Use or disclosure of the information contained herein is subject to specific written approval from CIRA

ICING HAZARDSRESILIENCE BY DESIGN

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 2

AIRCRAFT ICING

Recently there is an increased interest toward the icing topic involving two key areas:

SAFETY; PERFORMANCES;

RESILIENCE IN AIRCRAFT ICING THREATH

... is directly related to the variability of the inflight icing cloud conditions and to the frequency of catastrophic events to which the design of the aircraft ice protection and avoidance technologies have been adapted.

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 3

In flight icing: It is caused by water droplet impinging inflight on aircraft surfaces (usually wing/empennage leadingedges, nacelle lip, ..)

Two completely different phenomena

Ground icing: It is caused by moister collected on coldsurface while aircraft is on the ground (usuallywing/empennage upper surface)

GROUND AND IN-FLIGHT ICING

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 4

Ground icing

Ground icing can be caused also by freezing precipitation ormoisty air condensation on cold aircraft surface (typical is iceaccumulation on integral tanks wing)

No aircraft is allowed to take-off with contaminated surface(except in non-critical areas indicated in AFM) because even asmall amount of ice can:

Affect aircraft aerodynamics characteristics

Detach from the aircraft surface and either impact onother aircraft components or be ingested by enginecausing flame-out

GROUND ICING

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 5

Ground icingGround icing contaminants can cause:

• Longer take-off• Failure to liftoff• Lift-off, but not climb capabilities• Climb, but roll or pitch uncontrollability• Engine power loss

5

GROUND ICING

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 6

The ice accretion physics

Ice accretion is caused by the impact of supercooled water droplet on aircraft component surface

IN-FLIGHT ICING

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 7

Ice can cause: a reduction of lift, a reduction of stall angle, an increase in drag, a modification in longitudinal stability.

-5 0 5 10 15 20 25

2.01.81.6

1.41.2

0.8

0.2

0.0

0.4

1.0

Rime

GlazeMixed

Clean

-5 0 5 10 15 20 25

0.5

0.4

0.3

0.2

0.1

0.0

GlazeMixedClean

CdCl

a) b) -5 0 5 10 15 20 25

c)

0.05

0.00

-0.05

-0.10

-0.15

Rime

GlazeMixed

Clean

Cm

lift c

oeffi

cent

,

drag

coe

ffice

nt,

mom

ent c

oeffi

cent

,angle of attack

(deg.)α

angle of attack (deg.)α

angle of attack (deg.)α

Rime ice, in someconditions, may alsocause an increase inlift at low incidences.

Even a small amountof roughness on airfoilleading edge candecrease stallcharacteristics.

IN-FLIGHT ICING

Aerodynamics performance degradation

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 8

ICING: MOTIVATIONS

Following ATR Roselawns incident of 1984 and AIRBUS Rio de Janeiro incident of 2009 in 2014 new certification rules have been

issued by FAA and EASA that require the presence of SLD: ”SuperCooled Large Dropets” and Ice Crystals

AT PRESENT TIME NO AVALIABLE MEANS OF COMPLIACE EXIST (NEITHER NUMERICAL NEITHER EXPERIMETAL) TO CORRECTELY

SIMULATE SLD and ICE CRYSTALS

SAFETY

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 9

ICING: MOTIVATIONS

SLD: Have been recently included in certification envelop, can cause ice accretion behind aircraft protected area

SAFETY: SLD

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 10

CERTIFICATION

(Ref. DOT/FAA/AR-09/10)

Freezing DrizzleSLD cloud envelope extension

(Appendix O) Freezing Rain

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 11

ICING: MOTIVATIONS

Ice Crystal can cause ice accretion on probes and engine components and ice probes

SAFETY: ICE CRYSTALS

Lost of air dataEngine flame-out

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 12

ICING: MOTIVATIONS

SAFETY: ENGINE POWERLOSS

Non-convective Cloud

Convective/Cumulonimbus Cloud

Super cooled drops form ice on cold surfaces of inlet, fan, and front of compressor

Ice crystals form ice on warm surfaces inside the compressor

Supercooled liquid water accretion area(inlet, spinner, fan, and first stages of the core)

Potential ice particle accretion areas

Fan

Core air travels downstream to the combustor

(Souce of slide: Boeing)

air in engine is warm

cold ice particles drive down the temperatures of surfaces to freezing temperatures

some crystals melt and freeze on cooled surfaces

ice breaks off and causes surge/stall/thrust loss, sheds into compressor and quenches flame (flameout), or builds up and chokes airflow (rollback)

actual details are under investigation

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 13

CERTIFICATION

(Adapted slide courtesy of E. Duvivier, EASA)

Temperature-altitudeenvelope (heavy purple)determined by EHWGfrom engine events

Some events nowoutside envelope (esp.considering air-dataevents)

Realities - Currently we have some limitations in:

Unsubstantiated environmental definition (i.e. App D)

Basic understanding of the physics of accretion. Test facility capabilities to demonstrate

compliance.

