Articles with tag: "natural icing"

(Note: figures do not appear in the summaries below)

  1. NACA-TN-2212

    "in icing conditions, periodic attempts should be made to throwoff the accretions by increasing propeller speed."

    "The Effect of Ice Formations on Propeller Performance" 1

    Figure 18. Ice formation of encounter 1. Camber face. Peak efficiency loss, 10 percent.

    Abstract

    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 …

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  2. Tools

    Published: Mon 12 February 2024
    Updated: Wed 16 October 2024

    Aircraft designs for flight in icing are improved and proven effective by several tools, including analysis, icing wind tunnel test, and flight test in icing conditions.

    Design handbooks

    Design handbooks have charts and tables that can be used to perform analyses for aircraft icing and ice protection.

    Figure 2-47. Airfoil profiles for impingement parameter plots in Figures 2-48 through 2-59.
    from "Aircraft Icing Handbook", DOT/FAA/CT-88/8 apps.dtic.mil

    Analysis

    There are computerized icing analysis tools available from NASA, and from commercial vendors. There is also "bespoke" software created for special purposes.

    LEWICE3D. LEWICE3D prediction of collection efficiency (color contours) and the resulting ice shape (at discrete cuts) along a wing.
    from "Glenn Research Center Software" www1.grc.nasa.gov

    Laboratory tests

    A wind tunnel is a large tube with a fan to produce air flow at a calibrated airspeed. Wind tunnels are used to study many effects on aircraft, including icing. Artificially produced ice shapes (often 3D printed) may be adhered to airplane models, and the effects studied.

    To simulate in-flight icing conditions, "Icing Wind Tunnels" often use refrigeration …

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  3. NACA-TN-1391

    "liquid water concentration at any point in the cloud may be calculated by considering an air parcel lifted adiabatically from the condensation level"

    "Icing Properties of Noncyclonic Winter Stratus Clouds"

    Summary

    Adiabatic lift theory is used to estimate the liquid water content of clouds.

    Key Points

    1. Adiabatic lift theory is used to estimate the liquid water content of clouds.
    2. Drop size instrumentation was limited to a 4 inch cylinder for maximum drop size.
    3. "Calculations ... show that the liquid water concentration in noncyclonic stratus clouds is not likely to exceed 1.5 grams per cubic meter."

    Abstract

    Introduction
    In order to establish a rational basis for the efficient design of thermal ice-prevention systems for airplanes the Ames Aeronautical Laboratory of the National Advisory Committee for Aeronautics has undertaken experimental investigation of the meteorological conditions conducive to the formation of ice on aircraft. A C-46 airplane has been equipped to measure free-water …

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  4. NACA-TN-1598

    "It is significant that the control response of the airplane approached the point of being marginal when all of the airplane except the propeller had accreted ice"

    Figure 13. Formation of ice on horizontal stabilizer. Average icing rate, 4 inches per hour; liquid-water content, 0.4 grams per cubic meter; drop size, 17 microns. (Painted stripes are 1 in. wide)

    NACA-TN-1598, "Effects of Ice Formations on Airplane Performance in Level Cruising Flight" 1

    Summary

    Airplane levels effects of icing are measured, and broken into major components.

    Key Points

    1. Numerous, excellent quality photos show how icing flight test "should be done".
    2. Airplane levels effects of icing are measured, and broken into major components.
    3. "It is significant that the control response of the airplane approached the point of being marginal when all of the airplane except the propeller had accreted ice."

    Abstract

    A flight investigation in natural icing conditions was conducted by the NACA to determine the effect of ice accretion on airplane performance.

    The maximum loss in propeller efficiency encountered due to ice formation on the propeller blades was 19 percent. During 87 percent …

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  5. NACA-TN-313

    "an irregular shape is developed due to the ice formation, which is ruinous to the aerodynamic efficiency of the airfoils"

    NACA-TN-313, "The Formation of Ice upon Airplanes in Flight" 1

    Figure 2. Sketches of ice formation on wings and wires. (From notes and sketches on numerous flights.)

    Summary

    Ice shapes are recorded in flight tests in natural icing conditions.

    Key Points

    1. Types of ice formations are noted, clear ice (possibly SLD) and rime ice.
    2. The atmospheric conditions for the types of ice are noted.
    3. "Oily surface" icephobic substances are tested.
    4. Procedures for avoiding the most hazardous icing conditions are provided.

    Abstract

    This report describes the atmospheric conditions under which ice is deposited upon the exposed parts of airplanes in flight. It identifies the formation which is found under different conditions, and describes some studies of preventative means together with recommendations for avoiding the consequences of the formation.

    Discussion

    This is an almost "lost gem" of the NACA-era (cited only 10 times).
    It features:
    - Description of supercooled large …

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  6. NACA-TN-1472

    "... equations for calculating the rate of heat transfer from airfoils in icing conditions were verified"

    "The Calculation of the Heat Required for Wing Thermal Ice Prevention in Specified Icing Conditions" 1

    Figure 7. Cut-away view of the NACA 652-016 electrically heated airfoil model showing construction details.

    Summary

    Natural icing flight tests with an instrumented test airfoil are compared to 2D thermodynamic calculations.

    Key points

    1. Thermodynamic equations for a heated surface with water impingement are detailed.
    2. Test flights in natural icing conditions measured surface temperature for a heated surface.
    3. Runback water characteristics were noted.
    4. Heat transfer coefficients in icing were be inferred from measurements and calculations.
    5. "the design of heated wings on a fundamental, wet-air basis now can be undertaken with reasonable certainty."

    Abstract

    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 …

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  7. NACA-TN-1904

    "... the rotating-cylinder indications of drop-size distribution are so unreliable that they are of little or no value"

    NACA-TN-1904, "Observations of Icing Conditions Encountered in Flight During 1948" 1

    Summary

    Meteorological data from flight observations in icing conditions during the first 5 months of 1948 are presented.

    Key points

    1. The average liquid water content varies over distance traveled in icing.
    2. The value of the multicylinder method for determining drop size distributions is questioned.
    3. Other flight test instruments are described.

    Abstract

    Meteorological data from flight observations in icing conditions during the first 5 months of 1948 are presented. A total of 335 measurements of liquid-water content and mean-effective drop diameter were obtained by the multicylinder method in the course of 40 flights in icing conditions covering most of northern United States. Cumulus clouds were predominant during approximately two-thirds of the flights. A continuous record of liquid-water content covering a major portion of …

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  8. NACA-TN-1393

    "The rotating-cylinder method of measuring liquid water content is generally regarded as being the most accurate and dependable procedure thus far developed"

    Figure 5: Liquid water content and drop size by rotating cylinder measurement as compared with Weather Bureau scale of icing intensity. This is a graph of Mean effective drop diameter in microns vs. Liquid water content in g/m^3. Lines for the intensity values 1, 6, and 12 g/cm^2-h are shown, as well as several flight measurement values

    “A Flight Investigation of the Meteorological Conditions Conducive to the Formation of Ice on Airplanes"

    1

    Summary

    A multicylinder and other instruments measure natural icing conditions in flight.

    Key points

    1. The accuracy of multicylinder instruments used to determine liquid water content and median water drop size is assessed.
    2. An icing intensity index as related to the ice growth rate on a 3-inch diameter cylinder is detailed.
    3. Results from agree well with the Python implementation of the cylinder analysis.
    4. "Tentative" values for icing design conditions were determined.
    5. An effect of distance on icing conditions is noted.

    Abstract

    Data from flight measurements of the meteorological factors related to the intensity of icing conditions are presented. The physical factors that establish the distribution of liquid water in clouds of various types …

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