection rate exceeds the design rate.

2
NACA TN 2569 National Advisory Committee for Aeronautics.
A SUMMARY OF METEOROLOGICAL CONDITIONS ASSOCIATED WITH AIRCRAFT ICING AND A PROPOSED METHOD OF SELECTING DESIGN CRITERIONS FOR ICE-PROTECTION EQUIPMENT
Paul T. Hacker and Robert G. Dorsch. November 1951. 35p. diagrs. (NACA TN 2569)
Data on the meteorological parameters pertinent to the aircraft icing problem are so summarized as to give the frequency of occurrence of observed icing situations according to two of the parameters. The summarized data indicate that statistical relations exist between some of the parameters. A method, based upon the collection efficiency of an airfoil and the frequency of occurrence of icing situations with various liquid-water contents and mean-effective droplet sizes, is proposed for the selection of design criterions for ice-protection equipment.

3
TECHNICAL NOTE NO. 1855
RECOMMENCED VALUES OF METEOROLOGICAL FACTORS TO BE CONSIDERED IN THE DESIGN OF AIRCRAFT ICE-PREVENTION EQUIPMENT
By Alun B. Jones and William Lewis
SUMMARY
Meteorological conditions conducive to aircraft icing are arranged in four classifications: three are associated with cloud structure and the fourth with freezing rain. The range of possible meteorological factors for each classification is discussed and specific values recommended for consideration in the design of ice-prevention equipment for aircraft are selected and tabulated. The values selected are based upon a study of the available observational data and theoretical considerations where observations are lacking. Recommendations for future research in the field are presented.

4
Investigation of Meteorological Conditions Associated with Aircraft Icing in Layer-Type Clouds for 1947-48 Winter.
By Dwight B. Kline
NACA TN 1793 January 1949
Abstract
Measurements of liquid-vater content, drop size, and temperature during icing conditions encountered in flight are shown to be consistent with previously measured conditions and with proposed maximum icing conditions in supercooled layer-type clouds. Cumulative-frequency graphs of meteorological parameters are presented indicating the frequency with which various icing conditions have been encountered in the Great Lakes ares and surrounding states during two winters of flight observations.

5
Meteorological Analysis of Icing Conditions Encountered in Low-Altitude Stratiform Clouds.
By Dwight B. Kline and Joseph A. Walker
NACA TN 2506 March 1951
Abstract
Liquid-water content, droplet size, and temperature data measured in predominantly stratiform clouds during the 1948-49 and 1949-50 winters are presented. The horizontal and vertical extent of icing conditions and the relation of the existence of supercooled clouds to cyclone areas and precipitation regions are indicated. Liquid-water content measurements during 12 flights are shown in relation to theoretical amounts calculated from radiosonde data and cloud depth observations.

6
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS TECHNICAL NOTE NO. 1391
ICING PROPERTIES OF NONCYCLONIC WINTER STRATUS CLOUDS
By William Lewis, U.S. Weather Bureau
SUMMARY
Measurements of the vertical distribution of liquid water concentration and drop size have been made 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 these characteristics were used to construct a graph which give the liquid water concentration in terms of temperature at the cloud base and the height above the base. In clouds from which no snow was falling, the measured values were in good agreement with those given by the graph. Snowfall was found to deplete the liquid water content especially in the lower part of the eloud layer, causing dissipation of the cloud from the base upwards.

7
Observations of Icing Conditions Encountered in Flight During 1948.
By William Lewis and Walter H. Hoecker, Jr.
NACA TN 1904 June 1949
Abstract
Meteorological data from 40 flights in icing conditions are presented. The report also includes a discussion of the relation between the horizontal extent of icing conditions and the average liquid-water content observed therein, the reliability of flight measurements of drop-size distribution, and an apparent geographical influence upon the size of cloud drops.

8
A Further Investigation of the Meteorological Conditions Conducive to Aircraft Icing
By William Lewis, Dwight B. Kline, and Charles P. Steinmetz
NACA TN No. 1424 October, 1947
Abstract
Data from flight observations in icing conditions am liquid water content, temperature, and mean-effective drop diameter are shown to be consistent with previously proposed values. Data on drop-size distribution with the rotating-cylinder method, although consistent with previous data, were inconsistent with data derived from stationary cylinder investigations. The relation between temperature and maximum water content in layer clouds is iscussed and estimates are given for the highest values of water to be expected in layer clouds at various temperatures.

9
NACA RM E52J06
PRELIMINARY SURVEY OF ICING CONDITIONS MEASURED DURING ROUTINE TRANSCONTINENTAL AIRLINE OPERATION.
Porter J. Perkins. December 1952. 27p. diagra., photos., 3 tabs. (NACA RM E52J06)
Icing data collected on routine operations by four DC-4-type transport aircraft equipped with NACA pressure-type icing-rate meters and flying over a transcontinental route from January through May 1951 are presented. The four aircraft were in icing conditions approximately 1-1/2 percent of the total flying time. Nearly one-half of the icing conditions were encountered over the Great Lakes area.
Average liquid-water-content measurements did not exceed 1.0 gram per cubic meter and 80 percent of the measurements did not exceed 0.4 gram per cubic meter. The data are considered only preliminary and the program is continuing to provide additional data from world-wide air routes.

10
NACA RM E55F28a
STATISTICAL SURVEY OF ICING DATA MEASURED ON SCHEDULED AIRLINE FLIGHTS OVER THE UNITED STATES AND CANADA FROM NOVEMBER 1951 TO JUNE 1952.
Porter J. Perkins. September 1955. 44p. diagra., photos., 2 tabs. (NACA RM E55F28a)
A statistical survey and a preliminary analysis are made in an interim report of over 600 icing encounters obtained from a continuing program sponsored by the NACA with the cooperation of the airlines. Pressure-type icing-rate meters were installed on 11 airline aircraft of various types. Icing conditions measured during scheduled operations gave relative frequencies of liquid-water content, icing rate, total ice accumulations, cloud temperatures, as well as horizontal and vertical extent of icing clouds. Liquid-water contents were higher than data from earlier research flights in layer-type clouds but slightly lower than previous data from cumulus clouds.

11
NACA TN 4314
ICING FREQUENCIES EXPERIENCED DURING CLIMB AND DESCENT BY FIGHTER-INTERCEPTOR AIRCRAFT.
Porter J. Perkins. July 1958. 30p. diagrs., tabs. (NACA TN 4314)
Relative frequencies of occurrence and severity of icing cloud layers encountered up to an altitude of 30,000 feet are presented. Jet fighters on routine operations of the Air Defense Command (USAF) near Duluth, Minnesota, and Seattle, Washington, were equipped with icing meters for 1 year. Icing occurred on approximately 5 percent of the flights, with iceaccretion thickness averaging less than 1/32 inch on a small sensing probe. Probabilities of icing severity (including average liquid-water content and maximum ice accretion) were calculated using earlier data measured in icing clouds.

12
NACA RM E51D18
ANALYSIS OF METEOROLOGICAL DATA OBTAINED DURING FLIGHT IN A SUPERCOOLED STRATIFORM CLOUD OF HIGH LIQUID-WATER CONTENT.
Porter J. Perkins and Dwight B. Kline. July 1951. 18p. diagrs., photos. (NACA RM E51D18)
Flight icing-rate data obtained in a dense and abnormally deep supercooled stratiform cloud system in the vicinity of Lake Erie indicated the existence of liquid-water contents generally exceeding values in amount and extent previously reported over the mid-western sections of the United States. Additional information obtained during descent through a part of the cloud system indicated liquid-water contents that significantly exceeded theoretical values, especially near the middle of the cloud layer.

13
NACA TN 3984
STATISTICAL STUDY OF AIRCRAFT ICING PROBABILITIES AT THE 700- AND 500- MILLEBAR LEVELS OVER OCEAN AREAS IN THE NORTHERN HEMISPHERE.
Porter J. Perkins, William Lewis, and Donald R. Mulholland. May 1957. 31p. diagrs., tabs. (NACA TN 3984)
A statistical study is made of icing observations reported from weather reconnaissance aircraft flown by Air Weather Service (USAF). Wide areas of the Pacific, Atlantic, and Arctic Oceans were surveyed at fixed flight levels of 500 mb (18,000 ft) and 700 mb (10,000 ft). Icing statistics presented include the relative frequencies of the occurrence of icing, the estimated probability of flight in icing, and the relation of these probabilities to the frequencies of flight in clouds and cloud temperatures. Icing probabilities varied widely throughout the year from near zero in cold Arctic areas in winter up to 7 percent in areas where greater cloudiness and warmer temperatures prevail.

14
NASA MEMO 1-19-59E National Aeronautics and Space Administration.
SUMMARY OF STATISTICAL ICING CLOUD DATA MEASURED OVER UNITED STATES AND NORTH ATLANTIC, PACIFIC, AND ARCTIC OCEANS DURING ROUTINE AIRCRAFT OPERATIONS. Porter J. Perkins. January 1959. 89p. diagra., photos.. tabs. (NASA MEMORANDUM 1-19-59E)
Data and statistics needed in aircraft design and operation are presented from icing-cloud measurements and observations obtained during an extensive program conducted in cooperation with several airlines and the United States Air Force. Icing meters installed on 72 service aircraft supplied information for determining the liquid-water content and distance traveled in 1300 icing-cloud encounters. Other icing-cloud parameters measured were the temperature and depth of icing-cloud layers and a reference total ice accretion for each encounter. All results are tabulated and the measured parameters are summarized as frequency distributions.

Fundamental Properties of Water

15
Statistical Explanation of Spontaneous Freezing of Water Droplets.
By Joseph Levine NACA TN 2234 December 1950
Abstract
A statistical theory based on the presence of small crystallization nuclei suspended in water is developed to explain experimental results shoving that on the average small droplets can be supercooled to lower temperatures than large ones. Small nuclei of crystallization are assumed responsible for causing supercooled water to freeze spontaneously.
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. The most probable distribution curves of spontaneous freezing temperatures for water droplets of various sizes within the size range found in clouds are obtained.

16
Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets
By Robert G. Dorech and Paul T. Backer
NACA TN 2142 July 1950
Abstract
Data obtained by a photomicrographic technique on the spontaneous freezing temperatures of supercooled vater droplets of the size ordinarily found in the atmosphere are presented.
The spontaneous freezing temperature was found to depend on droplet size.
Frequency distribution curver of the spontaneous freezing temperatures observed for a given droplet size were obtained.

17
NACA TN 3810 EXPERIMENTAL VALUES OF THE SURFACE TENSION OF SUPERCOOLED WATER. Paul T. Hacker. October 1981. 30p. diagrs., photon., tab. (NACA TN 3810)
The surface tension of water has been determined experimentally for the temperature range, 0° to -22° C. The weak inflection point in the surface-tension temperature relation, as indicated by the International Critical Table values for temperatures down to -8° C, was substantiated if the measurement over the temperature range, 0° to -22° C. The surface tension increases it approximately a linear rate from a value of 75.96 +/-0.06 dynes per centimeter at -8° C to 79.67 +/-0.06 dynes per centimeter at -22° C.

18
NACA TN 2532
X-RAY DIFFRACTION STUDY OF THE INTERNAL STRUCTURE OF SUPERCOOLED WATER.
Robert G. Dorsch and Bemrose Boyd. October 1951. 14p. diagrs., photo. (NACA TN 2532)
X-ray diffraction data for water in the temperature range 21° C to -6° C are presented. The minimum between two diffraction peaks deepened continuously as the temperature was lowered. It was concluded that supercooled water apparently becomes progressively more ice-like in structure as the temperature is lowered.

19
NACA RM E51L17
A PHOTOGRAPHIC STUDY OF FREEZING OF WATER DROPLETS FALLING FREELY IN AIR Robart G. Dorsch and Joseph Levine. February 1952, 25 p., diagrs., photos, tabs. (NACA RM E51L17) The freezing of fee-falling water droplets in air was investigated by a photographic technique. Information on the following was obtained:
(1) droplet shape after freezing, (2) the occurrence of collisions of partly frozen or frozen and liquid droplets, and (3) the freezing temperatures of individual free-falling droplets.

20
NACA TN 3024
MAXIMUM EVAPORATION RATES OF DROPLETS APPROACHING OBSTACLES IN THE ATMOSPHERE UNDER ICING CONDITIONS.
Merman M. Lowell. October 1953. 56 p. diagrs. tabs. (NACA TN 3024)
Maximum possible evaporation rates of water droplets approaching obstacles in the atmosphere along stagnation lines or moving ith intake ducts of airplanes under icing conditions were calculated for a wide variety of ambient conditions, flight Mach numbers, degrees of stagnation of the incident relative air stream, and droplet diameters. Droplet diameter, body size, and flight Mach number effects were found to predominate, whereas wide variation in ambient conditions had little effect on evaporative losses. It was concluded that little or no evaporative loss occurs from droplets approaching small obstacles such as liquid-vater content measurement cylinders, whereas losses may be percent in the case of larger obstacles such as wings, or 50 percent in the case of ducts at high ram pressure. Losses in ducts in general, however, will usually be about 10 to 20 percent.

