Coolness!!; An entire section devoted to Mountain Flying!

If you're like me, there's flying... then flying at night... then flying in the MOUNTAINS!

Personally the mountains have always fascinated me, brought inner peace, and endless awe of the majestic and breath-taking sights. I have always wanted to learn to fly in the mountains, and this section is devoted to information to do just that.

It is my wish that fellow pilots learn and in turn teach others how to safely fly big mountains.

See you up there!

7−5−6. Mountain Flying

  1. Your first experience of flying over mountainous terrain (particularly if most of your flight time has been over the flatlands of the midwest) could be a never-to-be-forgotten nightmare if proper planning is not done and if you are not aware of the potential hazards awaiting. Those familiar section lines are not present in the mountains; those flat, level fields for forced landings are practically nonexistent; abrupt changes in wind direction and velocity occur; severe updrafts and downdrafts are common, particularly near or above abrupt changes of terrain such as cliffs or rugged areas; even the clouds look different and can build up with startling rapidity. Mountain flying need not be hazardous if you follow the recommendations below.

  2. File a Flight Plan. Plan your route to avoid topography which would prevent a safe forced landing. The route should be over populated areas and well known mountain passes. Sufficient altitude should be maintained to permit gliding to a safe landing in the event of engine failure.

  3. Don’t fly a light aircraft when the winds aloft, at your proposed altitude, exceed 35 miles per hour. Expect the winds to be of much greater velocity over mountain passes than reported a few miles from them. Approach mountain passes with as much altitude as possible. Downdrafts of from 1,500 to 2,000 feet per minute are not uncommon on the leeward side.

  4. Don’t fly near or above abrupt changes in terrain. Severe turbulence can be expected, especially in high wind conditions.

  5. Understand Mountain Obscuration. The term Mountain Obscuration (MTOS) is used to describe a visibility condition that is distinguished from IFR because ceilings, by definition, are described as “above ground level” (AGL). In mountainous terrain clouds can form at altitudes significantly higher than the weather reporting station and at the same time nearby mountaintops may be obscured by low visibility. In these areas the ground level can also vary greatly over a small area. Beware if operating VFR−on−top. You could be operating closer to the terrain than you think because the tops of mountains are hidden in a cloud deck below. MTOS areas are identified daily on The Aviation Weather Center located at:

  6. Some canyons run into a dead end. Don’t fly so far up a canyon that you get trapped. ALWAYS BE ABLE TO MAKE A 180 DEGREE TURN!

  7. VFR flight operations may be conducted at night in mountainous terrain with the application of sound judgment and common sense. Proper pre-flight planning, giving ample consideration to winds and weather, knowledge of the terrain and pilot experience in mountain flying are prerequisites for safety of flight. Continuous visual contact with the surface and obstructions is a major concern and flight operations under an overcast or in the vicinity of clouds should be approached with extreme caution.

  8. When landing at a high altitude field, the same indicated airspeed should be used as at low elevation fields. Remember: that due to the less dense air at altitude, this same indicated airspeed actually results in higher true airspeed, a faster landing speed, and more important, a longer landing distance. During gusty wind conditions which often prevail at high altitude fields, a power approach and power landing is recommended. Additionally, due to the faster groundspeed, your takeoff distance will increase considerably over that required at low altitudes.

  9. Effects of Density Altitude. Performance figures in the aircraft owner’s handbook for length of takeoff run, horsepower, rate of climb, etc., are generally based on standard atmosphere conditions (59 degrees Fahrenheit (15 degrees Celsius), pressure 29.92 inches of mercury) at sea level. However, inexperienced pilots, as well as experienced pilots, may run into trouble when they encounter an altogether different set of conditions. This is particularly true in hot weather and at higher elevations. Aircraft operations at altitudes above sea level and at higher than standard temperatures are commonplace in mountainous areas. Such operations quite often result in a drastic reduction of aircraft performance capabilities because of the changing air density. Density altitude is a measure of air density. It is not to be confused with pressure altitude, true altitude or absolute altitude. It is not to be used as a height reference, but as a determining criteria in the performance capability of an aircraft. Air density decreases with altitude. As air density decreases, density altitude increases. The further effects of high temperature and high humidity are cumulative, resulting in an increasing high density altitude condition. High density altitude reduces all aircraft performance parameters. To the pilot, this means that the normal horsepower output is reduced, propeller efficiency is reduced and a higher true airspeed is required to sustain the aircraft throughout its operating parameters. It means an increase in runway length requirements for takeoff and landings, and decreased rate of climb. An average small airplane, for example, requiring 1,000 feet for takeoff at sea level under standard atmospheric conditions will require a takeoff run of approximately 2,000 feet at an operational altitude of 5,000 feet. NOTE− A turbo-charged aircraft engine provides some slight advantage in that it provides sea level horsepower up to a specified altitude above sea level.

