Articles with tag: "conclusions"

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

  1. Conclusions of the Porter Perkins Series

    "our knowledge of aircraft icing and the penalties associated with it has not changed substantially in the last forty to fifty years" 1

    Figure 1. Tunnel installation of hollow steel air-heated propeller for icing investigation. A tall, lean man with a distinctively tall nose inspects the propeller.

    From NACA-TN-1586. I believe that this is Porter Perkins, circa 1946.

    Summary

    The three areas of the many and varied contributions of Porter Perkins are reviewed.

    Discussion

    I will focus on three areas of Porter Perkins' publications:

    • Foresight about supercooled large drop (SLD) icing
    • A shift in instrument calibration
    • Contributions to the Appendix C icing regulation

    Foresight about supercooled large drop (SLD) icing

    I am not sure that I agree with the quote at the top (from 1993) now. A lot of things have happened in three decades.

    Perkins and Rieke 1 foreshadowed in 1993 the potential effects of large-size water-drop icing conditions, now commonly termed supercooled large drop (SLD) icing:

    [Emphasis added]

    Protection from "Severe" icing encounters is not possible by definition. Likewise, there is little …

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  2. Conclusions of the Meteorology of Icing Clouds Thread

    There was remarkable progress in the three-year span 1946 through 1949.

    Figure 3. Liquid-water content, W, and average drop diameter in icing clouds.
    from "FLIGHT INVESTIGATION OF METEOROLOGICAL FACTORS CONDUCIVE TO AIRCRAFT ICING", William Lewis, 1947. 1

    Summary

    The most enduring legacy of the NACA publications on icing meteorology is their direct influence on the current icing regulations.

    Key Points

    1. NACA publications contributed heavily to the creation of the Appendix C icing regulation.
    2. The key flight tests and publications were complete by 1952.
    3. Some engineering judgement went into creating the icing regulation.
    4. There was remarkable progress in the three-year span 1946 through 1949.
    5. The data from 1949 compares well to more recent flight test measurements.

    Discussion

    The most enduring legacy of the NACA publications on icing meteorology is their direct influence on the current icing regulations.

    Icing Regulations and NACA publications

    A limited understanding of atmospheric icing conditions was achieved by 1945. NACA-TN-1246 (1947) notes a "Mt. Washington Weather Bureau meeting on …

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  3. Conclusions of the Ice Protection Thread

    "The industry has now passed through the experimental stages of heating and anti-icing ..." (1946) 1

    Lockheed 12-A. A large, metal construction, low wing, two engine, propeller drive airplane. The tail has three vertical fins. Figure 1. Lockheed 12-A airplane. Alterations were made to a standard commercial model which include provisions for heating the wings with exhaust gas, and the windshield with heated air. Figure 12. Three-quarter rear view of airplane, showing location of air discharge louvers in the wing upper surface and exhaust discharge at the wing tip. From NACA-ACR-A-53, 1941.

    Summary

    Ice protection system development continues to address new challenges.

    Key Points

    1. Design guides can lead you to "adequate" designs for several technologies.
    2. Design guides provide procedures to compare candidate systems.
    3. Optimal designs and new requirements may require system development.

    Discussion

    We have seen "the possible methods for overcoming the ice hazard" that were developed in the NACA-era in this Ice Protection Thread. The period up to and through WWII (1945) was largely characterized by expeditious tests to address immediate icing problems.

    The quote above "The industry has now passed through the experimental stages of heating and anti-icing ..." from 1946 was not completely the case, but NACA did move on to more planned scientific and engineering tests and analysis methods development. By the 1950's useful Engineering Design Manuals were available, so that …

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  4. Conclusions of the Meteorological Instruments Thread

    "difficulties with the calibration proved to be more serious than had been anticipated" 1

    Instruments used in NACA publications

    Summary

    The meteorological instruments and data from the NACA-era are still used today.

    Key Points

    1. The rotating multicylinder was the primary instrument that determine the values in the current Appendix C icing regulations.
    2. Other instruments gave supplementary data, but were calibrated against the rotating multicylinder.
    3. Later publications document the continuing use of the NACA-era instruments.