21
Kinetic Temperature of Wet Surfaces
A Method of Calculating the Amount of Alcohol Required to Prevent Ice, and the Derivation of the Psychrometric Equation
By J. K. Hardy of the Royal Aircraft Establishment Reports and Memoranda No. 2830 September 1945
Summary. - A method is given for calculating the temperature of a surface wetted either by a pure liquid, such as water, or by a mixture, such as alcohol and water. The method is applied to the problem of protecting, by alcohol, propellers and the induction system of the engine against ice. The minimum quantity of alcohol required is calculated for a number of arbitrarily chosen conditions. The effect of evaporation of alcohol is shown by repeating the calculations for a non-volatile fluid. The method can be applied to other problems i evaporation, for instance, to the evaporation of fuel in the induction system of the engine. The psychrometric equation, used in wet-bulb hygrometry, is deduced in ts general form. The effect of kinetic heating is included in this equation.

Meteorological Instruments

22
NACA TN 2615 THE CALCULATED AND MEASURED PERFORMANCE CHARACTERISTICS OF A HEATED-WIRE LIQUID-WATER-CONTENT METER FOR MEASURING ICING SEVERITY.
Carr B. Neel, Jr. and Charles P. Steinmetz. January 1952. 59p. diags. photos., 6 tabs. (NACA TN 2615)
Initial development has been made of an instrument which could be used to obtain statistical fight data on the liquid-water content of icing clouds and to Provide a direct indication of icing severity. The ment of the instrument consists of a wire which was heated by passing electrical through it. The wire was mounted in the air stream and the gages of cooling resulting from evaporation of impinging water droplets as a measure of the liquid-water content of the cloud. Comparisons are made of the liquid-water content is measured with heated wires and absorbent cylinders in an artificially produced cloud. Performance characteristics of a Heated-wire instrument are presented.

23
NACA RM E53D23
PROCEDURE FOR MEASURING LIQUID-WATER CONTENT AND DROPLET SIZES IN SUPERCOOLED CLOUDS BY ROTATING MULTICYLINDER METHOD
William Levis, Porter J. Perkins and Rinaldo J Brun. Appendix C. ALTERNATE METHOD OF REDUCING ROTATING MULTICYLINDER DATA. Paul T. Hacker. June 1953. 48p. diagra., photos. 4 tabs. (NACA RM E53D23)
The rotating multicylinder method for in-flight determination of liquid-vater content, droplet size, and droplet-size distribution in icing clouds is described. The theory of operation, the apparatus required, the technique of obtaining data in fight, and detailed methods of calculating the results, including necessary charts and tables, are presented.

24
NACA RM E50K01a National Advisory Committee for Aeronautics. FLIGHT CAMERA FOR PHOTOGRAPHING CLOUD DROPLETS IN NATURAL SUSPENSION IN THE ATMOSPHERE.
Stuart McCullough and Porter J. Perkins.
June 1851. 23p. diagrs., photos. (NACA RM E50K01a)
A camera designed for use in fight has been developed by the NACA Lewis laboratory to photograph cloud droplets in the natural suspension in the atmosphere. A magnification of 32 times is employed to distinguish for measurement purposes all sizes of droplets greater than 5 microns in diameter, Photographs can be taken at flight speeds up to 150 miles per hour at 5-second intervals. A field area 0.025 square inch is photographed on 7-inch-width roll film accommodating 40 exposures on an 16-foot length. Flight tests conducted in cumulus clouds have shown that approximate droplet-size distribution studies can be obtained and that studies of the microstructure and physics of clouds can be made with the camera.

25
Flight Instrument for Measurement of Liquid-Water Content in Clouds at Temperatures above and below Freezing.
By Porter J. Perkins
NACA RM E50J12a March 1951
Abstract
An instrument consisting of a small cylindrical element operated at high surface temperatures was developed to provide a simple and repid means of determining the liquid-water content of clouds at temperatures above and below freezing.
The instrument was sensitive to a wide range of liquid-water content and was calibrated against rotating multicylinder measurements at an air temperature of 20° F, an air velocity of 175 miles per hour, and a surface temperature in clear air of 475° F.

26
NACA RM 51E16
A SIMPLIFIED INSTRUMENT FOR RECORDING AND INDICATING FREQUENCY AND INTENSITY OF ICING CONDITIONS ENCOUNTERED IN FLIGHT.
Porter J. Perkins, Stuart McCullough and Ralph D.
Lewis. July 1951. 26. diagrs., photos. (NACA RM 51E16)
An instrument for recording and indicating the frequency and intensity of aircraft icing conditions encCountered in flight has been developed by the NACA Lewis Laboratory to obtain statistical icing data over world-wide air routes during routine airline operations. The operation of the instrument is based on the creation of a differential pressure between an ice-free total pressure system and a total pressure system in which small holes vented to static pressure are allowed to plug with ice accretion. The simplicity of this operating principle permits automatic operation, and provides relative freedom from maintenance and operating problems. The complete unit weughing only 18 pounds records icing rate, airspeed, and altitude on photographic film and provides visual indications of icing intensity to the pilot.

27
NACA TN 2458
AN INSTRUMENT EMPLOYING A CORONAL DISCHARGE FOR THE DETERMINATION OF DROPLET-8IZE DISTRIBUTION IN CLOUDS.
Rinaldo J. Brun, Joseph Levine, and Kenneth S. Kleinknecht. September 1981. 53p, diagrs.,p hotos. 4 taba. (NACA TN 2458)
A flight instrument that uses electric means for obtaining a measure of the droplet-size distribution in above-freezing clouds has been devised and given preliminary evaluation in flight. An electric charge is placed on the droplets and they are separated aerodynamically according to their mass. The desirable features of an instrument based on the method described are: (1) the instrument can be used in clouds with temperatures above freezing, (2) the size and the shape of the cylinders do not change during the exposure time, (3) the error caused by bounce-off is low, (4) the readings are instantaneous and continuous, and (5) the fast instrument response permits the study of variations in cloud structure.

28
NACA RM E51G05
ADAPTATION OF A CASCADE IMPACTOR TO FLIGHT MEASUREMENT OF DROPLET SIZE IN CLOUDS.
Joseph Levine and Kenneth S. Kleinknecht.
September 1951. 2p. diagrs., photos. (NACA RM E51G05)
A cascade impactor, an instrument for obtaining the size distribution of droplets borne in a low-velocity alr stream, has been adapted for flight cloud droplet studies. Data from two flights are presented.

29
NACA TN 2708
COMPARISON OF THREE MULTICYLINDER ICING METERS AND CRITIQUE OF MULTICYLINDER METHOD.
Wallace E. Howell, Mount Washington Observatory. June 1952. 40p. diagrs., photos., tabs. (NACA TN 2708)
Three multicylinder icing meters, fundamentally similar but differing from each other in important design details, were compared in use at the Mount Washington Observatory. Comparison of relative effectiveness of the instruments, evaluation of observational errors, determination of the effects of detailed design differences, and recommendations for further improvements of design are presented. An evaluation of the multicylinder method, concerned with the validity of the theoretical basis and the degree to which the instruments and the technique of their use permit accurate determinations of the physical measurements involved, is also included.

30
A Review of Instruments Developed for the Measurement of the Meteorological Factors Conducive to Aircraft Icing.
By Alun R. Jones and William Lewis NACA RM No. A9C09 April 1949
Abstract
The status of instruments suitable for the measurement of the meteorological factors conducive to aircraft icing is reviewed. The factors to be evaluated are listed, and tentative values for the desired and acceptable accuracy of measurement for each factor are suggested.
Nine instruments which appear to be the most promising for the procurement of the meteorological data are discussed with respect to the quantities they measure, principle of operation, range and accuracy, duration of a single reading, and advantages and disadvantages associated with their use. Recommendations are presented for the continued research and development of icing meteorological instruments.

31
NACA RM A54I23
A HEATED-WIRE LIQUID-WATER-CONTENT INSTRUMENT AND RESULTS OF INITIAL FLIGHT TESTS IN ICING CONDITIONS. Carr B. Neel.
January 1985. 33p. diagrs., photos., tab. (NACA RM A54I23)
A flight model of the heated-wire instrument was tested in natural icing conditions, and was shown to provide reliable measurements of liquid-water content. The rapid response of the instrument enabled detailed study of cloud structure. Cloud-duct tests showed measurements could be made up to 700 mph. Results of the flight measurements substantiated the high values of water content previously predicted. The highest value measured was 3.7 grams per cubic meter.

32
NACA TN 3592
AN OIL-STREAM PHOTOMICROGRAPHIC AEROSCOPE FOR OBTAINING CLOUD LIQUID-WATER CONTENT AND DROPLET SIZE DISTRIBUTIONS IN FLIGHT.
Paul T. Hacker.
January 1056. 36p. diagrs., photos., tabs. (NACA TN 3592)
An airborne cloud aeroscope by which droplet size, size distribution, and liquid-water content of icing and nonicing clouds can be determined has been developed and tested in flight and in wind tunnels with water sprays. The cloud droplets are continuously captured In a stream of ofl, which is then photographed. In most cases, droplet size distribution can be obtained from a single photograph. With the droplet size distribution known, the liquid-water content of the cloud can be calculated from the geometry of the aeroscope, the airspeed, and the oil flow rate. The aeroscope is described in detail, and some droplet size distributions and liquid-water contents obtained during tests are presented.

Impingement of Cloud Droplets

33
NACA TN 2476
An Empirical Method Permitting Rapid Determination of the Area, Rate, and Distribution of Water-Drop Impingement on an Airfoil of Arbitrary Section at Subsonic Speeds.
Norman R. Bergrun. September 1951 181p. diagrs., 11 tabs. (NACA TN 2476)

A method is developed which permits the determination of area, rate, and distribution of water drop impingement on airfoils of arbitrary section at subsonic speeds. The method, which is based on the results calculated over five airfoils cases requires only a few simple numerical computations once the velocity distribution over the airfoil bas been determined.

34
NACA TECHNICAL NOTE No. 1397
A METHOD FOR NUMERICALLY CALCULATING THE AREA AND DISTRIBUTION OF WATER IMPINGEMENT ON THE LEADING EDGE OF AN AIRFOIL IN A CLOUD
Norman R. Bergrun
SUMMARY
A method is presented for determining, by step-by-step integration, the trajectories of water drops around any body in two-dimensional flow for which the streamline velocity components are known or can be computed. The method is general and considers the deviation of the water drops from Stokes' law because of speed and drop size.
The equations are presented in general form and then, to illustrate the procedure, water-drop trajectories are calculated about a 12-percent-thick symmetrical Joukowski profile chosen to simulate an NACA 0012 section.
The method provides a means for the relatively rapid calculation of the trajectory of a single drop without the utilization of a differential analyzer.
In addition, consideration is given to the maximum possible rate of water-drop impingement on a body.

35
NACA RM E52B12
IMPINGEMENT OF WATER DROPLETS ON AN NACA 65,-212 AIRFOIL AT AN ANGLE OF ATTACK OF 4°.
Brun, Rinaldo J., Serafini, John S., and Moshos, George J. September 1983. 41p. diagrs., tab. (NACA RM E52B12)
The trajectories of droplets in the alr flowing past aa NACA 851-213 airfoil at aa angle of attack of 4° were determined. The collection efficiency, the area of droplet impingement, and the rate of droplet impingement were calculated from the trajectories. The results are applicable under the following conditions: chord lengths from 2 to 30 feet, altitudes from 1000 to 38,000 feet, airplane speeds from 180 miles per hour to the critical ight Mach number, and droplet diameters from 5 to 100 microns.

36
NACA TN 2999
IMPINGEMENT OF DROPLETS IN 90° ELBOWS WITH POTENTIAL FLOW. Paul T. Hacker, Rinaldo J. Brun and Bemrose Boyd. September 1953. 8p. diagrs., 2 tabs. (NACA TN 2099) Trajectories were determined for droplets in air flowing through 90° elbows especially designed for two-dimensional potential motion with low pressure losses. The elbows were established by selecting 88 walls of each elow two streamlines of the flow field produced by a complex potential function that establishes a two-dimensional flow around a 90° bend. An unlimited number of elbows with slightly different shapes can be established by selecting different pairs of streamlines as walls. The elbows produced by the complex potential function selected are suitable for use in aircraft air-intake ducts. The droplet impingement data derived from the trajectories are presented along with equations in such a manner that the collection efficiency, the area, the rate and the distribution of droplet impingement can be determined for any elbow defined by any pair of streamlines within a portion of the flow field established by the complex potential function. Coordinates for some typical streamlines of the flow field and velocity components for several points along these streamlines are presented in tabular form.

