Blast from the Past: NACA Icing Publications

Seeking "Icing Information Notes"

Donald Cook — Sun, 27 Sep 2026 12:00:00 -0700

Although horizontal extent is a common term in the icing literature, it has not been defined anywhere. Therefore, it is defined here in a way that is compatible with conventional usage.

Public Domain figure and text from DOT/FAA/AR-07/4, which are similar to one of the Notes. ¹

Summary

Dr. Richard Jeck, retired from the FAA, passed away in January 2026. ²

I am putting together a series on Dr. Jeck's works (He had over 60 technical publications, so this may take a while).

Circa 1997, Jeck started circulating "Icing Information Notes" ["Notes"] ³:

"in response to requests from the field or to clarify known areas of confusion in the interpretation and application of icing data and technical literature."

They were available on request.

He apparently wrote them until 2012, and there appear to have been over 30 in total.

I am seeking if anyone asked for and …

Predictions for the Third Ice Prediction Workshop Using Simple Methods

Donald Cook — Wed, 19 Aug 2026 08:00:00 -0700

"The main goal of these workshops is to assess state-of-the-art of icing prediction tools with 2D and 3D experimental data"

Summary

The series of Ice Prediction Workshops ¹ have the purposes:

The main goal of these workshops is to assess state-of-the-art of icing prediction tools with 2D and 3D experimental data. We aim to provide an impartial forum to evaluating the effectiveness of icing methods and to identify the areas needing additional research and development.

Several organizations have sponsored and contributed to the workshops, including AIAA, NASA, SAE, academia, and industry.

Two workshops have been completed. The third one "IPW-3" is scheduled for September 21-24, 2026.

Predictions of Cd and Cl values are made for the cases in IPW-3.

Recommendations for "the areas needing additional research and development" are made.

IPW-3

IPW-3 has two major tasks. We will focus here on the second task, TFG-2.

The Ice Prediction Workshop is …

The National Technical Reports Library

Donald Cook — Tue, 04 Aug 2026 16:00:00 -0700

"The National Technical Information Service acquires, indexes, abstracts, and archives the largest collection of U.S. government-sponsored technical reports in existence. "

The Defense Technical Information Center

The Defense Technical Information Center https://discover.dtic.mil/public-access-search/ site was a "go-to" resource for me. It had a better search engine than some alternatives.

I write "was", as it is now down, with a note:

"DoW S&T Reports Search is offline while we fine-tune the user experience. It will be back online soon."

This has persisted since at least August 1, 2026 (I had not checked it recently before that).

The National Technical Reports Library

I am in the process of updating links to use the National Technical Reports Library ntrl.ntis.gov. The search engine is not intuitive to me, but it can get the job done (well enough that I hope they do not decide to "fine-tune the user …

Estimating Icing Conditions with Highest Drag

Donald Cook — Mon, 27 Jul 2026 18:30:00 -0700

"These data will be useful in evaluating and formulating ice accretion analyses and also performance penalty predictions."

from NASA-TM-83556.

Summary

In "Ice Shape Drag Correlations" a correlation of drag due to icing was detailed using data from NASA-TM-83556 ¹. Here, we use the correlation to predict or estimate which icing conditions can result in the highest drag.

The icing conditions predicted to have the highest Cd values cluster in a limited range of Figures 1 and 2 of Appendix C ², even when wide ranges of airspeed and altitude are considered.

The Appendix C, Figure 1 Icing Environment

We will use the Appendix C Continuous Maximum Icing Conditions.

Appendix C Figure 1 defines LWC as a function of water drop size MVD (noted as "Median Effective Drop Diameter").

Public Domain image.

There is a standard horizontal extent of 17.4 nmi. defined that will be used here.

A true airspeed …

Ice Shape Drag Correlations

Donald Cook — Mon, 13 Jul 2026 12:30:00 -0700

"No certain explanation for the poor repeatability of glaze ice shapes is available at this time."

NASA-TM-83556.

Public Domain image from AEDC-TR-87-23.

Summary

We have seen several attempts to correlate drag for an airfoil with icing conditions.
Here, we will review prior correlations, and refine the methods to achieve a better, more widely applicable correlation.

Prior Correlations

One significant correlation is from NASA-TM-83556 ¹, that used test control parameters such as total temperature, LWC, and airspeed:

Public Domain image from NASA-TM-83556.

Another is from AEDC-TR-87-23 ², which used the calculated leading edge freezing fraction (N):

Public Domain image from AEDC-TR-87-23.

About the lines on Figure 3, AEDC-TR-87-23 states:

The curves for these figures were drawn as the author interpreted the data.

The curves are similar in shape because of the functional dependency of N on test conditions that affect the change in ice shape and, thus, Cd. Again, it depends …

Hard to find publications

Donald Cook — Sun, 12 Jul 2026 12:00:00 -0700

"The documents were so old, however, that they were not listed in the modern computerized library search systems, and some of these documents were out of print." ¹

NACA Cleveland library, circa 1945.

Summary

I can usually get even rare and obscure publications through inter-library loan from my public library, but these were reported as having no loanable copies available.

Discussion

I have tried the many excellent search tips at Gwern's Internet Search Tips, and now I am at the "request help" stage.

I would appreciate any help anyone can offer finding them as loanable print copies or digitally.

Recently made available

Richard Jeck: "Icing Characteristics of Low Altitude, Supercooled Layer Clouds." 1980 FAA/RD-80/24 ntrl.ntis.gov (link has no pdf file)
Thanks to the FAA Tech Center for providing a copy.
Heat Transfer Calculation for Aerofoils RAE Rep. No. Aero. 1783, Nov. 1942. Reprinted as NACA MRR …

Testing Messinger Freezing Fraction Correlations with the IceVal Database

Donald Cook — Tue, 09 Jun 2026 16:00:00 -0700

"an empirical relationship was obtained which correlated ice accretion thickness and ice angles with theoretical impingement parameters." ¹

Introduction

Studies have correlated icing conditions to ice shapes and their effects. Here, we will test one using the 3332 experimental ice shapes cases in the IceVal database ¹ without ice protection.

The studies had well-planned series of test conditions for their objectives. However, when we use all 3332 IceVal experimental shapes from tests with diverse objectives, things can get messy.

We will see that the final results are surprisingly good.

NASA/CR-2005-213852 ³

NASA/CR-2005-213852 "Evaluation and Validation of the Messinger Freezing Fraction" has been reviewed previously in Conclusions of the Ice Shapes and Their Effects thread.

It looked at correlating ice shape parameters to calculated leading edge freezing fraction.

The test cases within it are now a subset of the IceVal database.

40 condition were tested to verify an implementation …

Swept Airfoil Cases in IceVal

Donald Cook — Thu, 14 May 2026 15:00:00 -0700

"Use of these relationships allows the direct determination of ice shapes adjusted for any given icing and flight condition as well as for size and sweep of the airfoil" ¹

Experimental ice shapes compared to a LEWICE analysis.

Summary

There are 41 swept airfoil cases in the IceVal database ².

The quote at the top from Wilder briefly describes the the empirically based analytical method he described in ¹. However, it is not directly applicable to airfoils other than the ones he considered, which had dozens of icing tunnel ice shapes tests each. For more details on Wilder's method, see Wilder.

LEWICE ³, and other codes, offer potentially more widely applicable methods of ice shape prediction in swept airfoils.

LEWICE analysis for these cases tends to produce ice shapes that are consistently too small compared to experiment.

Empirically derived adjustments to the inputs to LEWICE are discussed that improve the …

Running LEWICE version 3.2.3 for the IceVal cases

Donald Cook — Thu, 14 May 2026 14:00:00 -0700

"The resulting analysis showed that LEWICE compared well to the available experimental data." ¹

An example of a good comparison between analysis and experiment.

Introduction

The IceVal database ², and its predecessors, were originally assembled to validate the LEWICE ³ ice shape prediction code.

Here, we will repeat that analysis with a more recent version of LEWICE, and look at the effects of using "corrected" angle of attack values in the analysis.

The LEWICE ice shapes results in the IceVal database were apparently run with LEWICE version 3.2.2 (We will abbreviate that as the Database LEWICE shape). The IceVal users guide is not explicit, other than "the latest version of the LEWICE ice shape prediction code". The 2008 LEWICE validation report was written at about the same time. It does not mention IceVal, but the validation report was for LEWICE version 3.2.2.

Comparisons with all IceVal …

A Geometric Analysis Method

Donald Cook — Thu, 14 May 2026 13:00:00 -0700

"This demonstrates that the automated process cannot (yet) be substituted for good engineering judgment."

From the LEWICE manual. ¹

A case where two methods detected similar upper surface ice horns.

Introduction

Reviewing 6000+ ice shape assessments to verify that they agree with engineering judgement is a daunting task. Even with professionalism and due-diligence, debatable results may be missed. So, there is motivation to automate the process as much as possible.

Here, I describe a step toward that goal. It is a work in progress, not a completed product.

Using the IceVal database to validate an assessment method

The IceVal database will be used here to validate a different comparison assessment method. This is one of the uses envisioned when compiling the database ²:

... by compiling a comprehensive database consisting of a standardized, reliable data set, and combining that with an easy-to-use graphical user interface (GUI), providing quick and easy access …

Overall comparison assessments between experiment and LEWICE

Donald Cook — Thu, 14 May 2026 12:00:00 -0700

"It is possible for any (or all!) ... parameters to be incorrectly output."

A case with identified horn locations that are debatable.

Introduction

Assessments of LEWICE ice shapes compared to experiment have been published twice.

The LEWICE THICK utility program was uses to identify ice horn locations and maximum heights. However, engineering judgement was used to adjust some values in the IceVal database. Cases with questionable ice horn identifications can be found in the database.

The difficulty of consistently identifying ice horns affects the comparison assessment between LEWICE and experiment.

Published assessments

The overall comparison of LEWICE ¹ analysis to experimental data to has been published twice.

The first was in 1999 ², and included 800 experiment cases. The second was in 2008 ³, and had more than 3000 experimental cases. These are the data that are included in the IceVal database ⁴.

The 1999 Assessment

The assessment published in 1999 …

Challenges Using the IceVal Database

Donald Cook — Thu, 14 May 2026 11:00:00 -0700

"No data is clean, but most is useful."

attributed to Dean Abbott.

Ice shape tracing points that are mis-ordered and mis-aligned with the airfoil.

Introduction

The IceVal database is a significant achievement that is still yielding dividends, decades later.

The IceVal description ¹ discusses some of the challenges of assembling the database:

While all of this data is available, in theory, for every test run, as a practical matter, this is often not the case. Because the data is managed by the individual researcher, and much of it is stored in hardcopy form, locating a specific data set may require a significant effort. Furthermore, because of differences in experimental technique from one researcher to the next, the extent to which the relevant conditions have been explicitly documented can vary widely. Moreover, since plans made prior to a test may change during the test based on interim results, it is not …

A Tour of the IceVal DatAssistant

Donald Cook — Thu, 14 May 2026 10:00:00 -0700

"... all publicly available IRT-generated experimental ice shapes with complete and verifiable conditions have now been compiled into one electronically-searchable database"

NASA Report E-16236 ¹.