    Discussion

    NACA-era instruments

    In this Meteorological Instruments thread we saw several instruments and technologies:

    • Rotating Multicylinders
    • Fixed Cylinder
    • Rotating-Disk Icing-Rate Meter
    • Capillary Collector
    • Rainbow Recorder
    • Dew-Point Recorder
    • Visibility Meter
    • Sooted Slides (and oiled slides)
    • Drop Photography
    • Heated probes
    • Inference from drop impingement
    • Modified pressure probe
    • Corona discharge (multicylinder)

    Instruments used to derive icing requirements

    The instruments and flight data from the NACA-era were used to develop the current "Appendix C" icing certification standard 2.

    Figure 3-1 Derivation of FAR Icing Standards

    3

    [As we saw in "Conclusions of …

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  5. Conclusions of the Ice Shapes and Their Effects Thread

    "an irregular shape is developed due to the ice formation, which is ruinous to the aerodynamic efficiency of the airfoils" 1

    Figure_14 of NACA-TN-1598. Airspeed loss caused by ice accumulation on various components of airplane. Total airspeed loss, 41 miles per hour, from 204 to 163 miles per hour.

    from NACA-TN-1598 2

    Summary

    Data from the post-NACA era are used to resolve open questions

    Key Points

    1. The Ice Shapes and Their Effects thread is summarized.
    2. Post-NACA era data is used to resolve some open questions.
    3. Correlations of drag due to ice have limited, "first order" accuracy.

    Discussion

    Review of the "Ice Shapes and Their Effects" thread so far

    In this thread, we saw:

    An almost "lost gem" of the NACA-era, NACA-TN-313, "The Formation of Ice upon Airplanes in Flight" with, in 1929: - Description of supercooled large drop (SLD) icing conditions
    - "Detect and exit" icing mitigation strategy
    - Natural icing flight tests of icephobic materials
    - Identification of different types of icing

    The effect of "protuberances" on an airfoil section lift and drag in NACA-TR-446, "Airfoil Section Characteristics as Affected by …

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  6. Conclusions of the Icing Thermodynamics Thread

    "The collection of ice by the cylinders is similar to the collection of ice by airplane components"

    Figure 1. Modes of energy transfer for an unheated airfoil in icing conditions. Image from Anon., "Aircraft Ice Protection", the report of a symposium held April 28-30, 1969, by the FAA Flight Standards Service; Federal Aviation Administration, 800 Independence Ave., S.W., Washington, DC 20590. I could not find this on the NTRS or on the FAA site. It is available at DTIC.

    Figure 1. Modes of energy transfer for an unheated airfoil in icing conditions.

    Conclusions of the Icing Thermodynamics Thread

    Summary

    Data from the post-NACA era are used to resolve open questions

    Key points

    1. The Icing Thermodynamics thread is summarized.
    2. Post-NACA era data is used to resolve some open questions.
    3. The "Messinger model" and extended Messinger models are prevalent in current icing analysis.

    Discussion

    Review of the Icing Thermodynamics thread so far

    In the Icing Thermodynamics thread, we saw:

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  7. Conclusions of the Cylinder Thread

    "The collection of ice by the cylinders is similar to the collection of ice by airplane components." 1

    Figure 1 of NACA-TN-2903, depicting a cylinder in cross flow with air flow lines and water drop trajectories impacting the cylinder

    Summary

    Data from the post-NACA era are used to resolve open questions

    Key points

    1. The Cylinders thread is summarized
    2. Post-NACA era data is used to resolve some open questions.
    3. NACA era data that are still used today are summarized

    Discussion

    Review of the Cylinders thread so far

    In the Cylinders thread, we saw:

    • A pioneering analysis of water drop impingement on a cylinder (NACA-TN-779)
    • The most cited aircraft icing publication, with more detail of water drop impingement on a cylinder, and the rotating multicylinder instrument ("Mathematical Investigation of Water Droplet Trajectories")
    • In flight icing measurements and an icing severity index (NACA-TN-1393)
    • An additional way to estimate drop size on a fixed cylinder (NACA-TN-1424)
    • Nine icing instruments compared (NACA-RM-A9C09)
    • The ability of the multicylinder method to determine drop distribution was questioned several times …
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