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 waves

These waves are formed when the wind blows at or near right angles to a mountain range or high isolated peaks. The flow of air is disturbed as it must go over or around the obstacle. A wind of at least 15 knots increasing in strength with height and an unstable atmosphere at low levels with a stable layer at altitude together with sufficient moisture will result in standing Altocumulus lenticular clouds as a signpost for heavy turbulence.

Mountain waves

These clouds have a stationary appearance but the winds are blowing continuously and the cloud is forming on the upwind side and dissipating on the downwind side. Below these lee wave clouds rotors usually are formed.

Rotors
A rotor is a large closed eddy that forms in the lee of a mountain or obstacle and represent an area of severe turbulence. Up and down draughts are measured in excess of 5000 ft/m, avoid them when possible! Rotor clouds are formed when there is enough moisture in the air.

Clouds
Clouds form when the temperature drops near the dew point and this change can occur rapidly in mountain area's due to the rising of the air. In good weather, thermal heating and cloud buildup are commonly found near the tops of ranges, upwind side. You will find these to be at their maximum between 2 and 3 pm and they usually disappear in the late afternoon.

A good example is the lenticular cloud. This cloud forms when there is sufficient moisture and the temperature drops towards the dewpoint by the upward movement of the air. The cloud dissipates when the upward movement of the air stops and descends again like a wave.

Changing weather
Weather can change with subtle changes in wind speed and direction, it would be wise to keep an watchful eye on weather conditions when doing the preflight and during the actual flight itself. Be prepared to back out before any major problem present itself, always have a way out.

Winter time
Usually there will be more snow in the winter, changing scenery in the mountains. And because snow is white the difference between clouds and snow is sometimes hard to see. Orientation will be difficult and certain features covered with snow are not so easy to detect so that familiar grounds during other seasons become unfamiliar during the cold season.

Mountain Illusions

Flying in the mountains with its large structures makes it very difficult to judge distance and scale. reason is that you look small compared to the mountains. Some glacier crevasses are capable of swallowing a complete aircraft without leaving any trace at all. To counter this scale illusion, look for familiar objects like trees or bush. It will help you judge how far your are from the large mountains. Being able to estimate your distance from any obstacle is important as you may have to make that reversal turn into the wind.

Obstacles
In snow covered area's it can be very difficult to see the different ranges as the can merge with each other due the the whit color of the snow. This can happen when climbing towards a mountain range and a peak covered with snow is located in between you and that range. You will almost not see it due to the slow relative movement of that peak. It thus looks as if that peak is part of the range, until you come very close..
This situation is worsened when there is an overcast of clouds.

False Horizons
The lack of a good external horizon (due to snow, sloping mountains, haze) will sometimes create altitude and airspeed problems. Having a good artificial horizon and altitude indicator in the aircraft helps, but you must look outside because of the terrain and learn to assess your attitude. Instruments lag behind the real situation, looking outside gives the opportunity to anticipate attitude changes. A good example of a false horizon is a sloping ridge, causing the pilot to fly the aircraft with a bank angle.
When there is any trees, the tree or bush line can be used to locate the horizon in steep area's. With the help of your instruments and outside indicators it remains difficult, even more so in hazy situations.