37
NACA Rept. 1159 IMPINGEMENT OF WATER DROPLETS ON WEDGES AND DOUBLE-WEDGE AIRFOILS AT SUPERSONIC SPEEDS.
John 8. Serafini. 1984. il, 34p. diagrs. (NACA Rept. 1159. Formerly TN 2971)
An analytical solution has been obtained for the equations of motion of water droplets impinging on a wedge in two-dimensional supersonic flow field with a shock wave attached to the wedge. The closed-form solution yields analytical expressions for the equation of the droplet trajectory, the local rate of impingement and the impingement velocity at any point on the wedge surface, and the total rate of impingement. The analytical expressions are utilised to determine the impingement on the for ward surfaces of diamond airfoils in supersonic flow fields with attached shock waves. The results presented include the following conditions: droplet diameters from 2 to 100 microns, from sea level to 30,000 feet, free-stream static temperatures from 420° to 460° R, free-stream Mach numbers from 1.1 to 2.0, semiapex angles for the wedge from 1.14° to 7.97°, thickness-to-chord ratios for the diamond airfoil from 0.08 to 0.14, chord lengths from 1 to 30 feet, and angles of attack from zero to the inverse tangent of the airfoil thickness-to-chord ratio.

38
NACA TN 3047
IMPINGEMENT OF WATER DROPLETS ON NACA 65A004 AIRFOIL AND EFFECT OF CHANGE IN AIRFOIL THICKNESS FROM 12 TO 4 PERCENT AT 4° ANGLE OF ATTACK. Rinaldo J. Brun, Helen M. Gallagher and Dorothea E. Vogt. November 1953. 45p. diagrs., tab. (NACA TN 3047)

The trajectories of droplets in the air flowing past an NACA 65A004 airfoil at an angle of attack of 4° 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. The effect of a change In airfoil thickness from 12 to 4 percent at 4° angle of attack Is presented by comparing the impingement calculations for the NACA 65A004 airfoil with those for the NACA 651-208 and 65-213 airfoils. The rearward limit of impingement on the upper surface decreases as the airfoil thickness decreases. The rearward limit of impingement on the lower surface increases with a decrease in airfoil thickness. The total water intercepted decreases as the airfoil thickness is decreased.

39
NACA TN 2952
IMPINGEMENT OF WATER DROPLETS ON NACA 651,-308 AND 651-212 AIRFOILS AT 4° ANGLE OF ATTACK.
Brun, Rinaldo J., Gallagher, Helen M., and Vogt, Dorothea E. May 1953. 41p. diagrs. (NACA TN 2952)

The trajectories of droplets in the air flowing past NACA 651,-208 AND 651-212, both at an angle of attack of 4°, were compared with a mechanical analog. The amount of water on droplet form impinging on the airfoils, the area of droplet impingement, and the rate of droplet impingement per unit area on the airfoil surface affected were calculated from the trajectories.

40
NACA TN 2904
IMPINGEMENT OF WATER DROPLETS ON A CYLINDER IN AN INCOMPRESSIBLE FLOW FIELD AND EVALUATION OF ROTATING MULTICYLINDER METHOD FOR MEASUREMENT OF DROPLET SIZE DISTRIBUTION, VOLUME-MEDIAN DROPLET SIZE, AND LIQUID-WATER CONTENT IN CLOUDS.
Rinaldo J. Brun and Harry W. Mergler. March 1953. 71p. diagrs., photo. 4 abs. (NACA TN 2904)

The trajectories of water droplets in an incompressible flow field around a cylinder were calculated with a mechanical analog. The collection efficiency, the area of droplet impingement on the cylinder, and the rate of droplet impingement were determined from the trajectories. An evaluation of the rotating multicylinder method for the measurement of droplet-site distribution, volume-median droplet size, and liquid-water content was made based on the results of the trajectory calculations.

41
NACA TN 2903
IMPINGEMENT OF CLOUD DROPLETS ON AERODYNAMIC BODIES AS AFFECTED BY COMPRESSIBILITY OF AIR FLOW AROUND THE BODY.
Rinaldo J. Brun, John 8. Serafini and Helen M. Gallagher. March 1953. 20p. diagra. (NACA TN 2903)

The trajectories of water droplets in a compressible-air flow field around a cylinder were computed with a mechanical analog. The results of the calculations at the flight critical Mach number were compared with calculations of trajectories in an incompressible flow field. For a cylinder, the effect of compressibility of the air on the droplet trajectories was negligible up to the flight critical Mach number. The results obtained with the cylinder were extended to airfoils. This extension is possible because the incompressible flow fields of both cylinders and airfoils are similarly altered by compressibility.

42
Determination of Rate, Area, and Distribution of Impingement of Waterdrops on Various Airfoils from Trajectories Obtained on the Differential Analyzer.
By A. G. Guibert, E. Janssen, and W. M. Robbins
NACA RM No. 9A05 February 1949
Abstract
The trajectories of waterdrops in air flowing over airfoils are determined for three airfoil-angle-of-attack combinations using the differential analyzer to solve the differential equations of motion of the waterdrops. From these trajectories the rate of water impingement, the area of impingement, and the distribution of impingement are determined as functions of two dimensionless moduli.
Comparisons are made of the rate of water impingement on these airfoils and the rate of water impingement on cylinders.

43
NACA TN 2931
A METHOD FOR DETERMINING CLOUD-DROPLET IMPINGEMENT ON SWEPT WINGS.
Robert G. Dorsch and Rinaldo J. Brun. April 1953. 20p. diagra. (NACA TN 2931)
The general effect of wing sweep on cloud-droplet trajectories about swept wings of high aspect ratio moving at subsonic speeds is discussed. A method of computing droplet trajectories about yawed cylinders and swept wings is presented, and illustrative droplet trajectories are computed. A method of extending two-dimensional calculations of droplet Impingement on nonswept wings to swept wings is presented. It is shown that the extent of impingement of cloud droplets on an airfoil surface, the total rate of collection of water, and the local rate of impingement per unit area of airfoil surface can be found for a swept wing from two-dimensional data for a nonswept wing. The impingement on a swept wing is obtained from impingement data for a non-swept airfoil section which is the same as the section in the normal plane of the swept wing by calculating all dimensionless parameters with respect to flow conditions in the normal plane of the swept wing.

44
NACA TN 3147
IMPINGEMENT OF WATER DROPLETS ON AN ELLIPSOID WITH FINENESS RATIO 10 IN AXI- SYMMETRIC FLOW.
Rinaldo J. Brun and Robert G. Dorsch. May 1954. 37p. diagrs., tab. (NACA TN 3147)
The presence of radomes and instruments that are sensitive to water films or ice formations in the nose section of all-weather aircraft and missiles necessitates a knowledge of the droplet impingement characteristics of bodies of revolution. Because it is possible to approximate many of these bodies with an ellipsoid of revolution, droplet trajectories about an ellipsoid of revolution with a fineness ratio of 10 were computed for incompressible axisymmetric air flow. From the computed droplet trajectories, the following impingement characteristics of the ellipsoid surface were obtained and are presented in terms of dimensionless parameters:
(1) total rate of water impingement, (2) extent of droplet impingement zone, and (3) local rate of water impingement. These impingement characteristics are compared briefly with those for an ellipsoid of revolution with a fineness ratio of 5 reported in NACA TN 3099.

45
NACA TN 3099
IMPINGEMENT OF WATER DROPLETS ON AN ELLIPSOID WITH FINENESS RATIO 5 IN AXISYMMETRIC FLOW.
Robert G. Dorsch, Rinaldo J. Brun and John L. Gregg. March 1954. 50p. diagra., tab. (NACA TN 3099)
The presence of radomes and instruments that are sensitive to water films or ice formations in the nose section of all-weather aircraft and missiles necessitates a knowledge of the droplet impingement characteristics of bodies of revolution. Because it is possible to approximate many of these bodies with an ellipsoid of revolution, droplet trajectories about an ellipsoid of revolution with a fineness ratio of 5 were computed for incompressible axisymmetric air flow. From the computed droplet trajectories, the following impingement characteristics of the ellipsoid surface were obtained and are presented in terms of dimensionless parameters:
(1) total rate of water impingement, (2) extent of droplet impingement zone, (3) distribution of impinging water, and (4) local rate of water impingement.

46
NACA TN 3153
VARIATION OF LOCAL LIQUID-WATER CONCENTRATION ABOUT AN ELLIPSOID OF FINENESS RATIO 5 MOVING IN A DROPLET FIELD.
Robert G. Dorsch and Rinaldo J. Brun. July 1954. 68p. diagrs., photos., 2 tabs. (NACA TN 3153)
Analyses of calculated water-droplet trajectories show that the concentration of liquid water at various points about an ellipsoid of revolution moving through a droplet field varies considerably. Curves of local concentration factor as a function of spatial position are presented in terms of dimensionless parameters.

47
NACA TN 3155
National Advisory Committee for Aeronautics. IMPINGEMENT OF WATER DROPLETS ON NACA 65A004 AIRFOIL AT 8 ANGLE OF ATTACK.
Rinaldo J. Brun, Helen M. Gallagher and Dorothea E. Vogt. July 1954. 27p. diagra. (NACA TN 3155)
The trajectories of droplets in the air flowing past an NACA 65A004 airfoil at an angle of attack of 8° 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 same airfoil at an angle of attack of 4°.

48
NACA TN 3410
VARIATION OF LOCAL LIQUID-WATER CONCENTRATION ABOUT AN ELLIPSOID OF FINENESS RATIO 10 MOVING IN A DROPLET FIELD.
Rinaldo J. Brun and Robert G. Dorsch. April 1955. 51p. diagra., photo., tab. (NACA TN 3410)
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 spatial position were obtained and are presented in terms of dimensionless parameters that describe flight and atmospheric conditions.

49
NACA TN 3338
A DYE-TRACER TECHNIQUE FOR EXPERIMENTALLY OBTAINING IMPINGEMENT CHARACTERISTICS OF ARBITRARY BODIES AND A METHOD FOR DETERMINING DROPLET SIZE DISTRIBUTION.
Uwe H. von Glahn, Thomas F. Gelder and William H. Smyers, Jr. March 1955. 73p. diagra., photos., tab. (NACA TN 3338)
A dye-tracer technique has been developed from which the droplet impingement characteristics of bodies can be determined by colorimetric analysis. The technique is applicable to various wind tunnels provided the humidity of the air stream can be maintained near saturation. A method is also presented whereby the droplet size distribution of the impinging cloud may be determined by relating the experimental impingement characteristics of a body to the theoretical trajectory results for the same body.

50
NACA TN 3587
IMPINGEMENT OF WATER DROPLETS ON A SPHERE.
Robert G. Dorsch, Paul G. Saper, and Charles F. Kadow November 1955, 29p. diagrs., tab. (NACA TN 3587)
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 reported calculations for the sphere.

51
NACA TN 3658
IMPINGEMENT OF WATER DROPLETS ON A RECTANGULAR HALF BODY IN A TWO-DIMENSIONAL INCOMPRESSIBLE FLOW FIELD.
William Lewis and Rinaldo J. Brun. February 1956. 27p. diagrs., tabs. (NACA TN 3658)
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.

52
NACA TN 3586
IMPINGEMENT OF WATER DROPLETS ON NACA 65A004 AIRFOIL AT 0 ANGLE OF ATTACK.
Rinaldo J. Brun and Dorothea E. Vogt. November 1955. 28p. diagrs. (NACA TN 3586)
The trajectories of droplets in the air flowing past an NACA 65A004 airfoil at an angle of attack of 0° 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 same airfoil at angles of attack of 4° and 8°.