    1. Density Altitude Advisories. At airports with elevations of 2,000 feet and higher, control towers and FSSs will broadcast the advisory “Check Density Altitude” when the temperature reaches a predetermined level. These advisories will be broadcast on appropriate tower frequencies or, where available, ATIS. FSSs will broadcast these advisories as a part of Local Airport Advisory, and on TWEB.

    2. These advisories are provided by air traffic facilities, as a reminder to pilots that high temperatures and high field elevations will cause significant changes in aircraft characteristics. The pilot retains the responsibility to compute density altitude, when appropriate, as a part of preflight duties. NOTE− All FSSs will compute the current density altitude upon request.

  10. Mountain Wave. Many pilots go all their lives without understanding what a mountain wave is. Quite a few have lost their lives because of this lack of understanding. One need not be a licensed meteorologist to understand the mountain wave phenomenon.

    1. Mountain waves occur when air is being blown over a mountain range or even the ridge of a sharp bluff area. As the air hits the upwind side of the range, it starts to climb, thus creating what is generally a smooth updraft which turns into a turbulent downdraft as the air passes the crest of the ridge. From this point, for many miles downwind, there will be a series of downdrafts and updrafts. Satellite photos of the Rockies have shown mountain waves extending as far as 700 miles downwind of the range. Along the east coast area, such photos of the Appalachian chain have picked up the mountain wave phenomenon over a hundred miles eastward. All it takes to form a mountain wave is wind blowing across the range at 15 knots or better at an intersection angle of not less than 30 degrees.

    2. Pilots from flatland areas should understand a few things about mountain waves in order to stay out of trouble. When approaching a mountain range from the upwind side (generally the west), there will usually be a smooth updraft; therefore, it is not quite as dangerous an area as the lee of the range. From the leeward side, it is always a good idea to add an extra thousand feet or so of altitude because downdrafts can exceed the climb capability of the aircraft. Never expect an updraft when approaching a mountain chain from the leeward. Always be prepared to cope with a downdraft and turbulence.

    3. When approaching a mountain ridge from the downwind side, it is recommended that the ridge be approached at approximately a 45 degree angle to the horizontal direction of the ridge. This permits a safer retreat from the ridge with less stress on the aircraft should severe turbulence and downdraft be experienced. If severe turbulence is encountered, simultaneously reduce power and adjust pitch until aircraft approaches maneuvering speed, then adjust power and trim to maintain maneuvering speed and fly away from the turbulent area.

AFS-803 (1999)



The purpose of this series of Federal Aviation Administration (FAA) Aviation Safety Program publications is·to provide the aviation community with safety information that is informative. handy, and easy to review. Many of the publications in this series summarize material published in various FAA advisory circulars, handbooks, other publications, and various audiovisual products produced by the FAA and used in ilS Aviation Safety Program. 

Some of the ideas and materials in this series were developed by the aviation industry. FAA acknowledges the support of the aviation industry and its various trade and membership groups in the production of this series.

Comments regarding these publications should be directed to the National Aviation Safety Program Manager, Federal Aviation Administration, Flight Standards Service, General Aviation and Commercial Division, Aviation Safety Program Branch, AFS-803, 800 Independence Avenue, SW, Washington. DC 20591.


We wish to thank all those who have contributed to this publication. including the Denver Flight Standards District Office; the Colorado Pilots Association; and,
Denver Automated Flight Service Station. This publication is limited in scope and should not be considered a complete mountain flying course. To complete your
mountain training, it is essential that you take a recognized mountain flying course that includes both ground and flight training. Only then should you consider
yourself qualified to safely enjoy the unique beauty and challenge mountain flying can offer.


Safety Window

Mountain flying opens up new opportunities for the general aviation pilot for unique and interesting destinations, plus a view of spectacular scenery. However, mountain flying, even more so than flight in the flatlands, is very unforgiving of poor training and planning. There is a narrow window of safety that an untrained pilot can easily stray out of without the experience and knowledge gained from a recognized training program and a mountain checkout by a qualified mountain flight instructor. This publication is not intended to be a complete mountain flying training course. Instead, it can be used as an overview before you take recognized training or a review afterward. Recognized training for this type of flying is a must and you are encouraged to attend a recognized mountain flying course that includes adequate mountain ground and flight training.

What is Mountain Flying?

