Winter weather: opportunities and risks
Winter high-pressure systems often ensure calm air, broad visibility and stable stratification. At the same time, low-pressure areas and frontal systems hold meteorological surprises in store. The special attraction of a winter flight lies in the interplay of clear air and snow-covered landscape, but it is precisely this effect that presents pilots with new challenges.
While local updrafts, thermals and showers dominate in summer, other parameters are decisive in winter:
- Snow showers instead of rain showers, often with sudden loss of visibility
- Supercooled precipitation as an immediate risk of icing
- Low temperatures that affect the aircraft structure and engine
- Short day lengths with appropriate scheduling
Icing plays the biggest role here. Supercooled rain leads to clear ice, which lies smoothly over the outer skin and affects performance and controllability. Layered clouds, on the other hand, produce rough ice, which grows particularly critically on the leading edges of the wings and tail unit and radically changes the aerodynamic behaviour. Decreasing lift, increasing stall speed and changed load conditions are typical consequences.
Careful flight preparation in winter
In winter, meteorological flight preparation always includes an assessment of the probability of icing, frontal dynamics and alternative options. Users of VFR flights must increasingly expect that a flight destination cannot be reached. The following therefore applies:
- Consider alternative locations
- Calculate fuel reserves generously
- Planning daylight windows
- Carry emergency winter equipment
- Observe personal minima
Emergency equipment includes warm clothing, gloves, hat, blanket, headlamp, drink, mobile phone, power bank and means of determining your position. Landing outside in sub-zero temperatures without equipment can endanger life and limb.
The machine in winter: De-icing and care
In winter, an aircraft must be completely free of snow, ice and frost before take-off. Even the thinnest layers of hoar frost reduce lift, increase drag and accelerate stalling. The outer skin of an aircraft behaves differently to a car - air flows through every surface and contributes to the overall performance. Particularly affected are
- Wings and tail units
- Control surfaces
- Propeller
- Pitot and dynamic pressure system
- Running gear and rudder forces
Soft brooms, towelling cloths or - if sufficiently sensitive - special liquids are suitable for de-icing. Ice scrapers, on the other hand, can damage painted surfaces or glazing. TKS liquid from a spray bottle works reliably and at the same time protects against new infestation.
If you have access to a heated hangar, you save time and materials. Alternatively, the morning sun can defrost the machine, but this requires additional time.
Before take-off: engine, battery and propeller
Winter operation puts a strain on the engine. Thick oil, cold bearings and weak batteries make starting difficult. At temperatures below around minus six degrees, engine preheating is recommended. Blowers or heater inserts that channel warm air into the engine compartment are ideal for this.
Before starting the engine:
- Keep propeller area clear
- Select a surface that is free of snow and ice
- Remove loose objects and pieces of ice
- Check battery or store in a warm place
With deeply discharged batteries, there is a risk that electrical systems will not be sufficiently supplied with power after starting, even if the engine is running. A winter-maintained battery that is removed and stored warm during longer periods of inactivity prevents such problems.
Rolling and starting: Slippery surfaces and longer distances
Movement caution is the top priority on snow-covered or icy taxiways. Brakes can cause lateral loss of grip, especially on low-wing aircraft with low ground clearance. The following applies when taxiing:
- little braking, keep speed low
- Avoid snow accumulations
- Search for an even track
Ground friction comes into play at the start. Take-off distances change significantly depending on the surface. If no specific values are given in the flight manual, rules of thumb can help: Powder snow, wet snow or slush can increase take-off roll distances by 25 to 50 per cent. At the same time, the maximum possible crosswind component decreases considerably - on ice sometimes to only a third of the normal value.
Icing in flight: engine, airframe and propeller
The engine often follows before the airframe ices up. Carburettor icing can already occur at just above freezing point, as the negative pressure in the carburettor greatly reduces the temperature in the intake tract. Signs are a drop in engine speed or a drop in pressure - then immediately activate the carburettor preheater and adjust the mixture.
IFR pilots should avoid visible moisture at sub-zero temperatures unless de-icing systems are in place. VFR pilots should turn back or initiate avoidance strategies at the latest when visibility deteriorates or there are signs of flow disturbances.
Navigation in winter: When the landscape is white
The white winter landscape makes visual navigation difficult. Distinctive landmarks disappear, lakes freeze over, roads and railway tracks lose contrast. Low sun, dazzling reflections and diffuse colour tones deceive distances and heights. Instrument monitoring, a GPS view and conservative terrain clearance are therefore particularly important.
Landing: grip, crosswinds and snow fields
Piste conditions are difficult to judge from the air. Snow reduces grip, ice almost completely. The following therefore applies to landing:
- touch down at minimum speed (provided no ice is suspected on the tail unit)
- Use brakes carefully
- Keep the nose wheel up for a long time
- Avoid asymmetrical substrates
- Realistically assess the crosswind component
After landing, every movement counts - especially on narrow taxiways between piles of snow, ditches or lamppost foundations.
Conclusion: Winter flying is worthwhile - with preparation
Despite additional work and precision, winter offers excellent flying conditions and fascinating impressions. The decisive factor is the willingness to take special circumstances seriously and to react in good time. Those who de-ice the aircraft, keep an eye on the weather, plan systematically and make conservative decisions can experience the cold season as a flying highlight. end.
Source references:
Aviation magazine