53
NACA REPORT 1215
IMPINGEMENT OF CLOUD DROPLETS ON A CYLINDER AND PROCEDURE FOR MEASURING LIQUID-WATER CONTENT AND DROPLET SIZES IN SUPERCOOLED CLOUDS BY ROTATING MULTICYLINDER METHOD
By R. J. BRUN, W. LEWIS, P. J. PERKINS, and J. S. SERAFINI
SUMMARY
Evaluation of the rotating multicylinder method for the measurement of droplet-size distribution, volume-median droplet size, and liquid-water content in clouds showed that small uncertainties in the basic data eliminate the distinction between different cloud droplet-size distributions and are a source of large errors in the determination of the droplet size. Calculations of the trajectories of cloud droplets in incompressible and compressible flow fields around a cylinder were performed on a mechanical analog constructed for the study of the trajectories of droplets around aerodynamic bodies. Many data points were carefully calculated in order to determine precisely the rate of droplet impingement on the surface of a right circular cylinder. From the computed droplet trajectories, the following impingement characteristics of the cylinder surface were obtained and are presented in terms of dimensionless parameters: (1) total rate of water impingement, (2) extent of droplet impingement zone, and (3) local distribution of impinging water on cylinder surface.
The rotating multicylinder method for in-flight determination of liquid-water content, droplet size, and droplet-size distribution in icing clouds is described. The theory of operation, the apparatus required, the technique of obtaining data in flight, and detailed methods of calculating the results, including necessary charts and tables, are presented. An evaluation of the multicylinder method includes the effect on final results of droplets that do not freeze completely on the cylinders after striking them, as well as probable errors in final results caused by the inherent insensitivity of the multicylinder method.

54
NACA Rept. 1317
CLOUD-DROPLET INGESTION IN ENGINE INLETS WITH INLET VELOCITY RATIOS OF 1.0 AND 0.7. Rinaldo J. Brun. 1957. ii, 35p. diagrs., tab. (NACA Rept. 1317. Supersedes TN 3593)
The paths of cloud droplets into two engine inlets are calculated. The amount of water in droplet form ingested by the inlets and the amount and distribution of water impinging on the inlet walls are obtained from these droplet-trajectory calculations. In both types of inlet a prolate ellipsoid of revolution (10- percent thick) represents either part or all of the forebody at the center of an annular inlet to an engine. The configurations can also represent a fuselage of an airplane with side ram-scoop inlets. The principal difference between the two inlets studied is that the inlet air velocity of one is 0.7 that of the other.

55
NACA TN 4268
DROPLET IMPINGEMENT AND INGESTION BY SUPERSONIC NOSE INLET IN SUBSONIC TUNNEL CONDITIONS
Thomas F. Gelder. May 1958. 56p. diagra., photos. (NACA TN 4268)
The amount of water in cloud droplet form ingested by a full-scale supersonic nose inlet with conical center body was measured. Local and total water impingement rates on the cowl and center-body surfaces were also obtained. All measurements were made with a dye-tracer technique. Inlet angles of attack of 00 and 4.20, droplet diameters from 11 to 20 microns, and ratios of inlet to free-stream velocity from 0.4 to 1.8 were studied. Measurements were confined to a free-stream Mach number of 0.237 and are extendable to other subsonic speeds by dimensionless impingement parameters.

56
NACA TN 3839
EXPERIMENTAL DROPLET IMPINGEMENT ON SEVERAL TWO-DIMENSIONAL AIRFOILS WITH THICKNESS RATIOS OF 6 TO 16 PERCENT. Thomas F. Gelder, William H. Smyers, Jr., and Uwe von Glahn. December 1956. 77p. diagra.. photos, tabs. (NACA TN 3839)
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° to 12°, and chord sizes from 13 to 96 inches were included in the study. The results are presented in the form of dimensionless impingement parameters in order to cover a wide range of flight and atmospheric conditions.

57
NACA TN 3770
IMPINGEMENT OF DROPLETS IN 60° ELBOWS WITH POTENTIAL FLOW.
Paul T. Hacker, Paul G. Saper, and Charles F. Kadow. October 1958. 54p. diagre., tabs. (NACA TN 3770)
Theoretical trajectories were determined for droplets in air flowing through 600 elbows. The elbows were established by selecting as walls of each elbow two streamlines of a two-dimensional flow field produced by a complex potential function. These elbows are suitable for use in aircraft air-inlet ducts. Droplet impingement data are presented in terms of dimensionless parameters along with empirical equations so that the results can be applied over a wide range of conditions and elbow sizes. A comparison of the 60° elbow with previous calculations for a comparable 90° elbow indicated that the impingement characteristics of the two elbows are very similar.

58
NACA TN 4092 EXPERIMENTAL DROPLET IMPINGEMENT ON FOUR BODIES OF REVOLUTION.
James P. Lewis and Robert S. Ruggeri. December 1957. 61p. diagra., photos. (NACA TN 4092)
The rate and area of cloud droplet impingement on four bodies of revolution were obtained experimentally in the NACA Lewis icing tunnel. Spheres, ellipsoidal forebodies of fineness ratios of 2.5 and 3.0, and a conical forebody of 30° included angle were studied at angles of attack of 0° to 6°, rotational speeds up to 1200 rpm, and an airspeed of 157 knots. The results are presented in the form of dimensionless impingement parameters in order to cover a wide range of flight and atmospheric conditions.

59
NACA TN 4035
IMPINGEMENT OF CLOUD DROPLETS ON 36.5- PERCENT-THICK JOUKOWSKI AIRFOIL AT ZERO ANGLE OF ATTACK AND DISCUSSION OF USE AS CLOUD MEASURING INSTRUMENT IN DYE-TRACER TECHNIQUE.
R. J. Brun and Dorothea E. Vogt. September 1957. 52p. diagra., tabs. (NACA TN 4035)
The trajectories of droplets in the air flowing past a 36.5-percent-thick Joukowski airfoil at zero angle of attack 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 are on the airfoil surface were calculated from the trajectories and cover a large range of flight and atmospheric conditions. With the detailed impingement information available, the 36.5- percent-thick Joukowski can serve the dual purpose of use as the principal element in instruments for making measurements in clouds and of a basic shape for estimating impingement on a thick streamlined body.

60
NACA RM E56E11
USE OF TRUNCATED FLAPPED AIRFOILS FOR IMPINGEMENT AND ICING TESTS OF FULL-SCALE LEADING-EDGE SECTIONS.
Uwe H. von Glahn. July 1956. 29p. diagrs, photos., tabs. (NACA RM E56E11)
Experimental studies were made with an NACA 651-212 airfoil section truncated at the 30- and 50- percent-chord stations and equipped with a trailing-edge flap. When the truncated airfoils were compared with the full-chord airfoils, the velocity distribution and the impingement characteristics were similar with the flap properly deflected, but were altered substantially without flap deflection. Use of flapped truncated airfoils permits impingement and icing studies in icing tunnels to be conducted with full-scale leading-edge sections over a greater range of conditions than previously possible.

Propeller Ice Protection

61
NACA TECHNICAL NOTE 1178
A FLIGHT INVESTIGATION OF THE THERMAL PERFORMANCE OF AN AIR-HEATED PROPELLER
John F. Darsow and James Selna
SUMMARY
Observations were made during flight in natural-icing conditions and by the collection of thermal data on the propeller during flight in clear air and in clouds at temperatures above freezing. The propeller was equipped with standard hollow steel blades which were altered to permit heated air to enter the blade cavities at the propeller hub and to leave the cavities at the blade tips. The distribution or air flow inside the blades was not controlled.

The observations in natural-icing conditions together with the thermal test data indicate that little or no protection to the leading-edge region of the propeller blades would result during flight in severe natural-icing conditions. In natural-icing conditions only light-icing conditions were encountered; however, ice accretions formed on the leading edges or the blades in the region of blade stations 30 to 40. The clear air and cloud tests showed the propeller blades to be inefficient heat exchangers in that more heat energy was discharged in the air flow leaving the propeller than was dissipated through the propeller-blade surfaces. The measured blade-surface temperatures indicated that inadequate heating was provided to the leading-edge region or the propeller and snow the need of providing means to increase the heat flow through the leading-edge region or the blades.

62
NACA TN No. 1691 August, 1948
Icing and De-Icing of a Propeller with Internal Electric Blade Heaters
Abstract
De-icing effectiveness of internal electric propeller-blade heater was determined at two icing and two operating conditions with heat applied continuously and cyclically, and the required heat-on and cycle times are shown.
Chordwise extent of icing was greater than that covered by bdlade heaters. Adequate de-icing in heated area with continuous heating was obtained with power available but maximum power input of 1250 watts per blade was insufficient for cyclic de-icing. Surface temperature-rise rates of 0.2° to 0,7° F per second were obtained and minimum cooling period for cylio de-icing was approximately 2.55 times the heating period,

63
De-Icing Effectiveness of External Electric Heaters for Propeller Blades.
By James P. Lewis
NACA TN No. 1520 February 1948
Abstract
Icing protection provided by external rubber-clad propeller blade heaters at several icing, heating, and propeller operating conditions has been determined. Effects of propeller speed, ambient-air temperature, liquid water concentration, heating power density, duration of heating, and total cycle time on power requirements and de-icing performance were investigated.
Power densities of 4 to 10 watts per square inch were required for cyclic de-icing with best chordwise distribution approaching uniformity. Heating times of approximately 24 seconds were required with ratio of heat-on to total cycle time of 1:4 giving best results.
Mean rate of rise of heater temperature of approximately 1.1° F per second was obtained.

64
An Electric Thrust Meter Suitable for Flight Investigation of Propellers.
By Porter J. Perkins and Morton B. Millenson
NACA RM No. B9C17 May 1949 Abstract
A lightweight instrument that utilizes resistance-wire electric strain gages to measure propeller-shaft thrust has been developed. A wind-tunnel investigation on a propeller installed on a single-engine pursuit airplane showed that the instrument gave & reliable indication of propeller-shaft thrust to an accuracy of 42 percent within its calibrated range. No attempt was made to determine the relation of indicated shaft thrust to net propeller thrust.

65
Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection against Icing. I - Unpartitioned Propeller Blades.
By Donald R. Mulholland and Porter J. Perkins
NACA TN No. 1586
May 1948
Abstract
An icing investigation of an air-heated hollow steel propeller with blades radially partitioned at 25-percent chord was conducted in the NACA Cleveland icing research tunnel.
Results showed that at 850 rpm a heating rate of 7000 Btu per hour per blade provided adequate icing protection at 23° F but not as low as 15° F. Surface temperatures indicated satisfactory chord-wise distribution. The blade heat-exchanger effectiveness was found to be 77 percent.

66
TECHNICAL NOTE NO. 1587
INVESTIGATION OF AIR-HEATING OF A HOLLOW STEEL PROPELLER FOR PROTECTION AGAINST ICING II - 50-PERCENT PARTITIONED BLADES
By Porter J. Perkins and Donald R. Mulholland
The icing protection afforded an internal air-heated propeller blade by radial partitioning at 50-percent chord to confine the heated air to the forWard half of the blade was determined in the NACA Cleveland icing research tunnel. A modified production-model hollow steel propeller, was used for the investigation. Temperatures of the blade surfaces for several heating rates were measured under various tunnel icing conditions. Photographic observations of ice formations on blade surfaces and blade heat-exchanger effectiveness were obtained.
With 50-percent partitioning of the blades, adequate icing protection at 1050 rpm was obtained with a heating rate of 26,000 Btu per hour per blade at the blade shank using an air temperature of 4000 F with a flow rate of 280 pounds per hour per blade, which is one-third less heat than was found necessary for similar ice protection with unpartitioned blades. The chordwise distribution of the applied heat, as determined by surface temperature measurements, was considered unsatisfactory with much of the heat dissipated well back of the leading edge. Heat-exchanger effectiveness of approximately 56 percent also indicated poor utilization of available heat. This effectiveness was, however, 9 percent greater than that obtained from unpartitioned blades.

67
Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection against Icing. III - 25-Percent Partitioned Blade
By Donald RB. Mulholland and Porter J. Perkins
NACA TN No. 1588
May 1948
Abstract
An icing investigation of an air-heated hollow steel propeller with blades radially partitioned at 25-percent chord was conducted in the NACA Cleveland icing research tunnel.
Results shoved that at 850 rpm a heating rate of 7000 Btu per hour per blade provided adequate icing protection at 23° F but not as lov as 15° F. Surface temperatures indicated satisfactory chord: vise distribution. The blade heat-exchanger effectiveness was found to be 77 percent.

68
NACA TECHNICAL NOTE 1494
A METHOD FOR ESTIMATING HEAT REQUIREMENTS FOR ICE PREVENTION ON GAS-HEATED HOLLOW PROPELLER BLADES
V. H. Gray and R. G. Campbell
SUMMARY
The propeller blade is analytically divided into a number of short radial segments, successively treated as separate heat exchangers. Expressions for the total external and internal heat transfer are combined to determine the surface temperatures of each segment. The thermodynamic steady-flow equation is given for the internal gas-flow process and expressions are obtained for the radial variations of gas temperature and pressure within the blade. For a given initial gas temperature in the blade shank cavity, the minimum gas flow is determined, which will provide surface temperatures of at least 32° F everywhere on the heated portion of the blade. An expression for the required heat-source input to the gas is included and a formula is given for calculating the required blade-tip nozzle area.