Rather than offer a definition of "mountain" flying, it should be pointed out that many of the subjects discussed in this publication can be found in non-mountainous areas or at low altitudes. For example, density altitudes over 8.500 feet can be found regularly on the eastern plains of Colorado in the summer. Also, dangerous mechanical turbulence and even mountain wave can be found in areas that aren't usually considered mountainous. Of course, places like the Rocky Mountains are where all of these concepts can be experienced first hand and you should have mastered them before you attempt a flight through these areas.

Pilot Requirements

Because of the more demanding nature of mountain flying, you should carefully consider your experience and background before beginning a flight into mountainous terrain. First, it is essential that you consider attending a recognized mountain flying course to give you the knowledge and skills you will need to be safe. There are numerous recognized courses taught, usually in the summer months. and you can contact an FAA Flight Standards District Office in mountainous areas for references.

Second, it's usually a good idea to wait until you have at least 150 hours of pilot in command time logged before taking mountain training. Pilots with this amount of time have usually had time to become more familiar and comfortable with the airplane and with planning flying trips. Mountain flying in many areas will stretch your abilities to fly the airplane proficiently, navigate, and deal with weather.

Aircraft Requirements

Mountain flying presents demands on both the pilot and the airplane that may require more performance than light training aircraft have to offer. There are, of course, stories that are told during hangar flying about flying very low power airplanes into high mountain airports. 160 horsepower should be considered minimum for the airplane with a pilot with minimum mountain experience. Even that, however, will greatly limit your ability to react to strong winds and the up and down drafts they may cause. The aircraft gross weight and its affect on performance should be carefully considered. A minimum of 60 horsepower per occupant should be considered minimum.

Weather Requirements

Ceiling Requirements

It is suggested that you cross mountain passes at an altitude at least 1,000 feet above the pass elevation. Since this altitude will usually put you over 10,000 MSL, the cloud clearance requirement is at least 1,000 feet below the clouds. Hence, you should make sure that you have at least a 2,000 foot ceiling over the highest pass you will cross. 

Determining the actual ceiling in the mountains, however, can present some problems. There simply aren't very many mountain weather reporting stations. Also, those that do exist are almost exclusively in valleys. Reported ceilings at a mountain valley airport may have to be 8,000 feet or higher to give 2,000 feet ceilings at the passes. 

Visibility Requirements

Many experienced mountain pilots recommend having at least 15 miles of visibility before attempting mountain flights. Since your navigating will be primarily by pilotage and dead reckoning, good visibility will help keep you oriented in a sometimes confusing array of geographical cues. 


Strong winds can cause some of the most dangerous A conditions you'll have to contend with in the mountains. To minimize the chance of encountering dangerous turbulence, mountain flying should not be attempted if the winds aloft forecast at mountain top levels are greater than 25 knots. Above this level, potentially dangerous turbulence, as well as very strong up and down drafts are likely. 

IFR and Night Mountain Flights

Experienced mountain pilots recommend that IFR and night flight in the mountains not be attempted. Instrument approaches and departure procedures require a highly skilled pilot and a very high performance airplane. Night obviously obscures most visual navigation cues, making terrain clearance difficult or impossible.

Weather Factors

Density Altitude

From your basic flight training, you probably remember that density altitude is the pressure altitude corrected for temperature. Since increasing temperature makes the air less dense, an airplane will perform as if it is at a higher altitude than on a colder day, given that the airplane is at the same height above sea level. You should also remember that the standard lapse rate (the rate at which temperature normally decreases with increasing altitude in unsaturated air) compounds the problem somewhat. At sea level, the standard temperature is 59 degrees Fahrenheit, however, at 10,000 feet MSL, the standard temperature is only 23 degrees. This means that at Leadville, Colorado (elevation 9,927 feet) when the temperature is only 24 degrees, the density altitude is already above the field elevation. We will discuss density altitude in more detail later.

Winds Aloft Reports

The winds aloft reports are very important to your mountain flight planning process. You should pay close attention to the forecasts at and above the mountain ridges of the terrain you will be flying into. In the west, that usually means the 9,000 and 12,000 foot forecasts. In the east, you will look at lower winds. Winds above 25 knots at these levels should be a warning sign that should cause you to think about delaying your trip. 

High and Low Pressure Patterns

As you analyze the mountain weather before your flight, pay special attention to the position of the highs and lows to give clues to the wind speed potential. For example, in the winter, a high often sets up over the Four Corners area in southwest Colorado. This is often coupled with a low pressure centered in eastern Colorado or western Kansas. The result can be very strong westerly winds and dangerous turbulence in the high terrain for days at a time.  

