VFR Winter Flying

Flying in winter time can be one of the most spectacular experiences there is. Especially in the mountains. But winter time means that we have to take special preparations to saveguard 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 multigrade 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.

Be prepared

Windchill table

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: multigrade oils can be used throughout winter. Make sure to carry an extra blanket and a windproof jacket. Windchill factor due to high winds can be really dangerous, click the table to the right for details.

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.

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 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.

Carburettor heat

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.

Freezing water

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.

Fuel system

As water freezes below zero it can block the fuel lines causing the engine to stop. Do check after refueling for water in the system, and let the fuel settle in the tanks before checking.

Electrical system

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 positive indication when the alternator is charging.
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.

Airframe

Having a clean airframe is 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.

Personal Preparation

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 survival is adequate for the number of souls in the aircraft. The ability to make a fire in the wild is important to keep warm.

Ice protection systems

A number of aircraft are equipped with ice protection systems like: pneumatic boots, de-icing fluids, propeller de-icing, windscreen de-icing and for the helicopters rotor-blade de-icing equipment.

Pneumatic boots

These rubber like tubes are attached to the leading edge of the wings, horizontal stabilizer and vertical fin. These boots are to be inflated and thus breaking the ice. But only if operated before the ice gets too thick or is still too thin, in which case the ice will form around the boot when it is extended. And this will not help at all.

De-icing fluids

In flight de-icing fluids can be used on the leading edge of the wing, propeller and other places on the aircraft. It oozes out of very small perforations in panels, these must be kept very clean to keep the system working properly. Propellers use this system too or are equipped with electrical heating to remove ice build up.

Windscreen de-icing

Usually done with heat from the exhaust of the engine. In twin engine aircraft a special combustion heater (Janitrol) is used for cabin heat. Although you will encounter de-icing systems based on electrical heating of the windshield.