69
NACA TN 2852
National Advisory Committee for Aeronautics.
AN INVESTIGATION UTILIZING AN ELECTRICAL ANALOGUE OF CYCLIC DE-ICING OF A HOLLOW STEEL PROPELLER WITH AN EXTERNAL BLADE SHOE.
Carr B. Neel, Jr. December 1052. 54p. diagrs., photos., 3 tabs. (NACA TN 2852)
A study of the heat requirements for cyclic de-icing of hollow steel propellers fitted with external blade shoes, utilizing an electrical analogue, showed how energy requirements could be decreased by changes in the method of operation of existing shoes and through proper blade-shoe design. Savings in total energy in the order of 80 percent would be possible in each case. Energy requirements were shown to increase with decreasing liquid-water content and air temperature.

70
NACA TN 3025
AN INVESTIGATION UTILIZING AN ELECTRICAL ANALOGUE OF CYCLIC DE-ICING OF HOLLOW STEEL PROPELLERS WITH INTERNAL ELECTRIC HEATERS.
Carr B. Neel, Jr. October 1953. 31p. diagrs., photo., 3 tabs. (NACA TN 3055)
An analytical study, utilizing an electrical analogue, of the heat requirements for cyclic de-icing of hollow steel propellers fitted with two types of internal electric heaters showed the impracticability of using an internal tubular heater, and illustrated the advantages of employing an internal shoe-type heater to distribute the heat more evenly to the blade surface. The importance of minimizing the thermal inertia of the system was demonstrated, and the magnitude of reductions in the total energy requirement made possible through reductions in heating period was indicated.

71
TECHNICAL NOTE 2212 THE EFFECT OF ICE FORMATIONS ON PROPELLER PERFORMANCE
By Carr B. Neel, Jr., and Loren G. Bright
SUMMARY
Measurements of propeller efficiency loss due to ice formation are supplemented by an analysis to establish the magnitude of efficiency losses to be anticipated during flight in icing conditions. The measurements were made during flight in natural icing conditions; whereas the analysis consisted of an investigation of changes in blade-section aerodynamic characteristics caused by ice formation and the resulting propeller efficiency changes. Agreement in the order of magnitude of efficiency losses tobe expected is obtained between measured and analytical results. The results indicate that, in general, efficiency losses can be expected to be less than 10 percent; whereas maximum losses, which will be encountered only rarely, may be as high as 15 or 20 percent. Reported. losses larger than 15 or 20 percent, based on reductions in airplane performance, probably are due to ice accretions on other parts of the airplane.
Blade-element theory is used in the analytical treatment, and calculations are made to show the degree to which the aerodynamic characteristics of a blade section. must be altered to produce various propeller efficiency losses. The effects of ice accretions on airfoil-section characteristics at subcritical speeds and their influence on drag-divergence Mach number are examined, and. the attendant maximum efficiency losses are computed. The effect of kinetic heating on the radial extent of ice formation is considered, and its influence on required length of blade heating shoes is discussed. It is demonstrated how the efficiency loss resulting from an icing encounter is influenced by the decisions of the pilot in adjusting the engine and propeller controls.

Induction System Ice Protection

72
TECHNICAL NOTE NO. 1790
INVESTIGATION OF ICING CHARACTERISTICS OF TYPICAL LIGHT-AIRPLANE ENGINE INDUCTION SYSTEM
By Willard D. Coles
SUMMARY
The icing characteristics of two typical light-airplane engine induction systems were investigated using the carburetors and manifolds of engines in the horsepower ranges from 65 to 85 and 165 to 185. The smaller system consisted of a float-type carburetor with an unheated manifold and the larger system consisted of a single-barrel pressure-type carburetor with an oil-jacketed manifold.
Carburetor-air temperature and humidity limits of visible and serious icing were determined for various engine power conditions. Several methods of achieving ice-free induction systems are discussed along with estimates of surface heating requirements of the various induct ion-system components.
A study was also made of the icing characteristics of a typical light-airplane air scoop with an exposed filter and a modified system that provided a normal ram inlet with the filter located in a position to Induce inertia separation of the free water from the charge air.
The principle of operation of float-type carburetors is proved to make them inherently more susceptible to icing at the throttle plate than pressure-type carburetors. The results indicated that proper jacketing and heating of all parts exposed to the fuel spray can satisfactorily reduce or eliminate icing in the float-type carburetor and the manifold. Pressure-type carburetors can be protected from serious Icing by proper location of the fuel-discharge nozzle combined with suitable application of heat to critical parts.

73
NACA TR 982
ICING-PROTECTION REQUIREMENTS FOR RECIPROCATING-ENGINE INDUCTION SYSTEMS
by Willard D. Coles, Vern G. Rollin, and Donald R. Mulholland
NACA-TR-982, 1950
SUMMARY
Despite the development of relatively ice-free fuel-metering systems, the widespread use of alternate and heated-air intakes, and the use of alcohol for emergency de-icing, icing of aircraft-engine induction systems is a serious problem. Investigations have been made to study and to combat all phases of thin icing problem. From these investigations, criterions for safe operation and for design of new induction systems have been established.
The results were obtained from laboratory investigations of carburetor-supercharger combinations, wind-tunnel investigations of air scoops, multicylinder-engine studies, and fight investigations. Characteristics of the three forms of ice, impact, throttling, and fuel evaporation, were studied. The effects of serveral factors on the icing characteristics were also studied and included (1) atmospheric conditions, (2) engine and air-scoop configurations, including light airplane systems, (3) type of fuel usd, and (4) operating variables, such as power condition, use of a manifold pressure regulator, mixture setting, carburetor heat, and water-alcohol injection. In addition, ice-detection methods were investigated and methods of preventing and removing induction-system ice were studied. Recommendations are given for design and operation with regard to induction-system icing.

74
NACA RM E53E07
INVESTIGATION OF AERODYNAMIC AND ICING CHARACTERISTICS OF A FLUSH ALTERNATE-INLET INDUCTION-SYSTEM AIR SCOOP.
James P. Lewis. July 1953. 42p. diagrs., photos. (NACA RM E53EO7)
An investigation of the aerodynamic and icing characteristics of a full-scale induction-system air-scoop assembly incorporating a flush-type alternate inlet was conducted in the NACA Lewis icing research tunnel. The investigation was made over a range of mass-air-flow ratios, angles of attack, airspeeds, air temperatures, liquid-water content, and droplet sizes. The ram inlet gave good pressure recovery in both clear air and icing, the rapid blocking of the carburetor screen occurred in icing. The alternate inlet had poor pressure recovery in both clear air end icing, but no serious screen icing was obtained. The investigation included the use of preheat air alone and a combination with ram- and alternate inlet air.

Turbine-Type Engine and Inlet Icing Studies

75
Natural Icing of an Axial-Flow Turbojet Engine in Flight for a Single Icing Condition.
By Loren W. Acker
NACA RM No. E8F01a August 12, 1948
Abstract
A flight investigation in natural icing conditions was conducted to determine the effect of ice formations on performance of axial-flow turbojet engines. Results are presented for a flight in which liquid-water content varied from 0.077 to 0.490 gram per cubic meter.
During 60 minutes in icing, tail-pipe temperature increased from 865° to 965° F and the jet thrust decreased from 1950 to 1700 pounds. The engine was satisfactorily accelerated to take-off power near the end of the icing period.

76
Preliminary Results of Natural Icing of an Axial-Flow Turbojet Engine.
By Loren W. Acker
NACA RM No. E8C18 August 1918
Abstract
A flight investigation in naturel icing conditions was conducted to determine effect of ice formations on performance of an axial-flow turbojet engine. Results are presented for a flight in which the icing rate varied from 5.1 to 2.1 inches per hour.
During 45 minutes in icing, tail-pipe temperature increased from 761° to 1065° F and jet thrust decreased from 1234 to 910 pounds. Ice penetrated to the second-stage stator blades.

77
Icing Characteristics and Anti-Icing Heat Requirements for Hollow and Internally Modified Gas-Heated Inlet Guide Vanes.
By Vernon H. Gray and Dean T. Bowden
NACA RM E50I08 December 1950
Abstract
Gas temperatures and flow rates required for anti-icing a two-dimensional cascade of turbojet inlet guide vanes were determined for hollow and internally modified vanes. The pressure losses caused by icing on unheated guide vanes were also determined.
Less heat was required for anti-icing internally modified blades than for the hollow blades. Pressure losses across the cascade were greater at an inlet temperature of 22° F than at 0° F because of the characteristic shapes of ice deposits at the two temperatures.

78
NACA TN 3837
INVESTIGATION OF HEAT TRANSFER FROM A STATIONARY AND ROTATING ELLIPSOIDAL FOREBODY OF FINENESS RATIO 3.
James P. Lewis and Robert S. Ruggeri. November 1956. 48p. diagrs., photo., tabs. (NACA TN 3837)
Experimental convective heat transfer wss obtained for a 20-inch-diameter forebody for airspeeds up to 240 knots, rotational speeds up to 1200 rpm, angles of attack of 0°, 3°, and 6°, and both uniform surface temperature and uniform input heat density. The results agree well with theoretical predictions. Affects of rotation were insignificant, and effects of angle of attack only minor. Transition from laminar to turbulent heat transfer varied over a Reynolds number range of 0.8 x 10^6 to 8 x 10^6. Limited transient heating data indicated that the change of surface temperature with time followed an exponential relation.

79
NACA TN 4093
INVESTIGATION OF HEAT TRANSFER FROM STATIONARY AND ROTATING CONICAL FOREBODY.
Robert S. Ruggeri and James P. Lewis.
October 1957. 30. diagrs., photo., tab. (NACA TN 4093)
Experimental convective heat transfer was determined for a conical forebody (15° half-angle) for free-stream velocities w to 400 feet per second, rotational speeds of to 1200 rpm, angles of attack of 9° and 6°, and for heating conditions of uniform surface temperature and uniform heater input power density. For the turbulent region, the results were in closer agreement with values predicted for two-dimensional bodies than with those predicted for a cone. Effects of rotation were insignificant. For the stationary spinner at 0° angle of attack, the heat-transfer coefficients were 6 to 13 percent greater on the lower surface than on the upper surface. Early boundary-layer transition occurred for all conditions investigated.

80
Investigation of Power Requirements for Ice Prevention and Cyclical De-Icing of Inlet Guide Vanes with Internal Electric Heaters.
By Uve von Glalm and Robert E. Blatz
NACA RM E50H29 December 1950
Abstract
An investigation was conducted to determine the electric pover requirements for turbojet-engine inlet guide vanes with continuous heating and with cyclical de-icing for a range of icing conditions.
Minimum total power requirements for continuous heating and cyclical de-icing are presented in terms of average surface datum temperature. An analysis is included to extend the experimentally obtained continuous heating data to vane sizes and icing conditions other than those investigated. Cyclical de-icing provides a total pover saving as high as 79 percent over continuous heating for a typical engine installation. Heat-on periods of 10 seconds or less with heat-off periods of 60 seconds are recommended for cyclical de-icing.

81
NACA Investigations of Icing-Protection Systems for Turbojet-Engine Installations.
By Uwe von Glahn, Edmund E. Callaghan, and Vernon H. Gray
NACA RM E51B12
May 1951
Abstract
A summary is presented of the investigations made in flight and in wind tunnels at the NACA Lewis laboratory to determine which components of turbojet engines are most critical in icing conditions and to evaluate several icing-protection methods.
Complete removal or retraction of compressor-inlet screens upon entering icing conditions is recommended. Surface heating appears to be the most acceptable icing-protection method, although hot-gas bleedback offers a simple method for obtaining icing protection on some installations.

82
NACA RM E57G09
TOTAL-PRESSURE DISTORTION AND RECOVERY OF SUPERSONIC NOSE INLET WITH CONICAL CENTERBODY IN SUBSONIC ICING CONDITIONS.
Thomas F. Gelder. September 1957. 41p. diagrs., photos. (NACA RM E57G09)
Ice was formed on a full-scale unheated supersonic nose inlet over a range of conditions in the NACA Lewis icing tunnel to determine its effect on compressor-face total-pressure distortion and recovery. The addition of ice to the inlet components increased distortion levels and decreased recovery values compared with clear-air results, the losses increasing with time in icing. The combination of glaze ice, high corrected weight flow, and high angle of attack yielded the highest levels of distortion and lowest values of recovery.

