Aircraft Icing

Aircraft Icing

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Gene Addy, MS, Aerospace Engineer, Icing Branch

NASA Glenn Research Center NASA Glenn Research Center

National Aeronautics and Space Administration www.nasa.gov

Ai Aircraft Icing

Aircraft Icing

Icing Incidents and Accidents

New York City Chicago Chicago The Phillippines Brazil

Aircraft Icing Incidents and Accidents Aircraft

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National Aeronautics and Space Administration Aircraft Icing What is aircraft icing? What is aircraft icing? How can it affect an aircraft? How can an aircraft be protected from icing? How can an aircraft be protected from icing? How might an icing test be set up?

Overview Overview

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National Aeronautics and Space Administration

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Aircraft Icing

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Describe difference between ground and inflight icing List three types of ice Li t t List two effects of ice accretion on aircraft List three types of ice protection systems Setup an icing test of an ice protection system

Objectives Objectives

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National Aeronautics and Space Administration

icing

flight icing flight

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Ground icing In In

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What is aircraft icing?

National Aeronautics and Space Administration Aircraft Icing (icing video here)

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40 deg

icing:

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inflight

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of inflight icing:

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small ~ 100 to 200 micrometers

small ~ 10-40 micrometers supercooled to as low as -40 deg supercooled to as low as aircraft creates nucleation site rate of freezing and accretion depends upon air temperature, Bounce off surfaces unless partially or fully melted by local above- airspeed, amount of water per unit area in cloud freezing environment accretion depends upon air temperature, airspeed, amount of water per unit area in cloud

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Liquid droplets Ice crystals

Basics of Basics

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National Aeronautics and Space Administration Aircraft Icing T = 32 F T = 14 F T = -4 F Mean Effective Drop Diameter, micrometers T = -22 F 1. Pressure altitude range: SL to 22,000 ft 2. Maximum vertical extent: 6,500 ft. 3. Horizontal extent: standard 17.4 knots CFR - 25 App.C Envelope

icing envelopes

0.70 0.80 0.90 0.30 0.40 0.50 0.60 0.00 0.10 0.20 g /cu. m. r Content, g L iquid Wate L

Aircraft icing envelopes Aircraft

National Aeronautics and Space Administration Aircraft Icing

Scalloped Ice Scalloped Ice

• Freeze on impact Flow before freeze • •

Ice Accretions

0.08 0.08

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0.06

Inflight Inflight Ice Accretions

0.06 0.04 c 0.04 / / c x / x 0.02 0.02

Gl Glaze Ice

Rime Ice

0.00 • 0.00 • -0.02 0.04 0.06 0.00 0.02 -0.02 -0.04 -0.02 y/c 0.02 0.04 0.06 0.00 -0.04 -0.02 y/c

Aircraft Aircraft

National Aeronautics and Space Administration Aircraft Icing 10 min NACA 23012 - 72 inch chord 1 -1 -2 LWC = 0.64 g/m3 MVD = 15 um Spray = 4 5 6 0 1 2 3 -1 -3 -2 -1 F o F 6 o o = 28.0 = 20.8 t s V = 175 kts AOA = 5 T T Same icing conditions - different size airfoils NACA 23012 - 18 inch chord

Accretions

-1 -2 4 5 6 0 1 2 3 -1 -3 -2 -1

Ice Accretions Ice

National Aeronautics and Space Administration 0.2 0.175 0.15 0.125 0.1 0.075 0.05 0.025

different size airfoils

NACA 23012 - normalized by chord length -0.025 -0.05 -0.075 -0.1

icing conditions - different size airfoils

0.1 0.05 -0.05 0.075 0.025 -0.025 -0.075

Same icing conditions Same

National Aeronautics and Space Administration 5 min 2.5 min 1 min 2 2 Aircraft Icing 0 0 -1 -1 -1 1 2 0 0 1 2 2 0 1 -1 -1 -1

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V = 200 kts LWC = 0.75 g/m3 Tt = -2.2 deg C MVD = 15 um AOA = 2.0 deg 1 min 2.5 min 5 min k d f Att Clean 4 l A Angle of Attack, deg

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-4 1 0 1.6 1.2 1.4 0.8 0 2 0.4 0.6 0.2 efficient, Cl Lift Co

Icing effects - Length of Exposure

National Aeronautics and Space Administration 4 4 3 3 5 min 2.5 min 1 min 2 2 Aircraft Icing 1 1 0 0 0 -1 -1 -1 1 2 0 0 1 2 2 0 1 -1 -1 -1 / 0 75 2 0 d V = 200 kts LWC LWC = 0.75 g/m3 Tt = -2.2 deg C MVD = 15 um AOA AOA = 2.0 deg

