Presented at: NCAR

By: Paul Pellicano

Date: November, 2013

Federal AviationAdministration

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DST

• Aircraft index based on certification basis– Certified for icing

• Transport category airplanes over 60,000 lb. wing anti-ice, wing leading edge devices, no negative service history

• 25.1420• Other transport• Small and commuter, Amendment 23-43 or higher• Small and commuter, Amendment 23-14 or higher with no

negative service history• Earlier than 23-14 or 23-14 with icing events

– Light icing, limited time in moderate icing

– Not certified for icing

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Agenda

•Ice accretion rate•MVD•PIREPS•GA

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Ice accretion rate

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Ice accretion rate

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DST

• FAA cannot require airplane specific data from manufacturers– No plan to require it for new airplanes

• Could ask– FAA not likely to get positive response– Data doesn’t exist for older airplanes

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MVD

• Accretion rate• MVD<40 and MVD>40 Appendix O

Certification

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PIREPS

• What will be “known” SLD?

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PIREPS

• AOPA ASF Socata Accident

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PIREPS

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In-Flight - Indirect

•Surface observations are needed at smaller airports to also increase safety of transport category airplanes

Event Phase Altitude, ft Airport Distance, nm

American Eagle 4184 Hold 10,000 ORD 60

Comair 3272 Descent 7,000 DTW 19

Comair 5054 Cruise 17,000 PBI 47

Continental Express 2733 Climb 11,500 – 17,400LIT 37

MEM 125

American Eagle 3008 Climb 7,000 – 11,700SPB 25

LAX 130

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In-Flight - Indirect

•Surface observations are needed at smaller airports to also increase safety of all airplanes

Event Phase Altitude, ft Airport Distance, nm

PUB 17DEN 115

Circuit City Approach 7,000

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General Aviation

• Comment 82 - Part 25 is NOT GA!  GA has the most to gain but is it properly addressed?

• Disposition - Paul stated Part 23 certification is the same as Part 25. It appears for now GA is address adequately in ConOps– For new part 23 airplanes – assume AFM language

will be similar

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General Aviation• Existing fleet

– Much bigger than projected new airplanes• Most “detect and exit”• Market impact• First may be business jets

– No explicit prohibition in SLD– Must exit severe icing

• Cockpit display– Include SLD and PIREPS– Training/AIM

• Ice accretion location versus accretion rate

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General Aviation

•SIGMETs– Two levels, one that would only impact airplanes with SLD or

severe icing AFM language?

•Smaller airports•Unmanned Aerial Systems

– Certification standards will require system or ground operator to know if aircraft in Appendix C and/or Appendix O

– Must be able to report FZDZ and FZRA

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General Aviation

•Part 23 rulemaking– Congressional mandate– NPRM 2015

•Rules high level and not prescriptive– “Must be able to safely operate in the icing conditions for which

certification is requested”

•ASTM Standards– Will define the icing conditions– AFM language expected to be similar to part 25

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Back-up Slides

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Current ASOS Deficiencies

•ASOS does not report FZDZ– Belief that LEWDI cannot detect drizzle size drops– Drizzle precipitation rates below ASOS specification

•ASOS does not report FZRA when snow is being reported

– Wet snow can adhere to ice detector

•FZRA Reporting May Be Inaccurate for short periods of time

– Ice detector has to be heated to deice

•ASOS does not detect PL

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Current ASOS Deficiencies

•Sources– Current Capabilities for Icing Nowcasting and Forecasting

in the Terminal Area, Marcia K. Politovich and Scott Landolt, Terminal Area Icing Weather Information System, Product Development Team, National Center for Atmospheric Research

• A Multisensor Approach to Detecting Drizzle on ASOS, Charles G. Wade, National Center for Atmospheric Research, Boulder, Colorado Published in Journal of Atmospheric and Ocean Technology, Volume 20, 2003

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Why we need ASOS

•Ground Operations •In-Flight

•Efficiency•Safety•Cost

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Ground Operations

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Ground Operations

Outside Air Temperature

Type IV Fluid Concentration

Neat-Fluid/Water (Volume %/Volume %)

Approximate Holdover Times Under Various Weather Conditions (hours: minutes)