83
Investigation of Aerodynamic and Icing Characteristics of Water-Inertia-Separation Inlets for Turbojet Engines. By Uwe von Glahn and Robert E. Blatz
NACA RM E50E03 July 1950
Abstract
Aerodynamic and icing investigations of several internal water-inertia-separation inlets designed to prevent entrance of water into a turbojet engine in an icing condition are presented. Comparisons of total Pressure loss, mass flow, and icing charecteristics are made.
Complete ioing protection of inlet guide vanes was not achieved. Approximately 8 percent af the volume of water entering the inlets remained in the air. For mon- icing operation, total-pressure losses were comparable to those of direct-ram inlets. Under icing conditions, considerable total-pressure losses were obtained with inertia-separation inlets.

Wing Icing Protection

84
NACA TR 831, 1945
AN ANALYSIS OF THE DISSIPATION OF HEAT IN CONDITIONS OF ICING FROM A SECTION OF THE WING OF THE C-46 AIRPLANE
J. K. Hardy
SUMMARY
A method is given for calculating the temperature that a surface, heated internally by air, will assume in specified conditions of icing. The method can be applied generally to predict the performance, under conditions of icing, of the thermal system for protecting aircraft. Calculations have been made for a section of the wing of the C-46 airplane, and the results agree closely with the temperatures measured. The limit of protection, when the temperature of the surface reaches 32° F, has been predicted for the leading edge. The temperature of the surface in conditions of icing with air at 0° F also has been calculated. The effect of kinetic heating and the effect of the concentration of free water and size of droplet in the cloud are demonstrated.

85
TECHNICAL NOTE NO. 1472
THE CALCULATION OF THE HEAT REQUIRED FOR WING THERMAL ICE PREVENTION IN SPECIFIED ICING CONDITIONS
By Carr B. Neel, Jr., Norman R. Bergrun, David Jukoff, and. Bernard A. Shlaff
SUMMARY
As a result of a fundamental investigation of the meteorological conditions conducive to the formation of ice on aircraft and a study of the process of airfoil thermal ice prevention, previously derived equations for calculating the rate of heat transfer from airfoils in icing conditions were verified. Knowledge of the manner in which water is deposited on and evaporated from the surface of a heated airfoil was expanded sufficiently to allow reasonably accurate calculations of airfoil heat requirements. The research consisted of flight tests in natural-icing conditions with two 8-foot-chord. heated airfoils of different sections. Measurements of the meteorological variables conducive to ice formation were made simultaneously with the procurement of airfoil thermal data.
It was concluded that the extent of knowledge on the meteorology of icing, the impingement of water drops on airfoil surfaces, and the processes of heat transfer and evaporation from a wetted airfoil surface has been increased to a point where the design of heated wings on a fundamental, wet-air basis now can be undertaken with reasonable certainty.

86
NACA RM E51J29
PRELIMINARY RESULTS OF CYCLICAL DE-ICING OF A GAS-HEATED AIRFOIL.
V. H. Gray, D. T. Bowden and U. von Glahn. January 1952. 38p. photos., diagrs., tab. (NACA RM 5129)

An NACA 65-212 airfoil of 8-foot chord was provided with a gas-heated leading edge for investigations of cyclical de-icing. De-icing was accomplished with intermittent heating of airfoil segments that supplied hot gas to chordwise passages in a double-akin construction. Ice removal was facilitated by a spanwise leading-edge parting strip which was continuously heated from the gas-supply duct. Preliminary results demonstrate that satisfactory cyclical ice removal occurs with ratios of total cycle time to heat-on period from 10 to 26.

87 NACA RM E51J30
PRELIMINARY INVESTIGATION OF CYCLIC DE-ICING OF AN AIRFOIL USING AN EXTERNAL ELECTRIC HEATER.
James P. Lewis and Dean T. Bowden. February 1952. 43p. photos, diagrs. (NACA RM E5130)
An investigation was conducted in the NACA Lewis icing research tunnel to determine the characteristics and requirements of cyclic de-icing of an airfoil by use of an external electric heater. The present investigation was limited to an airspeed of 175 miles per hour. Data are presented to show the effects of variations in heat-on and heat-off periods, ambient air temperature, liquid-water content, angle of attack and heating distribution on the requirements for cyclic de-icing. The external heat flow at various icing and heating conditions is also presented. A continuously heated parting strip at the airfoil leading edge was found necessary for quick, complete, and consistent ice removal. The cyclic power requirements were found to be primarily a function of the datum temperature and heat-on time, with the other operating and meteorological variables having a second-order effect. Short heat-on periods and high power densities resulted in the most efficient ice removal, the minimum energy input, and the minimum runback ice formations.

88
NACA TN 2480
COMPARISON OF HEAT TRANSFER FROM AIRFOIL IN NATURAL AND SIMULATED ICING CONDITIONS.
Thomas F. Gelder and James P. Lewis. September 1951. 51p. diagrs., photos., 3 tabs. (NACA TN 2480)
An experimental investigation of the heat transfer from an 8-foot-chord airfoil model in clear air and in simulated icing conditions was conducted in the icing tunnel. These results are compared with those obtained in a flight investigation with the same model at similar operating conditions. The tunnel results indicate the effect of tunnel turbulence by the forward movement of transition from laminar to turbulent heat transfer. The flight results indicate that the convective heat transfer in icing is considerably different from that measured in clear air and only slightly different from that obtained in the tunnel during simulated icing.

89
NACA TN 2914
A METHOD FOR RAPID DETERMINATION OF THE ICING LIMIT OF A BODY IN TERMS OF THE STREAM CONDITIONS.
Edmund E. Callaghan and John S. Serafini. March 1953. 33p. diagrs. (NACA TN 2014)

The effects of existing frictional heating were analyzed to determine the conditions under which ice formations on aircraft surfaces can be prevented. A method is presented for rapidly determining by means of charts the combination of Mach number, altitude, and stream temperature which will maintain an ice-free surface in an icing cloud. The method can be applied to both subsonic and supersonic flow. The charts presented are for Mach numbers up to 1.8 and pressure altitudes from sea level to 45,000 feet.

90
NACA TN 2861
ANALYTICAL INVESTIGATION OF ICING LIMIT FOR DIAMOND-SHAPED AIRFOIL IN TRANSONIC AND SUPERSONIC FLOW.
Edmund E. Callaghan and John S. Serafini. Jansary 1953. 18p. diagrs. (NACA TN 2861)

Calculations have been made for the icing limit of a diamond airfoil at sero 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 32° 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.

91 NACA RM E53C26
DE-ICING AND RUNBACK CHARACTERISTICS OF THREE CYCLIC, ELECTRIC, EXTERNAL DE-ICING BOOTS EMPLOYING CHORDWISE SHEDDING.
Robert 8. Ruggeri. May 1953. 32p. photos. , diagrs. (NACA RM E53C26)

The performance characteristics of three cyclic, electric, rubber-clad de-icing boots were evaluated. Each boot was operated in icing at design specifications of 21 watts per square inch for cycled areas, 13 watts per square inch for continuously heated parting strips, a heat-on time of 10 seconds, and a cycle ratio of 10. For a free-stream velocity of approximately 395 feet per second, the range of free-stream total temperature at which the icing protection afforded by the various boots became marginal was from 12° to 15° F for values of liquid-water content employed. The runback characteristics of the boots were similar. The forward cycled segments, upper and lower surfaces, were the most critical areas for the three boots investigated.

92
NACA RM E53C27
COMPARISON OF SEVERAL METHODS OF CYCLIC DE-ICING OF A GAS-HEATED AIRFOIL. Vernon H. Gray and Dean T. Bowden. June 1953. 66p. diagrs., photos., 2 tabs. (NACA RM E53C27)

Several methods of cyclic de-icing of a gas-heated airfoil were investigated to determine ice-removal characteristics and heating requirements. The cyclic de-icing system with a spanwise ice-free parting strip in the stagnation region and a constant- temperature gas-supply duct gave the quickest and most reliable ice removal. Heating requirements for the several methods of cyclic de-icing are compared, and the savings over continuous ice prevention are shown. Data are presented to show the relation of surface temperature, rate of surface heating, and heating time to the removal of ice.

93
NACA TN 3130
A PROCEDURE FOR THE DESIGN OF AIR-HEATED ICE-PREVENTION SYSTEMS.
Carr B. Neel, Jr. June 1954. 63p. diagrs., photo. (NACA TN 3130)

The procedure to be followed in the design of aircraft ice-prevention equipment in which the components are protected by means of internally circulated heated air is outlined. In addition to presentation of the required heat-transfer and air-pressure-loss equations, a simple electrical analogue is described which was devised to facilitate the design of an air-heated system. An illustration is given of the application of the analogue to a design problem.

94
NACA RM E54I03
INVESTIGATION OF POROUS GAS-HEATED LEADING-EDGE SECTION FOR ICING PROTECTION OF A DELTA WING.
Dean T. Bowden. January 1955. dp. diagrs., photos., tab. (NACA RM E5402)

An investigation was conducted in the NACA Lewis icing research tunnel to determine heating requirements and characteristics of a gas-heated porous leading-edge system for anti-icing of a delta wing. Adequate icing protection was obtained for all icing conditions investigated. Large savings in gas flow may be realized by sealing hall the upper-surface porous area. Gas flow through the porous area caused only a slight increase in airfoil drag ard had no appreciable effect on airfoil pressure distribution Glaze-icE formations on the unheated airfoil caused rapid increases in section drag.

95
NACA RM E56B23
HEAT REQUIREMENTS FOR ICE PROTECTION OF A CYCLICALLY GAS-HEATED, 36° SWEPT AIRFOIL WITH PARTIAL-SPAN LEADING-EDGE SLAT.
Vernon H. Gray and Uwe H. Von Glahn. May 1956. 73p. diagrs., photos., tabs. (NACA RM E56B23)

Heating requirements for satisfactory cyclic de-icing over a wide range of icing and operating conditions have been obtained for a gas-heated, 36° swept airfoil with a partial-span leading-edge slat. Comparisons of heating requirements were made between the slatted and unslatted portions of the airfoil and between cyclic de-icing and continuous anti-icing. Cyclic de-icing systems with and without leading-edge ice-free parting strips were also evaluated.

96
Effectiveness of Thermal-Pneumatic Airfoil-Ice-Protection System.
By William H. Govan, Jr., and Donald R. Mulholland. NACA RM E50K10a April 1951

Abstract
Icing and drag investigations were conducted in the NACA L wis icing research tunnel on a thermal-pneumatic de-icer mounted on a 42-inch-chord NACA 0018 airfoil. Marginal power densities for the leading-edge electrically heated area were obtained. Drag comparisons were made between the bare airfoil and the various operating conditions of the pneumatic section of the deicer during icing and nonicing of the airfoil surface.

Performance Penalties

97
NACA RM E53J30 EFFECT OF ICE FORMATIONS ON SECTION DRAG OF SWEPT NACA 634-000 AIRFOIL WITH PARTIAL-SPAN LEADING-EDGE SLAT FOR VARIOUS MODES OF THERMAL ICE PROTECTION.
Uwe H. von Glahn and Vernon H. Gray. March 1954. 59p. diagrs., photos. (NACA RM ES3J30)

Studies were made to determine the effect of ice formations on the section drag of a 6.9-foot-chord the partial-span leading edge flap. In general, the icing of a thin, swept airfoil will result in greater aerodynamic penalties than for a thick unswept airfoil. Glaze ice formations at the leading edge of the airfoil caused large increases in section drag even at a liquid-water content of 0.59 gram per cubic meter. The use of an ice-free parting strip in the stagnation region caused a negligible change in drag compared with a completely unheated airfoil. Cyclic de-icing when properly applied caused the drag to decrease almost to the bare-airfoil drag value.

98
NACA TN 2962
EFFECT OF ICE AND FROST FORMATIONS ON DRAG OF NACA 651-212 AIRFOIL FOR VARIOUS MODES OF THERMAL ICE PROTECTION.
Vernon H. Gray and Uwe H. von Glahn. June 1953. 68p. diagre., photos. (NACA TN 2962)

Studies were made to determine the effect of ice and frost formations on the drag of an 8-foot-chord NACA 65-212 airfoll. At high angles of attack (89), glaze-ice formations on the upper surface near the leading edge of an airfoil caused large increases in drag and incipient stalling of the airfoil. Runback icing on the lower surface, excepting for heavy span-wise ice ridges, presented no serious drag problems. Rime-ice formations on the leading edge did not cause large drag increases. Cyclic de-icing of the leading edge successfully decreased the drag almost to the bare airfoil drag value. Frost formations on airfoil surfaces drag increases asd may result in stalling of the airfoil.