Public Domain image from NASA Report Number: E-16236.

A quick tour of the IceVal DatAssistant

The IceVal DatAssistant is available from NASA. It runs on the Windows operating system (only).

The IceVal DatAssistant can do several functions. The main interest here is the database of experimental run conditions and results.

The tables of primary interest are IceShapeData, RunSpecs, and SprayConditions.

Public Domain image from NASA Report Number: E-16236.

In the time span 1988 to 2008 that the database covers, experimental test results were measured by cutting a thin slot into the ice, inserting a pre-made cardboard template, and manually tracing the ice shape. These were later digitized, and included in the database.

Public Domain image from NASA Report Number: E-16236.

Range of conditions tested

The primary …

6000 Ice Shapes - the IceVal DatAssistant

Donald Cook — Thu, 14 May 2026 09:00:00 -0700

"As with any scientific endeavor, the foundation of icing research ... is the data acquired during experimental testing."

NASA Report E-16236 ¹.

4132 ice shapes for the NACA0012 airfoil.

[Yes, that is how it is spelled.]

The IceVal DatAssistant ¹, ² from NASA contains 6330 ice shapes from experiments in the NASA Icing Research Tunnel ³ (3665 shape tracings) and from analysis with LEWICE ⁴ (2965 ice shapes).

Significant uses of the data were the LEWICE validation reports published in 1998 ⁵ ⁶ and 2008 ⁷, which established measures for the comparison of LEWICE analysis results to experimental data.

These data are tremendous aids to researchers and developers of icing analysis codes and test methods. It has been 27 and 18 years since these were published (respectively), and we should celebrate that the utility of the data has held up well. However, given that an entire generation of workers in the …

"A review of ice detection technologies"

Donald Cook — Tue, 13 Jan 2026 13:30:00 -0800

"These incidents underscore the urgent need for reliable, real-time ice detection systems to prevent dangerous icing conditions and enhance operational safety." ¹

Fig. 9. (a) (b) fixed cylinder, (c) Capillary collector, (d) rainbow recorder, (e) dew-point recorder.

Discussion

I am proud to note the publication of the article "A review of ice detection technologies" in the journal "Progress in Aerospace Sciences" link. I was a co-author with four others whom I thank (L. Maio, J. Moore, P. Potluri, C.K. Bosetti).

I contributed largely to the section "Early meteorological instruments in flight". You may find more information on the topic in the "Meteorological Instruments Thread".

Kudos to the "Progress in Aerospace Sciences" for being an open access journal.

Notes:

L. Maio, J. Moore, D.E. Cook, P. Potluri, C.K. Bosetti, A review of ice detection technologies, Progress in Aerospace Sciences, Volume 161, 2026, 101158, ISSN 0376-0421, doi.org/10 …

Aircraft Icing Forum Presentation

Donald Cook — Tue, 13 May 2025 09:00:00 -0700

Discussion

I had the honor of doing the first presentation for the FAA Aircraft Icing Forum

The Aircraft Icing Forum, hosted jointly by Cris Bosetti (FAA) and Dr. Peter Struk (NASA), provides a recurring monthly space to discuss aircraft icing research, technology, regulation, and related questions and challenges. The purpose of this forum is to provide an opportunity to share information, improve visibility, make connections, and advance the overall approach to aircraft icing knowledge and safety.

The presentation "Aircraft Ice Protection in the NACA Era" is available in either LibreOffice or pdf format:

AIF 2025 presentation.odp

AIF 2025 presentation.pdf

Achievements of the NACA Era

Donald Cook — Tue, 14 Jan 2025 12:00:00 -0800

"it shall be the duty of the advisory committee for aeronautics to supervise and direct the scientific study of the problems of flight with a view to their practical solution"

From commons.wikimedia.org.

For most of the reviews of the NACA-era aircraft icing publications, I have tried to be neutral about whether one is "better" than another (they all have merit), except for noting how often they were cited and used later. This may have de-emphasized some of the biggest achievements, which are often not contained in just one publication.

NACA did not invent several of these items. NACA did find good ideas from many sources, and collaborated with industry, academia, and other government entities. They fulfilled their mission statement several times.

... it shall be the duty of the advisory committee for aeronautics to supervise and direct the scientific study of the problems of flight with a view to …

The Icing Problem

Donald Cook — Fri, 03 Jan 2025 16:00:00 -0800

"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"

"THE ICING PROBLEM - CURRENT STATUS NACA TECHNIQUES AND RESEARCH" ¹

Abstract

This paper summarizes some of the techniques used in N.A.C.A. research programs, in flight and in tunnels, to solve aircraft icing problems and it indicates the scope of the data available for the design of aircraft icing protection systems. Sufficient data have been obtained, generalized where possible, and techniques have been established whereby icing-protection requirements for most aircraft components can be determined sufficiently accurately for engineering purposes. The Appendices discuss the icing facilities at the N.A.C.A. Lewis laboratory in detail, specific test equipment and techniques used in conducting tests in icing wind tunnels, and several icing instruments.

Introduction

This is an excellent summary by Uwe …

Some Considerations for the Need of Icing Protection of High-Speed, High-Altitude Airplanes

Donald Cook — Fri, 03 Jan 2025 15:00:00 -0800

"These high-speed aircraft cruise at altitudes at which little, if any, icing occurs."

"NACA Conference on Some Problems of Aircraft Operation" ¹

Abstract

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. It should be noted that the paper is intended to show only orders of magnitude rather than absolute values.

Discussion

INTRODUCTION
This volume contains copies of the technical papers presented at the NACA Conference On Some Problems of Aircraft Operation on November 17 and 18 , 1954 at the Lewis Flight Propulsion Laboratory . A list of the conferees, who are members of the aircraft industry and the military services, is included.

The conference in 1954 had 21 presentations, two of which were on aircraft icing topics.

Here, "Some Considerations for the Need of Icing Protection of High-Speed, High-Altitude Airplanes" by …

Icing Conditions to be Expected in Operation of High-Speed, High-Altitude Airplanes

Donald Cook — Fri, 03 Jan 2025 14:00:00 -0800

"high-speed, high-altitude airplanes will encounter much less icing than older type airplanes"

"NACA Conference on Some Problems of Aircraft Operation" ¹

Abstract

The formation of ice on aircraft in flight is caused by the freezing of supercooled liquid -water droplets as they strike the exposed surfaces of the aircraft. Icing conditions exist, therefore, when free water in the liquid state is present in the air at temperatures below freezing.
Such conditions are frequently found in clouds, but not all clouds at subfreezing temperatures produce icing. Some clouds are composed entirely of ice crystals, which, in the absence of liquid water, do not adhere to the aircraft and therefore do not cause icing. Subfreezing clouds thus may be divided into three classes depending on whether they are composed of ice crystals, liquid-water droplets, or a mixture of crystals and drops. The latter two types, liquid and mixed clouds, are icing clouds …

NACA Conference on Aircraft Ice Prevention 1947

Donald Cook — Fri, 03 Jan 2025 13:00:00 -0800

"A solution to a problem ... of ice can usually be found, but the solution always involves penalties."

Abstract

Discussion of research on design, development, and flight application of aircraft ice-prevention equipment. Subjects discussed are NACA research on the thermal ice-prevention system, flight investigation of meteorological factors conducive to aircraft icing, calculation of heat required for wing thermal ice-prevention in specified ice conditions, tension in radio antenna wires resulting from ice formation, analytical study of thermal ice-prevention systems applied to light aircraft, effect of ice formations on aircraft performance, etc.

Discussion

This documents the state of the art in 1947 for aircraft ice protection.

Presentations were made on 15 topics.

Here, we will see the abstract of each topic, a summary of results, selected figures, and where to find more information.

[Links are provided to sections summarized herein.]

INTRODUCTION

LIST OF CONFEREES

TECHNICAL DISCUSSIONS:

REVIEW OF NACA RESEARCH ON THE …

NACA Aircraft Icing Conferences

Donald Cook — Fri, 03 Jan 2025 12:00:00 -0800

"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" ¹

From Rodert, NACA Conference on Aircraft Ice Prevention. ²

NACA hosted several conferences, some of them including the topic of aircraft icing. At the conferences NACA had the opportunity to communicate their achievements to a wider audience. The presentations are typically briefer than publications, so you can learn quickly from them.

These works span much of the NACA aircraft icing publications era. "NACA Conference on Aircraft Ice Prevention" (1947) summarizes early works.

"Icing Conditions to be Expected in Operation of High-Speed, High-Altitude Airplanes" and "Some Considerations of the Need for Icing Protection of High-Speed, High-Altitude Airplanes" are from a conference in 1954, when emphasis had shifted to jet aircraft.

"The Icing Problem" (1956) summarizes much of the later work (however, there …

Prepping for the third anniversary

Donald Cook — Mon, 02 Dec 2024 16:00:00 -0800

The team is working furiously to complete reviews of all 132 publications from the "Historical Selected Bibliography of NACA-NASA Icing Publications" by the third anniversary of icinganalysis.com on January 15, 2025.

Linotype operators circa 1942. Public Domain Library of Congress.

NACA-RM-E56B23

Donald Cook — Sat, 30 Nov 2024 14:00:00 -0800

"This criterion, unavoidably subjective in nature, caused considerable scatter in the data"

"Heat Requirements for Ice Protection of a Cyclically Gas-Heated, 36° Swept Airfoil with Partial-Span Leading-Edge Slat" ¹

SUMMARY

Heating requirements for satisfactory cyclic de-icing over a wide range of icing and operating conditions have been determined for a gas-heated, 36° swept airfoil of 6.9-foot chord with a partial-span leading-edge slat. Comparisons of heating requirements and effectiveness were made between the slatted and unslatted portions of the airfoil. Studies were also made comparing cyclic de-icing with continuous anti-icing, and cyclic de-icing systems with and without leading-edge ice-free parting strips. De-icing heat requirements were approximately the same with either heated or unheated parting strips because of the aerodynamic effects of the 36° sweep angle and the spanwise saw-tooth profile of leading-edge glaze-ice deposits. Cyclic de-icing heat-source requirements were found to be one-fourth or less of the heat requirements for …

NACA-RM-E54I03

Donald Cook — Sat, 30 Nov 2024 13:00:00 -0800

"Ice formation on the unheated leading edge, which may occur prior to activation of the heating system, was removed in 1 to 1 1/2 minutes by a hot-gas-flow rate that would be sufficient for normal anti-icing."

"Investigation of Porous Gas-Heated Leading-Edge Section for Icing Protection of a Delta Wing" ¹

Abstract

SUMMARY

A tip section of a delta wing having an NACA 0004-65 airfoil section and a 60° leading-edge sweepback was equipped with a porous leading-edge section through which hot gas was bled for anti-icing. Heating rates for anti-icing were determined for a wide range of icing conditions. The effects of gas flow through the porous leading-edge section on airfoil pressure distribution and drag in dry air were investigated. The drag increase caused by an ice formation on the unheated airfoil was measured for several icing conditions. Experimental porous surface- to free-stream convective heat-transfer coefficients were obtained in dry …

NACA-RM-E53C27

Donald Cook — Sat, 30 Nov 2024 12:00:00 -0800

"... quick and reliable shedding of dangerous leading-edge ice caps and good heat utilization."

