Freezing Rain as an In-Flight Icing Hazard

TITLE AND SUBTITLE:
Freezing Rain as an In-Flight Icing Hazard

AUTHOR(S):
Ben C. Bernstein, Thomas P. Ratvasky, Dean R. Miller, and Frank McDonough

REPORT DATE:
June 2000

FUNDING NUMBERS:
WU-548-21-23-00

PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
John H. Glenn Research Center at Lewis Field
Cleveland, Ohio 44135-3191

PERFORMING ORGANIZATION REPORT NUMBER:
E-12260

SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES):
National Aeronautics and Space Administration
Washington, DC 20546-0001

REPORT TYPE AND DATES COVERED:
Technical Memorandum

SPONSORING/MONITORING AGENCY REPORT NUMBER:
NASA TM-2000-210058

SUPPLEMENTARY NOTES:
Prepared for the 8th Conference on Aviation, Range and Aerospace Meteorology sponsored by the American Meteorological Society, Dallas, Texas, January 10-15, 1999. Ben C. Bernstein and Frank McDonough, National Center for Atmospheric Research, P.O. Box 3000, Boulder, Colorado 80307 (work funded under NASA contract SETAR 0088); Thomas P. Ratvasky and Dean R. Miller, NASA Glenn Research Center. Responsible person, Dean Miller, organization code 5840, (216) 433-5349.

ABSTRACT:
Exposure to supercooled large drops (SLD-subfreezing water droplets with diameters greater than ~50 microns) can pose a significant threat to the safety of some aircraft. Although SLD includes both freezing drizzle (FZDZ) and freezing rain (FZRA), much of the SLD research and development of operational SLD forecast tools has focused on FZDZ and ignored FZRA, regarding is as less of a hazard to aviation. This paper provides a counterpoint case study that demonstrates FZRA as a significant in-flight icing hazard. The case study is based on flight and meteorological data from a joint NASA/FAA/NCAR SLD icing research project collected on February 4, 1998. The NASA Twin Otter Icing Research Aircraft experienced a prolonged exposure to \"classical\" FZRA that formed extensive ice formations including ridges and nodules on the wing and tail, and resulted in a substantial performance penalty. Although the case study provides only a singular FZRA event with one aircraft type, it is clear that classical FZRA can pose a significant in-flight icing hazard, and should not be ignored when considering SLD issues.

SUBJECT TERMS:
Aircraft icing; Aviation meteorology; Weather forecasting

NUMBER OF PAGES:
12

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2000/TM-2000-210058.pdf
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