Ice Crystal Icing

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Copyright © 2011 Boeing. All rights reserved.

Ice Crystal Icing

Bill McKenzie, 757/767 Technical PilotBoeing Training & Flight Services

Jeanne Mason, Senior Specialist EngineerBoeing Propulsion Systems Division

Copyright © 2011 Boeing. All rights reserved. Ice Crystal Icing_McKenzie-Mason.2

“I did not fly through a Mesoscale Convective System”

Ice Crystal Icing – View From the Flight Deck

Weather radar


Agenda

• What is Ice Crystal Icing– Engine effects– Weather– Reports from the Flight Deck

• Statistics and Example Event

• Industry Activity

• Boeing Activity

• Flight Crew Inputs


Core air travels downstream to the combustor

Potential ice crystal accretion areas

Fan

Ice shed from compressor surfaces can cause engine instability such as surge, flameout, or engine damageIce shed from compressor surfaces can cause engine instability such as surge, flameout, or engine damage

What Is Ice Crystal Icing?

The physics: • Crystals can form ice on engine surfaces warmer than freezing• These warm engine surfaces are in the compressor aft of the fan

The physics: • Crystals can form ice on engine surfaces warmer than freezing• These warm engine surfaces are in the compressor aft of the fan


What is Ice Crystal Icing? (continued)

• Frozen ice crystals impinging on a warm surface in the engine• Some crystals melt, wetting the surface• Crystals impinging on wetted surface stick, cool the surface to 0°C• Ice begins to form• At high altitude, ice can form deep in the engine core


What is Ice Crystal Icing?

It can also clog probes like the Total Aircraft Temperature (TAT) probe, (some airplanes) and the engine inlet temperature probe (some engines)

TAT probe


Weather


What’s New – Ice Crystals!

• Convective clouds which cause engine power loss range from isolated CBs to tropical storms and hurricanes

• Common factors – water lifted to very high altitude

• Ice crystals form just above the freezing level to cloud top

• Ice crystal mass can be 4x the certification standard for supercooled drops for engines

• Away from the core of the storm, in the anvil, ice crystals have been measured to be very tiny –size of baking flour

Convective / Cumulonimbus cloudConvective / Cumulonimbus cloud

Supercooled water(airframe icing)

Supercooled water(airframe icing)

High concentrations of ice crystals

>50K ft>50K ft

Upwind side:supercooled liquid sometimes goes higher

Upwind side:supercooled liquid sometimes goes higher

Freezing levelFreezing level

Mixed-phase icingMixed-phase icing

Heavy RainHeavy Rain


Ice Crystals are Hard to Recognize and Avoid• 80% of all events - little or no returns at flight level• Amber and red returns below the aircraft • Low updraft velocity, light to moderate turbulence• Aircraft in deepest (tallest) part of the cloud• Clouds can spread out hundreds of miles

Freezing level

TropopauseMany engine events occur withoutflight-level weather radar returns


Hurricane Michael, K-band Radar on Instrumented Aircraft

Canada

23,000 ft.19,250 ft

11,800 ft.

Not Visible on Pilot’s Radar GR

EEN

AMBE

R

RE

D

Freezing Level

Tallest cloud region – clouds above the tropopause – directly below = amber & red on normal radar

Test aircraft flight path – image from upward and downward looking K-band radarImage courtesy of Walter Strapp, Environment Canada. Reference: Abraham, J., J. W. Strapp, C. Fogarty, and M. Wolde, 2004:Extratropical transition of hurricane Michael. Bull. Amer. Met. Soc., 85, 1323-1339.


Canada

23,000 ft.19,250 ft

11,800 ft.

Not Visible on Pilot’s Radar GR

EEN

AMBE

R

RE

D

Freezing Level

Hurricane Michael, K-band Radar on Instrumented Aircraft

Image courtesy of Walter Strapp, Environment Canada

On board weather radar would only see green ahead. At freezing level it would also see amber and red


Aggressive Down Tilt Needed to See Amber at Freezing LevelAt Cruise on a tropical ISA+15 Day, 6 degrees down-tilt needed at 40 nm

36000 ft

15000 ftFreezing level

6 degrees


Typically, clouds which cause events are about 100 nmi/185km in diameter

0.5

0.6

0.7

0.8

0.9

1.0

1.1

1.2

1.3

1.4

1.5

15000 16000 17000 18000 19000 20000

Time (seconds)V

ertic

al A

ccel

(g's)

-25

-20

-15

-10

-5

0

5

10

15

20

25

30

Tem

pera

ture

(Cel

sius

)

Start End

Potential damageLight Turbulence

Moderate Turbulence

TAT Anomaly

Turbulence

Tallest cloud

region

“Satellite” Weather Analysis: A Recent Event

• Traversed 195 km/ 105 mi through tallest cloud region

• Pilots reported no radar returns at flight level

• Moderate turbulence at onset of TAT anomaly

• Engine performance shift: potential damage location


Ice Crystal Icing Reports from the Flight Deck

• Speckled green on weather radar

• Rain on the windscreen

• Small collection of ice particles on wiper post

• “Shhh” sound

• TAT near zero

• Humid cockpit

• Ozone smell

• No engine changes

Conditions “Sometimes” Reported

IMC (always) Rain effect


Statistics and Example Event


(5 engine types)