"Comparison of Several Methods of Cyclic De-Icing of a Gas-Heated Airfoil" ¹

Abstract

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.

Discussion

INTRODUCTION

The advent of high-speed, all-weather, jet-powered aircraft has emphasized the need for ice-protection systems that are light-weight, dependable, and automatic and that impose the least possible penalty on over-all aircraft performance. Anti-icing systems that evaporate …

NACA-TN-3143

Donald Cook — Fri, 29 Nov 2024 18:00:00 -0800

"Very few data are available on the physical properties of ice formations having a density other than that of clear, solid ice"

"Experimental Determination of Thermal Conductivity of Low-Density Ice" ¹

Abstract

SUMMARY

The thermal conductivity of 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 air stream.

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 equations for the thermal conductivity of packed snow as a function of snow density. The agreement of the curves for packed snow near the solid ice regime with the values of thermal conductivity, of ice indicates that the curves are applicable over the entire-ice-density range.

Discussion

This publication is included in …

NACA-TN-2212

Donald Cook — Mon, 25 Nov 2024 13:00:00 -0800

"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

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 …

NACA-RM-E53A22

Donald Cook — Wed, 20 Nov 2024 15:00:00 -0800

"radome icing has serious effects on the radar operation"

"An Analytical Study of Heat Requirements for Icing Protection of Radomes"

Abstract

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.

Discussion

INTRODUCTION

Radar is becoming of increasing importance in the design and operation of aircraft. Successful operation of these aircraft demands that the performance of the radar system including the radome be unimpaired by environmental factors including …

NACA-RM-E7H26a

Donald Cook — Wed, 20 Nov 2024 14:00:00 -0800

"The current use of improved airplane ice-prevention equipment has extended operations in icing conditions and thus accentuated the need for protecting aircraft antennas against structural failures resulting from ice accretions"

"Determination of Aircraft Antenna Loads Produced by Natural Icing Conditions" ¹

Abstract

A flight investigation was made to determine the effect of distance flown in the icing region, antenna length, and antenna angle on the tension occurring in aircraft antennae while in regions of aircraft icing.

The, experimental antennas were of lengths ranging from 15 to 43 feet and were placed at angles of 0° to 64° with the airplane thrust axis. Distances up to 256 miles were flown in diverse icing conditions at true airspeeds from 157 to 214 miles per hour and pressure altitudes at which icing conditions were encountered.

The results indicate that: The effect of ice formation on antenna tension increased with the angle of the …

NACA-RM-SE9D20

Donald Cook — Wed, 20 Nov 2024 13:00:00 -0800

"After 7 minutes of icing, however, one antenna element experienced a vibratory failure"

"Vibration and Investigation of CAA Type V-I09 Very-High-Frequency Aircraft Antenna" ¹

Abstract

Vibration and icing determinations on a CAA type V-109 very- high-frequency aircraft antenna were conducted in the NACA Lewis icing research tunnel. The antenna is an omnidirectional-range unit that consists of two aluminum elements mounted in a streamline plastic head forming a V in plan view with an apex angle of 80°.

Vibration determinations during a nonicing experiment produced element-tip total amplitude of approximately 1/4 inch at a tunnel-air velocity of 300 miles per hour.

During the icing investigation, a total amplitude as great as 7 inches was observed at the antenna-element tips with tunnel-air velocities greater than 160 miles per hour and a tunnel-air temperature of 20° F. At the higher tunnel-air temperatures, which produced a heavier and more severe ice accretion, the …

Radomes and Antennas

Donald Cook — Tue, 19 Nov 2024 12:00:00 -0800

"The current use of improved airplane ice-prevention equipment has extended operations in icing conditions and thus accentuated the need for protecting aircraft antennas against structural failures resulting from ice accretions"

These reviews are for studies of the effect of ice on radomes and antennas.

Gowan, W. H., Jr.: Vibration and Investigation of CAA Type V-I09 Very-High-Frequency Aircraft Antenna. NACA-RM-SE9D20. 1949. ntrs.nasa.gov

"After 7 minutes of icing, however, one antenna element experienced a vibratory failure"
> review: NACA-RM-SE9D20
Kepple, W. L.: Determination of Aircraft Antenna Loads Produced by Natural Icing Conditions. NACA-RM-E7H26a, 1948. ntrs.nasa.gov

"The current use of improved airplane ice-prevention equipment has extended operations in icing conditions and thus accentuated the need for protecting aircraft antennas against structural failures resulting from ice accretions"
> review: NACA-RM-E7H26a
Lewis,James P., and Blade, Robert J.: "Experimental Investigation of Radome Icing and Icing Protection", NACA-RM-E52J31, 1953. ntrs.nasa.gov

"At present …

NACA-RM-E55E17a

Donald Cook — Tue, 05 Nov 2024 18:00:00 -0800

"rain deflection by jet blast appears feasible for flight speeds"

"Preliminary Data on Rain Deflection from Aircraft Windshields by Means of High Velocity Jet-Air Blast" ¹

Abstract

A preliminary experimental investigation is being conducted to determine the feasibility of preventing rain from impinging on aircraft windshields by means of high-velocity jet-air blast.

The results indicate that rain deflection by jet blast appears feasible for flight speeds comparable with landing and take-off speeds of interceptor-type jet aircraft; however, attainment of good visibility through the mist generated by raindrop breakup presents a problem. For the simulated windshield and the lower windshield angles used in the investigation, air-flow rates of the order of 3.3 pounds per minute of unheated air per inch of windshield span were required for adequate rain deflection at a free-stream velocity of 135 miles per hour.

A method has been devised whereby it is possible to produce large-diameter …

NACA-TN-2855

Donald Cook — Tue, 05 Nov 2024 17:00:00 -0800

"For practical application ... the discharging of heated jets into an air stream requires knowledge of the temperature profiles downstream of the heated jet and of the depth of penetration"

"General Correlation of Temperature Profiles Downstream of Heated Air Jet Directed at Various Angles to Airstream" ¹

Abstract

An experimental investigation was conducted to determine the temperature profiles downstream of heated air jets directed at angles of 90°, 60°, 45°, and 30° to an air stream. The profiles were determined at two positions downstream of the jet as a function of jet diameter, jet density, jet velocity, free-stream density, free-stream velocity, jet total temperature, orifice flow coefficient, and jet angle. A method is presented which yields a good approximation of the temperature profile in terms of the flow and geometric conditions.

Discussion

INTRODUCTION

The discharging of heated high-velocity jets of air or vapor into an air stream is employed in many …

NACA-TN-2019

Donald Cook — Tue, 05 Nov 2024 15:00:00 -0800

"square orifices ... provided that a jet dimension equal to the diameter of the equivalent area circle was used"

"Penetration of air jets issuing from circular, square, and elliptical orifices directed perpendicularly to an air stream" ¹

Abstract

An experimental investigation was conducted to determine the penetration of air jets directed perpendicularly to an air stream. Jets issuing from circular, square, and elliptical orifices were investigated and the jet 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. The jet penetrations were determined for nearly constant values of air-stream density at three tunnel-air velocities and for a large range of jet velocities and densities. The results were correlated in terms of dimensionless parameters and the penetrations of the various shapes were compared.

Greater penetration was obtained with the square orifices and …

NACA-TN-1615

Donald Cook — Tue, 05 Nov 2024 14:00:00 -0800

"it was necessary to define the penetration as the point at which the temperature is 1° F above the free-stream total temperature"

"Investigation of the Penetration of an Air Jet Directed Perpendicularly to an Air Stream" ¹

An experimental investigation was conducted to determine the penetration of a circular air jet directed perpendicularly to an air strewn 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.

Discussion

INTRODUCTION The introduction of a gas or vapor into …

NACA-TN-1947

Donald Cook — Tue, 05 Nov 2024 13:00:00 -0800

"Excellent correlation was obtained between the results for a jet discharging into still air and ... into a moving air stream"

"Investigation of Flow Coefficient of Circular, Square, and Elliptical Orifices at High Pressure Ratios" ¹

Abstract

An experimental investigation has been conducted to determine the orifice coefficient of a jet directed perpendicularly to an air stream as a function of pressure ratio and jet Reynolds number for circular, square, and elliptical orifices. The effect of air-stream velocity on the jet flow was also determined for three tunnel-air velocities. Equations for the flow coefficients In terms of jet Reynolds number and pressure ratio were obtained for the various shapes. Excellent correlation was obtained between the results for a jet discharging into still air and the results for a jet discharging into a moving air stream, provided that the correct outlet pressure was used.

Discussion

INTRODUCTION The introduction of a gas or …

Air Jets

Donald Cook — Mon, 04 Nov 2024 12:00:00 -0800

"rain deflection by jet blast appears feasible for flight speeds"

From NACA-RM-E55E17a.

Introduction

Five of these publications are from the "Jet Penetration" section, and one is from the "Windshield Ice Protection" section of The Historical Selected Bibliography of NACA-NASA Icing Publications.

The first five publications determine by test the characteristics of air jets entering a moving airstream. The final publication applies this technology to windshield rain removal.

Windshield rain removal is often designed in the same group as ice protection. SAE AIR-1168/4 is titled “Ice, Frost, and Rain Protection” [SAE Aerospace Applied Thermodynamics Manual, 1969 (regularly updated, currently document sae.org)]. A design group I worked in was named "Ice and Rain Protection".

That was historically where the knowledge of water drops, air flow control, and mechanical systems resided.

So, it is not surprising that a rain-removal publication is in the "Selected Bibliography of NACA-NASA Aircraft Icing Publications".

Air …

NACA-RM-E57G09

Donald Cook — Tue, 15 Oct 2024 11:00:00 -0700

"the contour plots indicate that cowl-lip disturbances are the more controlling factor"

"Total Pressure Distortion and Recovery of Supersonic Nose Inlet with Conical Centerbody in Subsonic Icing Conditions" ¹

Abstract

Ice was formed on a full-scale unheated supersonic nose inlet in the NACA Lewis icing tunnel to determine its effect on compressor-face total-pressure distortion and recovery. Inlet angle of attack was varied from 0° to 12°, free-stream Mach number from 0.17 to 0.28, and compressor-face Mach number from 0.10 to 0.47. Icing-cloud liquid-water content was varied from 0.65 to 1.8 grams per cubic meter at free-stream static air temperatures of 15° and 0° F.

The addition of ice to the inlet components increased total-pressure- distortion levels and decreased recovery values compared with clear-air results, the losses increasing with time in ice. The combination of glaze ice, high corrected weight flow, and high angle of …

NACA-TN-4093

Donald Cook — Mon, 14 Oct 2024 23:00:00 -0700

"Rotational speeds up to 1200 rpm had no apparent effect on the heat-transfer characteristics of the spinner"

"Investigation of Heat Transfer from a Stationary and Rotating Conical Forebody"

Abstract

The convective heat transfer from the surface of a conical forebody having a hemispherical nose, an included angle of approximately 30°, and a maximum diameter of 18.9 inches was investigated in a wind tunnel for both stationary and rotating operation. The range of test conditions included free-stream velocities up to 400 feet per second, rotational speeds up to 1200 rpm, and. angles of attack of 0° and 6°. Both a uniform surface temperature and a uniform heater input power density were used.

