Articles with tag: "instruments"

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

   

   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. Porter Perkins

   "As the demand for all-weather protection on aircraft for unimpaired and continuous commercial and military service developed, the detrimental effects of ... icing on airplane performance became increasingly important" (1948)

   

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

   Summary

   Porter Perkins published on icing topics for over 50 years while at NACA, NASA, and other groups.

   Biographies and Memorials

   Porter J. Perkins is a senior aerospace engineer working in aviation safety as manager of airworthiness of research flight activity at the Lewis Research Center of the U.S. National Aeronautics and Space Administration (NASA), Cleveland, Ohio, U.S. He has specialized in research on aircraft icing for more than 25 years. His in-flight measurements to characterize icing clouds were later incorporated into U.S. icing protection certification standards. He has authored or co-authored more than 25 reports in the field of aircraft icing, and continues to participate in …

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3. Conclusions of the Meteorological Instruments Thread

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

   

   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.

   

   ³

   [As we saw in "Conclusions of …

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4. NACA-RM-E51E16

   "A measure of the concentration of liquid water in a supercooled cloud is of considerable value in determining the severity of aircraft icing conditions"

   "A Simplified Instrument for Recording and Indicating Frequency and Intensity of Icing Conditions Encountered in Flight"

   ¹

   Summary

   An instrument for automatically recording the occurrence of icing and liquid water content values is described.

   Key Points

   1. The instrument relied on the plugging of holes exposed to icing, which made a measurable pressure difference.
   2. The instrument was cyclically deiced with electric heating.
   3. Data was recorded on film that was later processed.
   4. The instrument was used on numerous flights.

   Abstract

   An instrument for recording and indicating the frequency and intensity of aircraft icing conditions has been developed by the NACA Lewis laboratory to obtain statistical icing data over world-wide air routes during routine airline operations. An accumulation of data of this type is needed to provide pertinent meteorological …

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5. NACA-TN-2458

   "Because the charge placed on the droplets is a function of the droplet size, the size spectrum can be determined ..." ¹

   "An Instrument Employing a Coronal Discharge for the Determination of Droplet-Size Distribution in Clouds"

   Summary

   Electrical charges imparted to water drops allowed easier measurement of impingement on cylinders.

   Key Points

   1. This was a multicylinder instrument that relied on the differential collection efficiency of different cylinder sizes.
   2. The measurement of electrical charge allowed easier measurement of impingement rates.
   3. There does not appear to be further use or development of the instrument.

   Abstract

   A flight instrument that uses electric means for measuring 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. Because the charge placed on the droplets is a function of the droplet size, the size spectrum …

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6. airfoil impingement drop distribution

   "... it is believed that a comparison of the water-drop impingement over several different airfoils ... is of interest"

   
   Figure 5 from NACA-TN-1397

   NACA-TN-1397, "A Method for Numerically Calculating the Area and Distribution of Water Impingement on the Leading Edge of an Airfoil in a Cloud." ¹

   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." ²

   NACA-RM-E52B12, "Impingement of Water Droplets on an NACA 651-212 Airfoil at an Angle of Attack of 4°." ³

   Summary

   Three publications detail water impingement calculations.

   Key Points

   1. Impingement analysis methods are detailed.
   2. Data for several airfoils are presented.
   3. Methods to estimate impingement without the use of a differential analyzer are included.
   4. An instrument is not described, but the later NACA-TN-3338 does describe drop size distribution measurements.

   Abstract

   NACA-RM-E52B12 ³

   The trajectories of droplets in the air flowing past an …

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7. Heated Probes

   "a simple and rapid means for measuring the liquid-water content of clouds" ¹

   NACA-RM-E50J12a, "Flight Instrument for Measurement of Liquid-Water Content in Clouds at Temperatures Above and Below Freezing"

   NACA-TN-2615, "The Calculated and Measured Performance Characteristics of a Heated-Wire Liquid-Water-Content Meter for Measuring Icing Severity"

   NACA-RM-A54I23, "A Heated-Wire Liquid-Water-Content Instrument and Results of Initial Flight Tests in Icing Conditions"

   We will detail NACA-RM-A54I23 herein, as that was the final in the series of publications detailing the development, and will include some detail from the earlier NACA-RM-E50J12a and NACA-TN-2615.

   Summary

   Electrically heated probes can measure water exposure rate, from which LWC can be calculated.

   Key points

   1. The technology evolved over the span of the three publications.
   2. A heated wire probe can provide measurements with low lag (~1 second), faster than other technologies available in the NACA-era.
   3. There was an earlier "cloud indicator" based on similar technology.
   4. The technology is still used …

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8. Water Drop Imaging

   "it is necessary to measure the sizes of the droplets within the clouds." ¹

   NACA-RM-E50K01a, "Flight Camera for Photographing Cloud Droplets in Natural Suspension in the Atmosphere"

   NACA-RM-E51G05, "Adaptation of a Cascade Impactor to Flight Measurement of Droplet Size in Clouds"

   NACA-TN-3592, "An Oil-Stream Photomicrographic Aeroscope for Obtaining Cloud Liquid-Water Content and Droplet Size Distribution in Flight"

   Summary

   Three strategies were explored for water drop imaging.
   In NACA-RM-E50K01a, a telephoto arrangement allowed imaging water drops in situ.
   In NACA-RM-E51G05, water drops were put through a particle size sorting cascade, impacting on slides, and imaged.
   In NACA-TN-3592, water drops were captured in an oil stream exposed to the ambient flow, and then imaged.