Length of Exposure

- Length of Exposure

5 min Clean 2.5 min 1 min Angle of Attack, deg -2 0.08 0.04 0.06 0.02

Icing effects Icing effects

d oefficient, Cd Drag Co National Aeronautics and Space Administration Glaze Runback 2 2 Rime 2 Aircraft Icing -1 -1 -1 0 1 2 -1 1.5 0.0 -1.5 0 1 2 -1 Runback Clear

Type of Ice Type of Ice

Rime Rime

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Glaze Angle of Attack, deg

effects

-4 1 1 0 1.4 1.6 1.2 0 6 0.8 0 2 0.4 0.6 0.2 Cl Coefficient, C Lift C

Icing effects Icing

National Aeronautics and Space Administration 4 4 3 3 Glaze 2 2 Runback Rime 2 Aircraft Icing 1 1 0 0 0 -1 -1 -1 2 0 1 0 1 2 -1 -1 1 5 1 5 0.0 1.5 -1.5 Rime Glaze Clear Clear Runback

Type of Ice Type of Ice

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Angle of Attack, deg -2

effects

-4 0.1 0.09 0 06 0.07 0.08 0.04 0.05 0.06 0.01 0.02 0.03 nt, Cd rag Coefficie D

Icing effects Icing

National Aeronautics and Space Administration Aircraft Icing

Ice Protection Systems

Heated-air Electrothermal

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Thermal Thermal (evaporative and running wet) Mechanical Freezing Point Depressant (FPD)

How to protect aircraft from icing: • • • • National Aeronautics and Space Administration Aircraft Icing

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Is design power adequate? Is area coverage adequate? Is ice contamination (if any) acceptable?

o o o Design test of IPS

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icing Scale tunnel for test in conditions

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Build model model

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icing Select facility

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icing icing natural conditions Determine

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an Ice Protection System

A A new aircraft has been designed that incorporates a new bleed- air thermal ice protection system. Task: plan a test of the new ice protection system Steps involved include: icing icing Select

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probable scenarios

Test an Ice Protection System Test

National Aeronautics and Space Administration Aircraft Icing

air temperature well below freezing pt

Warm – air temperature near freezing pt. Cold Cold – air temperature well below freezing pt. Lower power available for icing protection

Hold Descent

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For this airplane, the phases of flight critical for icing are: probable scenarios

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National Aeronautics and Space Administration 20 20 20 MVD Aircraft Icing 0.5 0.15 0.15 LWC F , 3.7 14.3 27.7 Tt, ‐ F , ‐ ‐ Ts, 2 2 ‐ AOA kts , 180 180 180 V, ft , 15000 15000 10000 Alt., icing natural conditions Determine hase Hold Hold p p g Descent icing Cold Select Warm Flight probable scenarios National Aeronautics and Space Administration Aircraft Icing

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icing Select facility icing

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natural natural conditions Determine

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Size of tunnel

A Temperature Cloud (LWC, MVD) Altitude capability Cost

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icing Select Icing winds tunnels available both in the U.S. and abroad. Considerations: probable probable scenarios

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National Aeronautics and Space Administration y Aircraft Icing Bleed Air System Build Build model icing Select facility

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natural natural conditions Determine

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icing Select Must fit in tunnel Must retain aspects of wing pertinent to icing – i.e. the leading edge must be closely representative of the aircraft’s Ice protection system must be representative representative probable probable scenarios

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National Aeronautics and Space Administration Aircraft Icing icing Scale Scale tunnel tunnel for test in conditions i icing natural conditions D Determine icing S l Select probable scenarios Heat transfer: Prandtl No. & Nusselt No. Mass transfer: Schmidt No. & Sherwood No.

Build model  

Thermal IPS heat transfer Water evaporation (mass transfer) Similarity parameters

very little – greatly affects collection efficiency very little MVD, some LWC

How to account for this?

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Geometric Cloud conditions Altitude Altitude

icing  Select facility

Scaling • • •

National Aeronautics and Space Administration Aircraft Icing

analogy

Heat transfer: Nusselt number = f(Re) Mass transfer, Sherwood number = f(Nu)

Momentum transfer heat transfer and mass transfer rates Momentum transfer, heat transfer, and mass transfer rates are similar If transfer rate for one can be established, the other two If transfer rate for one can be established, the other two can be inferred Similarity holds only under certain conditions In aeronautics, momentum transfer (Reynolds number) is well established

Reynolds analogy Reynolds • • • •

National Aeronautics and Space Administration

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Aircraft Icing

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LWC LWC

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(flight and tunnel): Reynolds number, Cloud parameters: a) Water loading, a) Water loading, b) Inertia parameter, Recovery temperature,

Method Method

Match (flight and tunnel): Match 1. 2. 3.

