Rotorcraft Winter Flying | EASA Community

Michel MASSON • 15 March 2024

in community Rotorcraft

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Spring is coming, we can feel that in the air. Days are getting longer, and nature shows the first signs of awakening. But winter isn’t over yet, especially in Northern Europe and in mountainous areas. Mainly intended for GA pilots, this article aims to allow you to safely enjoy the rest of your winter flying. It provides tips on preparing yourself and your aircraft and how to cope with snow, icing, white out, snow take-off and landing, and other challenges that come with winter flying. Flying helicopters during winter presents unique challenges. This article delves into these challenges, associated risks, and ways to mitigate them.

Prepare yourself and your passengers

Some of the best flying happens in perfect winter days with blue skies, cold dense air and beautiful sceneries.

By preparing yourself, your aircraft and your flight, you will safely enjoy some truly memorable flights and avoid or manage typical winter flying risks.

As a pilot, you have a well-developed set of flight preparation routines. Good practices are provided in several EASA Community Rotorcraft articles, for instance:

For winter flying, pay special attention to the following points:

Weather and routing (ceilings, visibility, wind).
The landscape for VFR navigation might be totally different to what you’re used to in the summer. Lots of things change colour and features you might use for navigation might not be as easy to see as you might expect.
Local airfield conditions (departure, destination, possible alternates), also check webcams where available to compare the real conditions with the forecasts.
Take a little extra time before and after your flight for a good walk-around and tie-down.
Dress warmly for the occasion and don’t forget your helmet, gloves, boots and sunglasses – remind your passengers to also dress warmly. When you are warm, even your walk-around will be much more comfortable and you are less likely to skip any important steps. Caution: A coat left in the car or crew room is no good to you when you end up diverting to an unprepared landing site. Dress to survive.
Note that extra clothing means extra weight so add some extra 5 kg per person to the mass and balance calculations.

Get the helicopter ready

Ensure that your aircraft is fit for flying in winter conditions.

If the helicopter is parked outside, exercise caution while approaching it. Frozen ground can be slippery, and the skids may either be stuck to the ground or concealed by snow.
Check for ice and snow on the aircraft. The additional weight of the ice or snow adds to the total weight of the aircraft, reducing performance and increasing the power required for taking off. Ice and snow can also affect the centre of gravity, with the risk of shifting beyond acceptable limits.
The formation of frost, ice or snow also changes the airflow over the blades (rotary wings), reducing the overall lift that blades can produce. Both the main and tail rotor blades can be contaminated. Yes, starting the rotors will shed the some of the ice but flying ice is a hazard to ground crew and will damage paintwork and transparencies so it is not recommended.
Perform a thorough walk-around and gently remove snow and ice to fly a ‘clean aircraft’. Use your hands, towels and brush. Only use hot water if necessary, as it may refreeze. Always wipe down any left-over moisture to prevent refreezing. Take care of critical places like the pitot tube(s), static port(s) and windscreen.
Before and after each flight, thoroughly examine the fuel system for any signs of water or ice contamination. Water within the fuel system has the potential to freeze and obstruct the fuel flow. Additionally, it may cause damage to fuel lines and other components.
Keep fuel tanks full to avoid condensation.
Caution: Moving a cold aircraft filled will fuel into a warm hangar will raise the fuel’s temperature. As the cold fuel gradually warms, it expands, potentially leading to overflow on the floor, causing a fire hazard. Do you aircraft have a minimum temperature for starting (it may be referred to as a ‘Cold Soak’ temperature)?
Fuel does not readily vaporise at cold temperatures: this makes starting more difficult.
Use engine oil grade suitable for winter operations. Low temperatures affect oil viscosity and batteries lose a high percentage of their effectiveness. This will additionally make engine starting more challenging.
Before starting the engine, inspect the oil breather tube for ice blockages. Blockages in the tube can lead to increased pressure within the engine, potentially causing seal failures or even forcing the oil cap off, resulting in oil loss and potential damage to the engine.
Ensure that oil temperature is sufficient before initiating the engine run-up. Gradually increase the throttle and refrain from sudden and forceful power increases. Treat your engine gently!
During flight, regularly scan the engine instruments. The oil temperature should be in the green. Operate the engine to keep it warm enough, considering that cold air increases heat exchange. In cold weather, the moisture within the oil may not evaporate, potentially leading to engine issues.

Account for the flying environment

Winter brings specific challenges including in-flight icing, snow, white-out conditions, adverse weather, winds and turbulences, and snow take-off and landing. The better you prepare for these challenges, the more you and your passengers will safely enjoy the flight.

Weather

Check NOTAMs, METAR and TAF. It may be challenging, as only 6% of the world's airports provide METAR and even fewer provide TAF. You may have to rely on the METAR and TAF from the nearest airport, which may be far away, or call the tower. Certain apps and websites provide weather information. AirportWeather.com for instance, provide weather reports (AW-METAR) and forecasts (AW-TAF) for every airport, updated every 10 minutes (as opposed to METARs which are updated every 30/60 minutes and TAFs which are updated every 6 hours).
If you plan to land on an aerodrome, check the opening hours and consider that some require prior permission to land. Check that the aerodrome provides all the facilities you need.
If local airfield webcams are accessible, use them to assess the actual conditions before departure. Contact the airfield in advance to obtain the latest updates or consider reaching out to someone in the vicinity to obtain local weather updates.
Accept changing your plan if the conditions deteriorate during the flight or the reports indicate poor conditions in the area. Don’t take chances!

