Aero-Tips!

A good pilot is always learning -- how many times have you heard this old standard throughout your flying career? There is no truer statement in all of flying (well, with the possible exception of "there are no old, bold pilots.")

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Aero-Tips 12.28.06

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" weather.

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 stall."

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.

FMI: Aero-Tips