Mountain Wave

When the wind speed is above about 25 knots and flowing perpendicular to the ridge lines, the air flow can form waves, much like water flowing over rocks in a stream bed. The waves form down wind from the ridge line and will be composed of very strong up and down drafts, plus dangerous rotor action under the crests of the waves. If enough moisture is present, lenticular clouds can form to give a visual indication of the wave action. These clouds are reported in the remarks section of hourly sequence reports as ACSL (altocumulus standing lenticular) or CCSL (cirrocumulus standing lenticular). 

Winds Through Passes

Just as the flow through a carburetor speeds up in the restriction of the throat, wind flowing through the narrow restriction of a mountain pass will also speed up. When the winds are forecasted above about 20 knots, be aware that the speed in passes may cause turbulence and drafts that should be avoided.

Orographic Lifting

As the wind blows moist air upslope, it will cool and may form clouds. If, as is often the case winter, the air is stable, the clouds will stay close to the mountain, forming a "cap" cloud. However, if the air is unstable, as is usually the case in the summer, this initial lifting will be enough to start convection and result in thunderstorms forming.


Microbursts have received much space in the aviation and popular press in the pasl several years because of their implication in many serious airline accidents. Many light aircraft accidents have also been caused by these events. The wet microburst is found in the middle of an active thunderstorm or intense rain shower and avoiding the strong downdraft is relatively easy. The dry microburst, however, is somewhat more insidious because it occurs with little or no warning in the clear air beneath virga.

Dry microbllrsts are common in and near the Rockies and other mountainous areas of the western U.S. in the summer. The formation of the dry micro burst is likely when thunderstorms with bases above about 3,000 to 5,000 feet AGL exist and the temperature/ dew point spread on the surface is more than about 40 degrees. If dust is blowing underneath one of these high based thunderstorms, stay clear until the event passes (usually only a few minutes). 

Temperature Inversions

Mountain valleys are often conducive to the formation of temperature inversions and valley fog at night. This should play a part in your arrival and departure planning. Since the inversion breaks and the fog dissipates by late morning, you may have to delay slightly at some airports.

Density Altitude Effects on the Airplane

There are numerous ways that density altitude affects the airplane.  For example, a normally aspirated engine will lose 3% of its power per thousand feet of density altitude increase. Next, as density altitude increases, the wings have less dense air with which to create lift. Since a propeller is an airfoil, it, too, will be less efficient.

Effects on Performance

All of these factors affect the overall performance of the airplane. At higher density altitudes, takeoff and landing distances are increased, rate of climb and actual service ceiling are decreased, true airspeed is higher for a given indicated airspeetl, and turning radius is larger at high altitude at a given indicated airspeed. To help regain some of the lost takeoff and landing performance at high density altitudes. you should reduce the weight at which you fly the airplane to no more than 90% of maximum gross weight. For a typical light airplane with a maximum gross weight of 3,000 pounds, reducing the loaded weight to no more than 2,700 pounds will regain much of the lost performance. A check of your airplane's performance data should show that takeoff and landing distances, climb rates, and single engine performance for multiengine aircraft is greatly improved at this reduced weight. Turbocharged aircraft will gain some improvement, but it will be somewhat less than that gained by non-turbocharged aircraft.

Since your true airspeed is higher for a given indicated airspeed, many pilots will respond to the visual cues of higher ground speed on takeoff by rotating at a lower !AS than normal. Instead, you should use the same lAS for takeoffs and landings as you would at sea level (or that the Pilots Operating Handbook specifies). Rotating at too slow an airspeed may cause the airplane to take an even longer ground run than necessary. 

Turning radius is proportional to the square of true airspeed. For example, if you increase your TAS by only 10%, your turn radius will increase by 20%. In the pattern this may result in a wider than expected turn to final resulting in overshooting. At high density altitudes, many pilots will fly slightly wider patterns to account for the wider turns. 

Higher density altitudes also affect best rate and angle of climb airspeeds. Best rate of climb lAS decreases as altitude increases, while best angle lAS increases slightly. Refer to your airplane's handbook to be sure you are flying the correct airspeeds to get the performance you expect.

Planning A Cross-country Flight

Any cross-country flight requires careful preparation, but a mountain cross-country trip deserves even greater attention to detail. Weather A clear understanding of the weather conditions is essential for a safe flight into muutJtainuus terrain. However, weather reporting stations in the mountains are sparse and getting a good briefing just from hourly weather service observations is difficult. You may need to phone some of the airports over which you will be flying to get current conditions. Pilot reports are also very helpful and you should give them as you fly along your route. 