Degrees Celsius

Degrees Fahrenheit

Freezing Fog

Snow, Snow

Grains or Snow

Pellets†

Freezing Drizzle*

Light Freezing

Rain

Rain on Cold Soaked Wing**

Other‡

-3 and above

27 and above

100/0 1:45-3:10 0:40-1:20 0:50-1:30 0:35-0:55 0:10-1:15

75/25 1:00-1:45 0:30-0:55 0:40-1:05 0:25-0:40 0:09-0:50

50/50 0:20-0:35 0:07-0:15 0:10-0:20 0:07-0:10 CAUTION:

No holdover time guidelines exist

below -3 to -14

below 27 to 7

100/0 0:20-1:20 0:30-0:55 ***0:20-1:00 ***0:10-0:25

75/25♦ 0:25-0:50 0:20-0:40 ***0:15-1:00 ***0:10-0:25

below -14 to -25 or LOUT

below 7 to -13 or

LOUT

100/0♦♦ 0:15-0:40 0:15-0:30

* Use light freezing rain holdover times if positive identification of freezing drizzle is not possible

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Ground Operations

• Aircraft are currently not certificated for operations in

freezing precipitation.

• However, they are not prohibited from take-off in

freezing precipitation provided:

–the PIC follows the ground guidance

–there are no AFM limitations

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Airplane Limitations

•Airplanes certified for flight in icing– Cloud icing conditions defined in CFR part 25, Appendix C

•After the 1994 Roselawn accident– Airworthiness Directives require immediate exit from severe

icing in AFM Limitations section– “Freezing drizzle and freezing rain may be conducive to severe

icing”

•New airplanes– Part 25 rulemaking– Part 23 rulemaking

• In interim, most new part 23 airplanes insert prohibition in AFM Limitations section

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Proposed Part 25 Rule

•Airplanes certified for flight in icing must show– Safely operate in SLD;– Detect SLD and safely exit all icing; or– Safely operate in a portion of SLD, detect unapproved SLD

conditions and safely exit all icing

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In-Flight - Direct

•Approach and landing– A part 23 icing Aviation Rulemaking Committee (Reference 4)

identified 48 events (23 fatal) on part 23 airplanes from 1979 to 2009 in which there was evidence of supercooled large drop (SLD) conditions.

– The majority of these (75%) was on approach and landing, and in 20% of these events snow was present.

– The prevalence of “wet snow” is indicated by the fact the mean the average mean ambient temperature was 29.2°F, and the median was 32.0°F

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In-Flight - Direct

•Fatal accident of an air ambulance on approach to Rawlins, WY, in 2005

•Light snow and mist were the only precipitation reported, temperature of 32°F.

•Witnesses in the vicinity of RWL reported surface weather conditions varying from freezing rain to heavy snow

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In-Flight - Indirect

•The lead scientist in the development of the NCAR Integrated Icing Diagnostic Algorithm has stated (Bernstein, 1999) that “surface observations are the most powerful forecasting tool we have for finding SLD [Supercooled Large Droplet] conditions aloft, and FZDZ observations are our best indicator of the simultaneous occurrence of FZDZ aloft.” Final Report: Freezing Drizzle Algorithm Development,” September 21, 1999, Prepared for the National Weather Service by Raytheon Information Technology and Scientific Services (RITSS)

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In-Flight - Indirect

•Surface observations of freezing drizzle (FZDZ) were an excellent indicator of FZDZ aloft when near the observation (70% occurrence within 25 km) and at altitudes up to 5,000 ft., NASA CR-2001/210954 “Evaluation of NCAR Icing/SLD Forecasts, Tools, and Techniques Used During the 1998 NASA SLD Flight Season,” August 2001, Ben Bernstein, National Center for Atmospheric Research

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Cost•On Oct. 31, 2002, twelve United Airlines 737 aircraft incurred jet engine damage after experiencing a winter storm at Denver, Colorado.

– The damage was primarily bent fan blade tips, and was consistent with ice being ingested into the engines.

– Total damage was reported by United Airlines as being over $2 million dollars, with one engine requiring replacement.

– The damage was noted after the aircraft landed at their destination airports.

•The METAR and weather observer

at Denver reported mist and light snow – Ground personnel reported the

presence of freezing drizzle.