TIPS ON WINTER FLYING (PART 1)
Acknowledgements: Don Hankwitz, Airport Operations Specialist
(Ed. Note: Winter is upon us again in the Northern hemisphere, so a few reminders …… )
Most pilots are familiar with winter conditions in their particular area. However, often a distance of a few miles may change the environment enough to present new problems to an inexperienced pilot. There are certain precautions that are significant to winter flying:
Flight planning during winter months will require special knowledge to protect the aircraft as well as the pilot. Extra precautions should be taken. Often roads that are well travelled during the summer months will be abandoned in the winter. To be forced down far from civilisation may create a serious problem of survival. With today's extensive highway system, most flights in small aircraft would not be extended more than a few minutes if a well -travelled route was followed. Even the vehicles on the road can give valuable information. You may see cars and trucks coming toward you with fresh snow adhering to the front of the vehicles. In most cases, you may as well start making a 180-degree turn due to reduced visibility ahead.
· File a flight plan. A flight plan, in conjunction with an ELT, and a little knowledge on winter survival may save your life. Experience has shown that the advice of operators located in the area where the operation is contemplated is invaluable, since they are able to judge requirements and limitations for operation in their area.
· In making appointments, always give yourself an out by informing your contact that you intend to fly and will arrive at a certain time, unless the weather conditions are unfavourable. You, the pilot, have complete responsibility for the GO/NO-GO decision based on the best information available. Do not let compulsion take the place of good judgment.
OPERATION OF AIRCRAFT
The thoroughness of a pre-flight inspection is important in temperature extremes. It is natural to hurry over the pre-flight of the aircraft and equipment but this is the time you should do your best pre-flight inspection.
Fuel Contamination - Fuel contamination is always a possibility in cold climates. Even with the best of fuel and precautions, if your aircraft has been warm and then is parked with half empty tanks in the cold, the possibility of condensation of water in the tanks exists.
Fuelling Facilities - Fuel drums, even if refinery sealed, can contain contaminants. Cases are on record of fuel being delivered from unidentified containers which was not aviation fuel. As a precaution, we suggest:
• Where possible, fuel from pumped sources fitted with filters; otherwise, filter it manually. NOTE: A funnel with a dirty worn out chamois skin, or a new one which is wet with water, is not a filter, and many filters are available which are more effective.
· Fill your tanks as soon as possible after landing, and drain fuel sumps to remove any water which may have been introduced.
• Be sure the fuel being delivered is, in fact, aviation fuel and is the correct grade (octane) for your engine.
Aircraft Fuel Filters and Sumps - Fuel filters and sumps (including each tank sump) should be equipped with quick-drains.
· Sufficient fuel should be drawn off into a transparent container to see if the fuel is free of contaminants. Experienced operators place the aircraft in level flight position, and the fuel is allowed to settle before sumps and filters are drained.
· All fuel sumps on the aircraft are drained including individual tank sumps.
· Extra care should be taken during changes in temperature, particularly when it nears the freezing level. Ice may be in the tanks which may turn to water when the temperature rises, and may filter down into the carburettor causing engine failure. During freeze-up, water can freeze in lines and filters causing stoppage. If fuel does not drain freely from sumps, this would indicate a line or sump is obstructed by sediment or ice. There are approved anti - ice additives that may be used.
· Where aircraft fuel tanks do not have quick-drains installed, it is advisable to drain a substantial amount (1 quart or more) of fuel
Aircraft Preheat - Low temperatures can change the viscosity of engine oil, batteries can lose a high percentage of their effectiveness, instruments can stick, and warning lights, when "pushed to test," can stick in the pushed position. Because of the above, preheat of engines as well as cockpit before starting is considered advisable. The following precautions are recommended:
• Preheat the aircraft in a heated hangar, if possible.
• Use only heaters that are in good condition and do not fuel the heater while it is running.
• During the heating process, do not leave the aircraft unattended. Keep a fire extinguisher handy for the attendant.
• Do not place heat ducting so it will blow hot air directly on parts of the aircraft; such as, upholstery, canvas engine covers, flexible fuel, oil and hydraulic lines or other items that may cause fires.
Engine Starts - 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 the 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. This results in poor compression and harder starting. Sometimes aircraft fires have been started by over prime, when the engine fires and the exhaust system contains raw fuel. Other fires are caused by backfires through the carburettor. It is good practice to have a fireguard handy 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 carburettor heat may assist in fuel vaporization until the engine obtains sufficient heat.
Radios - Should not be tuned prior to starting. Radios should be turned on after the aircraft electrical power is stabilized, be allowed to warm - up for a few minutes and then be tuned to the desired frequency.
Removal of Ice, Snow, and Frost - A common winter accident is trying to take off with frost on the wing surface. All frost, snow, and ice should be removed before attempting flight.
· It is best to place the aircraft in a heated hangar. If so, make sure the water does not run into the control surface hinges or crevices and freeze when the aircraft is taken outside.
· Don't count on the snow blowing off on the take-off roll. There is often frost adhering to the wing surface below the snow. Alcohol or one of the ice removal compounds can be used.
· Caution should be used if an aircraft is taken from a heated hangar and allowed to sit outside for an extended length of time when it is snowing. The falling snow may melt on contact with the aircraft surfaces and then refreeze. It may look like freshly fallen snow but it usually will not blow away when the aircraft takes off.
Blowing Snow - If an aircraft is parked in an area of blowing snow, special attention should be given to openings in the aircraft where snow can enter, freeze solid, and obstruct operation. These openings should be free of snow and ice before flight. Some of these areas are as follows:
• Pitot Tubes
• Heater intakes
• Carburettor intakes
• Anti torque and elevator controls
• Main wheel and tail wheel wells, where snow can freeze around elevator and rudder controls.
Fuel Vents - 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.
Taxiing - A pilot should keep in mind that braking action on ice or snow is generally poor.
· Short turns and quick stops should be avoided.
· Do not taxi through small snowdrifts or snow banks along the edge of the runway. Often there is solid ice under the snow.
· If it is necessary to taxi downwind and the wind is strong, get help or don't go. Remember, if you are operating on skis, you have no brakes and no traction in a crosswind.
PART 2 FOLLOWS……