Route Selection

Mountain route selection is much more than drawing a straight line between your departure and destination airports and filing "direct". A better route is usually found by following highways, river drainages, and valleys. These routes will usually be lower and offer better emergency landing sites. Also, you should check with local experienced pilots if you are planning a trip.

Flight Plans and Logs

Your trip into the mountains will usually be VFR, dictating pilotage and dead reckoning navigation. To plan for this type of flight, you will need to prepare a log with times and headings to fly between checkpoints. This may seem like a nuisance to be used by student pilots, but it will keep you from fumbling with charts into an unfamiliar area to get recommendations on routes to use, and guessing once in flight, possibly leading to disorientation and getting lost.

As you plan your desired route, also consider what alternate routes or airports may be available in the event of an emergency. If the weather is marginal, make sure you have a clearly defined alternative if it deteriorates to the point that you cannot continue to your destination.

Once you've planned your flight, you should also file (and then activate once airborne) a flight plan with the local flight service station. If, for some reason, you must make an off airport landing, having a flight plan activated will get search crews out looking for you quickly and improve your chances of survival. If for some reason you must change your planned route, be sure to update your flight plan with flight service. 

Usable Frequencies

When planning your flight, study the VFR charts for the frequencies and locations to use for making position reports and getting weather updates. In many mountainous areas, Flight Watch will not be usable; so you will need alternatives. In most places, you will be able to reach a flight service station through an RCO or VOR site. Have these frequencies written on your flight log for ready reference when you need them.

Winter Operations

Winter operations at mountain airports may present some things that you aren't normally faced with in the flatlands. Check the NOTAMs carefully for any unusual runway conditions due to snow, ice, or other hazards. If you will need engine preheat services or de-ice services, call ahead since some smaller airports do not have these available. Finally, if your destination is a popular ski country airport, you may find parking space limited or simply not available. Again, a call ahead may save a change in plans. 

Operations During A Cross-country Flight

Starting, Taxi, and Run-up

Starting and taxi at high altitudes are performed as you would at sea level, except you must lean the mixture significantly to avoid fouling the spark plugs. Run-up is also normal except a full power run-up of non turbocharged engines should be used to set mixture for takeoff power. The POH should be followed strictly for turbocharged engine operation.


For takeoff, the minimum flap setting recommended by the POH is usually recommended for best performance. A full power check should be performed on the runway. adjusting mixture for best power if necessary, and checking for proper engine RPM, manifold pressure, and fuel flow. As discussed earlier, rotation and liftoff
should be at normal indicated airspeeds. It is important not to over rotate to avoid high drag and poor takeoff performance.


A normal climb profile is usually sufficient for most mountain airports you will visit. Your POH should be the guide for selecting the proper speeds for the conditions. For most light aircraft, the initial climb will be at the best rate of climb lAS until reaching at least 1,000 feet AGL, then a smooth transition to cruise climb. There are some conditions, such as climbing out of airports in deep mountain valleys, when you may need to use the best rate of climb airspeed until reaching cruise altitude, but those conditions are relatively rare. Monitor pitch attitude, airspeed, and climb rate during the climb to make sure you are getting the best performance from the airplane. 

An engine failure right after takeoff is a serious situation any time. In almost every case, with less than 500 feet of altitude. you should not attempt to return to the airport. Make an off airport landing straight ahead, maintaining control of the airplane until landing. 

Ridge and Pass Crossing 

On most mountain flights, you will need to cross at least one ridge or pass. Experienced pilots recommend crossing a ridge or pass at the ridge elevation plus at least 1,000 feet. If the winds at mountain top level are above 20 knots, increase that to 2,000 feet. Plan to be at that altitude at least three miles before reaching the ridge and stay at that altitude until at least three miles past it. This clearance zone will give you a reasonable safety zone to avoid the most severe turbulence and down drafts in windy conditions. 

If conditions or airplane performance dictate, you may need to fly along the windward side of a ridge to find updrafts for gaining altitude before crossing a ridge. You may also need to circle before reaching the ridge if climbing out of a valley airport. 

When you actually cross a ridge, you should do so at a 45 degree angle to the ridge. This allows you to turn away from the ridge quicker if you encounter a severe downdraft or turbulence. Once you have crossed the ridge, turn directly away from it at a 90 degree angle to get away from the most likely area of turbulence quickly. Plan your crossing to give yourself the ability to turn toward lower terrain quickly if necessary. 