Engine Events Per Year

• GE90-94B• CF6-80C2• RB211-535E4• PW2000• JT8D/MD-80

Industry Awareness is Increasing

• Since 2003, increased: – Identification of events – Awareness and reporting

• Since 2008: – 2 new engines affected – Vibration symptom added


7 Engine Flameouts on a Single Descent

Three events involving multiple engine flameouts (7 flameouts total)

High-altitude ice crystals indicated as the cause of engine power loss

• Convective storm near Manila

• Aircraft was descending through turbulent weather

• Avoiding strong radar returns

• 26000 ft: engines 3 and 4 flamed out and recover

• 24000 ft: engines 1 and 2 flameout and recover

• 18000 ft: engines 1, 2 and 4 flameout and recover

Boeing and Engine Company Proprietary Data


Flight Data Review Recorder Data for Event 1

Aural Bank WarningAural Bank WarningMax A/P WheelMax A/P Wheel

FlameoutFlameout

Rudder InputRudder Input~18 seconds~18 seconds


Event Analysis

• To date, all large transport engines have recovered and operated at commanded thrust for remainder of the flight

• In this event, thrust asymmetry exceeded autopilot authority, requiring flight crew input, even though engines recovered

• Confusion factors included– Weather– Turbulence– Re-route / diversion– Thrust changes


Industry Activity


New Regulations ComingResearch Projects are Underway

• New regulation for ice crystals will be published in 2012

• Four areas of research underway:– Instruments for measuring ice crystal icing in the

atmosphere– Experimental data characterizing the ice crystal

environment – Research on engine ice crystal accretion and shedding– Engine test facilities representative of flight environment

This work will take time to complete before practical problem solving can begin


NASA/FAA/Boeing/Environment Canada/Airbus

Atmospheric Research Is Still Planned

• Flight program for High Ice Water Content (HIWC) Atmospheric Characterization goal: definition of convective atmosphere containing ice crystals to use as engineering standard

• Flight Program planned for 2012, 2013 – focused on the weather that produces engine events


Boeing Activity


Boeing Publication Activity

• Technical Bulletin

• Symposiums

• Aero magazine articles

• MyBoeingFleet (web site)

• Flight Crew Training Manual

• Supplementary Procedure

• QRH Checklists

Pilot Reports

and

Event Analysis

Pilot Reports

and

Event Analysis


Key Message In All Publications: Avoid

Avoid ice crystal icing weather• During flight in IMC, avoid flying

directly over significant amber or red radar returns, even if there are no returns at airplane altitude

• Use the weather radar controls to assess weather radar reflectivity below the airplane flight path. Refer to weather radar operating instructions for additional information

• Deviations of up to 50 nm may be needed to follow the guidance

• We know this is not always practicalSpecific model/engine checklist steps will be covered in the breakout sessions


Technical Bulletin

Table of Contents1. A New Threat2. Pilot Reports3. Indications of Ice Crystal Icing4. Industry Efforts5. Research6. Key Points for Flight Crews7. More Information8. Frequently Asked Questions9. Pilot Questionnaire10. Information for Dispatchers


Background Published Aero Magazine Articles

1st quarter 20104th quarter 2007


Background Information on ‘MyBoeingFleet’

Also available on CD-ROM

Events, Training and Resources\Safety Tools and Training Aids\Ice Crystals at High Altitude


Flight Crew Training Manual

Released July 2011


Supplementary Procedure (SP.16)

FCOM Volume 1

1. General description and avoidance recommendation

2. Refers to the new QRH non-normal checklist

3. Will be published at the same time as the QRH non-normal checklist

(Available at the breakouts)


New Ice Crystal Icing Checklist767 Example

First Actions: Set thrust manually, exit weather

4. Engine related steps added as needed

Condition statements are airplane dependent


Boeing Publications

All Model Tech Bulletin

April 2011

Flight Crew Training Manual

July 2011

Supplementary Procedures

2011/2012

Non-normal Checklists

(not 737)2011/2012

MyBoeingFleetJan 2011

Training Video & Articles

Flt Ops Conf.Sept 2011

Presentation

MyBoeingFleet4th qtr 2011

Additional presentations &

Articles

Published at the

same time


Project End Vision

Airline line pilots are:• Familiar with ICI phenomenon • Aware there is a non-normal checklist• Aware of the need for more event data

Airline management pilots:• Have materials available to help them

educate their line pilots


Summary

• Ice Crystal Icing Events are occurring on many engines

• Industry is working to better understand the meteorology and theengine icing phenomenon

• Boeing is focused on providing the best information to crews

• New material is being published by Boeing (Bulletins, Training, Supplementary Procedure, Checklists)


Flight Crew Input Is Needed!

• Most of what we understand is based on pilot reports and flight recorder data

• More flight crew reports of ice crystal encounters (with or without engine power loss) would be valuable to:

– Develop flight crew cues

– Validate current Boeing and industry understanding

– Better understand the process of ice crystal accretion inside engines


Flight Crew Input Is Needed!

Your pilot report will helpJeanne Mason

PO Box 3707 MC 9U-UUSeattle, WA 98124-2207

[email protected]

Your pilot report will helpJeanne Mason

PO Box 3707 MC 9U-UUSeattle, WA 98124-2207

[email protected]

Please use the questionnaire1. Fill out now

or 2. Put in flight bag

or3. Fill out the form on

‘MyBoeingFleet’


Questions?

Ice Crystal Icing

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