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"there are no old, bold pilots.")
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I've recently reviewed Dennis Newton's Severe Weather
Flying for a print publication. This third
edition of a classic weather-avoidance text, in continuous print
since 1983, aims to teach strategies to avoid flying in "severe"
One area Newton discusses at length is airframe ice. ANN readers
know that the whole concept of "known ice" is being reviewed by the
Federal Aviation Administration, and a reported new approach to the
legalities of flight in such conditions is being contested by AOPA.
For purposes of this writing I'll focus not on the legalities of
icy flight, but a practical outcome of Newton's research in
creating the third edition of his book.
Weight, or aerodynamics?
Is ice mainly a hazard because of the weight it adds to the
airframe, or the affect ice has on the aircraft's design?
A lot of data has been taken in icing [wind] tunnels and in
flight testing," reports Newton. "It is possible to give some
ballpark numbers to point out the relative magnitude" of
ice-related degradation. For instance, "the weight of ice does not,
in itself, present a serious problem." However, "even small
buildups of ice on airfoil leading edges can decrease maximum lift
coefficient by about 30 percent. Most of the damage to lift is done
by the first accumulation... even a small buildup will
significantly reduce the angle of attack at which an airfoil will
The old saw that some airplanes can "handle" ice better than
others because of their load-carrying capability simply isn't true.
"Handling" ice is a function of how ice builds on the wings,
propeller and tail... and that's not predictable until ice actually
begins to form.
Wings, or propeller?
Some think that ice on the wings isn't as bad as ice on the
propeller(s), to generate ice-overcoming thrust. Settling an
argument about whether it's better to keep the propeller(s) clean
(for thrust) or the wings, Newton writes "the propeller advocates
lose the contest handily, according to the data." In other words,
stalling or hard landings are more an issue with ice accumulation
than not having enough power to stay aloft.
Aero-tip of the day: Surviving an icing
encounter is all about preserving aerodynamics by keeping airfoils
clear of ice.