Enroute Considerations

As you fly your mountain trip, continually visualize what the weather and winds are doing so you can take best advantage of them. For example, if flying in a valley, it is usually best to fly on the side of the valley that will have the updrafts, the side the wind is blowing toward. Turbulence due to the rough terrain may make the flight uncomfortable, but may also require that you fly at maneuvering speed. Remember that maneuvering speed decreases as the airplane's weight decreases. You should know what your maneuvering speed is for the weight at which you are flying and be able to go to it quickly if you encounter rough air. 

Pilotage and dead reckoning will be your primary type of navigation. VORs are usable in limited areas, but suffer from limited range and other problems. LORAN and GPS systems work quite well. however, and can be used effectively to maintain your positional awareness.


When you first arrive over a mountain airport, take a good look around before you descend to it and plan your departure track. Look for escape routes and emergency landing sites in the event of an engine failure right after takeoff. Also, study the terrain you will have to climb over as you depart. Plan your approach path as you start your descent. Some mountain airports are confined in valleys that make a normal approach difficult. Study your options before committing to a lower altitude.

Approach and Landing

Approach and landing should be normal at most mountain airports. Plan to fly a stabilized approach to the desired touchdown spot. Since mountain winds are sometimes tricky, be aware of windshear and go around if necessary. 

Emergency Procedures

Even the best prepared pilots may someday find themselves caught in an emergency situation that will require quick thinking and excellent skill to save themselves and their passengers. Even though these situations cannot be totally prepared for, there are some things you can do to increase your chances of handling the
problem in the best way possible. 

Survival Equipment

There are volumes written on what type of equipment to carry for survival in the event of a forced landing and you should take the time to use these sources to put together a good survival kit before launching into the mountains. At a minimum, however, you should have food and water for each occupant of your airplane to last at least three days, winter clothing for each occupant, a medical kit to stabilize crash injuries, and signaling devices. Your food supply might be as simple as granola bars, but camp supply outlets will have other options. You can pick up water in plastic bottles at a food store. To survive after an off airport landing, you must stay warm and dry, so good winter clothing like parkas and boots will be necessary. Remember that even though it may be summer in the valleys, the mountain tops will still get quite cold at night. A medical kit should contain basic supplies like bandages and pain relievers. If any of your party takes prescription drugs, you should consider carrying a supply of them. Signaling devices can be as simple as a military style signaling mirror (the glass type), which is highly effective, or a standard aircraft-band handheld transceiver.

Oxygen Use

In most cases, you will be flying at altitudes below those which regulations require oxygen use. However, you should review the symptoms of hypoxia and if you are susceptible to it because of smoking or other conditions, have supplemental oxygen on board and use it.

Deteriorating Weather Enroute

A particularly difficult situation for most pilots to deal with is weather that deteriorates enroute. The urge to continue is very strong, with the thought that it will get better if we just continue a little farther. However, continuing is often the worst thing you can do. When the weather begins to deteriorate, begin to consider what your options are. Your flight planning should have included planning for alternate routes or airports and those should be exercised before getting into poor weather. Divert to an alternate airport or return to your departure airport and reconsider the weather conditions.

If the weather closes off all other possible options, the best thing to do might be to make an off airport landing. Making a landing under control while you still have enough visibility to select a good site is preferable to continuing into poor weather and crashing into terrain that you can't see.

Engine Failure

Sudden engine failure should be planned for and practiced during recurrent training with a competent instructor. You'll need to know the first few things on the checklist by memory since you may be closer to the ground than usual and may not have time to dig out the POH checklists. As you fly along, pick out possible emergency landing sites before any problems arise and form a continuously updated course of action so you are prepared if the engine really does fail.

The exact procedure to follow when an engine fails is different for each type of aircraft, so know what yours is. In every situation, though, your first duty is to fly the airplane! Next, turn immediately toward lower terrain to increase your altitude above ground and possibly give you a lower (and warmer) site to land. Try to select a site near habitation or a road. Your landing site may be on a slope. Landing uphill will reduce the ground roll and reduce the chance of falling off an embankment or cliff.

Landing in a forested area presents some difficult choices. In the western U.S., most of the mountain forests are tall evergreen trees, with a few smaller trees like aspen. If you mush into the tops of tall pine or cedar trees, the airplane may stop, caught in the tree tops, then nose over, falling the last 50 to 100 feet nose first. A better choice is to select an aspen grove that will have trees that are much more flexible that will dissipate the airplane's energy without doing as much damage to the cabin area. Before landing, secure all seat and shoulder belts securely. Open the cabin door and emergency exits to keep them from becoming jammed in the crash. If possible, before touchdown turn off fuel, battery, and ignition switches to reduce the chance of fire. 

