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Members of the AFC Pilot Safety Committee will regularly submit informational articles beginning in 2011 to encourage and promote the highest levels of safety within the AFC Pilot community. Enjoy!
Wheels Up for Safety at AFC - Winter Flying, January 2011
Now that the temperature has turned cold and all 49 states have snow on the ground (as of this writing - Florida has no snow, Hawaii has some in the mountain peaks) we need to be thinking about how this effects us as pilots, the planes that we fly and our passengers.
Lead Acid batteries are sensitive to cold temperatures. Have them serviced before the cold weather sets in. Consider keeping the battery on a trickle charger if you are in a hangar.
Aircraft with oil coolers will bypass the cooler when the engine and oil are cold. Single grade oils will thicken in colder temperatures where multigrade oil is formulated to operate in a wide range of temperatures. Most multi grade oils are formulated for wide temperature ranges. If you are using a single grade oil make sure it is appropriate for the temperatures you are operating in.
Check for tire wear as worn tread is an invitation to hydroplaning you should replace Tires if necessary. If the aircraft has wheel pants you might want to think about removing them for winter operations. Wheel pants can collect snow and ice up inside them, if they freeze up the wheels when you go to land you might be in for some excitement as the frozen tire may not spin upon touchdown. An entry should be made in the aircraft records by your A&P if you remove the wheel pants.
Open areas of an unfilled fuel tank can allow surfaces for condensation to occur followed by that moisture becoming solid ice in our tank. Consider keeping the tanks full during the winter months.
Air inlet openings designed for cooling are susceptible to snow accumulation in blowing snow storms. These should be checked thoughly during your preflight. Oil coolers, Engine cooling, Instrument cooling, Cabin ventilation and make sure the Pitot tube and static openings are not covered by frozen precipitation.
We certainly want to ensure that the cabin heating system is working correctly. If exhaust fumes are allowed to enter the cabin we could be exposed to an unacceptable amount of Carbon Dioxide. Carbon Dioxide poisoning can incapacitate and kill. If we haven’t used the cabin heater since last March, it might be a good time to have a mechanic take a look at it. Most small aircraft heaters consist of a cuff surrounding an exhaust pipe. An exhaust leak fills the cabin with carbon monoxide. A simple monoxide detector is a cheap piece of protection.
Preheating is recommended if temperatures drop below 20º F. Preheating the cabin as well as the engine, will allow gyros to spin-up with less wear and tear. Preheating the battery will allow for easier starts. I’ve found that a $20 ceramic heater placed in the cabin overnight really warms it up and you and your passengers will be more comfortable.
Preparing yourself and passengers
It is recommended and good practice to wear multiple layers of loose fitting clothing because the air between layers provide additional insulation. However, be careful loose clothing is more likely to snag on aircraft structures and components.
Carry a warm hat and gloves in the plane, preferably in your pockets. I also carry a couple of blankets that are kept folded up under the rear seats. If a passengers gets cold or has not adequately dressed they can use the blanket.
Remove any snow or ice from clothing before entering cockpit. Melting snow in a warm cockpit may run down into controls or components and later refreeze.
Maintain body temperature below perspiration level. Perspiration reduces clothing’s insulation qualities. If an emergency landing is necessary, you may only have what you are wearing. Dress to survive.
I always make it a point to tell my passengers that Winter flying can be difficult due to the weather. When I first contact my passengers I make sure they understand this and that we will not be flying in the snow and ice.
Conducting the flight
If you are an IFR rated pilot that is current I suggest filing an IFR flight plan, that way you are always in contact with ATC in case you need them in the event of an emergency. If you are a VFR pilot then I recommend filing a flight plan and using flight following when available. This may be a major factor in your survival in cold weather.
Depending on where you fly in the country it might make sense to stay close to roads in case you have to put down. I had an Angel Flight a few months ago that took me over northern Nebraska and I really got to thinking about what I would do if I had an emergency landing. It’s very desolate out there and although I would have had a successful off airport landing (It’s really flat out there) there was no civilization for many miles and getting picked up by someone could take a long time. I also wondered if there was any kind of cell phone access in the areas I was flying over.
Types of Ice
Clear ice - The formation of a layer of hard, smooth, glossy ice. It is relatively transparent or translucent. Clear ice is heavy and difficult to remove.
Rime ice - The formation of a white or milky and opaque granular deposit of ice. Rime ice is the most common type of icing.
Mixed ice - A combination of clear ice and rime ice.
Frost – Forms on the top of wings, stabilizers and windshields.
SLD – Super cooled cloud droplets freeze instantly and are larger than 50 microns.
Temperatures for ice formation –
Clear: 0 to -5 C
Clear or Mixed: -5 to -10 C
Mixed or Rime: -10 to -15 C
Rime: -15 to -20 C
The possibility of icing occurs as temperatures reach just below zero. At just below zero, there is the highest threat of severe icing. As temperatures continue to become colder, the threat diminished. The types of icing fall between different temperatures. The best place for ice formation is in the tops of clouds.
Frost forms on the tops of wings because the air is cooler above the wing than below. There is radiant heat from the ground rising thus warming the bottom of the wing. Frost does not change the basic aerodynamic shape of the wing, but the roughness (think sandpaper) of its surface spoils the smooth flow of air thus causing a slowing of the airflow. This slowing of the air causes early air flow separation over the affected airfoil resulting in a loss of lift. A heavy coat of hard frost will cause a 5 to 10 percent increase in stall speed. Even a small amount of frost on airfoils may prevent an aircraft from becoming airborne at normal takeoff speed. Also possible is that, once airborne, an aircraft could have insufficient margin of airspeed above stall so that moderate gusts or turning flight could produce incipient or complete stalling. It is important to remove frost from the wings and tail before flying.
Remember that winter operations require greater vigilance and pilot proficiency. “A Superior pilot is one who uses Superior Judgment to avoid situations that require Superior skill.”
AOPA has a free online webinar titled “Cold Weather ops”, it is free to view and worth watching. http://www.aopa.org/asf/webinars/. Elsewhere in the newsletter are some useful links to publications and training material by the FAA and AOPA.
If you have any questions or comments please feel free to send me an e-mail at email@example.com
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