General Aviation
Accident Prevention Program
U.S. Department of Transportation
Federal Aviation Administration
Tips On Winter Flying
FAA - P - 8740-24
AFS - 800 0879
Takeoffs in cold weather offer some distinct advantages, but they also offer some
special problems. A few points to remember are as follows:
- Do not overboost supercharged engines. This is easy to do because at very low
density altitude, the engine "thinks" it is operating as much as 8,000 feet
below sea level in certain situations. Care should be exercised in operating
normally aspirated engines. Power output increases at about 1% for each ten
degrees of temperature below that of standard air. At -40°F an engine will
develop 10% more than rated power even though RPM and MP limits are not exceeded.
- If the temperature rises, do not expect the same performance from your aircraft as when
it was operated at the lower density altitudes of cold weather.
- 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.
If your aircraft is equipped with a heated pitot tube, turn it on prior to
takeoff. It is wise to anticipate the loss of an airspeed indicator or most any
other instrument during a cold weather takeoff - especially if the cabin section has not
been preheated.
Climbout - During climbout, keep a close watch on head temperature
gauges. Due to restrictions (baffles) to cooling air flow installed for cold
weather operation and the possibility of extreme temperature inversions, it is possible to
overheat the engine at normal climb speeds. If the head temperature nears the
critical stage, increase the airspeed or open the cowl flaps or both.