Survival After Landing

After landing, get everyone out of the aircraft immediately until you are sure there is no chance of fire. Next. make sure that the emergency locator transmitter is turned on. If a handheld radio is part of your survival kit, use it to attempt contact with an FAA facility or an overflying aircraft. Stay warm and dry, and above all, stay with the airplane! Time and time again, searchers have found people who have survived the crash only to die trying to walk to safety. Carry a good survival kit, plan well, and file a flight plan and your best choice will be to stay with the airplane until searchers arrive.

Emergency Summary

As with any type of flying, always leave yourself a way out. If things begin to go wrong, take prompt corrective action. Don't let yourself get caught flying into a worse situation. If you get into an emergency situation, don't hesitate to declare an emergency. Get all the help you can working for you. And finally, save the people and sacrifice the airplane. An airplane can be replaced, but your family and friends can't.

The Pilots Operating Handbook

Your POH contains a wealth of information about your airplane. Because of the demands mountain flying places on both pilot technique and airplane performance, you should spend time with your POH learning how to get the most from your airplane. You will need to know exact speeds for takeoff and landing at the weights you'll be using, best rate and angle of climb speeds and how they change with altitude, best glide speeds, and maneuvering speed at various weights. You should also pay close attention to takeoff and landing runway requirements at the high density altitudes you will encounter. Make a log of what you find so you can refer to them quickly.


As you can see from this brief overview of mountain flying, there is a lot to consider when planning trips into the high country. Without the proper training, you put yourself and your passengers at increased risk unnecessarily. A recognized training program that gives you the knowledge and skill to be safe in the mountains will
also improve your overall flying proficiency. Please take the time to get the training you need to be safe and enjoy your mountain flying experience.


  • F. Caracena, R. L. Holle, and C. A. Doswell III, Microbursts - A Handbook For Visual Identification, U.S. Department Of Commerce, February, 1989
  • Federal Aviation Administration Accident Prevention Program, The Impossible Turn, U.S. Department of Transportation
  • Federal Aviation Administration Accident Prevention Program, Wind Shear, U.S. Department of Transportation
  • Colorado Pilots Association, Colorado Mountain Flying Course
  • Northwest Mountain Region, Denver Air Route Traffic Control Center, High Mountain Flying In Ski Country U.S.A.
  • Advisory Circular AC-0057, Hazardous Mountain Winds and their Visual Indicators
  • Advisory Circular AC 61-23C, Pilot's Handbook of Aeronautical Knowledge
  • FAA-P-8740-2, Density Altitude 
  • FAA-P-8740-5, Weight and Balance, An Important Safety Consideration for Pilots
  • FAA-P-8740-13, Engine Operation for Pilots 

* * * *

This is a Back to Basics, Aviation Safety Program Product.
Federal Aviation Administration Aviation Safety Program (AFS-81 0)

The Aviation Safety Program, Federal Aviation Administration
800 Independence Avenue S.W., Washington, D.C. 20591

Flight Standards Service
800 Independence Avenue S.W, Washington, D.C. 20591

Contact your local FAA Flight Stand Office's Safety Program Manager for information.

FAA Aviation Safety Program
U.S. Department of Transportation
Federal Aviation Administration
Washington, D.C.

by Sparky Imeson


Sitting next to a fireplace with crackling wood on a blustery winter day can result in daydreaming of taking a relaxing trip to the mountains – without even considering those pesky mosquitoes – that becomes reality for many pilots during the summer months.

"Know before you go" is sound advice for the novice pilot flying over or through the mountains.

Mountain flying is not a hit-and-miss proposition where you meander through the mountains, navigating valleys and ridges, and then by luck plant the airplane onto a backcountry strip. Rather it is precise flying made safer by using every available clue about the weather and the terrain to accomplish the operation desired.

All flying involves risk. Mountain flying is a calculated risk where exposure to hazards can compromise the safety of flight. The decision-making evaluations concerning mountain flight are appraised for a safe outcome. Mountain flying is not accomplished by rote memory, it is done by thinking about the outcome of various courses of action available to the pilot and weighing the options. This requires an understanding of the conditions of flight, the limitations of the airplane, the limitations of the pilot, and the procedures and techniques to be followed.

You will want to conduct your excursion to those scary old precipice-formed highlands in a safe manner, so, being a conscientious pilot you are going to research the various procedures and the techniques for the operation. You will probably find some mountain flying techniques that may tax a novice pilot. In trying a new technique or procedure, if you find it causes you worry or concern instead of presenting a challenge, don't do it. Fly your experience level, not that of someone writing about how you should be doing it.