The Nusselt-Reynold's number relations provided good correlation of the heat-transfer data for the complete operating range at 0° angle of attack with and without spinner rotation, and for 6° angle of attack with rotation. Rotational speeds up to …

NACA-TN-3837

Donald Cook — Mon, 14 Oct 2024 22:00:00 -0700

"Many aircraft components are essentially simple bodies of revolution; examples of these are radomes, body noses, engine accessory housings, and the large spinners of turboprop engines"

"Investigation of Heat Transfer from a Stationary and Rotating Ellipsoidal Forebody of Fineness Ratio 3" ¹

Abstract

The convective heat transfer from the surface of an ellipsoidal fore-body of fineness ratio 3 and 20-inch maximum diameter was investigated in clear air for both stationary and rotating operation over a range of conditions including air speeds up to 240 knots, rotational speeds up to 1200 rpm, and angles of attack of 0°, 3°, and 6°. The results are presented in the form of heat-transfer coefficients and the correlation of Nusselt and Reynolds numbers. Both a uniform surface temperature and a uniform input heater density distribution were used.

The experimental results agree well with theoretical predictions for uniform surface temperature distribution. Complete agreement was not obtained …

NACA-RM-E51B12

Donald Cook — Mon, 14 Oct 2024 21:00:00 -0700

"Serious icing of a turbojet-engine installation may render the engine inoperative in a matter of minutes."

"NACA Investigations of Icing-Protection Systems for Turbojet-Engine Installations" ¹

Abstract

Investigations have been made in flight and in wind tunnels tc determine which components of turbojet installations are most critical in icing conditions, and to evaluate several methods of icing protection. From these studies, the requirements necessary for adequate icing protection and the consequent penalties on engine performance can be estimated.

Because investigations have indicated that the compressor-inlet screen constitutes the greatest icing hazard and is difficult to protect, complete removal or retraction of the screen upon encountering an icing condition is recommended. In the absence of the screen, the inlet guide vanes of an axial-flow-type turbojet engine constitute the greatest danger to engine operation in an icing condition; a centrifugal- type engine, on the other hand, is relatively unsusceptible to icing once the …

NACA-RM-E50H29

Donald Cook — Mon, 14 Oct 2024 20:00:00 -0700

"Experience has shown that ... the inlet guide vanes of an axial-flow turbojet engine constitute the most critical component to be protected from icing"

"Investigation of Power Requirements for Ice Prevention and Cyclical De-Icing of Inlet Guide Vanes with Internal Electric Heaters" ¹

Abstract

An investigation was conducted to determine the electric power requirements necessary for ice protection of inlet guide vanes by continuous heating and by cyclical de-icing. Data are presented to show the effect of ambient-air temperature, liquid-water content, air velocity, heat-on period, and cycle times on the power requirements for these two methods of ice protection.
The results showed that for a hypothetical engine using 28 inlet guide vanes under similar icing conditions, cyclical de-icing can provide a total power saving as high as 79 percent over that required for continuous heating. Heat-on periods in the order of 10 seconds with a cycle ratio of about 1:7 …

NACA-RM-E50I08

Donald Cook — Mon, 14 Oct 2024 18:00:00 -0700

"Ice formations ... may have the following effects, which when combined may become serious enough to necessitate a shutdown of the engine: reduced engine thrust, increased,fuel consumption, and increased tail-pipe temperature."

"Icing Characteristics and Anti-Icing Heat Requirements for Hollow and Internally Modified Gas-Heated Inlet Guide Vanes" ¹

Abstract

A two-dimensional inlet-guide-vane cascade was investigated to determine the effects of ice formations on the pressure losses across the guide vanes and to evaluate the heated gas flow and temperature required to prevent icing at various conditions. A gas flow of approximately 0.4 percent of the inlet-air flow was necessary for anti-icing a hollow guide-vane stage at an inlet-gas temperature of 500° F under the following icing conditions: air velocity, 280 miles per hour; water content, 0.9 gram per cubic meter; and inlet-air static temperature, 0° F. Also presented are the anti-icing gas flows required with modifications of the hollow …

NACA-TN-2126

Donald Cook — Mon, 14 Oct 2024 16:00:00 -0700

"Use of the hot-gas method of anti-icing has been restricted ... because of difficulty in controlling the rate of heat dissipation"

"Improvements in Heat Transfer for Anti-Icing of Gas-Heated Airfoils with Internal Fins and Partitions" ¹

Abstract

The effect of modifying the gas passage of hollow metal airfoils by the additIon of internal fins and partitions was experimentally investigated and comparisons were made among a basic unfinned airfoil section and two airfoil designs having metal fins attached at the leading edge of the internal gas passage. An analysis considering the effects of heat conduction in the airfoil metal was made to determine the internal modification effectiveness that may be obtained in gas-heated components, such as turbojet-inlet guide vanes, support struts, hollow propeller blades, arid. thin wings.

Over a wide range of heated-gas flow and tunnel-air velocity, the increase in surface-heating rates with internal fin was marked (up to 3.5 times …

NACA-RM-E8F01a

Donald Cook — Mon, 14 Oct 2024 15:00:00 -0700

"The engine was satisfactorily accelerated to take-off power after approximately 45 minutes in the icing condition"

"Natural Icing of an Axial-Flow Turbojet Engine in Flight for a Single Icing Condition" ¹

Abstract

An investigation has been conducted In natural icing conditions to determine the effect of ice formations on the performance of an axial-flow turbojet engine. One flight was made in an icing condition in which the liquid.-water content varied from 0.077 to 0.490 gram per cubic meter and the average droplet size varied from 5.4 to 12.1 microns. During a period of 60 minutes in icing, at an engine speed of 11,000 rpm, the tail-pipe temperature increased from 8650 to 9650 F and the jet thrust decreased from 1950 to 1700 pounds. Near the end of the icing period, the engine was satisfactorily accelerated to take-off power.

Discussion

As this publication is brief …

NACA-RM-E8C18

Donald Cook — Mon, 14 Oct 2024 14:00:00 -0700

"Ice formations penetrated to the second-stage rotor blades"

"Preliminary Results of Natural Icing of an Axial-Flow Turbojet Engine" ¹

Abstract

A flight investigation is being conducted in natural icing conditions to determine the effect of ice formations on the performance of an axial-flow turbojet engine. One flight was made in icing conditions in which the icing rate varied from 5.1 to 2.1 inches per hour. During a period of 45 minutes in icing, the tail-pipe temperature increased from 761° to 1065° F and the jet thrust decreased from 1234 to 910 pounds. Ice penetrated to the second-stage stator blades. No general conclusions can be reached from these data because the icing condition was relatively light.

Discussion

As this publication is brief (18 pages, with 12 of those photos or blank), it is reproduced nearly in its entirety herein.

The jet engine inlet in this case did not have …

NACA-TN-1246

Donald Cook — Sat, 12 Oct 2024 13:00:00 -0700

"The icing of the unprotected installation presents a serious operational problem"

"Wind-Tunnel Investigation of Icing of an Engine Cooling-Fan Installation" ¹

Abstract

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 occurred within 2 minutes and complete stoppage of the 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 …

Abstracts for The Historical Selected Bibliography of NACA-NASA Icing Publications

Donald Cook — Fri, 11 Oct 2024 14:00:00 -0700

"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 …

Engine Inlet Icing

Donald Cook — Thu, 10 Oct 2024 12:00:00 -0700

"The desirability for all-weather operation of turbojet aircraft has necessitated extensive research on methods of icing protection for the various engine components"

From NACA-RM-E8C18.

Discussion

Publications taken largely from The Historical Selected Bibliography of NACA-NASA Icing Publications, "Turbine-Type Engine and Inlet Icing Studies" section are reviewed here.

Reviews

NACA-TN-1246 "Wind-Tunnel Investigation of Icing of an Engine Cooling-Fan Installation"

"The icing of the unprotected installation presents a serious operational problem"

NACA-RM-E8C18 "Preliminary Results of Natural Icing of an Axial-Flow Turbojet Engine"

"Ice formations penetrated to the second-stage rotor blades"

NACA-RM-E8F01a "Natural Icing of an Axial-Flow Turbojet Engine in Flight for a Single Icing Condition"

"The engine was satisfactorily accelerated to take-off power after approximately 45 minutes in the icing condition"

NACA-TN-2126 "Improvements in Heat Transfer for Anti-Icing of Gas-Heated Airfoils with Internal Fins and Partitions"

"Use of the hot-gas method of anti-icing has been restricted ... because of difficulty in controlling the …

NACA-RM-E51L17

Donald Cook — Wed, 09 Oct 2024 12:00:00 -0700

"complete knowledge of the physical conditions under which supercooled clouds may exist, and the factors that cause a supercooled cloud to transform to an ice-crystal cloud is necessary"

"A Photographic Study of Freezing of Water Droplets Falling Freely in Air" ¹

Abstract

SUMMARY

A photographic technique for investigating water droplets of diameter less than 200 microns falling freely in air at temperatures between 0° C and -50° C has been devised and used to determine:
(1) The shape of frozen droplets
(2) The occurrence of collisions of partly frozen or of frozen and liquid droplets
(3) The statistics on the freezing temperatures of individual free-falling droplets

A considerable number of droplets were found to have a non-spherical shape after freezing because of various protuberances and frost growth, and droplet aggregates formed by collision. The observed frequency of collision of partly frozen droplets showed good order of magnitude agreement with the …

NACA-TN-2532

Donald Cook — Mon, 07 Oct 2024 12:00:00 -0700

"supercooled water was concluded to become progressively more ice-like as the temperature is lowered"

"X-Ray Diffraction Study of the Internal Structure of Supercooled Water" ¹

SUMMARY

A Bragg X-ray spectrometer equipped with a volume-sensitive Geiger counter and Soller slits and employing filtered molybdenum Kα, radiation was used to obtain a set of diffracted intensity curves as a function of angle for supercooled water. Diffracted intensity curves in the temperature region of 21° to -16° C were obtained. The minimum between the two main diffraction peaks deepened continuously with lowering temperature, indicating a gradual change in the internal structure of the water. No discontinuity in this trend was noted at the melting point. The internal structure of supercooled water was concluded to become progressively more ice-like as the temperature is lowered.

Discussion

The extensive equations included in this publication area not detailed herein.

APPARATUS AND PROCEDURE

A Bragg X-ray spectrometer equipped …

NACA-TN-2510

Donald Cook — Wed, 02 Oct 2024 12:00:00 -0700

"a need has arisen for a more complete understanding of the physical properties of supercooled water because few of the physical properties of water have been investigated at temperatures much below 0° C"

"Experimental Values of the Surface Tension of Supercooled Water" ¹

Abstract

The results of surface-tension measurements for supercooled water are presented. A total of 702 individual measurements of surface tension of triple-distilled water were made in the temperature range, 27° to -22.2° C, with 404 of these measurements at temperatures below 0° C. The increase in magnitude of surface tension with decreasing temperature, as indicated by measurements above 0° C, continues to -22.2° C. The inflection point in the surface-tension-temperature relation in the vicinity of 0° C, as indicated by the International Critical Table values for temperatures down to -8° C, is substantiated by the measurements in the temperature range, 0° to -22.2° C …

NACA-TN-2234

Donald Cook — Mon, 30 Sep 2024 12:00:00 -0700

"very few supercooled droplets exist at temperatures lower than -35° C and the existence of an icing cloud at such low temperatures is probably an unusual occurrence."

