By Lauren Scott, CFI
Flying near mountainous terrain offers incredible rewards: breathtaking scenery, beautiful destinations, and arriving more quickly to desirable locations. However, mountain flying presents many unique challenges for pilots. A skilled Pilot in Command will take into account the risks, and do his or her best to mitigate and prepare for them. Consider the following ten areas carefully before embarking on a flight in mountainous terrain.
This is really important! Some flight schools will not even accept students for mountain flying training if they have less than 250 hours of PIC. This may seem extreme, but the mountain environment can leave little room for error, and the ability to maintain aircraft control is vital. Mountain Flying LLC (www.mountainflying.com) emphasizes the importance of knowledge of stalls, aircraft control (including airspeed control +/-3 knots), and proficiency at accuracy landings. Every pilot is different, but honestly evaluate whether your skills and proficiency are up to the challenge. If not, consider doing some training with a CFI to become familiar with operating in the mountains before you venture off alone or with passengers.
Another big one! If your aircraft has a mediocre climb rate on a winter day near sea level, please consider renting an aircraft with better performance for a mountain trip. It is recommended to use a plane with at least 160 hp. As all student pilots learn, increased pressure and density altitudes have a significant impact on the performance of the plane; for every increase of 1000’ in density altitude, normally-aspirated engine performance decreases by about 3% AND the true airspeed increases by about 2%. In addition. On summer days in mountainous terrain, the temperature and density altitude can remain high well after sunset. Please be very familiar with and use your plane’s performance charts before flying in the mountains. Some suggest reducing the maximum gross takeoff weight by 10% to help compensate for the reduced performance.
Related to aircraft performance, keep in mind that your plane will take off and land differently at high density altitude. Expect a longer takeoff run and pay close attention to maintain the proper indicated airspeed. At higher, less dense altitudes, the true airspeed will be higher, which has led some pilots to feel that they’re going faster, and they mistakenly rotate or approach at too low an airspeed, close to the stall. Also verify the POH for the appropriate Vx and Vy speed in case they change at altitude. Make sure the approach to landing is stable, and do not hesitate to go around if necessary. Some experienced mountain pilots make it a habit to fly a wider than normal pattern because of the increase in true airspeed, to allow for a wider turn radius. Know and follow your engine manufacturer’s recommendations for leaning the engine for best power on takeoff at high density altitude.
Be familiar with airspace symbols, weather minimums, and entry requirements for the airspace you will be flying through. While in lower terrain a pilot may be able to fly below MOAs and Restricted or Prohibited Airspace, it may not be possible in the mountains (and there are often a lot of these special use airspace areas over the mountains in the western United States. Be aware that Class E airspace may begin at higher elevations than the usual 700 or 1200 AGL, indicated by a blue shaded line, with Class G underlying it. Above 10,000 MSL, Class E weather minimums increase to 5 sm visibility, 1,000’ below, 1,000’ above, and 1 mile horizontally from clouds. Class G also has higher minimums above 10,000’ MSL.
Many aspects of the weather are influenced by mountainous terrain. Let’s look at some major factors.
a. Winds Aloft
Unless there is a very stable, high-pressure air mass on a calm, cool day, mountain flying will usually mean dealing with some sort of wind: strong winds, gusts, turbulence, wind shear, up and down drafts, and even mountain waves. Be familiar with weather patterns in the area where you will be flying, and expect windy conditions. It is best to fly when winds aloft at the ridge line are no more than 20-25 knots; otherwise you can expect turbulence and possibly wind shear. Cross ridge lines at least 1000’ AGL when calm, and if winds are in excess of 20 knots, cross them at least 2000’ AGL. If needed to gain altitude, consider circling above the airport after takeoff to climb up to a safe altitude. Approach ridge lines at a 45-degree angle, to give yourself an easier out if you encounter strong turbulence and need to turn back away from the ridge. If there is an Airmet issued for moderate or stronger turbulence, consider postponing your flight.
If you happen to encounter an up- or downdraft, well-known pilot and writer Barry Schiff writes: “Maintaining altitude while flying through up- and downdrafts is counterproductive. Raising the nose to hold altitude in a downdraft results in losing airspeed, which prolongs the time spent in the downdraft. Instead, maintain attitude, accept the altitude loss, and pass through the downdraft as quickly as possible to minimize its effect.” (https://www.aopa.org/news-and-media/all-news/2018/january/pilot/proficient-pilot-turbulent-advice)
b. Surface Winds
Whenever possible at uncontrolled fields, listen to the ASOS/AWOS report several miles out to determine the best runway for landing, and/or observe the wind sock by flying over the field at 500’ above traffic pattern altitude. Winds in mountainous areas may shift quite suddenly, so pay attention to the wind sock. Ensure a stabilized approach, use proper crosswind correction, and go-around when necessary. Apply the proper crosswind correction all the way through touchdown, slowing down, and during taxi operations. Tie the airplane down securely for parking, as winds can pick up unexpectedly.
Some seasoned mountain flying pilots recommend having a minimum visibility of 10 sm during mountain flying operations. With the rising terrain, morning fog and temperature inversions are common, causing reduced visibility in some areas. There is a network of FAA webcams available in remote locations like Alaska, Canada, and Colorado to help pilots get a picture of what is happening with the weather in real-time. See www.avcams.faa.gov for details.