99
Effects of Ice Formations on Airplane Performance in Level Cruising Flight.
By G. Merritt Preston and Calvin C. Blackman NACA TN No. 1598 May 1948

Abstract

Flight investigation in natural icing conditions was conducted to determine effect of ice accretion on airplane performance.
Maximum loss in propeller efficiency encountered was 19 percent. During 87 percent of the propeller icing encounters, losses of 10 percent or less were observed. Ice formations on all 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.

100
NACA TN 2866
ICING PROTECTION FOR A TURBOJET TRANSPORT AIRPLANE: HEATING REQUIREMENTS, METHODS OF PROTECTION, AND PERFORMANCE PENALTIES.
Thomas F. Gelder, James P. Lewis

The heating requirements for several methods of icing protection for a typical turbojet transport airplane operating over a probable range of icing conditions are evaluated, and the airplane performance penalties associated with providing this protection from various energy sources are assessed. Continuous heating requirements and airplane penalties for the turbojet transport are considerably increased over those for lower-speed aircraft. Heating requirements can be substantially reduced by use of a cyclic de-icing system and choice of the proper energy source.

101
NACA TN 3564
EFFECT OF PNEUMATIC DE-ICERS AND ICE FORMATIONS ON AERODYNAMIC CHARACTERISTICS OF AN AIRFOIL.
Dean T. Bowden. February 1956. 59p. diagrs., photos. (NACA TN 3564)

Measurement of drag, lift, and pitching moment of an NACA 0011 airfoil were made in icing conditions using pneumatic de-icers having either spanwise or chordwise inflatable tubes. Lift and drag penalties due to de-icer inflation and to ice remaining after deicer inflation are presented. Inflation of the spanwise-tube de-icer caused a much greater increase in drag than inflation of the chordwise-tube de-icer. The two de-icers were equally effective in removing ice. Lift and drag penalties resulting from ice formed with the de-icer inoperative are also presented, as well as spoiler data for analyzing drag increases due to ice formations.

102
NACA TN 4151
CORRELATIONS AMONG ICE MEASUREMENTS, IMPINGEMENT RATES, ICING CONDITIONS, AND DRAG COEFFICIENTS FOR UNSWEPT NACA 65A004 AIRFOIL.
Vernon B. Gray. February 1958. 45p. diagrs., phots., tabs. (NACA TN 4151)

An empirical relation is derived by which changes in section drag coefficients due to ice on an NACA 65A004 airfoil are calculable from known icing and operating conditions. The correlation is obtained by use of measured ice heights and ice angles. Initial ice weights are in agreement with droplet impingement data; in glaze conditions, ice weights increase at progressively greater rates with time.

103
NACA TN 4155
AERODYNAMIC EFFECTS CAUSED BY ICING OF AN UNSWEPT NACA 65A004 AIRFOIL. Vernon H. Gray and Uwe H. von Glahn. February 1958. 47p. diagr tabs. (NACA TN 4155)

At angles of attack less than 4° both rime and glaze-ice formations increased drag, reduced lift, and reduced diving moments. At angles of attack greater than 4°, drag coefficients increased with glaze-ice formations and decreased with rime ice; Lift coefficients generally increased with glaze ice and were variably affected by rime ice; pitching-moment changes were rather erratic and depended on the ice shape. When the airfoil was iced at high angles of attack and rotated to lower angles, large negative pitching moments ware obtained. Ice formations on the airfoil had no significant effects on control-surface hinge moments.

104
NASA TN D-2166
National Aeronautics and Space Administration.
PREDICTION OF AERODYNAMIC PENALTIES CAUSED BY ICE FORMATIONS ON VARIOUS AIRFOILS.
Vernon H. Gray. February 1964. 19p. OTS price, $0.50. (NASA TECHNICAL NOTE D-2166)
An equation is presented by which changes in drag coefficients due to ice formations on airfoils with thickness ratios up to 15 percent may be calculated from known icing and flight conditions. Based on limited data, changes in lift and pitching-moment coefficients due to ice on thick, blunt airfoils may be estimated from the corresponding changes in drag coefficients; for thin airfoils at higher angles of attack no general relation is obtained.

Windshield Icing Protection

105
NACA TECHNICAL NOTE 1434
A METHOD FOR CALCULATING THE HEAT REQUIRED FOR WINDSHIELD THERMAL ICE PREVENTION BASED ON EXTENSIVE FLIGHT TESTS IN NATURAL ICING CONDITIONS
Alun R. Jones, George H. Holdaway, and Charles P. Steinmetz
SUMMARY
An equation is presented for calculating the heat flow required from the surface of an internally heated windshield in order to prevent the formation of ice accretions during flight in specified icing conditions. To ascertain the validity of the equation, comparison is made between calculated values of the heat required and measured values obtained for test windshield in actual flights in icing conditions.
The test windshields were internally heated and provided data applicable to two common types of windshield configurations; namely the V-type and the type installed flush with the fuselage contours. These windshields were installed on a twin-engine cargo airplane and the icing flights were conducted over a large area of the United States during the winters of 1945-46 and 1946-47. In addition to the internally heated windshield investigation, some test data were obtained for a windshield ice-prevention system in which heated air was discharged into the windshield boundary layer.

106
NACA RM E55E17a
National Advisory Committee for Aeronautics.
PRELIMINARY DATA ON RAIN DEFLECTION FROM AIRCRAFT WINDSHIELDS BY MEANS OF HIGH-VELOCITY JET-AIR BLAST.
Robert S. Ruggeri. July 1955. 17p. diagrs., photos. (NACA RM E55E17)

Results indicate that rain deflection by jet-air blast appears feasible for flight speeds comparable with landing and take-off; however, visibility through the mist generated by raindrop breakup presents a problem. For the simulated windshield used, air-flow rates of about 3.3 lb/min-in. of span were required for adequate rain deflection at an airspeed of 135 mph. A method was devised whereby large-diameter water drops (1000 to 1500 μ) can be produced in a moving air stream, without breakup, at speeds in excess of 175 mph.

Cooling Fan Icing Protection

107
NACA TECHNICAL NOTE 1246
WIND TUNNEL INVESTIGATION OF ICING OF AN ENGINE COOLING FAN INSTALLATION
James P. Lewis
SUMMARY
An investigation was made of the icing characteristics and means of ice protection of a typical radial-engine cooling-fan installation. The investigation was made at various icing and performance conditions in the icing research tunnel of the NACA Cleveland laboratory.
The icing of the unprotected cooling-fan installation was found to present a serious operational problem. Reduction in air flow below the minimum value required for engine cooling-air flow through the fan assembly occurred in as little as 5 minutes under normal icing conditions. Steam de-icing was found to be effective for the cowling lip and inlet duct. Alcohol de-icing of the fan blades and stator vanes was found to be unsatisfactory. Electrical heat de-icing of the fan blades was found to be effective but de-icing of the stator vanes was not completely effective at the power densities investigated.

Radome Icing Protection

108
NACA RM E53A22 National Advisory Committee for Aeronautics. AN ANALYTICAL STUDY OF HEAT REQUIREMENTS FOR ICING PROTECTION OF RADOMES.
James P. Lewis. March 1953. 20p. diagrs. (NACA RM E53A22)

The heat requirements for the icing protection of two radome configurations have been studied over a range of design icing conditions. Both the protection limits of a typical thermal protection system and the relative effects of the various icing variables have been determined. For full evaporation of all impinging water, an effective heat density of 14 watts per square inch was required. When a combination of the full evaporation and running wet surface systems was employed, a heat requirement of 5 watts per square inch provided protection at severe icing and operating conditions.

109
NACA RM E52J31 National Advisory Committee for Aeronautics.
EXPERIMENTAL INVESTIGATION OF RADOME ICING AND ICING PROTECTION.
James P. Lewis and Robert J. Blade. January 1953. 60p. diagrs., photos. (NACA RM E52J31)

In an investigation of radome icing and icing protection in the NACA Lewis icing research tunnel, the impingement of water and the formation of ice on two radome configurations were found to agree well with theory and experience. The ice formations on the radomes produced serious effects on radar performance. The ethylene glycol fluid-protection system gave adequate icing protection for both anti-icing and de-icing. The radomes were investigated at air-speeds up to 290 miles per hour, air total temperatures of -15° to 20° F, water contents up to 1.0 gram per cubic meter, and angles of attack of 0° and 4°.

Antenna Icing

110
Determination of Aircraft Antenna Loads Produced by Natural Icing Conditions.
By William L. Kepple
NACA RM No. 17:26a February 1948
Abstract
Presents the effect of distance flown in the icing region, antenna length, and antenna angle on the tension occurring in aircraft antennas.
Antenna tension increased with antenna angle. The maximum tensions recorded were:
0° to 15° - 68 pounds
44° - 274 pounds
64° - 438 pounds

111
Vibration and Icing Investigation of CAA Type V-109 Very-High-Frequency Aircraft Antenna.
By William H. Gowan, Jr.
NACA RM NO. SE9D20
Abstract
Vibration and icing characteristics were investigated in the NACA icing research tunnel on a CAA type V-109 very-high-frequency aircraft antenna proposed for omnidirectional-range operation. Vibration of the antenna elements was observed for both icing and non-icing conditions. Maximum vibration amplitude observed was approximately 7 inches at the end of an element 24 inches long during icing, and failure of an element occurred in one instance during icing. Vibration without ice accretion was not severe.

Inlet and Vent Icing Protection

112
Investigation of Aerodynamic and Icing Characteristics of Recessed Fuel-Vent Configurations.
By Robert S. Ruggeri, Uwe von Glahn, and Vern G. Rollin
NACA TN No. 1789 March 1949
Abstract
An investigation was conducted to determine aerodynamic and icing characteristics of several recessed fuel-vent configurations.
The vent configuration having diverging ramp sidewalls, 7° ramp angle, and vent tubes manifolded to a plenum chamber gave greatest vent-tube pressures for all conditions investigated. Configurations with diverging ramp sidewalls gave greater vent-tube pressures than configurations with parallel sidewalls. In similar cloud-icing conditions, only the configuration with a plenum chamber maintained adequate vent-tube pressures throughout 60-minute icing periods. No complete closure of vent-tube openings due to ice formations occurred for configurations investigated.

Jet Penetration

113
NACA TECHNICAL NOTE 1615
INVESTIGATION OF THE PENETRATION OF AN AIR JET DIRECTED PERPENDICULARLY TO AN AIR STREAM
Edmund E. Callaghan and Robert S. Ruggeri
SUMMARY
An experimental investigation was conducted to determine the penetration of a circular air jet directed perpendicularly to an air stream as a function of jet density, jet velocity, air-stream density, air-stream velocity, jet diameter, and distance downstream from the jet. The penetration was determined for nearly constant values of air-stream density at two tunnel velocities, four jet diameters, four positions downstream of the jet, and for a large range of jet velocities and densities. An equation for the penetration was obtained in terms of the jet diameter, the distance downstream from the jet, and the ratios of jet and air-stream velocities and densities.

114
Penetration of Air Jets Issuing from Circular, Square, and Elliptical Orifices Directed Perpendicularly to an Air Stream.
By Robert S. Ruggeri, Edmund E. Callaghan, and Dean T. Bowden
NACA TN 2019 February 1950
Abstract
The penetration of air jets directed perpendicularly to an air stream was experimentally determined. Jets issuing from circular, square, and elliptical orifices were investigated and the penetration at a position downstream of the orifice was determined as a function of Jet density, jet velocity, air-stream density, air-stream velocity, effective Jet diameter, and orifice flow coefficient. Results are correlated in terms of dimensionless parameters and the penetrations obtained with various shapes are compared.
Greater penetrations were obtained with square orifices than with circular orifices of equal area.

115
Investigation of Flow Coefficient of Circular, Square, and Elliptical Orifices at High Pressure Ratios.
By Edmund E. Callaghan and Dean T. Bowden
NACA TN 1947
Abstract
An experimental investigation was conducted to determine orifice coefficients of a jet directed perpendicularly to an air stream as a function of pressure ratio and Jet Reynolds number for elliptical, square, and circular orifices. Effect of air-stream velocity on jet flow was determined for three tunnel-air velocities. Equations for flow coefficient in terms of jet Reynolds number and pressure ratio were obtained for various shapes.
Excellent correlation was obtained between results for jet discharging into still air and results for jet discharging into moving air stream, provided that correct outlet pressure was used.

