LESSONS MY COMANCHE TAUGHT ME

THINKING ABOUT ICE

by "TC" Johnson

It is 7am and just getting light as I get another cup of coffee and glance at the temperature outside. Minus 8 F. Even the dog isn't anxious to stay out.
 

Last night, I cancelled the flight I was going to take today in my "Twinky", a 1964 twin Comanche. When I checked the weather, there were supposed be lingering clouds from a weak front that came through the Rocky Mountain West where I live. If this mission had been to fly a charter with the C-340 or Navajo's I occasionally fly ... no problem.  So, what's the difference?
 

First, the charter birds are equipped with boots, hot props, and deicing type wind screens. My little bird has none of those features.

Second, this was an easy trip to postpone; I'll go tomorrow where I'll be faced with some scattered clouds and very cold temps. I could have gone today, one reason being that the temperatures are quite cold.  I have flown the PA-30 through blizzards, but I do like to pick my fights with ice.
 

So, here is my thinking when I plan a winter flight: I call Flight Service or get on the web and check for temperatures, clouds, and wind.  For temperatures, I'm interested in avoiding the zero to -10 C. range where ice seems to be found. Where there are clouds and below freezing temperatures, there is always a possibility of ice.  And, finally, since I live in the mountains, I want to know where the winds are hitting the ridges and causing "lifting" of the moisture.  I've encountered unexpected ice in cloud tops for this reason, and along the mountain fronts that exist in the Rockies.  Those of you in the east may worry more than me about the northeast quadrant of a low pressure system, but for the same reasons.
 

In all of my flying, I like to have an "out" at my disposal. So, for tomorrow's flight, I'll have some clouds but with predicted ceilings that allow me to dive out of any unexpected icing into the clear. At that point I can land and scrape the ice off or, if it is light, continue VFR until it sublimates off. When faced with going into possible icing conditions, I usually climb for the coldest temperatures I can find so that I'll be flying in ice crystals instead of super-cooled drops.  If I start getting ice at those levels, I can come down, as usually a 4,000' change of altitude will get me out of the condition.

In the mountain west, we are faced with "scare-mets" talking about ice at
least 10 months of the year, so knowing exactly where you might find ice, as
opposed to safe areas, lets us fly throughout the year.  Last year, Rich Clover and I took our Comanche's to Alaska. At one point Rich was at 17,000' in ice crystals, while I was below him at 10,000' (lowest altitude available on the airway).  I was picking up a little ice at a temperature of -1, but it was sloughing off just as fast. Rich wasn't picking up enough to count.  A King-Air just above me started picking up moderate ice, but he had enough power to climb out of it.
 

When you do start picking up a "little ice", do something about it.  Get with ATC and change altitude, turn around, whatever, but be aggressive before the ice loads up.  Immediately pick up your speed as much as possible, this gets the nose a bit further down as the attitude of the airplane flattens out and you build up energy for a potential climb. An inch or more of ice is dangerous and, if need be, it can constitute an emergency. Declare an emergency if you need to get ATC's attention and worry about the paper work later in a nice warm office.  If you are landing with ice on your bird, keep your speed up and land without flaps.

A few weeks ago I stalled in a Cessna 340 at between 110 and 120 knots indicated, but was only a few inches off the runway. I had a little over 2" of double horn ice on the leading edges and 3" the vertical stabilizer, so I flew the ILS clean at 140 knots due to ice making all those nice markings on the airspeed indicator worthless.
 

Another trick to keep up your sleeve is the "VFR on Top" option. This doesn't mean you have to be on top of all the clouds.  You can be between layers or underneath, but all the VFR rules apply including 500' increments of altitude for direction of flight. Last week I was coming into Rock Springs, Wyoming, when I heard a pirep from a jet-prop airliner, reporting moderate ice on descent into Rock Springs. I checked the ceilings and they were 3000' or so agl in the area, but below the airway system. I converted my IFR flight plan with center to VFR on Top when I came to a hole a hundred miles NE of KRKS and dropped below the airways and minimum vectoring altitudes--but in VFR--and went into KRKS with no problem.

An hour or so previously, a V-tail Bonanza, which is is known to be a poor ice carrier, had taken off from KRKS on an eastbound IFR and climbed into the clag.  It iced up and killed all aboard.

Our Comanches are also poor ice carriers; but, in spite of their clean laminar flow wing, they are fairly forgiving, although not as forgiving as the fat "hershey bar" winged airplanes such as the Aztec."

So, I've learned you don't need to let winter weather get you down.  Get a briefing on ice, plan your flight with options, and be ready to take evasive action.

By the way, there is one exception.  Nothing I have ever flown goes out in freezing rain, and that is everything up to and including the Boeing 747. FAA approved operation manuals for charter operators and air carriers do not allow flight into freezing rain no matter how much deicing and anti-icing the plane has, and we should adhere to the same rules with our Comanches.  I certainly do.

"TC" Johnson, born in 1938, began his aviation career with the USAF as an instructor in navigation and electronics warfare.  He took his first pilot lesson in 1966 and soloed after four hours.  Ten months and some 700 hours later he was hired by Pan Am, got his MEL in the Boeing 707 and earned his ATR in the 747.   He spent 25 years with Pan Am, and nine more years with Delta, flying various Boeings and the Airbus. Retired now after 25,000 hours in airline cockpits, "TC" owns a Twin Comanche, and is Chief Pilot for Star West Aviation at Evanston, WY.