Ice Crystal Icing –Detection & Avoidance Research · Copyright © 2011 Boeing. All rights reserved. Ice Crystals Characteristics 80% of all events - few or no returns at flight

Copyright © 2015 Boeing. All rights reserved.Copyright © 2015 Boeing. All rights reserved. Author, 1/5/2016, Filename.ppt | 1

Jeanne Mason, Associate Technical Fellow, Boeing Propulsion Engine OperabilityMelissa Bravin, Boeing Propulsion Engine OperabilityErick Hall, Boeing Flight Operations Engineering

Ice Crystal Icing –Detection & Avoidance Research

Copyright © 2015 Boeing. All rights reserved.

Ice Crystal Icing – Ice on the Engine Core Flowpath

Fan

Ice shed from compressor surfaces can cause engine instability

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

Potential ice crystal accretion areas

Core air travels downstream to the combustor

Copyright © 2015 Boeing. All rights reserved.Copyright © 2011 Boeing. All rights reserved.

Ice Crystals Characteristics80% of all events - few or no returns at flight levelAmber and red returns below the aircraft Low updraft velocity, light to moderate turbulenceAircraft in deepest (tallest) part of the cloudClouds can spread out hundreds of miles

Freezing level

TropopauseMany engine events occur without flight-level weather radar returns


Ice Crystal Icing Reports from the Flight DeckConditions Reported:

• 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• St. Elmo’s fire• Engine vibration

IMC (always) Rain effect


Equator

Tropical

TropicalSubtropical

Subtropical

General Statistics From Current Database Latitude 32°S - 52°N, with 92% contained within the tropical and

subtropical latitude band Altitudes from FL110 to FL450 with a median of FL350Generally warmer than ISA standard day (ISA + 5 to +25)


HIWC Cloud IdentificationEngine events typically occur when the airplane traverses greater than 100 km of

significant convective anvil cloud associated with a mesoscale convective systems (MCS).

• These MCS have a large, often oval region of convective anvil cloud above cruise flight levels

• Within that region, there often are embedded convective core/updraft areas which push moisture up above the tropopause, resulting in overshooting cloud

Oval Enhanced Region-Analyzed on IR satellite

IR Enhanced distance


Engine ICI Event Analysis

Author, 1/5/2016, Filename.ppt | 7

no turbulencevery light turbulencelight turbulenceModerate turbulence

Using the turbulence characterization of NASA/TM-2012-217337 Flight Tests of Turbulence Prediction and Warning System (TPAWS) -Hamilton et al, Langley Research Center

Pilot’s responses from questionnaires


• To provide insight into frequency that commercial flights potentially encounter HIWC cloud, 10,025 flight tracks in Asia-Pacific region analyzed for large MCS encounters

• None had ice crystal icing engine event• Found flights when enhanced distance greater than

100 km • Cruise level (FL390-FL410)• Results:

• 60 MCS with enhanced distance greater than 100 km with no adverse effect Grzych et al| 8

Not all big MCS cause events – Boeing is researching what is unique about clouds that do

Commercial FlightsAnalysis of Frequency of Flight in HIWCNull = No Engine Event

Oval Enhanced Region-Analyzed on IR satellite

IR Enhanced distance


Convective Maximum

Such regions are hypothesized to be associated with local maximum in ice water content Some convective clouds peak in intensity overnight, diminishing during daytime

hoursCommercial aircraft fly during all hours of the day

–Flight crews have more challenges / fewer cues to identify weather at night, since ice crystals are poor reflectors of radar energy

Flight test measurements will be taken only in day-time hours for safety reasons

SAE 2015-01-2130

ICI Event Characteristics


Detailed Investigation of Japan and South China Sea Regions50 cases in these two regions 11 cases have been chosen for detailed

meteorological analysis General Properties of 11 cases analyzed From April to November (monsoon and

tropical storm season) All oceanic MCS 9 in cruise, 2 in descent -56°C to -7°C SAT, median -43°C Evenly distributed across solar-time FL 185-400, median FL 370

Cases chosen for detailed analysis

Remaining cases

SAE 2015-01-2130


The area of cloud reaching cold temperatures can be a surrogate for high altitude ice concentrations

Mesoscale Convective Systems are Like a Pot of Boiling Water

MCS

Freezing level

Tropopause or Enhanced Level -69C

Enhanced Level Overshoot -79C

High IWCHigh IWC


Analysis MethodConvective cloud in which event occurred

was tracked from 24 hours before event to 6 hours after eventMTSAT IR images used: approximate

cloud top temperaturesMoving box defined to encompass cloud –

statistics inside box computed versus time Prime statistics: Total area of cloud colder than

equilibrium ‘enhanced’ level (top altitude a rising air parcel reaches before becoming negatively buoyant) – bright-white + red cloud at left Total area of cloud 10°C colder;

enhanced level overshoot (ELO) – red cloud at left Red areas are indicators of center of

updraft in cloudSAE 2015-01-2130


These results suggest that the airplane must be near a local convective core for an engine event

SAE 2015-01-2130 An Investigation into Location and Convective Lifecycle Trends in an Ice Crystal Icing Engine Event Database – Bravin et al

When Does the Engine Event Occur Relative to the Peak of the Convection Lifecycle

Study of 11 cases in Japan – South China Sea region: engine events occur in close proximity in time and space to the peak cloud area


Results of 11 CasesParameter Range Average CommentEnhanced Distance Traversed

72-272 km 194 km Similar to findings of Grzych and Mason (2010)

Event time – time of max enhanced (black line)

-1.2 to + 8.6hrs.

2.1 hrs. Events typically after peak in enhanced level area

Event time – time of max ELO (red line)

-0.8 to 3.5hrs.

0.88 hrs. Events closely aligned in time to peak in area of local ELO– average < 1 hour

Aircraft minimum distance to center of ELO

22-54 km 41 km Aircraft always passed fairly close to center of an ELO, close to the time of its maximum area

Aircraft penetratedELO (red) area?

8 of 11 cases (2 of 3 that did not were in descent)

Events tend to occur at or close to the peak in ELO area

SAE 2015-01-2130


SummaryBoeing database has been updated from Mason et al. (2006) with 46 events to

current 162 eventsTypes of clouds, temperature levels, and length of cloud traversed similar to

previous studies Regional influences hard to identify due to low frequencies in each regionNo evidence overall of a time-of-day bias in events, even though research

literature reports time-of-day influences on deep convective cloud frequenciesMost significant new finding is that events occur in MCS close to a local active cell

near the time of its peak intensity, identified herein as an "Enhanced Level Overshoot" (ELO). Time of the event ELO may be quite different from the time of the MCS system overall peak intensity

15ICE-0113


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Ice Crystal Icing –Detection & Avoidance Research · Copyright © 2011 Boeing. All rights reserved. Ice Crystals Characteristics 80% of all events - few or no returns at flight