"Statistical Explanation of Spontaneous Freezing of Water Droplets" ¹

Abstract

A statistical theory based on the presence of small crystallization nuclei suspended in water is developed, to explain experimental results showing 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.

Discussion

In this study, data from the …

NACA-TN-2142

Donald Cook — Wed, 25 Sep 2024 12:00:00 -0700

"Although supercooled water has been observed and reported for over two centuries, considerable disagreement exists as to the degree of supercooling possible and the factors that influence supercooling."

"Photomicrographic Investigation of Spontaneous Freezing Temperatures of Supercooled Water Droplets" ¹

Abstract

A photomicrographic technique for investigating supercooled water droplets has been devised and used to determine the spontaneous freezing temperatures of supercooled. water droplets of the size ordinarily found. in the atmosphere. The freezing temperatures of 4527 droplets ranging from 8.75 to 1000 microns in diameter supported on a platinum surface and 571 droplets supported on copper were obtained.

The average spontaneous freezing temperature decreased with decrease in the size of the droplets. The effect of size on the spontaneous freezing temperature was particularly marked below 60 microns. Frequency-distribution curves of the spontaneous freezing temperatures observed for droplets of a given size were obtained. Although no droplet froze at a …

Properties of Water

Donald Cook — Mon, 23 Sep 2024 12:00:00 -0700

"Although many important advances have been made in the control of ice formation on aircraft in flight, little progress has been made toward an understanding of the fundamental processes involved in the formation of ice or the prediction of such formation."

From NACA-RM-E51L17.

Introduction

There was limited data for properties of liquid water below the temperature of 0° C (supercooled water) at the start of the NACA-era. The five studies reviewed here sought to improve the data available.

The authors were well-informed of other studies available at the time. New instruments were conceived and built for these studies.

These five studies largely considered water drops, although much of the data are also applicable to more general aircraft icing analysis.

Four of the studies concern the temperature at which supercooled water drops will spontaneously freeze (freeze without outside influence other than temperature).

Several of the studies note similarities of the properties …

Anti-Ice Heat Required Calculations with LEWICE

Donald Cook — Mon, 20 May 2024 13:00:00 -0700

Public domain image by Donald Cook.

Prerequisites

You need to have completed Anti-Ice Heat Required Calculations.

Introduction

Here, we will see that the values calculated by a multi-node analysis in LEWICE are comparable to the values calculated previously.

Running LEWICE for anti-icing calculations involves (necessarily) more complex inputs. The user has to select which set of external heat transfer assumptions to use. The detailed output files require post-processing to extract the total heat required value.

Discussion

The LEWICE manual describes "deicer" cases that also may be used for anti-ice heat requirement analysis.
An input is the "IDEICE" value in the case.inp file. By default, this is 0, and an unheated surface ice analysis is performed. However, with IDEICE > 0, ice protection analysis is performed, as detailed in a cased.inp file. A key input in that file is ievap, which for the cases below is set to ievap=1 …

Anti-Ice Heat Required Calculations

Donald Cook — Mon, 20 May 2024 12:00:00 -0700

Public domain image by Donald Cook.

Prerequisites

You need to have completed Anti-Ice Heating Calculations Theory.

Introduction

For this we will use "Engineering Summary of Airframe Icing Technical Data", ADS-4, as the anti-ice examples are more detailed than those in the "Aircraft Icing Handbook", DOT/FAA/CT-88/8-1.

The ADS-4 analysis method uses NACA-TN-2799, from 1952, for the heat and mass balance calculations. This method implements solutions as nomographs (for more details, see the post NACA-TN-2799). We will not be using the nomographs. The heat balance equations are similar to the Standard Computational Model, which we will use.

The calculations are implemented in the file "aircraft_a_ads4.py" (and associated files) available at github.com/icinganalysis/icinganalysis.github.io. Readers are encouraged to run the analysis to the duplicate results.

Discussion

"Aircraft Icing", AC 20-73A, briefly mentions the terms Qa and Qr:

Qa Heat available
Qr Heat required

Heat required is …

Anti-Ice Heating Calculations Theory

Donald Cook — Mon, 13 May 2024 12:00:00 -0700

From ADS-4 ntrl.ntis.gov.

Prerequisites

You need to have completed Aircraft Icing Handbook Energy Balance Examples.

Introduction

We will review "Engineering Summary of Airframe Icing Technical Data", ADS-4 https://ntrl.ntis.gov/NTRL/dashboard/searchResults/titleDetail/AD608865.xhtml, as the anti-ice examples are more detailed than those in the "Aircraft Icing Handbook Volume 1", DOT/FAA/CT-88/8-1 ntrl.ntis.gov.
We will also look at "Ice, Frost, and Rain Protection", SAE AIR1168/4 sae.org, for practical guidance for analysis.

The ADS-4 and SAE AIR 1168/4 analysis methods use nomographs to implement graphical solutions. We will not be using the nomographs. While the notation is different, the analysis method from ADS-4 is very similar to the Standard Computational Model in the Aircraft Icing Handbook Merged Sections which we will use here.

The energy balance equation is:

Q"Source + Q"Sink = 0

Define Q"Sink by:

Q"Sink …

Using Appendix C for Ice Shape Analysis

Donald Cook — Mon, 29 Apr 2024 11:00:00 -0700

Public domain image by Donald Cook.

Summary

Search within the Appendix C Continuous Maximum Icing definition for the thickest ice shape.

Prerequisites

You need to have completed Run a 2D simulation.

Introduction

"Aircraft Ice Protection" AC 20-73A faa.gov offers guidance on analysis for icing conditions. We will not cover the certification aspects in detail.

Much of the detail is on ice protection systems.

This advisory circular (AC) tells type certificate and supplemental type certificate applicants how to comply with the ice protection requirements of Title 14 of the Code of Federal Regulations (14 CFR) parts 23, 25, 27, 29, 33, and 35.

However, it is also useful for analysing ice shapes on unprotected surfaces.

It is noted that:

Determination of critical ice shape configurations is not straightforward and may require engineering judgment.

SAE AIR5903, "Droplet Impingement and Ice Accretion Computer Codes" sae.org notes:

A balancing of accurate and …

Introduction to Variations

Donald Cook — Mon, 08 Apr 2024 20:00:00 -0700

From AC 20-73A faa.gov.

Summary

Different methods (test, analysis methods) can yield different ice shapes for the same conditions
Measurements of ice shape parameters characterize the differences
What is "too large" of a difference depends on unique factors for a particular case
Engineering judgment is required to navigate the differences

Discussion

A method to characterize ice shapes

"Aircraft Ice Protection" AC 20-73A faa.gov lists ice shape parameters that can be used to compare ice shapes:

Applicants may use the lists of ice shape and water catch evaluation parameters in tables R-1 and R-2, ranked against their adverse airplane effects, to compare simulated and natural ice shapes. These lists are from SAE ARP5903 (Reference R20).

Table R-1. Ranking of Ice Shape Evaluation Parameters

Rank	Parameter	Units	Conservatism criteria
1	Upper (suction surface) horn height		Equal or greater horn peak thickness (height)
2	Upper Horn Angle	degree	Criticality of location …

Computer Freezing Rate Analysis Tools Examples

Donald Cook — Mon, 08 Apr 2024 19:00:00 -0700

from Users Manual for the NASA Lewis Ice Accretion Prediction Code (LEWICE) (1990 version) ntrs.nasa.gov

Prerequisites

You need to complete the Aircraft Icing Handbook Water Catch Examples.

You need to select a computerized tool to work with. See Analysis Toolset for obtaining LEWICE, and some other options.

If you have chosen to use LEWICE, but you have not run it before, see the LEWICE Quick Start.

Introduction

We will compare energy balance terms and freezing rates calculated with the Standard Computational Model and LEWICE (or the tool that you have selected).

The values found by differing methods are generally similar, but rarely identical.

Aircraft Icing Handbook Example 2-4

The mass of ice accretion on the NACA 0012 section will be calculated. Using the same flight conditions as Example 2-1. and the droplet size distribution and value from Example 2-3:

Airfoil                         c = 3.1 foot chord NACA 0012  
Flight …

Aircraft Icing Handbook Energy Balance Examples

Donald Cook — Mon, 08 Apr 2024 18:00:00 -0700

Public domain image by Donald Cook.

Prerequisites

To learn the energy terms and equations, readers should first review the "Standard Computational Model", which combines the applicable sections original DOT/FAA/CT-88/8-1 and the update into one text.

Introduction

The term "standard computational model" has not seen wide use. Most recent literature refers to the "Messinger Model" or "Modified Messinger Model". That may or may not mean the "standard computational model" presented here. As noted for calculating evaporation:

There are a variety of formulations of this term.

That could also apply to several of the terms in the model. "Modified Messinger Model" could mean about anything, you would need to look at the details.

The energy examples in the handbook are less detailed than the ones we previously saw for impingement.

The "Standard Computational Model" is implemented here in the python programming language and is available via github.com/icinganalysis …

Computer Impingement Analysis Tools Examples

Donald Cook — Mon, 08 Apr 2024 17:00:00 -0700

from Users Manual for the NASA Lewis Ice Accretion Prediction Code (LEWICE) (1990 version) ntrs.nasa.gov

Prerequisites

You need to complete the Aircraft Icing Handbook Water Catch Examples.

You need to select a computerized tool to work with. See Analysis Toolset for obtaining LEWICE, and some other options.

Aircraft Icing Handbook Example 2-2

Example 2-2
This example illustrates the estimation of the impingement parameters E, β, h, Su and SL using graphical data (reference 2-12). The graphical data is all presented with Ko as the independent variable. Much data is available in this form.

The conditions of Example 2-1 for a NACA 0012 airfoil are assumed: thus Ko = 0.05. It also is assumed for simplicity that the angle of attack, α, is 0 degrees. From figure 2-11, E, the total impingement efficiency, is estimated to be 0.23 for these conditions. So about 23 percent of the water …

Aircraft Icing Handbook Merged Sections

Donald Cook — Mon, 08 Apr 2024 16:00:00 -0700

Introduction

The "Aircraft Icing Handbook" DOT/FAA/CT-88/8-1, 1991 ntrl.ntis.gov.
Also note that there was a perhaps little known update in 1993: ntrl.ntis.gov.

Several errors and omissions were corrected in the update, so it is essential to consult the update.

As the update only include certain affected pages, it makes it difficult to read as there is much interruption paging back and forth between sources. Here, selected sections of the two sources are merged for easier reading.

The reproduction quality of the online sources is variable, and parts of the update are barely legible. Here, the text is used (not just scanned images of text). In some cases, I have included text of the equations.