National Aeronautics and Space Administration 338.9 339.2 353.5 353.5 354.0 383.1 383.4 Sherwood Sherwood 0.6259 0.6271 0.6267 0.6267 0.6290 0.6266 0.6277 Schmidt Schmidt Aircraft Icing 356.7 356.7 372.08 372.08 372.06 403.19 403.17 Nusselt Nusselt Prantl Prantl 0.7113 0.7113 0.7121 0.7121 0.7120 0.7118 0.7117 F , 2.5 2.5 Tr F Tr 26.5 26.5 15.5 15.5 15.5 k0 k0 1.523 1.523 icing Scale Scale tunnel tunnel mw mw 29.96 1.504 29.96 1.504 9.024 9.024 9.024 1.523 8.808 1.414 8.808 1.414 for test in conditions 2xr 2xr ‐ Re Re 128591 128591 139772 139772 139772 164186 164186 20.0 27.8 20.0 20.0 27.8 20.0 24.5 MVD MVD icing natural 0.50 LWC LWC 0.85 0.15 0.15 0.25 0.15 0.21 conditions Determine F , 3.7 3.1 14.3 14.3 15.1 Tt F Tt 27.7 26.9 ‐ ‐ F , 4.0 0.9 22.0 22.0 17.8 ‐ ‐ Ts F Ts 20.0 24.3 ‐ ‐ icing Select kts , probable 180 180 106 180 scenarios V kts V 180.0 105.6 129.8 psia psia Palt, 8.30 8.30 10.1 8.287 14.29 14.26 14.13 ft* ft* Build model ., 766 823 15000 15000 15000 10000 Alt Alt Hold Hold Ref Ref Ref Ref Scale Scale Scale icing Descent Select facility Cold Warm Hold Warm National Aeronautics and Space Administration Aircraft Icing Is design power adequate? Is area coverage adequate? Is ice contamination (if any) acceptable? any) acceptable?

o o o Design test of IPS diti icing Scale tunnel for test in conditions icing natural Determine conditions icing Select probable scenarios Build model Investigate various bleed-air flowrates, pressures, and temperatures to determine adequacy and optimum operation Help determine adequacy of jet location and distribution as well as extent of IPS coverage distribution as well as extent of IPS coverage t

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Set test matrix to: icing S l Select facility

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National Aeronautics and Space Administration Aircraft Icing

≈

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dx dx

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Boundary layer approximations are valid Boundary layer approximations are valid

Pr and Sc dp dp

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Reynolds analogy assumptions valid? Flight tests usually required to verify IPS operation Flight tests usually required to verify IPS operation

Caveats Caveats

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National Aeronautics and Space Administration Aircraft Icing

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is NASA involved in aircraft icing?

ircraft Safety eronautics Tests irspace Systems

A Fundamental Aeronautics A Integrated Systems A

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National Advisory Committee for Aeronautics (NACA) Continues to conduct aeronautical research

Why is NASA involved in aircraft icing? Why

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National Aeronautics and Space Administration Aircraft Icing

NASA

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does NASA do?

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Studies ice accretion process Investigates effects of ice on aircraft Develops engineering tools for use in designing and certifying aircraft for flight in icing conditions Promotes the development of ice protection systems All All of the information presented here is from NASA- sponsored research

What does NASA do? What

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National Aeronautics and Space Administration Aircraft Icing 2.0 lewice limits 1.0 , in.

ice shape x in x 0.0 Lewice -1.0 # HF1011236LE R i -2.0 T 1.5 0.5 -0.5 -1.5 n. y, in I Ice Tracing - Run # HF1011236LE Ice accretion simulation codes:

LEWICE GLENNICE

NASA Ice accretion simulation codes: NASA

• • National Aeronautics and Space Administration Aircraft Icing Ice accretion codes, 3D: LEWICE3D

NASA Ice accretion codes 3D: NASA

National Aeronautics and Space Administration Aircraft Icing Ice accretion codes, 3D: LEWICE3D

NASA Ice accretion codes 3D: NASA

National Aeronautics and Space Administration Aircraft Icing Dry, aerodynamic wind tunnel studies are conducted using artificial ice shapes. The use of these methods allows for more thorough (real ice melts and sublimates) and cost-effective investigations.

NASA aerodynamic performance tests and fundamental flowfield investigations

National Aeronautics and Space Administration Aircraft Icing Describe difference between ground and Describe difference between ground and inflight icing List three types of ice List three types of ice List two effects of ice accretion on aircraft List three types of ice protection systems Setup an icing test of an ice protection Setup an icing test of an ice protection system

Conclusions Conclusions

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National Aeronautics and Space Administration Aircraft Icing National Aeronautics and Space Administration