Taking precautions against icy weather a must

Safety First

Posted: Wednesday, October 18, 2000

It's October already can you believe it? It seems that we didn't have much of a summer this year. Aviation, whether for pleasure or business, depends on good weather for a successful flying season.

With the advent of October comes the first portent of winter here in Southeast Alaska. Mornings tend to be cold and crisp with layers of fog forming over water and settling in low points around the area.

I live in the valley out near the glacier. The middle of September there was a layer of ice, due to fog, on the car and the porch. If there is ice on my car I know that aircraft must have had ice on their wings in early morning. Soon pilots will be re-experiencing the joy of ice removal from their aircraft.

Frost and a layer of ice on the surfaces of an aircraft, even a small accumulation, can cause a significant loss of lift. During flight an accumulation of ice decreases lift, increases weight and drag. Ice on an airfoil changes the shape of the surface. A small change can result in the need to hold a higher angle of attack in order to maintain lift. If the shape of the wing is disturbed too much you won't have to worry about maintaining lift. You will never get off the ground in the first place.

If you are fortunate, or unfortunate, enough to get off the ground with a load of ice, controlling the aircraft could be quite interesting. As weight increases, due to ice or frost (yes frost has weight too), the stall speed of the aircraft increases. So there is a triple whammy here. An increase in angle of attack, to maintain lift, an increase in weight and a loss of laminar flow across the wing, all add up to an accident waiting to happen.

While the removal of ice and frost from the wings and tail of the aircraft is imperative for safe flight, obviously the rest of the airplane needs attention also. If ice accumulates while the aircraft is parked on the ramp it would seem prudent to remove all of the ice and not just the accumulation on the wings and tail.

Ice removal can be achieved by using chemical ice removers or even water. If water is used it is important to see to it that every trace of water is removed from the wings and tail assembly. If water is allowed to remain on these surfaces, even small in amounts, it could trickle back in flight and freeze on the hinges. If the hinges freeze it would be near to impossible to break the ice free in flight.

All of this brings to mind a situation that I heard of a couple of years ago. I spoke to a pilot on the phone who was flying a twin engine aircraft from Anchorage to Seattle. While enroute he encountered icing conditions at altitude. The aircraft was not anti-ice or de-ice equipped. The pilot had to make a landing in Yakutat because he was forming a load of ice on the aircraft wings. The pilot found out after he landed that ice had formed on the tail and belly of the aircraft and that there were blocks of ice inside the engine nacelles also.

I thought that it was strange because the engine nacelles were the warmest place on the aircraft. The pilot assured me that there were blocks of ice that fell out on the ground when he opened the cowling on each engine. Stranger things have happened I suppose. That was one lucky pilot.

Plan to keep your aircraft in a dry hangar or cover it to prevent ice buildup. Be sure that you remove all ice and water, during freezing cold days, to prevent ice from forming.

Remember this fall and winter to be aware of the possibility of icing on your aircraft both before you take off and while in the air. Unless your aircraft is equipped for known icing, don't take chances.

Patricia Mattison is the Safety Program Manager for the Juneau Flight Standards office of the Federal Aviation Administration.



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