   Key Points

   1. Three methods for obtaining images of water drops are discussed.
   2. Images of enough water drops allowed the calculation of the drop size distribution.
   3. These instruments had limited influence in the NACA-era.

   Abstract

   NACA-RM-E50K01a:

   A camera designed …

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9. NACA-RM-A9C09 Instruments

   "This [rotating disk] device should prove very useful in both the formative and statistical investigations."

   "A Review of Instruments Developed for the Measurement of the Meteorological Factors Conducive to Aircraft Icing" ¹

   
   from NACA-RM-E51E16 ²

   Summary

   "A review ... of meteorological factors conducive to aircraft icing reveals outstanding needs" for icing instrumentation.

   Key points

   1. Nine instruments, based on differing technologies, are qualitatively assessed.
   2. "The [multicylinder] method has assumed the position of a standard against which other instruments are calibrated, and is apt to remain so..."
   3. "This [rotating disk] device should prove very useful in both the formative and statistical investigations."
   4. "A reliable method for the measurement of drop-size distribution should be developed"

   Abstract

   The status of instrument suitable for the measurement of the meteorological factors conducive to aircraft icing is reviewed. The meteorological factors to be evaluated are listed, and tentative values for the desired and acceptable accuracy of measurement for …

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10. Meteorological Instruments

    "A review ... of meteorological factors conducive to aircraft icing reveals outstanding needs"

    Meteorological Instruments Thread

    

    Summary

    Several instruments were developed and improved during the NACA-era to measure icing conditions.

    Numerous modes of physics were explored, and distant descendants of some devices are still used today.

    See also Icing on cylinders, and Calibration of the NACA Icing Wind Tunnels.

    Reviews

    Rotating Multicylinders

    • NACA-TN-2708, Comparison of Three Multicylinder Icing Meters and Critique of Multicylinder Method.
    • NACA-RM-E53D23, Procedure for Measuring Liquid-Water Content and Droplet Sizes in Super-cooled Clouds by Rotating Multicylinder Method.

    Nine instruments NACA-RM-A9C09

    • Rotating Multicylinders
    • Fixed Cylinder
    • Rotating-Disk Icing-Rate Meter
    • Capillary Collector
    • Rainbow Recorder
    • Dew-Point Recorder
    • Visibility Meter
    • Sooted Slides
    • Drop Photography

    Water drop imaging

    • NACA-RM-E50K01a
    • NACA-RM-E51G05
    • NACA-TN-3592

    Heated probes

    • NACA-RM-E50J12a
    • NACA-TN-2615
    • NACA-RM-A54I23

    Inference from airfoil impingement

    • NACA-TN-1397
    • NACA-TN-2476
    • NACA-RM-E52B12

    Corona discharge

    • NACA-TN-2458

    Modified pressure probe

    • NACA-RM-E51E16

    Conclusions of NACA Icing Instruments

    Possible additions

    • Vonnegut, B., Cunningham, R. M., and Katz …

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11. NACA-TR-1215 Thermodynamics

    "... the effect on final results of droplets that do not freeze completely on the cylinders"

    

    "Impingement of Cloud Droplets and Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method" [Thermodynamics topics] ¹

    Summary

    Conditions where not all water drops freeze are considered.

    Key points

    1. Conditions where not all water drops freeze on the multicylinder instrument are considered.
    2. Rotating cylinder Ludlam limits are compared to flight test data.

    Abstract

    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 …

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12. NACA-TR-1215

    "... the effect on final results of droplets that do not freeze completely on the cylinders"

    

    "Impingement of Cloud Droplets and Procedure for Measuring Liquid-Water Content and Droplet Sizes in Supercooled Clouds by Rotating Multicylinder Method." ¹

    Summary

    Conditions where not all water drops freeze are considered.

    Key points

    1. NACA-TN-2903, NACA-TN-2904, and NACA-RM-E53D23 are "superseded" (collected together).
    2. Conditions where not all water drops freeze on the multicylinder instrument are considered.
    3. The terms "freezing fraction" is introduced into the NACA publications.

    Abstract

    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 …

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13. NACA-RM-E53D23

    "The meteorological data obtained with the multicylinder method are the only data available for the design of ice-protection equipment for aircraft"

    "Procedure for Measuring Liquid-Water Content and Droplet Sizes in Super-cooled Clouds by Rotating Multicylinder Method"¹

    

    Summary

    Detailed procedures for the use of multicylinders are described.

    Key points

    1. Detailed procedures for the in-flight use of multicylinders are described.
    2. Detailed procedures for analyzing results from of multicylinders are described, with a flight data case.
    3. Differences in analysis method details can drive MVD and LWC differences in the range of 5% to 10%.

    Abstract

    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.

    Discussion

    Procedures

    A set of rotating cylinders were constructed …

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14. NACA-TN-2708

    "...At low airspeeds and with large cylinders, the determination should be relatively good."

    "Comparison of Three Multicylinder Icing Meters and Critique of Multicylinder Method" ¹

    Summary

    Multicylinder instruments had good agreement for liquid water content and median effective drop diameter, but poor agreement for the distribution type.

    Key points

    1. Three multicylinder instruments had good agreement for liquid water content and median effective drop diameter, but poor agreement for the distribution type
    2. The Langmuir drop size distributions were revised (but the revised versions were not widely adopted)

    Abstract

    Three multicylinder cloud meters, fundamentally similar but differing in important details, were compared in use at the Mount Washington Observatory. Determinations of liquid water content were found to agree within the limits of the probable error, but the two instruments designed by the National Advisory Committee for Aeronautics indicated larger drop sizes than did the Observatory's instrument, apparently because of spurious ice catch …

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