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.")

Aero-News has called upon the expertise of Thomas P. Turner, master CFI and all-around-good-guy, to bring our readers -- and us -- daily tips to improve our skills as aviators. Some of them, you may have heard before... but for each of us, there will also be something we might never have considered before, or something that didn't "stick" the way it should have the first time we memorized it for the practical test.

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Aero-Tips 10.04.06

It's October, and we're already seeing a lot of Pilot Reports (PIREPs) for airframe ice in the northern US.

All ice is hazardous to airplanes. The characteristics of ice provide a clue as to how rapidly the situation may become uncontrollable, and how quickly the airframe may shed ice once you leave ice-accumulating conditions. There are three types of airframe ice:

Rime ice. Rime ice forms a milky, opaque layer. It looks like the frosty crystals that coat the interior walls of your home freezer. Rime ice results when a freezing-temperature surface (like an airplane) impacts very small liquid water droplets. Small droplets are usually suspended in stratus-type clouds, so rime ice usually occurs in warm fronts and slow-moving cold fronts, in stratus clouds. Because the droplets are very small rime ice may accumulate slowly (but don't count on it); since stratus clouds usually extend over wide areas there is a chance rime ice accumulation can become extremely hazardous. The good news is that, owing to the small crystalline structure of rime ice, it will often melt or sublimate off the airframe fairly quickly once you exit icing conditions.

Clear ice. Clear ice results from in-flight collisions with larger, supercooled water droplets such as you'll find in cumulus-type clouds. Clear ice is thick and hard, like the ice form an ice cube tray. A glossy, translucent ice layer forms, disrupting air flow and spreading aft along wings and tail to potentially obstruct the motion of control surfaces. Although you may enter and exit cumulus clouds quickly, remaining in icing conditions for short periods, the large size of water droplets in cumulus means a dangerous coating of clear ice can form extremely rapidly. This thick, hard ice is hard to remove, and may not melt or sublimate away just because you exit ice-accumulating conditions.

Mixed ice. As the name implies, mixed ice is a combination of rime and clear ice. Mixed ice usually forms in stationary fronts or occlusions, where you encounter cumulus clouds embedded in layers of stratus. Mixed ice may become dangerous quickly, like clear ice, and may be as difficult to remove.

Regardless of type, all airframe ice disrupts lift development and can create wildly unpredictable flight characteristics. It's wise to avoid all areas of potential ice formation, and to escape to ice-free air at the first sign of ice accumulation -- even if flying a "known ice" airplane.

Aero-tip of the day: Recognize the potential for ice formation, and have a preplanned escape route should ice begin to form.

FMI: Aero-Tips