What you need to know about mountain flying.
Mountain flying presents a unique challenge that can be difficult even for experienced pilots. Conditions that are common in mountainous terrain are often factors in CFIT accidents. Controlled Flight into Terrain (CFIT) account for 17% of total aviation fatalities. So, what can you do to ensure a safe flight in mountainous terrain?
Causes of CFIT in Mountainous Terrain
The majority of accidents happen during the takeoff, initial climb, final approach, and landing. When flying in higher altitudes this is often due to a pilot's unfamiliarity with flying in high density altitudes. High density altitude is defined as “pressure altitude corrected for nonstandard temperature variations.” What it means is that the air will be less dense which will affect the power output and performance characteristics of your aircraft. Takeoff and landing runs will be longer, rate of climb will be reduced, and ground speeds will be faster for the same IAS at lower density altitudes. Pilots who are not familiar with these effects may be ill prepared for the time/distance to climb it’ll take to clear obstacles rising terrain.
Another difficulty presented by mountain flying is the unique weather created by the terrain. Clouds and fog can often be extremely hazardous since they can often hide or mask the tops of mountain peaks before it is too late for the pilot to take corrective action to avoid the obstacles.
Wind also behaves differently among mountains than on flat land. Mountain waves can cause turbulence thousands of feet above the peaks and for miles downstream. Updrafts and downdrafts as the wind blows through valleys and around peaks can create dangerous turbulence as well as severe up and downdrafts.
Combating Dangerous Conditions
There are ways you can make your flight over and around mountainous terrain safer. It is important to remember not to attempt the flight if the conditions are too dangerous. If mountain top winds are forecasted to be greater than 25 knots, the FAA recommends postponing or rerouting the flight.
Often radio communications and radar coverage may be limited due to the obstruction of the peaks. This means good visibility is even more important in order to see the obstacles you need to avoid while flying in mountainous terrain. The FAA recommends 15 miles of visibility before attempting the flight. If flying IFR, it’s a good idea to maintain VFR visibility minimums. It is also important to pay close attention to weather reports before leaving and meticulously plan each flight so you know what to expect.
When making a flight plan, remember that a direct route may not always be the best route. If flying over the mountains, it is best to maintain at least a 1000 foot clearance above the peaks. In some cases, the safest action may be to plan a route around the high peaks rather than risk going over them or through the valleys.
It is important to always have a plan in case you need to end your flight before you reach your destination. Be prepared with alternative airports to land at and always be on the lookout for areas to make an off-airport landing if needed.
Flying in mountain terrain is dangerous even for experienced pilots, so it is often helpful to talk over your flight plan with other pilots who are familiar with the area you are flying and to be as thoroughly prepared as possible.
- Aviation Weather Theory
- CFIT Avoidance