Current proposed rule and guidance recognizes today’s realities but lays the ground work for future advances in knowledge and capability.

Proposed cloud envelope extension (Appendix D)

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 14

Engine Harmonization Working Group has defined a Technical Plan with overarching goal of the flight campaigns (executed within the HAIC and HIWC international projects) to acquire a benchmark database of the atmospheric environment that causes engine & air data sensor failures that threatens air transportation safety. The strategy includes:

Set new design and certification standards for engines and sensors to operate within this environment

Develop engine ice models/simulations and guide future experimental activities for means of compliance & fundamental ice growth studies

Develop HIWC detection methods (onboard, ground-based, space-based) and weather diagnostic & forecast tools to enable threat avoidance

Understand the fundamental cloud microphysical processes that cause High IWC to occur and, by doing so, improve the ability to forecast or detect it

CERTIFICATION

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 15

CERTIFICATION

CS 25@Amdt 16 and CS E@Amdt 4, Published in March 2015 ICING ENVIRONMENT expanded for CS- 25 - large

airplanes and CS-E (turbine engines)

CS 25@Amdt 18 , Published in June 2016 Introduce the “Comparative Analysis as an acceptable

Mean of Compliance to 25.1420 (SLD requirement)

Proper implementation of the new regulations requires: Further Development of Means of Compliance (appendix P + O) Appendix O detection means for the “detection and avoidance”

certification strategy

New certification requirements

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 18

1. Ice accretion on rotating elements => Enginecomponents

2. Ice accretion on rotors => unsteady ice accretion andice shedding

3. Increase wind turbine operativity => Ice accretion onwind turbine

4. Propeller icing: propeller ice evaluation and iceprotection

HELICOPTERS AND OTHER CHALLANGES

ICING: MOTIVATIONS

-0.10

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0.00

0.05

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X/C

Y/C

NACA 0012R = 6.7R = 8.5R = 9.2Panel MultiStep R=8.5Euler 3m R=8.5

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 19

Ice Accretion and Ice Protectiono Ice accretion simulationo Ice protection systems simulationo Aerodynamic degradation due to ice accretion

CIRA ICING NUMERICAL CAPABILITIES

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 20

SUMMARY OF CIRA ICING SOFTWARE

2D ice Accretion code – MULTIICE Coupled with both panel methods and field methods Fully validated User friendly interface Lagrangian approach

3D ice Accretion code – HELICE Lagrangian approach Coupled with both panel methods and field

methods

IMPIN 2D and 3D Eulerian approach for water impingement

calculation coupled with ice accretionEulerian approach by immersed boundaryTERMO: Thermal ice protection systemsUse of Open source or commercial software for ice accretion and ice protection simulation

CIRA ICING NUMERICAL CAPABILITIES

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 2121

• Identification of the optimal designparameters: frequencies ofexcitation, PZT dimensions.

• Simulation (FE modeling) of thesystem performance transmitted shear action at the ice-structure interface

PZT

structure

ice

h(i)

h(s)

0x

z

Piezoelettrico Struttura

Ghiaccio

• Theoretical and numerical modeling of the PZT de-icing system

CIRA: ICE PROTECTION

Lamb-wave ice protection/ice detection

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 22

Test Room with environmental controlledparameters

Optical path:Led light + analyzer + polarizer + diffuser screen

Digital high resolution camera (magnifications up to 200X)

Sample Holders with micrometric handling on 3 axes

Camera conditions scoreboard (pressure control by vacuometer and temperature control by thermocouple)

22

CIRA: ICE PROTECTION PASSIVE

Development of idrophobic coating

Development of idrophobic coating (passive ice protection) and/or integrated passive/active ice

Tools and procedure for coating performance evaluation

Idrophobic-coatings

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 23

A EUROPEAN “CORE SPECIALIZED” ASSET

World largest in size

World highest speed

World widest test envelope

World largest icing instrumentation stock

CIRA: ICING WIND TUNNEL - IWT

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 24

Parking hallControl

room

Transformer building

HX

Fan SystemEngine Flow Simulation

Air Station

ElectricalRoom

Coolingstation

CIRA: ICING WIND TUNNEL - IWT

IWT LAY-OUT

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 26

FanHXs

SBS Test Sections

TEST SECTION

DIMENSION (m)