Icing

Humidity favours icing, avoid flying in cold humid air.
Icing typically develops between -20°C and 5°C, picking up ice is therefore more likely in January and February and this period may expand to October, November, December as well to March and April in colder regions. Icing can also occur outside the winter season.
Caution: Check for ice accumulation during the flight! Ice destroys the airflow over the rotors and fuselage, decreases ability to create lift and increases drag. Ice accumulation also adds weight to the aircraft, which poses the risk of exceeding the mass and balance limitations. Exceeding these limits can affect stability, control, and manoeuvrability. If engines are not well protected, ice and snow breaking of the fuselage and intakes can cause flame outs or damage.

Helicopter performance

As previously mentioned, ice impairs performance in several ways.
Flying in colder air however improves engine performance, as cold air is denser, contains more oxygen by volume unit, and improves heat exchange and engine efficiency.
Refer to EHEST Leaflet HE 12 Helicopter Performance | EASA (europa.eu) for more information.

Wind

Wind can be strong in winter, always account for wind conditions during flight.
Tailwinds speed up the helicopter, while crosswinds and headwinds slow it down, make sure to factor these into your planning – yes it might be stating the obvious but don’t skip things like this if you are in a rush.
Wind affects fuel consumption and endurance, make sure to have enough for the whole flight or consider getting to back to base, divert or Land and LIVE

White out

Advice for helicopter pilots in harsh winter conditions | Magazine | Business Air News from European Helicopter Center's Peter Blom defines white-out as “a condition when a pilot loses orientation capability due to missing contrasts in his surroundings due to snow, fog and so on. It may occur on snow covered terrain on a cloudy day, or as a result of falling snow or snow surrounding the helicopter due to the helicopter downwash (a self-induced white-out). This may provoke dangerous flying conditions and total loss of the control of the helicopter”.
The tips below have their own value and also contribute to avoid or mitigate white-out.

Starting up on slippery surface

Free the helicopter from ice and snow and free skids from snow.
Maintain focus on the instruments and keep both feet and hands on the flight controls
Make sure yaw pedals are neutral.
Release any rotor brake smoothly.

Taking off

Lift the nose slightly first if the helicopter is parked with nose down.
In case of white-out, abort the take-off or perform an obstacle-free max performance take-off with a slightly forward movement, always keeping a visual reference. Avoid low hovering.

Avoiding or coping with icing conditions in flight

Avoid picking up ice during the flight: monitor weather and altitude, and climb or descend to avoid icing layers.
Check for ice accumulation on the windshield, skids, mirror and fuselage.
Ice accumulation can also be detected through vibrations and higher need for power or torque than normal because of degraded lifting performance and increased mass.
Understand and use onboard de-icing systems if your aircraft is equipped with such equipment.
Caution: If the aircraft doesn’t have an icing clearance, operations in known icing conditions are prohibited!

Flying in snow

Avoid low altitude flying over snow-covered surfaces without visual references, as optical illusions may occur.
Do not fly into heavy snow showers and other serious DVE conditions,
If you cannot distinguish between the ground and the horizon, consider turning around or landing.
While helicopters can fly in snow, pilots must carefully assess visibility, surface conditions and other factors to ensure a safe flight.
Rain and snow can significantly impact a pilot’s visibility. While the helicopter itself can still function normally, precipitation can make navigation harder and impair See-and-Avoid, reducing the capability to detect terrain, obstacles and other aircraft.
Snow affects the pilot’s visibility due to reduced contrast and depth perception.
If white-out occurs during flight, reduce speed, turn 180 degrees, make use of your instruments to maintain control over the helicopter, and then recover visual references.

Approach and landing

Never attempt to land without visual references and utilise landing lights when available.
To prevent self-induced white-out, pause in a high hover and attempt to blow the snow away. Beware that snow may suddenly recirculate when the helicopter is close to the ground.
If you cannot blow the snow away, don’t land.
If you must land there, know the landing site and have been trained for it, you can alternatively perform a fast approach and touch down (not recommended for the novice) with a slightly forward movement and avoid low hovering. Turn the nose of the helicopter, so the reference is always visible and fly close to it.

Landing

Do not land in snow depths exceeding 30 cm unless the helicopter is equipped with bearpaws. Bearpaws provide better traction and prevent skids from sinking into deep snow.
The tail should be clear and the ground suitable for landing.
Always use a visual reference, like a tree, pylon, building, etc.
When there is snow, land to a point, not in an area. A large open field is your enemy when references are scarce. This limits your options and requires thorough recce to make sure your reference is not also an obstacle. Check for instance this Norwegian Safety Investigation Authority Aviation report 2014/03 where a private pilot encountered DVE, made the wise decision to land, but unfortunately rolled over during touch-down because of lack of references in the open field he chose to land in.
When landing, gradually lower the collective while applying a slightly forward cyclic input to position the front of the helicopter lower than the back of the skids. Just before fully lowering the collective, perform up-and-down movements with the collective to assess the snow conditions and evaluate the risk of breaking through.
If white-out starts developing, immediately discontinue the landing.

Helicopter walk around and parking

If the helicopter is equipped with skids, land it where it doesn’t pose a hazard to other people. If it is equipped with wheels, park it where it doesn’t endanger other people. Steering can be difficult and braking action poor if the surface is icy or snowy. Taxi speed should be commensurate with conditions.
Let the engine and other parts cool down before the walkaround and visual inspections.
Before leaving the helicopter, secure it safely. If parked outside, use covers, tie downs, etc.

Debrief your flight

Flight debriefing is a good practice. Identify things that went wrong or not as planned and the decisions you took. Review also the things that you managed particularly well.

Ask yourself what have I learned in this flight? How different was this flight compared to previous flights? How comfortable was I during the flight? Are there things I would now do differently?

Share your experience with others, in person and on social media, and report any incident.

Refer to the articles with videos Post-Flight Debrief | EASA Community (europa.eu) and Occurrence Reporting | EASA Community (europa.eu).