Cold-Weather Flying, Part 2

Tuesday, February 13, 2018

Matt Gabbard, CFII, Ferry Pilot

Matt has been flying for over two decades and has extensive knowledge of different aircraft and avionics, he is a talented photographer and enjoys traveling, history and astronomy. 

Quote to live by: "Whatever you are, be a good one." ~ Abraham Lincoln


From my Desk to the Sky... Cold-Weather Flying, Part 2

In the last post, we discussed preparing for flying in the winter time, both for pilot and aircraft. In this blog, I’d like to remind the reader of some of the hazards associated with winter weather flying, including a few close calls I experienced. Hopefully you will be able to glean some bits of useful information so that you will avoid finding yourself in a similar situation.

I’ll start with the most obvious of winter weather hazards: ice.

Airframe icing should be treated the same as thunderstorms – we should avoid it if possible.

It is true that pilots have flown in convective activity and lived to tell about it, and the same can be said for flying into icing conditions. But I would imagine that in both scenarios, the pilot would like to never again repeat the experience. So how do we stay away from ice?

A good study of the big weather picture is a great start. I begin by looking for the locations of fronts and low pressure systems on a weather map (http://aviationweather.gov/progchart/sfc).  Then I’ll look at the freezing levels and cloud tops (http://aviationweather.gov/icing). Since the new Graphical Forecast for Aviation (http://aviationweather.gov/gfa) came out last fall, replacing the Area Forecast, cloud tops forecasts can be a little lacking. If possible, see if there are any pilot reports (PIREPs). I can usually look out the window and sort of tell if the overcast layer above is somewhat thin, and seeing what the PIREPs say can confirm this (if they are saying the tops are relatively low). PIREPs are also useful for seeing if there is actual icing occurring.

But be aware - no PIREPs doesn’t necessarily mean no icing. There just may not be anybody dumb enough to be flying at that particular place and time!

The type and reporter of a PIREP should also elicit a second look. What I mean by this is simple: if a 737 going 300 knots is picking up moderate ice, how much ice will our little piston single or twin going 150 knots (or less) pick up? PIREPs are great, but it’s all relative.

Once you’ve found where the freezing level is, the next thing to do is see if you will be flying in visible moisture, and if the temperature will be anywhere close to freezing at your altitude. Where are the fronts near your route? What are the bases and tops of the clouds?

Know this information and keep a close eye out for escape routes, including 1) warm air; 2) clear air on top; 3) VFR conditions.

I also like to look at the surface temperatures and dew points. This helps to see how moist or dry the air is at the surface, and comparing your departure point and destination will give you an idea of a trend.

Another weather product I look at is the winds aloft (http://aviationweather.gov/windtemp), but only partly because of the wind. This page will give you three main types of forecasts and observations: an interactive map featuring winds and temperature plots; a winds/temps plots map that features a map with selectable altitudes and a drop-down box with wind speed, temperature, temperature difference and wind streamlines; and finally a winds/temps data map, selectable by the user for the various winds aloft forecasting stations. If you can’t get a good picture of the forecast temperature (and wind info) at your cruising altitude from this page, I’m not sure you can find it anywhere.

As with any forecast, we should take it with a grain of salt, and always keep an eye on the actual conditions as we’re flying. Providing PIREPs of our own will help other pilots and the whole forecasting process in general.

While general aircraft icing from exposure to visible moisture and below freezing temperatures is a very bad thing, it becomes worse when the ice forms due to freezing rain or drizzle. This happens when liquid precipitation falls from warmer air through a temperature inversion into colder air below. I have one experience with this phenomenon, and hopefully that’s all I’ll have in my flying career.

My mission was to take an airplane to its buyer in southwest Ohio, but first I was to drop off two of our mechanics/pilots in the Cincinnati area in order for them to inspect and bring home an aircraft we were purchasing. The weather wasn’t great as we departed, with rain and marginal VFR conditions prevailing.

The big weather picture showed that a warm front was moving through from west to east, and the temperature at our cruising altitude was well above freezing.

Although we weren’t able to maintain VFR and had to obtain an IFR clearance for the rest of the flight, we landed at our first stop with pretty good weather and no other issue. I checked the weather again before departing, concluding that I would be able to maintain VFR for the 75 nautical mile or so trip to my final destination. The ceilings were high enough, although there would be some rain showers to circumvent. As I proceeded eastbound at around 3500 feet, I realized that my windshield was receiving some ice.

I was still in good VFR conditions, but the glazing over of the windshield became worse as time went on. There was also a noticeable buildup of some ice on the wings.

I proceeded with the defrost on full blast, but the situation became worse and with only 10-15 miles remaining, I couldn’t see ahead of me at all. Remembering that warmer air was above and behind me, I did a 180 degree turn and began to climb. Almost immediately the ice began to liquify and streak off the windshield, slowly clearing. I climbed to about 4300 feet and headed toward an airport I had passed that was about halfway to my destination. With some ice still on the wings, I landed safely and waited for the warmer air to move further east. I was able to put the airplane in a hangar to thaw out while I borrowed the courtesy car to go to town for some lunch (and nerve settling). In only an hour and a half, the warm air had permeated the whole region and I was able to complete my mission.

The moral of that story is don’t assume that just because the conditions are VFR that you will not be affected by some sort of freezing precipitation.

This was the only time I have encountered freezing rain, and the only time I can remember of picking up airframe ice outside of clouds. If I had continued and tried to land with such limited forward visibility, I probably wouldn’t have been successful. And there was a real temptation to attempt to land because I was so close to my destination. I’m glad I turned around.

Finally, while flying in the winter can be rewarding with crisp, beautiful skies, excellent visibility and increased aircraft performance, we need to make sure that our takeoff and landing surfaces are safe to operate on.

After it snows in your area, or more importantly, at your destination, take the time to find out if the runways you intend to use are contaminated by that, or any other precipitation.

Just recently I was taking another airplane to (ironically) the same airport in southwest Ohio, and I had to delay my departure a day because the runway conditions were unsafe. The airport’s snow plow had broken down after an initial plowing, and while that helped, it wasn’t enough to remove all the snow and ice. Even on the next day when I finally arrived there, the runway was still completely covered. I reminded myself to take my time and employ the soft-field landing technique. Thankfully the winds were calm and the landing and ensuing soft-field takeoff were uneventful.

Don’t neglect to call the FBO at your destination and ask about the conditions. You’ll be in for a surprise if you reach your destination and find you can’t land.

Flying in the winter can be rewarding, but it can be just as challenging and dangerous. If you really take the time to prepare yourself and your aircraft, and do a very detailed weather study for the day of your flight, you will be successful. But ignoring forecasted adverse conditions and being overconfident can get you in trouble quickly. Take your time, do your homework and be cautious. If you do these things, there is no reason you can’t safely fly during the winter months, and enjoy doing so.