Editor’s Note: This article first appeared in Twin & Turbine, Jan. 2004, and is reprinted here by permission.
Whether you’re cruising the Rockies or the Appalachians, mountain flying is a spectacular way to enjoy the benefits of an aircraft. Unfortunately, many pilots think of the mountains as a “no-fly zone.” Some aviators go out of their way to fly high over their tops or even circumnavigate them completely, and therefore miss out on some of the best scenery and vacation destinations around. If you’re one of those types, fear not! Mountain flying opens up a whole new world.But before you go charging off into the hills, be sure to get some instruction on how to fly the mountains safely. Mountains present unique challenges to aviators, who sometimes get in deep trouble by not giving them proper respect. A mountain checkout flight is all that is required to get started. The checkout will enable you to operate around some pretty impressive terrain, and start building your skills and confidence for more challenging mountain flights in the future. Here’s how to get started.
Begin by finding a flight school that offers mountain-flying instruction, preferably one you don’t have to be an expert mountain pilot to get to. Most schools located near high terrain offer specialized curriculum to help flatlanders learn to fly safely in the high country. The courses may vary in length and depth of coverage, so be sure to look for one that provides a thorough introduction to basic mountain airmanship. Of course, you’ll want to find one that provides hands-on flying experience in the mountains.A great place to learn is in Denver, Colo. Denver sits on the high plains (more than 5,000 feet MSL) adjacent to the eastern slopes of the Rocky Mountains. Three 14,000-foot peaks are visible from downtown, and there are 54 “fourteeners” in Colorado. A typical checkout there might involve flying out of a metro-area field with an instructor, entering the mountains at a designated point, picking your way through canyons, around the tallest peaks, crossing several high mountain passes, and making stops at three or four mountain airports before clearing the mountains and returning to your starting point.Once you get a checkout flight scheduled, you’ll have to do some homework prior to the day you go. Reading a good introductory book on mountain flying helps get you in the proper mindset. As you can imagine, barreling down a canyon at 120 knots is not the time to have your instructor introducing mountain-flying concepts for the first time. However, it’s a great place to build on skills that you’ve already read about. Two good books on the market are The Mountain Flying Bible by Sparky Imeson, and Flying the Mountains: A Training Manual for Flying Single-Engine Aircraft by Fletcher Fairchild Anderson. Reading either one will give you a solid foundation on which to build your skills.
The next step is to plan the flight. Your instructor may ask you to plot out a roundtrip course through the mountains, with various stops or waypoints along the way. It will be your job to pick the best way to navigate it. If you think you’re going to just hit “direct to” on your GPS, you’re missing the whole point of this lesson. You’ll be looking up at mountains all around you, so a direct course will probably lead straight into the first mountain in front of you. If you try to weave your way through following the GPS course the best you can, you might end up flying into a box canyon with similar results. Don’t count on those VORs or ADFs, either. Radio navigation signals are often unreliable in the mountains, and flying a constant radial won’t work unless you fly above the peaks. Real mountain flying requires seat-of-the-pants work. As a hardcore mountain pilot, you’ll know exactly where you’re going by relying on pilotage and dead reckoning. You’ll fly landmark-to-landmark, entering valleys and crossing passes using course, time, and speed.Mountain pilots choose routes by carefully considering how high the ground is and which valleys and passes offer the safest travel. Staying clear of the highest terrain is relatively straightforward: You plan your route around the highest peaks, making sure to identify in advance the exit of every canyon you plan on flying into.The width of canyons is very important when selecting your route. You never want to enter a canyon that is so narrow it prevents your ability to turn around. Can you draw your airplane’s turning radius on a sectional? How much wider does it get if you add 50 knots? How about with a 20-knot crosswind at your altitude? These things are important to consider before you start venturing down narrow canyons. A good way to learn how to visualize your turn radius is to try hugging some high terrain adjacent to an open area. Fly parallel to a ridge — nice and tight — then make a 180 degree turn away toward the open area and look at your distance from the ridge. Repeat this process at different airspeeds and wind conditions. You’ll find that the slower you go, the tighter the turning radius.Once you plot out the best course based on the terrain, it’s time to look more closely at the vertical profile of your trip. Note the elevations of every waypoint, then consider the distance between them and plan your climbs. Even choosing the lowest terrain available will often require you to climb several thousand feet before crossing a high mountain pass. Pay attention to color changes on VFR charts for elevation. A shift in color from tan to light brown can mean a 2,000-foot cliff in front of you. Keep in mind that even without a cliff, mountain terrain usually rises faster than your airplane is able to climb.When selecting airports and runways, remember that high altitude affects aircraft performance. We all learned that density altitude is pressure altitude corrected for non-standard temperature. If you typically only fly into large airports at sea level, you might not have worried about density altitude since your last FAA written exam. But if you fly the mountains, you’re going to have to get used to calculating it again. Some airports in the Rocky Mountains, for example, are above 9,000 feet MSL. On a hot and humid day, density altitude can easily creep upwards of 15,000 feet. Expect long takeoff rolls and reduced climb performance. Consult your aircraft’s performance charts to make sure you’ll have enough pavement. And don’t forget to account for the slope and surface conditions of the runway in your calculations. Not all mountain airports are flat and nicely paved.If you’re flying piston engines in the high country, remember to lean the mixture on the ground prior to takeoff. The fuel-air ratio in your engine is based on the weight of the fuel and air entering the combustion chamber. When you operate at a high-altitude airport, the weight of the air being drawn into the combustion chamber is decreased because the air is less dense, even though the volume being drawn in is the same. In order to maintain the proper balance between the weight of the fuel and the weight of the air, you must reduce the amount of fuel by leaning the mixture. This is the only way to achieve maximum power for takeoff, which will still be less than what you get at sea level. Turbine engines also lose power because of the altitude, but their fuel-air mixtures are adjusted automatically.
