Learning when to heed weather warnings

Safety first

Posted: Wednesday, January 12, 2000

Well, we're still here. The predicted end of life on earth (as we know it) didn't occur. Those of us who were fearful of the dreaded Y2K bug are still surfing the Web at warp speed. Now we all can get back to business as usual.

Business as usual means different things to different folks. To me it means to pick up the aviation banner and march forth to do battle in the safety arena.

January is a month of snow, sleet, ice and other assorted bad weather. Occasionally there is a rare clear day that tantalizes even the most recalcitrant pilot to fly away winter boredom. Weather being what it is here in Southeast, a beautiful clear day can quickly change to cloudy skies followed closely by snow and low visibility.

A reduction in visibility can happen rapidly or slowly and insidiously. A rapid reduction in visibility usually can be handled by a 180 degree turn to return to the departure airport. Slowly deteriorating visibility is the most hazardous. Thinking that visibility will improve as the flight progresses, the pilot continues to fly on towards the intended destination. Expecting to see an improvement a pilot may continue until all hope of a course reversal is lost.

Flight into low visibility often results in a Controlled Flight Into Terrain, or CFIT. Whiteout conditions and flat light are two of the largest contributors to this type of accident. Other restrictions to visibility are rain showers, low clouds, fog, and in other parts of the world blowing sand and dust.

Low visibility and the threat of bad weather doesn't seem to deter some pilots. Just the other day I was looking out of my dining room window when I heard an approaching airplane. I couldn't see it, due to clouds and snow, but it was there nonetheless. It is possible that visibility was better at altitude than it was from my earthbound house, but I somehow doubt it.

Poor visibility is only one weather problem to conquer. Another potential problem is icing. Small airplanes don't deal well with ice accumulation, even in seemingly insignificant quantities. Once the airfoil leading edge is covered with even a thin layer of ice lift is lost.

Rime ice is particularly hazardous. It forms rapidly and causes an airfoil to change shape and lose lift. Clear ice is difficult to see. It is virtually transparent and flows back on the leading edges and form a clear glaze over the aircraft structure that is difficult to remove.

I once had an experience with unforecast icing in the clouds on an instrument flight. There was a rapid accumulation of a combination of rime and clear ice on the Cessna 172 I was flying, at an altitude 10,000 ft. The plane began to descend, whether I wanted it to or not, due to lack of lift, to 7,000 feet, where it was warmer and the ice was able to break off. Only then was I able to maintain altitude. Fortunately the terrain was at about 6,000ft. If icing had occurred in an area where there were really high mountains I would have had a distinct problem. I could have been a statistic!

The best thing to do is to get the most thorough weather briefing possible and then take a good look for yourself. If you have even the smallest doubt as to the safe outcome of a flight, put it off. Delay until you have a good weather outlook and you feel confident about taking that flight. A Happy and Safe 2000 to all my readers.

Patricia Mattison is the safety program manager for the Juneau Flight Standards district office of the Federal Aviation Administration.



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