VFR Winter Flying
Flying during the winter season can be one of the most spectacular experiences there is. Especially so in mountain areas when everything is white capped.
But winter time means that we have to take special preparations to safeguard ourselves and the aircraft from the cold, so that flying remains fun even in the cold season and does not become a life threatening situation.
The aircraft engine needs to be prepared for the colder season, a possible oil change to multi-grade and or a winterization kit to deflect the cold air and keep the cylinders warm. Cabin heat systems will need to be checked for proper operation.
Anti- or deicing systems must be fully checked and operational as the chance of encountering lower freezing levels with enough moisture becomes more likely during winter.
Prepare the aircraft before the onset of winter so its ready to go when you are. In this space we learn how to cope with winter and the effects it has on the pilot, passengers and aircraft.
Before the start of winter, preferably late autumn, reread the aircraft flight manual and in particular the sections on winterization. An oil change could be needed for your engine, remember: multi-grade oils can be used throughout the year. Make sure to carry an extra blanket and a windproof jacket. Wind chill factor due to wind can be really high, see below for details (Limits: minimum temp (OAT) greater than 50 °F (10 °C), wind speeds greater than 4 mph (3.5 kts)).
Wind chill table
Heating and Defrost
Aircraft heating systems in light aircraft are based on the exhaust over which cold air is blown and then fed into the cabin. CO (carbon monoxide) poisoning is a possibility when cracks are present in the exhaust. Renew the CO detector annually especially before the start of winter and have the system checked for any cracks. During preflight do look at the exhaust and comply with FAA SAIB CE-10-33 exhaust inspections.
Getting into the aircraft with damp clothes will result in fogged-up windows on the inside. Sort of IFR flying when the defrost system isn't working properly. Dangerous. Open some form of ventilation, even the frigid cold air will clear the windshield.
If your aircraft is equipped with a heated pitot, make sure it works. Switch it on and the pitot tube should be warm within 30 seconds, then turn it off again.
Induction icing can occur throughout the year depending on the temperature and moisture content of the air. Carb heat and alternate air inlet should be checked during maintenance and every flight just before take off. Any problems must be fixed.
When water freezes it will expand. Pitot tubes with standing water will get blocked, can rupture and the pitot static system will not work properly. Standing water in flaps, ailerons and or elevators can freeze and create an imbalance and even flight control problems possibly resulting in a possible stall/spin event. Make sure that any drain hole is clear from any dirt or debris.
As water freezes below zero it can block the fuel lines causing the engine to stop running. Do check after refueling for water in the system, and let the fuel settle in the tanks after refueling before checking.
Batteries lose much of their power below freezing point (0 °C), they can even freeze up and be damaged. Having a fully charged battery is essential for winter operations. Have the alternator checked as well, as this is the component which charges the battery during flight. The ammeter must show a slight positive indication when the alternator is charging normally.
When flying in extremely cold weather removing the battery (and sometimes the oil when the engine is still warm) after the flight for storage inside, can help operations the next day. Using a battery charger to keep the battery in optimum condition assures that the engine can be started.
CTEK Sweden AB sells dedicated computerized lead battery chargers which can be left on the battery 24/7 keeping it in perfect condition. This piece of equipment is worthwhile to invest in!
Make sure the clean airframe is clean, more so important in the winter. Mud, slush and dirt can build up in wheel pants, elevator hinges, block brake operation and when frozen can hinder proper operation of the aircraft or endanger it. Putting the aircraft in a hanger during winter time is the best protection. If this is not possible then the option of covers should be contemplated. And it saves a lot of work cleaning the aircraft from any snow and frost before the flight.
Preparing yourself, and the passengers, is as important as preparing the aircraft. Warm clothing and isolating footwear is essential. A winter survival kit on board the aircraft is almost mandatory, make sure that the equipment is adequate for the number of souls in the aircraft. The ability to make a fire in the wild is important to keep warm. Think about a bush pilot course coupled with survival training, the experience you pick up from that is tremendous.