Mountain flying represents a real challenge for most flatland pilots. At the same time the rewards are tremendous, offering very spectacular sceneries and views. It also means that the pilot needs training, develop skills and knowledge to fly safely in such an environment. We provide some basic knowledge on this subject, but this is no substitute for real training in the actual environment.

Make sure that you receive thorough training with a qualified instructor or experienced mountain pilot. Flying in mountain area's leaves little room for error. Effects of density altitude and degraded performance needs to be recognized. Get a good demonstration of soft, short field take-off and landings. Practice minimum radius turns, just in case you need one. Our first item will be the effects of density altitude, be prepared for a developing story here.

Mountain wind conditions

The weather can change very rapidly in the mountains and must be a serious consideration when flying in these conditions. At a very minimum an understanding of the major patterns is necessary for those only wanting to overfly any mountain ranges at higher altitudes as mountain waves sometimes extend to above the tops.

Wind
Wind is always present in the mountains and it helps to see airflow as water and think about how water would flow over the terrain. Where it would accelerate through passes and move over the valley floors, mix with other wind flows and tumbles over constructions. This will give you an rough idea where turbulence will occur and how to avoid or minimize it.
Downdraughts and turbulence will generally be found on the lee side of structures and will usually increase when wind speeds are higher.

When the wind speed is below 15 knots the flow is rather predictable, above this speed the flow patterns become more difficult to predict. In this case you need to focus more on wind lanes on water surfaces or bush than on upper cloud movement or winds.

Up and downdraughts
The strong vertical movements, especially on windy days, can be very daunting. These movements may exceed 3000 ft/m and most light aircraft are unable to climb out of a downdraught this strong. Move out of the down flowing air and try to locate the up flowing air, usually up- or downwind.

Turbulence and Maneuvering speed
Turbulence is created when an obstruction is placed in the path of airflow. Obstructions like hills, buildings and trees produce small scale turbulence. The intensity of the turbulence varies with wind speed, direction and the size and shape of the obstruction. Wind shear (changes in speed and direction) is also reported in turbulence. Just maintain a safe margin above stall speed, below maneuvering speed (Va), and fly attitude rather than airspeed. Ride the waves.

Remember that Va is the speed above any full or abrupt control movement (by pilot or turbulence) can cause excessive stress on the aircraft structure and depends on the weight of the aircraft. So remain below Va. Only fly above Va when the air is smooth and never descend to an altitude when turbulence is expected and with an airspeed above Va.
Va depends on aircraft weight too: the lower the weight the easier it is to overstress it.

Ensure that all loose objects are stowed and that passengers have their seat belt on before flight into mountainous terrain. Keep in mind that passengers have a lower tolerance for turbulence than you as a pilot might have. When they become quiet it is time to pay attention to them. Be prepared for unexpected turbulence and please do inform (not scare) all onboard, make sure that the flight is enjoyed by all.

Mountain Light situations

The light in the mountains can produce definition and depth illusions. When the sun is shining and deep dark shadows are present in valleys and when you are flying with sunglasses it can be very difficult to see any structure, let alone obstacles. The same can be said when a light haze is present and the sun is low as can be in the morning or in the afternoon. Do keep an eye on the position of the sun so you will not be surprised when flying around a peak or range and get blinded when turning.

Whiteout
To see any depth on snow covered surfaces has always been difficult, especially so when the light from the sun is spread out by haze and/or a cloud cover. All objects seem to disappear into the background and have the same color, any horizon is lost and it will become very difficult to estimate altitude and distance even clouds below your altitude are difficult to see. This can happen very fast when flying over glaciers under a cloud cover, make sure to be prepared to turn around when visual indications are lost.

Brightout
Disorientation can occur when flying over snow covered terrain under clear sky and bright sunlight. Shadows are not visible due to the reflection of the snow. Everything appears to be flat. Could be a problem for low and slow aircraft.

Contrast
An illusion of good contrast can be seen when a rock or ridges are visible above the snow. It gives the impression that you can perfectly estimate your height above ground, while in fact it is still difficult. Pilots of slow flying aircraft like helicopters are prone to this illusion.