SPEED (Mach)

TEMP (°C)

MAIN 2.25x2.35 0.41 -32 < t < +40

SECONDARY 1.15x2.35 0.7 -40 < t < +40

ADDITIONAL 3.60x2.35 0.25 -32 < t < +40

OPEN-JET 2.25x2.35 0.34 -32 < t < +40

CIRA: ICING WIND TUNNEL - IWT

IWT AEROLINES

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 27

CIRA: FUTURE PLANS

“Area 1”: Facilities for ice accretion simulation

“Area 2”: Icing instrumentation

“Area 3”: Ice accretion simulation

“Area 4”: Development of Technologies for ice protection

“Area 5”: Technological demonstrator

To reach the objective the following areas have been identified:

CIRA FUTURE MACRO OBJECTIVES

Increase and extend productivity

Increase and extend capabilities

Development of new technologies

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 28

“Area 1”: Facilities for ice accretion simulation

Improvements of productivity and of theactual icing envelop with improvement onthe existing facility

CIRA technical objectives:

Extension/improvements of IWT capabilities to freezing drizzle conditions

New nozzles

New calibrations

CIRA: FUTURE PLANS

-0.2

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1

1.2

-40 -30 -20 -10 0 10 20 30 40 50X (mm)

Skew

ness TC# 10 Y=0mm Z=152.4mm ADA small

TC# 10 Y=0mm Z=228.6mm ADA small

Study and small demonstrator of Spray-bar for SLD

New spray-bar system

Improvement thermal IWT envelope

New SBS calibration

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 29

“Area 2”: Icing instrumentation

Improvement of icing instrumentation to reducemeasurements uncertainties, to implement newcertification requirements and to increase IWTcompetitiveness and productivity

New techniques for particle sizing (assessment/inter-comparison)

Droplet temperature measurements

New techniques for remote ice shape measurements

New techniques for cloud uniformity measurement and characterization

High speed camera for ice shedding studies

CIRA: FUTURE PLANS

CIRA technical objectives:

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 30

“Area 3”: Ice accretion simulation

Improve numerical simulation capabilities to provide an extend offer thatinclude both numerical and experimental activities

Improvement and maintenance of ice accretion tools (SLD, 3D, rivulets, …)

Improvements and maintenance of ice protection simulation tools

Degradation of aerodynamics performances

Ice shedding simulation (shedding and trajectories debris) (with possibility of PT1 simulation for debris characterization and test article manufacturing with 3D printing)

SEASIDE (PROTON/GKN) Courtesy

CIRA: FUTURE PLANS

CIRA technical objectives:

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 31

Continue development of both passive and active iceprotection system and identify new innovative iceprotection concepts

“Area 4”: Development of technologies for ice protection

Passive systems (coatings, hybrid passive active systems)

Lambda wave concepts

Electro thermal systems

Integrated ice detection ice protection

New concept (integrated Laminar flow control and ice protection)

CIRA: FUTURE PLANS

CIRA technical objectives:

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 32

“Area 5”: Technological demonstrator

Development and test in CIRA IWT new demonstrators representatives of UAV, Regional aircraft and helicopters Demonstrate technologies for ice accretion; Validate ice accretion and ice protection numerical simulation

tools; Verify CIRA IWT capabilities improvement.

2D demonstration (SMOS)

Oscillating airfoil demonstration

3D demonstration

Typical UAV demonstration

Typical regional aircraft demonstration (conventional and innovative leading edge)

Helicopter test rig

AG2: Pol. Milano Courtesy

CIRA: FUTURE PLANS

CIRA technical objectives:

Use or disclosure of the information contained herein is subject to specific written approval from CIRA 33

Lighter, more efficient / low power and easy to integrate and operate (maintenance, reparability) breakthrough Ice Protection Technologies

High performance and high durability Hydro/Icephobic coating and combination with Ice Protection Technologies

Validated & verified Engineering Tools (numerical tools, test facilities) with special focus to SLD & Glaciated and Mixed Phase icing conditions

Ice Accretion & Ice Protection System performance prediction

Ice shedding, Ice block trajectory & Impact

Aerodynamic performance degradation & Handling Quality

Ice detection and ice protection integration

AIRCRAFT IN-FLIGHT ICING CHALLENGES

CONCLUSIONS