|Standing lenticular clouds on the lee side of the Rocky Mountains indicate the presence of the Mountain Wave. (Click photo for larger version.)|
The importance of getting a complete weather briefing when flying in the mountains is hard to overstate. Conditions that might seem benign elsewhere can quickly turn deadly due to the intensifying effect the mountains have on the weather. Wind speeds increase, turbulence gets worse, and frontal effects are often magnified due to the lifting effect of the mountains. As an air mass crosses a mountain range, parts of it rise and fall thousands of feet many times while being subject to heating and cooling by the sun.Under these conditions, forecasters have a daunting task to provide accurate weather reports for pilots. For example, in some areas, a mountain airport can report a ceiling of 2,000 feet AGL, yet the clouds may be touching the ground less than a mile from the field. The FAA has devised a special term to describe this condition: mountain obscuration (MTOS). Most mountain airports are located in valleys, and they report ceilings in feet above the airport. So you can have conditions where an airport has a 2,000-foot ceiling, but the 3,000-foot peaks all around it are buried in the clouds. Check the airport AWOS, but also consider how that weather will interact with the terrain around it. MTOS areas are identified daily by forecasters in the form of AIRMETs.Mountain AWOS stations are another good source of information. Located on peaks or in passes, they contribute to the weather picture in areas where there are no airports. Colorado, for example, has six mountain AWOS stations placed in strategic locations in the Rocky Mountains. Be sure to ask your briefer to provide readings from any stations along your route. You can also hear their recordings by dialing them directly. Call the state’s aeronautic office or check its Web site for a listing of mountain AWOS phone numbers. Don’t forget to tune in for recorded updates en route, too. Mountain AWOS stations locations and frequencies can be found on sectional charts.Winds aloft forecasts (FDs) can tell you a great deal about the weather in the mountains. You will be hugging the terrain, but that terrain might be 14,000 feet high. Looking at wind speed and direction at 9,000 and 12,000 feet will give you an idea of what level of turbulence to expect, and where you might find the updrafts and downdrafts. Remember: The report’s forecast levels through 17,999 feet are based on true altitude, while levels at 18,000 feet and above are based on pressure altitude. When using the forecast for mountain flying, don’t expect the wind directions to be very accurate once you get into higher terrain. Peaks and valleys channel wind in every direction you can imagine, and can double or even triple the speed due to the venturi effect. The winds-aloft forecast’s real strength is helping you visualize overall trends acting on an area. Be sure and ask the briefer to give you winds aloft on both sides of the range you are flying.A good way to visualize mountain air movement patterns is to try and imagine what water would do if it were flowing around the peaks. Like rocks in a stream, mountains cause air to pile up on the upwind side and form a turbulent burble on the downwind side. The stream analogy works really well as long as the air is stable. If the air is unstable, uneven heating and cooling can cause air to flow up and down the mountains and change the pattern a bit. Some of these movements are predictable. Valley breezes are caused by warm air being heated up at lower elevations and blowing up adjacent slopes, typically during the hottest parts of the day. The reverse, a mountain breeze, happens at night when cool high-elevation mountain air blows down into the valleys at night.Another important mountain weather phenomenon is the mountain wave. A mountain wave occurs when air blows over a mountain range, creating a smooth updraft as it hits the mountains, then turning into a turbulent downdraft as it crosses the crest of the ridge. These “waves” continue in a similar up-and-down pattern well past the mountains. Here again the stream analogy works well. You’ve probably seen the standing water waves that occur downstream from a series of rapids. Air can do a similar thing if the winds are strong enough. From the first ridge in a mountain range, and for many miles downwind there can be a series of updrafts and downdrafts. Telltale signs of mountain wave conditions are standing lenticular clouds above the mountains and roll or rotor clouds in the wind eddies on the leeward side. Mountain waves are caused by strong winds aloft combined with stable air conditions, and are very common in the winter.All the extreme movement of air in the mountains creates pockets of wind shear and turbulence. You can avoid the worst of it by visualizing wind patterns. Unfortunately there is no way to predict exactly where all these hazards will occur. If you stumble into bad turbulence or wind shear, concentrate on holding attitude while allowing altitude variations. Try to determine the source and fly directly out of it. If you’re not sure what’s causing it or it becomes severe, turn around. Pilot reports (PIREPs), if available, are the most current resource on these invisible hazards. Read them and don’t forget to file new ones for pilots behind you.