Some readers may prefer the online web formatting over the pdf formatting. The figures are included inline, again to reduce paging back and forth. The cited references are also noted …

Aircraft Icing Handbook Water Catch Examples

Donald Cook — Mon, 08 Apr 2024 15:00:00 -0700

Public domain image by Donald Cook.

Introduction

The "Aircraft Icing Handbook", DOT/FAA/CT-88/8-1, provides examples of two-dimensional water catch rates for the ice accretion process.

The Handbook uses something like "US Customary" or "Engineering" units in the calculations. This may limit the direct reuse of the equations.

These calculations can be reasonably accomplished through hand calculations, or a spreadsheet. However, they can be important "stepping stones" to build more complex capabilities.

Code written in the python programming language is available via github.com/icinganalysis, file "intermeadiate/basics_water_catch_calculations.py" (and associated files) for the solutions, under the LGPL license. Internally, the code uses (mostly) SI units (see A Brief Digression on Unit Systems for details). There are unit conversion functions in the python code. Values here are reported in the handbook units.

You are encouraged to run the provided code, or to start building your own library of such …

LEWICE Quick Start

Donald Cook — Mon, 08 Apr 2024 14:00:00 -0700

from User's Manual for LEWICE Version 3.2 ntrs.nasa.gov

Summary

The "least that you need to know" to start using LEWICE, the NASA-provided icing simulation tool.

Prerequisites

See Analysis Toolset for how to obtain LEWICE.

Introduction

Decades ago there was training available for using LEWICE. I do not know of recent training. You are largely on your own, with the manual and supporting material.

This certainly does not contain complete information, but it will help you get started in the basics of running LEWICE.

Discussion

The LEWICE manual provides these instructions:

3.1.
LEWICE Quick Start Guide
This section is intended for users unfamiliar with LEWICE and/or DOS Shell commands. The commands below (indented bold lines) should be typed at the C:\ prompt in a DOS Shell window on a Windows machine. Alternatively, the user can use the Windows interface for any of the commands shown. Windows …

Analysis Toolset

Donald Cook — Mon, 08 Apr 2024 13:00:00 -0700

Figure 15 of NACA-TN-2904 ntrs.nasa.gov.

Summary

You will have to choose a toolset to perform the example analyses.

Example calculations are provided in the Python programming language, and using the NASA-provided LEWICE code.

Introduction

You are highly encouraged to perform the analysis described in the examples (and not just read the examples). Some examples can be accomplished with hand calculations, while other require computational capabilities.

You need to select your toolset.

Consider your current and future uses

A toolset is an investment of your time and resources. By performing the calculation of the examples used here, you will build your personal and software capabilities and skills.

Your toolset at a particular time may not be entirely your choice. Your company, institution, or customer may have policies on which kinds of software are required, encouraged, discouraged, or prohibited. Some codes have by-country use restrictions. You may have signed an …

Aircraft Icing Intermediate Level

Donald Cook — Mon, 08 Apr 2024 12:00:00 -0700

From "Aircraft Icing Handbook Volume 1", DOT/FAA/CT-88/8-1 ntrl.ntis.gov

Summary

After The Basics, you are ready for Intermediate level aircraft icing topics:

Using handbook analysis methods
Using computer icing analysis tools to produce ice shapes
Preliminary ice protection system sizing

The Intermediate Level is a work in progress, as there may yet be many revisions and additions. However, it may be useful "as is" to some readers.

Prerequisite: Select your toolset

You are encouraged to run code to reproduce the examples used here. By doing so, you can build your personal and software capabilities and skills.

Example calculations are provided here in the Python programming language, and using the NASA-provided LEWICE code.

There are several reasons why you might use a different toolset. See Analysis Toolset for more details and options.

Every analysis is an approximation

We can also say that every test is an approximation …

Resources

Donald Cook — Mon, 12 Feb 2024 18:00:00 -0800

Introduction

The good news is that these resources comprise thousands of pages of reading.
The bad news is that these comprise thousands of pages of reading.

A few experts that I know have confessed that they have not read all of what I consider to be "The Big Three", let alone everything listed here. So, you can probably get along by not reading everything.

Most of the resources are online and available at no cost. Some are copyrighted, and available for purchase or online access rental. Your local library may be able to borrow some of them for you through inter-library loan.

The Big Three

These total to over 800 pages (over 1200 if one counts all three volumes of DOT/FAA/CT-88/8), but they can give you broad exposure to aircraft icing technology. However, they are now a little dated (the most recent, DOT/FAA/CT-88/8, was …

Terminology

Donald Cook — Mon, 12 Feb 2024 17:00:00 -0800

Introduction

These terms are taken largely from ADS-4, with updates and additions. See the Resources for other, more extensive terms lists.

Selected Aircraft Icing Terms

Airfoil chord: the longest line possible between the leading edge and trailing edge of an airfoil. See figure.

Airspeed: The speed of the aircraft through the air. Sometimes measured in knots (nautical mile per hour) or KTAS. A nautical mile is about 6076 feet or 1852 m, or 1.15 statute ("standard") miles.

Angle of attack: Angle between airfoil chord and line of flight. See figure.

Anti-icing: The prevention of ice formation on airframe surfaces. The use of heat is the most common means of anti-icing.

Appendix C: Appendix C of the United States Chapter 14 Code of Federal Regulations Part 25 that defines icing conditions used for certification of large transport category aircraft.

Appendix O: Appendix O of the United States Chapter 14 Code …

Ice Protection Basics

Donald Cook — Mon, 12 Feb 2024 16:00:00 -0800

Several areas of the airplane may require ice protection:

from ADS-4 (1963)

Forms of ice protection

There are several forms of ice protection used on airplanes. The most commonly used for is thermal ice protection, which provides heat to the area to be protected.

Thermal ice protection provides "Anti-Icing" protection. Anti-icing with enough heating to prevent the formation of ice by evaporating all of the impinging water is termed "Fully evaporative anti-icing". This can be a demanding amount of power for large areas.

At lower power, "Running Wet" protection prevents ice over the heated area, but may not evaporate all of the water, which can freeze further aft of the heated area and form "Runback Ice". Analysis and test is required to show that the runback ice is acceptable.

Runback ice on an airfoil with a heated leading edge from a laboratory test:

From "Evaluation of Alternative Altitude Scaling Methods …

Tools

Donald Cook — Mon, 12 Feb 2024 16:00:00 -0800

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.

from "Aircraft Icing Handbook", DOT/FAA/CT-88/8 ntrl.ntis.gov

Analysis

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

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 …

Ice Shapes

Donald Cook — Mon, 12 Feb 2024 15:00:00 -0800

Types of ice shapes

As ice accumulates on a wing, it changes the shape of the airfoil. The ice that forms is sometimes called an "Ice accretion" in the literature. The shape of the ice depends on details of the flight and icing conditions.

At warmer temperatures (about -10°C to 0°C, depending on airspeed and other factors), ice shapes tend to produce "Glaze Ice" shapes with "horns". The nomenclature varies by domain. Pilot training materials generally note this type of ice as "Clear Ice".

from "Pilot Guide: Flight in Icing Conditions", AC 91-74B faa.gov

At colder temperatures, the ice appears milky and opaque, and is termed "Rime Ice".

from "Pilot Guide: Flight in Icing Conditions", AC 91-74B faa.gov

At temperatures in between, "Mixed Ice" can form.

from "Pilot Guide: Flight in Icing Conditions", AC 91-74B faa.gov

These types of ice can have varying effects on …

Water Drops

Donald Cook — Mon, 12 Feb 2024 14:00:00 -0800

The size of water drops in clouds

The water that causes most aircraft in-flight icing is small drops in clouds. Average drop sizes are typically 10 to 50 "Micrometers" (μm) in diameter (for comparison, a human hair is about 50 to 100 micrometers in diameter).

Typical drop sizes, approximately proportional. Public domain image by Donald Cook.

In a particular cloud, not all water drops are the same size. The "Langmuir Drop Size Distributions" describe an idealized approximation of how the drop sizes vary in a cloud about an average or median drop size. It has seven bins, each with a representative drop size and fraction of the total water content in the cloud.

from "Aircraft Icing Handbook Volume 1", DOT/FAA/CT-88/8-1 ntrl.ntis.gov

The impingement of water drops on aircraft surfaces

Calculating the amount of water that hits or impinges on the surface of an airplane as …

Flight

Donald Cook — Mon, 12 Feb 2024 13:00:00 -0800

Effects of icing in flight

Airplanes can fly because engines produce thrust that propels it forward, and wings produce lift to counteract weight.

A wing is a well-shaped airfoil that can produce lift with minimal drag. If ice accumulates on a wing in flight, that changes the shape of the airfoil, which is then likely to not be as efficient at producing lift. Drag can also increase.

Effects of ice:

Adapted from "Aviation Weather For Pilots and Flight Operations Personnel", AC 00-6A (Cancelled) faa.gov
Public domain image by Donald Cook.

Note that "Aviation Weather Handbook", FAA-H-8083-28 faa.gov states:

The actual weight of ice on an airplane is insignificant when compared to the airflow disruption it causes.

The lift an airfoil can produce is affected by the "Angle of Attack" of the wing with respect to the air motion over it.

Public domain image by Donald Cook.

The coefficient …

The Basics

Donald Cook — Mon, 12 Feb 2024 12:00:00 -0800

"Glaze Ice" formed in flight on an airplane:

from "Effects of Ice Formations on Airplane Performance in Level Cruising Flight." NACA-TN-1598, 1948. ntrs.nasa.gov

Summary

The Basics provide "the least that you need to know" to begin the study of Aircraft Icing.

Introduction

The Basics acquaint you with the specialized terminology and concepts of aircraft in-flight icing. This is intended for engineers, scientists, and administrators newly interested in aircraft icing, or for those familiar with some but not all aspects of aircraft icing.

The Basics assume little knowledge of aircraft, and do not require math skills (there are only a few numbers that give ranges of typical values). The Basics are short and minimal, "the least that you need to know". Once you are oriented with the concepts and terms, you will be better able to ask questions and shape online searches for what you would like to know …

Introducing The Basics of Aircraft Icing

Donald Cook — Mon, 12 Feb 2024 11:00:00 -0800

"The least that you need to know"

Public domain image by Donald Cook

Summary

The Basics introduce core concepts and vocabulary of aircraft icing with images, "the least that you need to know".

Discussion

The Basics seek to facilitate initial learning about aircraft icing by:

focus on the needs of beginning learners
readily connecting to other resources for further learning
maximizing reuse
maximizing access

Other sources may not do these well.

Background

One of the most-read posts that I have written was A Gentle Introduction to Aircraft Icing, so I think that there is interest in this topic.

My learning experience

I got a MSME degree from the University of Wisconsin Internal Combustion Engine lab. That prepared me well for some aspects of aircraft icing (heat transfer, thermodynamics, drop physics, computational fluid dynamics). However, that by itself was not enough.