Pilots are familiar with the various hazards associated with thunderstorms: heavy rain, turbulence, wind shear, hail, and strong winds, and reduced visibility, to name a few. Remember that to form, thunderstorms must have sufficient moisture, a lifting force, and unstable air. Mountains naturally provide the lifting force, so just add some unstable air and moisture, and you have the perfect combination for thunderstorm development. This is particularly the case during summer afternoons, so watch out and make sure to fly at least 20 nm away from any thunderstorm cells, and try to fly earlier in the day, before thunderstorm development is more likely to occur. Also steer clear of virga; while beautiful, the rain that falls from clouds and evaporates before reaching the ground can be full of strong up and down drafts and be hazardous to small aircraft.
Even when not operating in the mountains, flying at night presents its own set of unique risks and considerations. In the mountains, those same considerations are only magnified. Besides the minimum 3 takeoffs and landings to a full stop to meet recency of experience requirements for carrying passengers, pilots must evaluate whether they are proficient for night flying, especially in mountainous areas. One of the greatest risks is flying into terrain. Use all available resources to make sure the flight path clears terrain, including sectionals and/or electronic charts. Have a clear, well thought-out plan for arrivals and departures. Consider investing in an electronic app that displays virtual terrain information, such as this one by ForeFlight:
Another hazard is losing an engine at night, and not being able to see to select a suitable emergency landing site. When possible, follow roads at night. The headlights make cars easy to see for navigation, and roads make an excellent emergency landing location. Another hazard at night is hypoxia susceptibility at lower altitudes. During day-time flights, hypoxia may be noticed around 10,000’, but at night, as our eyes depend more upon the oxygen-sensitive rods than cones, hypoxia effects may be noticed as low as 5000’. Know your hypoxia symptoms, and select a cruising altitude high enough to clear terrain without flying higher than necessary. Make extra sure you have a flashlight/headlamp, extra batteries, and an organized cockpit so you can locate things as you need them. Review the optical illusions that can occur at night: black hole illusion, bright or dim lights leading to a high or low approach, false horizon, etc., and be ready to rely on your instruments to help maintain situational awareness and aircraft control. Use the utmost caution flying at night in mountainous terrain, and choose to fly during the day instead if possible.
Remember that suitable visual checkpoints may be sparse in the mountains. Look for prominent peaks, towns, lakes, roads, and mines. When possible, follow highways or roads (or at least rivers, and valleys), as they are easy to follow and provide suitable emergency landing sites. It may take a little longer than going direct, but if you lose your engine or have some other emergency, you’ll have a place to land, and emergency vehicles can much more easily provide assistance. File a flight plan and if possible, use VFR flight following services (oftentimes in mountainous terrain, radar coverage may begin around 6000’ MSL.) LEAN the mixture according to the POH for operating at higher density altitudes. For takeoff, carefully identify and brief a plan for a loss of power on takeoff or climbout, and consider holding the brakes to check for full power and engine instruments in the green before commencing the takeoff roll. During the winter, make sure to check the NOTAMS carefully for ice, runway closures, and engine pre-heat and deicing services at destination airports.
Since flying in mountainous terrain requires higher cruising altitudes than flying near lower ground, pilots can find themselves suffering from hypoxia more easily. Know the symptoms of oxygen deprivation, and participate in a high-altitude training course if you ever have the chance, so you can identify your own typical symptoms. Fly just high enough to clear the terrain safely, and consider carrying a couple of extra items in your bag to help identify or treat hypoxia: a fingertip pulse-oximeter, and a can of Boost portable oxygen. Remember the regulations for using supplemental oxygen if your flight will require altitudes above 12,500’. If hypoxia is suspected, descend to a lower altitude as soon as possible, and consider landing at an alternate airport to wait a few minutes to make sure you’re feeling well before continuing on.
Do not hesitate to declare an emergency if the need arises! Be proficient with engine-out procedures and have at least the first few checklist items memorized. If you lose an engine, aviate first: pitch for best glide speed and turn toward lower terrain to increase your glide distance and find a warmer and lower place to land, preferably near habitation or a road. If in a forested area, try to aim for lighter weight trees like aspens, which will bend, rather than pine, which could trap the aircraft up high. If a crash landing occurs, evacuate all occupants until determining there is not chance of fire. Turn on the ELT, try to reach assistance with the radio or cell phone, stay warm and dry, and stay with the aircraft until help arrives.
When flying in mountainous areas, be prepared for an off-airport landing. Consider carrying enough food and water to last 1-2 days. Bring winter clothes in case of an emergency, a first aid kit, signaling device, personal GPS unit, and handheld radio. Emergency blankets or sleeping bags take up very little room but can literally save your life if you are stranded in a remote area overnight. Some Alaskan bush pilots wear a survival vest while flying loaded up with survival gear, so that if they do have to make an emergency landing, whatever they might need is right there on their person, instead of being impossible to access after a crash.
Mountain flying can provide some of the most rewarding flying experiences for us as pilots. Be safe, be prepared, pack a good camera, and enjoy the ride!