Published in Midwest Flyer – December 2017/January 2018 issue
EDITOR’S NOTE: Here are a few tips taken directly from the FAA’s General Aviation Accident Prevention Program guide: TIPS ON WINTER FLYING, FAA-P-8740-24, AFS-800 0879
Winter flying in most parts of the United States can adversely affect flight operations. Poor weather conditions with fast moving fronts, strong and gusty winds, blowing and drifting snow, and icing conditions are just part of the conditions that require careful planning in order to minimize their effects. Operation in this environment requires special winter operating procedures.
These pages are designed to refresh the pilot’s memory in cold weather operations. Pilots should assure themselves that they have obtained adequate cold weather knowledge appropriate to the aircraft used, and the geographical and weather environment. Winter flying is not particularly hazardous if the pilot will use a little extra caution and exercise good judgment in analyzing weather situations.
The material presented here has been taken from many discussions of winter flying techniques with highly qualified pilots in various parts of the United States. The experience gained in accident investigations has also been included in this guide.
Core of Batteries
Wet cell batteries require some special consideration during cold weather. It is recommended that they be kept fully charged or removed from the aircraft when parked outside to prevent loss of power caused by cold temperatures and the possibility of freezing.
Be sure to follow the manufacturer’s procedures.
In moderately cold weather, engines are sometimes started without preheat. Particular care is recommended during this type of start. Oil is partially congealed and turning engines is difficult for the starter or by hand.
There is a tendency to over-prime which results in washed-down cylinder walls and possible scouring of the walls. This also results in poor compression and, consequently, harder starting. Sometimes aircraft fires have been started by over-priming, when the engine fires (ignites) and the exhaust system contains raw fuel. Other fires are caused by backfires through the carburetor. It is good practice to have a fireguard (someone with a fire extinguisher or fire blanket) standing by during these starts.
Another cold start problem that plagues an un-preheated engine is icing over the spark plug electrodes. This happens when an engine only fires a few revolutions and then quits.
There has been sufficient combustion to cause some water in the cylinders, but insufficient combustion to heat them up. This little bit of water condenses on the spark plug electrodes, freezes to ice, and shorts them out. The only remedy is heat. When no large heat source is available, the plugs are removed from the engine and heated to the point where no more moisture is present.
Engines can quit during prolonged idling because sufficient heat is not produced to keep the plugs from fouling out. Engines which quit under these circumstances are frequently found to have iced-over plugs.
After the engine starts, use of carburetor heat may assist in fuel vaporization until the engine obtains sufficient heat. Use carburetor heat as required. In some cases, it is necessary to use heat to vaporize the fuel. Gasoline does not vaporize readily at very cold temperatures. Do not use carburetor heat in such a manner that it raises the mixture temperature barely to freezing or just a little below. In such cases, it may be inducing carburetor icing. An accurate mixture temperature gauge is a good investment for cold weather operation. It may be best to use carburetor heat on takeoff in very cold weather in extreme cases.
Fuel tank vents should be checked before each flight. A vent plugged by ice or snow can cause engine stoppage, collapse of the tank, and possibly very expensive damage.
The guide is filled with good information that every aviator should be familiar with and utilize. You can download the entire guide from: https://www.faasafety.gov/gslac/alc/libview_normal.aspx?id=10520 or https://www.aopa.org/training-and-safety/pic-archive/operations/winter-flying-(2).
Please plan ahead and be winter-wise when you fly!