When I started in an Aircraft Systems design group, it …

Conclusions of the Porter Perkins Series

Donald Cook — Mon, 15 Jan 2024 21:00:00 -0800

"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 …

Porter Perkins Flight Safety Publications

Donald Cook — Mon, 15 Jan 2024 20:00:00 -0800

"Most, if not all of the recent accidents on record having icing as the probable cause could have been prevented if the flight crews understood the serious nature of the situation and had applied appropriate corrective action." ²

Summary

Three publications on flight safety by Porter Perkins are reviewed.

Discussion

These publications are copyrighted. The first one, however, has a reuse license, and so much of the discussion will center on it.

"Tailplane icing and aircraft performance degradation" 1992 ¹

Ice on the tailplane (horizontal stabilizer) was identified as a risk on some aircraft:

Although the sensitivity of airplanes to inflight icing has been recognized for many years and can be minimized by ice protection systems, the advent of the medium-altitude turboprop commuter transport aircraft has resulted in renewed attention to the icing problem. This review of icing has been prompted by several recent accidents that apparently were caused by …

Reproducing NACA-TN-2738 Calculations

Donald Cook — Mon, 15 Jan 2024 18:00:00 -0800

"In view of the number and complexity of the possible sources of error, it is not possible at this time to make a reliable estimate of the total accuracy" ³

Summary

Calculations are made to assess the probability of encountering certain icing conditions.

Introduction

In Porter Perkins Ice Shapes and Ice Protection, references NASA TM 83564 ¹ and NASA TM 86906 ², the probability of encountering certain icing conditions was assessed, using methods from NACA-TN-2738 ³. Here, we will attempt to reproduce those calculations.

Discussion

In NACA-TN-2738, data were divided by geographical region.

The NASA Technical Memos did not state where the natural icing test flights were. However, as three of the authors were based out of the NASA Lewis Research Center, Cleveland, Ohio, I will assume that the flights operated out of there and were in the Eastern United States region.

So, the appropriate chart to use is Figure …

Porter Perkins Ice Shapes and Ice Protection

Donald Cook — Mon, 15 Jan 2024 17:00:00 -0800

"An approach to characterizing the severity of an icing encounter is to relate that encounter to the frequency of its occurrence." ¹

Introduction

Three publications with Porter Perkins as an author are included here. Two publications are related, as they cover a flight test campaign to gather detailed ice shape data. The third publication describes a potential improvement to ice protection.

There is much to see in these publications with multiple authors, and I will focus on what I believe to have been Perkins' contributions.

Ice Shapes, NASA TM 83564 ¹ and NASA TM 86906 ²

NASA TM 83564:

Summary

This paper deals with the initial results of the NASA Lewis Research Center's flight research in quantifying the performance of an aircraft in various measured icing conditions. Flight research performed in natural icing conditions supports a number of major program elements at NASA. One of these elements is to develop …

Airships

Donald Cook — Mon, 15 Jan 2024 16:00:00 -0800

"a 2-hour flight in ... a mixture of wet snow and freezing rain ... produced no adverse effects on the operation of the airship."

NACA-TN-4220, A Flight Evaluation and Analysis of the Effect of Icing Conditions on the PG-2 Airship

Summary

Icing threats to airships are assessed.

Abstract

SUMMARY

A series of test flights was conducted by the U. S. Navy over a 3-year period to evaluate the effects of icing on the operation of the ZPG-2 airship. In supercooled. clouds, ice formed only on the forward edges of small protuberances and wires and presented no serious hazard to operation. Ice accretions of the glaze type which occurred in conditions described as freezing drizzle adversely affected various components to a somewhat greater extent. The results indicated, a need for protection of certain components such as antennas, propellers, and certain parts of the control system.

The tests showed that icing of the large …

Meteorology publications by Porter Perkins

Donald Cook — Mon, 15 Jan 2024 14:00:00 -0800

"Statistical values that represent the meteorological and climatic variations, which are associated with icing, will indicate what to expect in normal flight operations." ⁶

From NACA-TN-4314.

Summary

Several publications by Porter Perkins were included in The Historical Selected Bibliography of NACA-NASA Icing Publications in the "Meteorology of Icing Clouds" section.

Discussion

The first several publications are only briefly described, as their major results are incorporated into the final publication, NASA Memo 1-19-59E, which will be reviewed at length.

Note that NACA-RM-E52J06 outlines the need for data from broader sources, that is a theme in these publications:

The majority of the research flights into icing conditions were made by attempting to select weather conditions, flight paths, and altitudes, which would yield heavy or continuous icing. Multiple traverses were often made when such conditions were found. It is impossible, therefore, to determine from this information the extent or frequency of specified icing …

Propeller publications by Porter Perkins

Donald Cook — Mon, 15 Jan 2024 13:00:00 -0800

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

I believe that this is Porter Perkins, circa 1946.

Summary

Porter Perkins investigations of propeller icing are reviewed. These are the earliest investigations by him that I found.

Discussion

Two areas are discussed, the gas heating of propellers, and the measurement of thrust.

Gas heating of propellers

Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection against Icing, I - Unpartitioned Blades. NACA-TN-1586, 1948. ¹
Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection against Icing, II- 50-Percent Partitioned Blades. NACA-TN-1587, 1948. ²
Investigation of Effectiveness of Air-Heating a Hollow Steel Propeller for Protection against Icing, III - 25-Percent Partitioned Blades. NACA-TN-1588, 1948. ³

SUMMARY

An investigation to determine the effectiveness of icing protection afforded by air-heating hollow …

Porter Perkins

Donald Cook — Thu, 11 Jan 2024 12:00:00 -0800

"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 …

Celebrating 25 Years of the NTRS

Donald Cook — Tue, 02 Jan 2024 12:00:00 -0800

The NACA Technical Reports Server, circa 1999. From NASA/TM-1999-209127. This has been superseded by the NASA Technical Reports Server ntrs.nasa.gov.

Dust off your Netscape Navigator browser ¹ and research like it's 1999!

Or, experience the archived version for December, 1998, at web.archive.org.

Notes

Hmm, it appears that Netscape Navigator has not been supported since 2008. Oh well, just use firefox then. ↩

Conclusions of the Impingement on Surfaces thread

Donald Cook — Mon, 13 Nov 2023 12:00:00 -0800

"It is thus desirable to have an economical method for solving the basic water droplet trajectory equations for an arbitrary airfoil." ¹

The Use of Ko for Impingement Correlations

The use of a modified water droplet inertia parameter Ko permits consolidation into only a few graphs of most of the published water drop trajectory data.
From Werner, J. B., Ice Protection Investigation for Advanced Rotary-Wing Aircraft. ¹
(This is a candidate for "The Greatest Thing That You Have (Probably) Never Read").

To paraphrase NACA-TN-3839 ², the studies in this Impingement on Surfaces thread "were a rather ad hoc collection of shapes and sizes". One unifying parameter emerged to correlate the results, the "Ko" modified water drop inertia parameter.

"Mathematical Investigation of Water Droplet Trajectories" ³

"Mathematical Investigation of Water Droplet Trajectories" ³ defined a term Ko (see the link for definitions of other terms):

Ko is not given a name …

A Tentative Identification of Water Drop Trajectory Investigators

Donald Cook — Thu, 09 Nov 2023 12:00:00 -0800

NACA-TN-2094 and investigators operating the water-drop-trajectory analog

Figure 15 of NACA-TN-2904

Summary

While no one is identified in Figure 15 of NACA-TN-2904, I speculate that these investigators are Helen M. Gallagher, and Dorothea E. Vogt. (I do not know which name goes with which individual). While neither Gallager nor Vogt is credited in NACA-TN-2904, it is possible that they contributed to the analysis, as they did in several other water-drop trajectory publications.

Discussion

Yes, I have used this figure a lot, as it is one of the best of the hundreds I have viewed from the NACA-era. This image is also notable in that of the hundreds of NACA-era documents that I have read, this is the only one where the people appear to be women.

I have not been able to find photos of Gallager or Vogt for comparison (and photos of any NACA-era authors are hard to find …

Impingement on Other Surfaces

Donald Cook — Tue, 07 Nov 2023 12:00:00 -0800

"the ideal flow field ahead of a ribbon is not a very satisfactory representation of the actual flow field in front of a rectangular body"

NACA-TN-3658, "Impingement of Water Droplets on a Rectangular Half Body in a Two-Dimensional Incompressible Flow Field" ¹

Summary

Water-drop impingement on a rectangular body is calculated.

Abstract

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.

Discussion

We have already seen most of the titles on the "Impingement on Other Surfaces" topic:

Brun, Rinaldo J., and Mergler, Harry W.: 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 …

Impingement on Airfoils

Donald Cook — Thu, 02 Nov 2023 12:00:00 -0700

"Although the airfoils used in these studies were a rather ad hoc collection of shapes and sizes, this report makes these data generally available and correlates the data as much as possible."

From NACA-TN-3839.

NACA-TN-2931, "A Method for Determining Cloud-Droplet Impingement on Swept Wings"

and

NACA-TN-3839, "Experimental Droplet Impingement on Several Two-Dimensional Airfoils with Thickness Ratios of 6 to 16 Percent"

Summary

Several airfoils were analyzed and tested for water-drop impingement in the NACA-era.

Abstract

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 data were obtained at 152 knots and are extended to other conditions by dimensionless impingement parameters.
In general …

Impingement in Elbow Ducts

Donald Cook — Tue, 31 Oct 2023 12:00:00 -0700

"Icing of air-intake ducts and scoops with subsequent reduction in pressure recovery and in air flow may adversely affect the operation of the aircraft."

From NACA-TN-2999. ¹

NACA-TN-2999, "Impingement of Droplets in 90° Elbows with Potential Flow" ¹

and

NACA-TN-3770, "Impingement of Droplets in 60° Elbows with Potential Flow" ²

Summary

The impingement of water-drops in idealized elbow ducts is calculated with potential flow.

Abstract

NACA-TN-2999

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 as walls of each elbow 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 …

Impingement in Engine Inlets

Donald Cook — Wed, 25 Oct 2023 13:00:00 -0700

"In spite of the simplicity, the configurations are reasonable approximation of those found on aircraft"

NACA-TR-1317.

From NACA-TR-1317.

NACA-TR-1317, "Cloud-Droplet Ingestion in Engine Inlets with Inlet Velocity Ratios of 1.0 and 0.7."

and

NACA-TN-4268, "Droplet Impingement and Ingestion by Supersonic Nose Inlet in Subsonic Tunnel Conditions."

Summary

"Important general concepts" of impingement on engine inlets are illustrated.

Introduction

In the first title here, the use of potential flow to determine water-drop trajectories gets pushed to the limit. In a demonstration of the pragmatism that ran through much of the ice protection development at NACA, investigators produced results on configurations that could be analyzed that were close enough to real aircraft geometries.

In NACA-TN-3770, we enter the supersonic jet age, with a dye-tracer method test of a supersonic inlet (but at a lower Mach number). We will see a test of "the configurations are reasonable approximation".

Discussion

Inlet impingement …

Shadow Zones and Concentration Zones

Donald Cook — Tue, 24 Oct 2023 12:00:00 -0700

"... local concentration factors should be considered when choosing the location of devices that protrude into the stream from aircraft fuselages or missiles, or when determining anti-icing heat requirements for the protection of these devices."

