more on taking off in freezing events
folks, awhile ago I started a thread regarding taking off in certain freezing events. here is the latest that I think should be of interest to all pilots of all aircraft.
jon
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ALPA Alerts Pilots About Operating in Light Ice or Snow Pellets
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On February 21, the Association issued ALPA Safety Alert 2006-02 to warn pilots that some U.S. airlines have wrongly interpreted a recent FAA notice to permit takeoffs in light ice pellets or light snow pellets, though no data support doing so.
ALPA issued several recommendations with the safety alert:
a.. Until the airline industry develops holdover times for deicing/anti-icing fluid during conditions of ice pellets and snow pellets, flight crews should exercise extreme caution while operating in these conditions.
b.. ALPA does not endorse operations in ice pellets or snow pellets, regardless of whether ground crews have applied anti-icing fluid to the airplane.
c.. Flight crews must exercise extreme caution when operating in freezing precipitation without anti-icing fluid on the airplane.
d.. Flight crews must always comply with their airline's guidance.
e.. Flight crews, in conjunction with their airline, must use their best judgment in determining whether to take off.
f.. A pilot in command who believes that the safety of flight may be compromised must always exercise command authority.
In October 2005, the FAA Flight Standards Service issued FAA Notice N 8000.309, "Dispatching During Precipitation Conditions of Ice Pellets, Snow Pellets, or Other Icing Events for which No Holdover Times Exist." The notice recommended that airlines not authorize their flight crews to take off in ice pellets and other extreme weather conditions because of lack of data available to flight crews to support such operations. Such data would include deicing/anti-icing holdover times, failure criteria for deicing/anti-icing fluids, aircraft performance, and other mitigating factors that would reduce the risks of operating in these conditions.
Some airlines have interpreted the FAA notice to permit operations in ice pellets or snow pellets if (1) no deicing or anti-icing fluid is applied to the airplane and (2) the operator can determine that no contamination is adhering to flight surfaces.
This interpretation of the FAA notice does not account for the possibility of residual ice remaining on an untreated wing after exposure to ice pellets. Even momentary exposure to ice pellets may create a layer of clear ice adhering to the upper surface of the wing, thus degrading aerodynamic performance by an undetermined amount. This contamination may be extremely difficult to detect visually. Also, meteorological conditions may worsen between the time of a visual contamination check of the airplane's unprotected surfaces and the beginning of the takeoff roll.
ALPA's Ground Deicing Project Team has been actively involved with the U.S. and Canadian governments and the airline industry in developing adequate deicing/anti-icing holdover times for ice pellets and snow pellets. Testing is scheduled to continue through 2006 to reach consensus on effective holdover times for these conditions.
ALPA will encourage the FAA and Transport Canada to conduct flight and wind tunnel tests that support holdover times that more accurately reflect real-world conditions. At present, Transport Canada has chosen to continue with the guidance offered by current deicing/anti-icing holdover time tables--i.e., that no holdover times exist for ice pellets, snow pellets, or other icing events.