There are 3 known weather phenomena associated with winter flying that can affect the safety of any flight, and these relate to the ability of pilots to see their environment clearly and their ability to cope with challenges to their depth perception.
Those 3 weather phenomena are:
- Flat Light;
- White Out;
- Self Induced White Out.
Flat light is an optical illusion commonly known as sector or partial white out, a condition which can cause a pilot to lose their depth of field and contrast vision abilities. This danger is commonly accompanied by overcast sky conditions which inhibit good visual cues, and occur primarily in snow covered areas. This condition can also occur in blowing dust conditions, over sand, mud flats and water as well.
Flat light can completely obscure terrain features which can make it impossible to judge distance and closure rates. This reflected light can give pilots the illusion of ascending or descending while in level flight conditions causing pilots to alter their flight path unknowingly and possibly descending into the terrain.
This situation occurs when the pilot becomes engulfed in a uniform white glow which can occur when flying through snow, dust, sand, mud or water. Because there are no shadows in this situation pilots can not see the horizon or clouds, and all depth of field orientation is lost.
Because there are no visual references a white out situation can be very dangerous for pilots, therefore flying VFR in white out conditions should be avoided.
Self Induced White Out
Self induced white out is commonly associated with helicopter operations when arriving or departing a snow covered area. Rotor downwash picks up snow particles and recirculates them through the rotor system and can happen even on very bright days with good contrast and still result in a complete loss of visual cues.
If the helicopter pilot has not prepared themself for this immediate loss of visibility the results can be disastrous.
When All Visual References Are Lost
When all visual references are lost pilots should first and foremost trust their cockpit instruments, followed by a 180 degree turn to exit the white out area and find outside visual cues. Getting caught in a no visual reference situation can be fatal.
Physical awareness may tell you that you are flying straight and level; however, you may actually find yourself in a spiral dive with centrifugal force pressing against you. Also, remember that just because you have a good set of visual cues does not mean that there isn’t snow covered terrain not visible to you directly in your flight path!
How To Lower Flat Light Risks
- Always leave yourself an out;
- Do not continue flying when you have just one visual reference left;
- Make sure you don’t lose sight of your visual references points at any time, and never turn away from your reference point;
- Fly with your head straight looking forward and always believe what your flight instrumentation is telling you.
The Proper Sunglasses Can HelpMost pilots only think about sunglasses for when they are flying at altitude and in bright sunlight strong uv ray conditions; but the proper sunglasses can help with dangerous lighting conditions as well.
A good pair of sunglasses with tan lenses are excellent for conditions such as flat light, white out, self induced white out and haze or low visibility light conditions. Tan lenses will improve contrast and help with depth perception, and therefore are a great choice for winter flying.
You can find a great pair of sunglasses with tan lenses here: Pilot Sunglasses
When dealing with flat light or white out conditions during winter flying always remember that there are many factors to consider. Your pilot instinctive responses must be immediate and based upon a well thought out plan of action.
These unique visual conditions are insidious and sneak up on you without warning and at any time making the environment a real challenge to completing a safe flight.
Here is a video detailing some of these very important points about winter flying:
Most important of all: FLY THE AIRCRAFT!
In the meantime keep your wings straight and level Hersch!
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