From NACA-TN-3410.

NACA-TN-3153, "Variation of Local Liquid-Water Concentration about an Ellipsoid of Fineness Ratio 5 Moving in a Droplet Field" ¹

and

NACA-TN-3410, "Variation of Local Liquid-Water Concentration about an Ellipsoid of Fineness Ratio 10 Moving in a Droplet Field" ²

Summary

The concentration of water-drops varies with distance from a surface in flight.

Abstract

Trajectories of water droplets about an ellipsoid of revolution with a fineness ratio of 5 (which often approximates the shape of an aircraft fuselage or missile) 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 …

Bodies of Revolution

Donald Cook — Wed, 18 Oct 2023 19:00:00 -0700

"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."

Summary

Water-drop impingement on several bodies of revolution is quantified.

Discussion

NACA-TN-4092 ⁴ notes:

The impingement characteristics of bodies of revolution are of interest because such bodies are representative of many aircraft components subject to icing such as radomes, body noses, engine accessory housings, and the large spinners of turboprop engines.

NACA-TN-3099 ¹ is the first in a series and has a rather complete description of the analysis methods, so the discussion below refers to that, unless noted otherwise.

Flow field

Potential flow can be determined in 2D radial coordinates as well as 2D Cartesian coordinates. This was used to assess several geometries.

The air velocity components for incompressible nonviscous flow about a …

Methods of Water Drop Impingement Quantification

Donald Cook — Mon, 16 Oct 2023 15:00:00 -0700

"One of the first essentials ... is a method for estimating or calculating the area over which water will strike the wing, and the distribution of water impingement over that area"

From NACA-TN-1397.

From NACA-TN-3839.

Summary

Several methods were used to quantify the water-drop impingement on a surface, such as a wing.

Discussion

We already saw in the Icing on Cylinders thread calculations made for impingement on a cylinder. The technique was expanded in NACA-TN-1397 to include Joukowski type airfoils. This allowed a transformation of the flow solution around a cylinder to be mapped into airfoil coordinates, and then used to solve for water drop trajectory calculations, similar to those used for cylinders.

NACA-TN-1397 said one could calculate "the trajectory a single drop without the utilization of a differential analyzer". We saw the differential analyzer in the Icing on Cylinders thread, in particular detail in NACA-TN-2904. However, the example given (Table …

Water Drop Impingement on Surfaces

Donald Cook — Wed, 11 Oct 2023 12:00:00 -0700

"For a complete appraisal of the problem of ice prevention on aircraft, further water-droplet impingement data are needed" ¹

Figure 5 of NACA-TN-1397

Water Drop Impingement on Surfaces Thread

Summary

Water-drop impingement quantification is key to aircraft ice protection design.

Introduction

Part of designing for aircraft icing is determining how much ice the airplane can accumulate. For ice protection systems, determining how much water that might freeze hits a surface is a key detail.

An important effect is that the airflow around a surface such as a wing airfoil deflects water-drops, so that all of the water-drops in the frontal area view will not hit the surface.

Water-drop impingement quantification methods were developed to assess how many drops can hit where on a surface. Direct test methods involved the use of blotter paper to absorb water drops on a surface. Mathematical analysis of the paths individual water drops were developed …

Newsletter Archive

Donald Cook — Sat, 30 Sep 2023 12:00:00 -0700

NACA Cleveland library, circa 1945.

Summary

Newsletters are sent to subscribers. The text is available here a few weeks after publication.

Info about the Blast from the Past Newsletter

Newsletters

Links contained are not updated.

9-30-2023
10-9-2023
10-16-2023
10-23-2023
10-30-2023
11-06-2023
11-13-2023
01-08-2024
01-15-2024

The Blast from the Past Newsletter

Donald Cook — Sat, 30 Sep 2023 12:00:00 -0700

“The greatest of all our problems is ice.”

"The situation changed in the mid-1920s when the intrepid aviators of the U.S. Air Mail Service attempted to maintain scheduled day-and-night operations between New York and Chicago... As one of their pilots noted at the time about the hazards of the New York-Chicago route, “the greatest of all our problems is ice.”" ¹

From NACA-TN-313, 1929. ²

Summary

To subscribe to the newsletter: Subscribe! (via sender.net)

Discussion

I have an email newsletter with the latest posts and other site-related news, which you can receive regardless of the weather. Another advantage of subscribing to the newsletter is access to the secret* blog drafts that are in-work, before the public sees them, and access to the secret* newsletter archives. There is no cost to subscribe.

[* Well, not so secret if one is acquainted with github.]

Typical publishing sequence:

email newsletter, subscribers may …

Site Improvements

Donald Cook — Sat, 16 Sep 2023 07:00:00 -0700

"I am surprised to find that there are so many details which have not been anticipated before ..."

Reported in "Lew Rodert, Epistemological Liaison, and Thermal De-Icing at Ames". ¹

Summary

Since I started "Blast from the Past: NACA Icing Publications" 20 months ago, I have made over 100 posts. I have extensively revised some, and made improvements to all of them, so it is time to repost them.

I will be posting links and short summaries to them in the original sequence on mastodon historians.social/@icinganalysis at a rate of three per week (about the pace that I originally posted them), so it will take almost a year to cycle through them. And I do plan on also creating new posts.

If you want to read at you own pace, you can go to the Latest Posts tab at the top of the page for the complete list of …

Blast from the Past: NACA Icing Publications

Seeking "Icing Information Notes"

Summary

Predictions for the Third Ice Prediction Workshop Using Simple Methods

"The main goal of these workshops is to assess state-of-the-art of icing prediction tools with 2D and 3D experimental data"

Summary

IPW-3

The National Technical Reports Library

"The National Technical Information Service acquires, indexes, abstracts, and archives the largest collection of U.S. government-sponsored technical reports in existence. "

The Defense Technical Information Center

The National Technical Reports Library

Estimating Icing Conditions with Highest Drag

"These data will be useful in evaluating and formulating ice accretion analyses and also performance penalty predictions."

Summary

The Appendix C, Figure 1 Icing Environment

Ice Shape Drag Correlations

"No certain explanation for the poor repeatability of glaze ice shapes is available at this time."

Summary

Prior Correlations

Hard to find publications

"The documents were so old, however, that they were not listed in the modern computerized library search systems, and some of these documents were out of print." 1

Summary

Discussion

Recently made available

Testing Messinger Freezing Fraction Correlations with the IceVal Database

"an empirical relationship was obtained which correlated ice accretion thickness and ice angles with theoretical impingement parameters." 1

Introduction

NASA/CR-2005-213852 3

Swept Airfoil Cases in IceVal

"Use of these relationships allows the direct determination of ice shapes adjusted for any given icing and flight condition as well as for size and sweep of the airfoil" 1

Summary

Running LEWICE version 3.2.3 for the IceVal cases

"The resulting analysis showed that LEWICE compared well to the available experimental data." 1

Introduction

Comparisons with all IceVal …

A Geometric Analysis Method

"This demonstrates that the automated process cannot (yet) be substituted for good engineering judgment."

Introduction

Using the IceVal database to validate an assessment method

Overall comparison assessments between experiment and LEWICE

"It is possible for any (or all!) ... parameters to be incorrectly output."

Introduction

Published assessments

The 1999 Assessment

Challenges Using the IceVal Database

"No data is clean, but most is useful."

Introduction

A Tour of the IceVal DatAssistant

"... all publicly available IRT-generated experimental ice shapes with complete and verifiable conditions have now been compiled into one electronically-searchable database"

A quick tour of the IceVal DatAssistant

Range of conditions tested

6000 Ice Shapes - the IceVal DatAssistant

"As with any scientific endeavor, the foundation of icing research ... is the data acquired during experimental testing."

"A review of ice detection technologies"

"These incidents underscore the urgent need for reliable, real-time ice detection systems to prevent dangerous icing conditions and enhance operational safety." 1

Discussion

Notes:

Aircraft Icing Forum Presentation

Discussion

Achievements of the NACA Era

"it shall be the duty of the advisory committee for aeronautics to supervise and direct the scientific study of the problems of flight with a view to their practical solution"

The Icing 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"

"THE ICING PROBLEM - CURRENT STATUS NACA TECHNIQUES AND RESEARCH" 1

Abstract

Introduction

Some Considerations for the Need of Icing Protection of High-Speed, High-Altitude Airplanes

"These high-speed aircraft cruise at altitudes at which little, if any, icing occurs."

"NACA Conference on Some Problems of Aircraft Operation" 1

Abstract

Discussion

Icing Conditions to be Expected in Operation of High-Speed, High-Altitude Airplanes

"high-speed, high-altitude airplanes will encounter much less icing than older type airplanes"

"NACA Conference on Some Problems of Aircraft Operation" 1

Abstract

NACA Conference on Aircraft Ice Prevention 1947

"A solution to a problem ... of ice can usually be found, but the solution always involves penalties."

Abstract

Discussion

CONTENTS

"The documents were so old, however, that they were not listed in the modern computerized library search systems, and some of these documents were out of print." ¹

"an empirical relationship was obtained which correlated ice accretion thickness and ice angles with theoretical impingement parameters." ¹

NASA/CR-2005-213852 ³

"Use of these relationships allows the direct determination of ice shapes adjusted for any given icing and flight condition as well as for size and sweep of the airfoil" ¹

"The resulting analysis showed that LEWICE compared well to the available experimental data." ¹

"These incidents underscore the urgent need for reliable, real-time ice detection systems to prevent dangerous icing conditions and enhance operational safety." ¹

"THE ICING PROBLEM - CURRENT STATUS NACA TECHNIQUES AND RESEARCH" ¹

"NACA Conference on Some Problems of Aircraft Operation" ¹

"NACA Conference on Some Problems of Aircraft Operation" ¹

"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" ¹

"Heat Requirements for Ice Protection of a Cyclically Gas-Heated, 36° Swept Airfoil with Partial-Span Leading-Edge Slat" ¹

"Investigation of Porous Gas-Heated Leading-Edge Section for Icing Protection of a Delta Wing" ¹

"Comparison of Several Methods of Cyclic De-Icing of a Gas-Heated Airfoil" ¹

"Experimental Determination of Thermal Conductivity of Low-Density Ice" ¹

"The Effect of Ice Formations on Propeller Performance" ¹

"Determination of Aircraft Antenna Loads Produced by Natural Icing Conditions" ¹

"Vibration and Investigation of CAA Type V-I09 Very-High-Frequency Aircraft Antenna" ¹

"Preliminary Data on Rain Deflection from Aircraft Windshields by Means of High Velocity Jet-Air Blast" ¹

"General Correlation of Temperature Profiles Downstream of Heated Air Jet Directed at Various Angles to Airstream" ¹

"Penetration of air jets issuing from circular, square, and elliptical orifices directed perpendicularly to an air stream" ¹

"Investigation of the Penetration of an Air Jet Directed Perpendicularly to an Air Stream" ¹

"Investigation of Flow Coefficient of Circular, Square, and Elliptical Orifices at High Pressure Ratios" ¹

"Total Pressure Distortion and Recovery of Supersonic Nose Inlet with Conical Centerbody in Subsonic Icing Conditions" ¹