En Route Techniques
Now your route is thoroughly planned and you have all the weather information you can find, so you depart on your way. There are a few techniques to maximize safety as you engage the terrain along your route.Safely crossing passes requires visualizing wind direction and speed. Since the wind typically drives air up one side of the mountain and back down the other, you will encounter updrafts on the windward side and downdrafts on the lee side of a mountain. The prevailing easterly flow of the jet stream means typically the updrafts are on the west sides and the downdrafts are on the east sides in the Rockies and Appalachians. That means you’ll likely encounter a helpful updraft approaching a ridge while headed eastbound, followed by downdrafts after you cross. Westbound is often more dangerous, with downdrafts occurring right as you approach the ridge, followed by updrafts after you’ve already cleared it. Since the downdrafts can easily exceed your airplane’s ability to climb, plan on crossing a minimum of 1,000 feet above the ridgeline. If winds aloft are more than 30 knots, give yourself a 2,000-foot margin above the pass.Do not approach a ridge until you have sufficient altitude to cross with a safety margin. If you encounter too much sink, you must have enough altitude to turn away towards lower terrain. To make that turn as easy as possible, its wise to turn your aircraft to a 45-degree angle to the ridge before you cross. That way you can quickly turn back towards lower terrain if necessary. The ridge is not considered crossed until you reach a point where you could easily glide power-off to the other side. At that point you can turn back on course.Flying in canyons safely requires a few simple techniques as well. You already know not to fly in narrow canyons that lack sufficient room to turn around. When flying in wider canyons, you need to position yourself in the canyon to make the best use of the space. The natural tendency is to fly down the center of the canyon to remain clear of the walls on either side. But this effectively cuts the canyon width in half if you need to turn around. Most canyons will have air flowing through them, sinking down one side and going up and out the other. If the canyon is wide, fly along the updraft side. If you need to turn around, you can turn into the center. If the canyon is narrow, fly on the downdraft side so if you need to turn around you can turn into the updraft.Most canyons lead to a ridge, so their floors have a definite slope. If the wind is blowing down the canyon from the ridge, you can expect a downdraft as you approach the ridge. If the wind is blowing up the canyon, an updraft awaits you at the ridge. Keep this in mind as you enter and exit from the canyon. If you’re exploring a canyon for the first time, enter from the high end and fly towards the low end. That way your safety margin increases as you go. Keep an eye out for power lines, too. Towers are sometimes placed on opposing ridges with the lines strung across the canyon in between. Most lines are marked with orange balls, but some may not be. Enlist help from passengers to identify towers as you go.The most important rule of thumb when flying in canyons is to always leave yourself an “out.” You should always have enough altitude to make a power-off, 180-degree turn back toward lower terrain. By keeping this margin, you will always have an escape in the event of a mechanical problem, severe downdraft, or turbulence. If the canyon starts to narrow, climb out of it or turn around. If you find yourself in trouble in a confined area, slow to minimum maneuver speed by trading airspeed for altitude, then make the steepest bank possible using flaps to turn around and exit the area. This method offers the best chance to avert a forced landing.
Plan for the Worst, Expect the Best
Since the unthinkable can happen, emergency planning is a wise precaution for all mountain flights. Could you make a forced landing if you had to? How easy would it be to get rescued? Many places in the mountains are so remote a rescue team will not reach you for several days, especially in winter when there is deep snow cover. Will you be able to survive that long? Given the choice of flying on one side of a mountain that follows a highway, or around the other side that is wilderness, you should follow the road if terrain and weather permits. Not only does a road offer a place to land in the event of an emergency, it also provides a route for rescuers to quickly reach you.Pack enough survival gear in the airplane for you and your occupants. A duffel bag with a few days worth of food and water, an axe or saw, matches, fishing equipment, warm clothing, blankets, signaling device, and a compass will probably never get used. But it doesn’t take up much room … and if something happens, it can save your life. Also make sure your ELT battery is fully charged and that you file a flight plan on every flight, even if it’s just a short, VFR trip. You never want to forgo launching automatic search and rescue if you don’t show up at your destination.If after reading this article you think that mountain flying sounds too dangerous, don’t worry. Hundreds of successful trips are flown in the mountains every day. All that’s needed is a little training, a diligent attitude towards flight planning, and a mindset that says you will constantly evaluate the situation and quickly change plans if necessary. Combine all that with an unbreakable rule that says no matter where you fly, you will always leave yourself an out, and you can fly the mountains safely. The mountain checkout flight walks you through all this so you can emerge a better pilot and get rid of that “no-fly zone” for good. The icing on the cake is that it’s likely to be the most beautiful checkride you’ll ever have.
More articles to help you become a better pilot are available in AVweb’s Airmanship section.