116
NACA TN 2855
National Advisory Committee for Aeronautics.
GENERAL CORRELATION OF TEMPERATURE PROFILES DOWNSTREAM OF A HEATED AIR JET DIRECTED AT VARIOUS ANGLES TO AIR STREAM.
Robert S. Ruggeri. December 1952. 59p. diagrd., tab. (NACA TN 2855)
An experimental investigation was conducted to determine the temperature profile downstream of a heated-air jet directed at various angles to an air stream. The profiles were determined at two positions downstream of the jet as a function of jet diameter, jet density, free-stream density, jet velocity, free-stream velocity, jet total temperature, orifice flow coefficient, and jet discharge angles. A method is presented which yields a good approximation of the temperature profile in terms of dimensionless parameters of the flow and geometric conditions.

117
NACA TN 2466
National Advisory Committee for Aeronautics.
A GENERAL CORRELATION OF TEMPERATURE PROFILES DOWNSTREAM OF A HEATED AIR JET DIRECTED PERPENDICULARLY TO AN AIR STREAM.
Edmund E. Callaghan and Robert S. Ruggeri. September 1951. 37p. diagrs. (NACA TN 2466)
An experimental investigation was conducted to determine the temperature profile downstream of a heated air jet directed perpendicularly to an air stream. The profiles were determined at several positions downstream of the jet as a function of jet density, free-stream density, jet velocity, jet temperature, free-stream velocity, and orifice flow coefficient. A method is presented which yields a good approximation of the temperature profile in terms of dimensionless parameters of the flow and geometric conditions.

Heat Transfer

118
Improvements in Heat Transfer for Anti-Icing of Gas-Heated Airfoils with Internal Fins and Partitions.
By Vernon H. Gray
NACA TN 2126 July 1950
Abstract
The effectiveness of internal finning in airfoils was analyzed to determine design variables by which local surface heat transfer may be efficiently controlled. Comparative investigations of gas-heated hollow airfoils indicate that surface-heating rates for ice prevention may be increased up to 3.5 times by the addition of metal fins and flow-confining partitions to the airfoil internal passage.

119
NACA TN 2799
National Advisory Committee for Aeronautics.
SIMPLE GRAPHICAL SOLUTION OF HEAT TRANSFER AND EVAPORATION FROM SURFACE HEATED TO PREVENT ICING.
Vernon H. Gray. October 1952. 19p. diagrs. (NACA TN 2799)

Equations expressing the heat transfer and evaporation from wetted surfaces during ice prevention have been simplified and regrouped to permit solutions by simple graphical means. Working charts for quick and accurate anti-icing calculations are also included.

120
NACA TN 3045
National Advisory Committee for Aeronautics.
ANALOGY BETWEEN MASS AND HEAT TRANSFER WITH TURBULENT FLOW.
Edmund E. Callaghan. October 1953. 19p. diagrs. (NACA TN 3045)
An analysis of combined heat and mass transfer from a flat plate has been made in terms of Prandtl'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.

121
NACA TN 3104
National Advisory Committee for Aeronautics.
EXPERIMENTAL INVESTIGATION OF SUBLIMATION OF ICE AT SUBSONIC AND SUPERSONIC SPEEDS AND ITS RELATION TO HEAT TRANSFER.
Willard D. Coles and Robert S. Ruggeri. March 1954. 29p. diagrs., photo. (NACA TN 3104)
An experimental investigation was conducted in the 3.84- by 10-inch tunnel to determine the mass transfer by sublimation, heat transfer, and skin friction for an iced surface at subsonic and supersonic speeds. The results show that the Stanton numbers of sublimation and heat transfer were increased 40 to 50 percent for an iced surface of moderate roughness as compared with those obtained for a bare plate. For ice surfaces of equivalent roughness, the ratio of sublimation to heat-transfer Stanton numbers was found to be 0.90. Sublimation Stanton numbers obtained at a Mach number of 1.3 showed no appreciable deviation from those obtained at subsonic speeds. Sublimation as a means of removing ice formations of appreciable thickness is so slow as to be of little value in the de-icing of aircraft at high altitudes.

122
NACA TN 3143
National Advisory Committee for Aeronautics.
EXPERIMENTAL DETERMINATION OF THERMAL CONDUCTIVITY OF LOW-DENSITY ICE.
Willard D. Coles. March 1951. 12p. diagrs., photo. (NACA TN 3143)
The thermal conductivity or low-density ice has been computed from data obtained in an experimental investigation of the heat transfer and mass transfer by sublimation for an iced surface on a flat plate in a high-velocity tangential airstream. The results are compared with data from several sources on the thermal conductivity of packed snow and solid glaze ice. The results show good agreement with the packed-snow values, and the extension of the curves for packed snow to the solid ice regime indicates that the curves are applicable to ice over the entire density range.

123
NACA TN 3396 National Advisory Committee for Aeronautics.
ICING LIMIT AND WET-SURFACE TEMPERATURE VARIATION FOR TWO AIRFOIL SHAPES UNDER SIMULATED HIGH-SPEED FLIGHT CONDITIONS.
Willard D. Coles. February 1955. 33p. diagra., photos. (NACA TN 3396)
Variation of wet-surface temperature and the conditions that will result in ice-free surfaces for high-speed flight through clouds were investigated experimentally. The results are compared with calculated values obtained with an analytical method. The analytical results were generally conservative, giving wet-surface temperatures 20 to 40 F lower than the experiments and predicting the formation of ice at values of ambient-air temperature up to 120 F higher than the experiments. The location of analytically determined critical regions on the bodies for the initial formation of ice was experimentally substantiated.

124
NACA RM E53F02
National Advisory Committee for Aeronautics.
PRELIMINARY RESULTS OF HEAT TRANSFER FROM A STATIONARY AND ROTATING ELLIPSOIDAL SPINNER.
U. von Glahn. August 1953. 35p. diagrs., photo., 2 tabs. (NACA RM E53F02)
The convective heat-transfer coefficients were determined for an ellipsoidal spinner of 30-inch maximum diameter for both stationary and rotating operation. The range of conditions studied included air-speeds up to 275 miles per hour, rotational speeds up to 1200 rpm, and angles of attack of zero and 4°. The results indicate that a higher heat transfer occurred with rotation of the spinner. Transition from laminar to turbulent flow occurred over a large range of Reynolds numbers primarily because of surface roughness of the spinner.

Miscellaneous

125
NACA Preprint No. 225
CORRELATION OF AIRFOIL ICE FORMATIONS AND THEIR AERODYNAMIC EFFECTS WITH IMPINGEMENT AND FLIGHT CONDITIONS
Vernon H. Gray
ABSTRACT
An empirical equation is developed by which changes in drag coefficients due to ice formations on an NACA 65A004 airfoil may be calculated from known icing and flight conditions; this equation is then extended to include available data for other airfoils up to 15-percent thickness ratio. The correlation was obtained primarily by use of ice heights and ice angles measured on the 4-percent thick airfoil. The final equation, however, does not include the ice measurements, but relates changes in drag coefficients due to ice with the following variables: icing time, airspeed, air temperature, liquid-water content, cloud droplet-impingement efficiencies, airfoil chord, angles of attack, and leading-edge radius-of-curvature.
Changes in lift and pitching-moment coefficients due to ice on an NACA 0011 airfoil are also related to the corresponding changrs in drag coefficients; additional data on lift and pitching-moment changes due to ice are limited to the 65A004 airfoil, for which complex trends preclude a relationship within the scope of this paper.

126
THE ICING PROBLEM CURRENT STATUS OF NACA TECHNIQUES AND RESEARCH
Uwe H. von Glahn
ABSTRACT
Icing of aircraft components such as airfoil surfaces and engine-inlet systems creates a serious operational problem. Aircraft are now capable of flying in icing clouds without difficulty, however, because research by the NACA and others has provided the engineering basis for icing protection systems. This paper summarizes some of the techniques used in NACA programs to solve aircraft icing problems and indicates the scope of the data available for the design of aircraft icing protection systems. The NACA Lewis icing facilities, specific test equipment and techniques used in conducting tests in icing wind tunnels, and several icing instruments are discussed in detail.

127
NASA TECHNICAL MEMORANDUM X-54700
(Also NASA TM-82265)
SOME CONSIDERATIONS OF THE NEED FOR ICING PROTECTION OF HIGH-SPEED, HIGH-ALTITUDE AIRPLANES
Uwe von Glahn
SUMMARY
The icing problems of high-speed, high-altitude aircraft are confined to climb and let-down conditions. The performance losses in icing can be minimized by the use of an icing protection system at the expense of structural complexities and installed weight. The elimination of airframe protection systems for aircraft subject only to short icing encounters appears attractive, provided the performance penalty due to icing is not excessive. This paper considers the performance penalty caused by icing during climb in terms of reduction in rate of climb and in range for aircraft without airframe icing protection and is intended to show only orders of magnitude rather than absolute values.

128
NACA TN 4220
National Advisory Committee for Aeronautics.
A FLIGHT EVALUATION AND ANALYSIS OF THE EFFECT OF ICING CONDITIONS ON THE ZPG-Z AIRSHIP.
William Lewis and Porter J. Perkins, Jr. April 1958. 66p. diagrs., photos, tab. (NACA TN 4220)
Test flights conducted by the U. S. Navy in a number of typical icing conditions are described. The airship operated successfully in all icing conditions encountered, but the desirability of limited protection for certain components was indicated. Icing in clouds was confined to wires and small components, but freezing rain and drizzle produced some icing on the envelope also. Theoretical calculations are presented which suggest that, while hazardous icing in freezing rain can occur under certain meteorological conditions, the probability of encountering these conditions is very small in coastal areas and approaches zero 200 to 300 miles offshore.

129
NASA TECHNICAL MEMORANDUM X-54700 (Also NASA TM-82266)
ICING CONDITIONS TO BE EXPECTED IN THE OPERATION OF HIGH-SPEED, HIGH-ALTITUDE AIRPLANES
William Lewis
SUMMARY
This paper considers the specific problems concerned with the prot- able frequency and severity of icing conditions to be expected in the operation of high-speed, high-altitude aircraft, as compared with the icing conditions encountered on older types of aircraft. There are two general aspects of this problem. The first phase of this discussion will be concerned with the frequency and probably severity of icing conditions at high altitudes. High-altitude airplanes, however, must still climb and descend through the lower layers of the atmosphere where icing conditions are more frequent; therefore, the second phase of this discussion will deal with the effect of aerodynamic heating, due to high airspeed, on the icing potentialities of clouds encountered at low altitudes.

130
NACA Conference on Aircraft Ice Protection
June 26-27, 1947
SUMMARY
NACA's latest research results were presented in 15 papers at the June 1947 Conference on Aircraft Ice Prevention. The papers are compiled herein.

131
SOCIETY OF AUTOMOTIVE ENGINEERS PREPRINT NO. 424
HEAT REQUIREMENTS FOR ICE PREVENTION ON GAS-HEATED PROPELLERS
V. H. Gray
SUMMARY
The investigation has established that feasible rates of heated gas flow can provide ample surface heating of propeller blades except at the leading edge, where complete ice prevention requires large rates of gas flow, resulting in considerable wastage of heat elsewhere in the blade and at the discharge nozzle. This waste heat can be reduced to a small fraction of its original value by carefully designing the blade internal passage so that use is made of flow-confining partitions and metal fins attached at the blade leading edge.

[Note: ¹ does not have an abstract for FAA-ADS-4 below. The abstract here was taken from the last page of FAA-ADS-4.]

132
FAA-ADS-4
Bowden, D.T., Gensemer, A. E., and Speen, C.A.
Engineering Summary of Airframe Icing Technical Data. Federal Aviation Agency, 1964.

An engineering study was made of the existing technical reports, paper, and publications on the subject of airframe icing technical data. These documents were gathered world wide. Key data was summarized into this report. The report presents data on aircraft icing conditions, methods of preventing and removing ice on aircraft in flight, and methods of testing ice protection systems to ensure adequacy.

As an engineering summary, the report is organized so as to be useful to an aeronautical engineer desiring to adequately protect an aircraft designed for flight in icing conditions. The report is divided into six sections. The first discusses statistical icing data to be used as design criteria for ice protection evaluations and systems. The second section is concerned with the physics of ice collection, and presents formulas and charts for determinations of the rate, size, and shape of ice formations on aircraft. The third section discusses the known methods of ice protection, and presents formulas and data to be used in design. The fourth section shows specific and typical applications of ice protection systems to light and heavy aircraft. The fifth section presents data on detection of icing by visual means and by ice detector and indicator systems. The final section discusses the various methods of testing aircraft for adequacy of icing protection with and without ice protection systems. Included are data on icing tunnel testing, dry air flight testing, flight testing in natural icing, and flight in simulated icing.

Notes