You might encounter the admonition, "Don't fly in the mountains until you have a minimum of 250-hours flight time." Some flight schools teaching mountain flying courses will not accept a student for training unless that student has a minimum of 250 hours of flight time. While this may be a realistic guideline, it is difficult to determine that a pilot can operate at a backcountry airstrip based on the number of flight hours he has logged. Without the proper background and training, hours alone do not "prove" the pilot is capable of flying the backcountry. Obviously the more hours a pilot has, the greater his experience level.

I am not convinced that this is a valid value judgment. Some pilots with fewer than 200 hours have impressed me with the operating safety and pilot skills. Other pilots with more than 1,500 hours of flight time have scared the bejeezus out of me.

A more realistic "ruler" to gauge whether or not it is safe for a pilot to operate at a backcountry strip is to demand perfection in three areas:

  1. Knowledge of stalls – what will the airplane do if stalled during a slip or during a skid?
  2. Airspeed control – be able to maintain the approach airspeed within about +/- 3 knots on approach.
  3. Spot method for landing – learn this technique and use it on all landings.


  • DON'T fly into unimproved mountain strips without a minimum of 150 hours of flight experience. Even then, be proficient at slow flight maneuvering, being able to maintain the approach airspeed within 3 knots and know how to perform the spot method for landing.

  • DON'T let a passenger pressure you into initiating the flight if you are uncomfortable about the weather conditions or aircraft performance.

  • DON'T plan a cross-country flight into the mountains when the wind at mountaintop level exceeds 25 knots unless you are experienced in operating in strong updrafts, strong downdrafts and moderate or greater turbulence. This recommendation does not preclude taking a "look-see." Sometimes with a stable air mass the air will contain very little turbulence during these high-wind conditions; at other times mountaintop winds of 15 knots in an unstable air mass may make the flight dangerous. Expect the wind velocity to double or more in mountain passes and over the ridges due to a venturi effect.

  • DON'T choose a route that would prevent a suitable forced-landing area.

  • DON'T leave the airplane without a valid, compelling reason if you execute an emergency or precautionary landing. Temporary evacuation may be necessary if a fire hazard exists.

  • DON'T go if the weather is doubtful or "bad."

  • DON'T become quiescent with weather reports of ceilings of 1,000 to 2,000 feet in the mountains. The ceiling is reported above ground level. Many weather reporting facilities in the mountains are surrounded by mountains that extend thousands of feet higher than the reporting station. Clouds may obscure the mountains and passes in the vicinity.

  • DON'T fly VFR or IFR in the mountains in an unfamiliar airplane make and model. It is required that you learn the flight characteristics, slow flight and stalls in various configuration beforehand.

  • DON'T make the landing approach at too slow an airspeed. Some pilots feel they have to make a low approach on the backside of the power curve to get into a mountain strip. The "handing on the prop" operation is dangerous. Use a stabilized approach for all landings. Airspeed while maneuvering to the airstrip is 1.3 Vso. Begin slowing the airspeed on final approach to cross the threshold at about 1.15 Vso.

  • DON’T make the landing approach too slow. Some pilots feel they have to make a low approach on the backside of the power curve to get into a mountain strip. This “hanging on the prop” is a dangerous operation. Use a stabilized approach for all landings.

  • DON’T operate low-performance aircraft into marginal mountain strips. If in doubt about your takeoff, use the “sufficient runway length” rule of thumb.

  • DON’T rely on cloud shadows for wind direction (unless you are flying at or near the cloud bases). Expect the wind to be constantly changing in direction and velocity because of modification by mountain ridges and canyons.

  • DON’T fly close to rough terrain or cliffs when the wind approaches 20 knots or more. Dangerous turbulence may be encountered.

  • DON’T fail to realize that air, although invisible, acts like water and it will “flow” along the contour of the mountains and valleys. Visualize where the wind is from and ask yourself, “What would water do in this same situation?”

  • DON’T slow down in a downdraft. By maintaining your speed, you will be under the influence of the downdraft for a lesser period of time and lose less altitude overall.

  • DON’T forget or fail to realize the adverse effect of frost. Less than 1/8 inch of frost may increase the takeoff distance by 50 percent and reduce the cruise speed by 10 percent. Often, if the airplane becomes airborne, the smooth flow of air over the wings is broken up by the frost and the extra drag prevents the airplane from climbing out of ground effect.

  • DON’T give insufficient attention to the importance of fuel and survival equipment. It is important to keep the airplane light, but don’t skimp on these items.

  • DON’T fly the middle of a canyon. This places you in a poor position to make a turnaround and it subjects you to shear turbulence.

  • DON’T fail to use the same indicated airspeed at high-altitude airports that you use at low-altitude or sea level airports for the takeoff or for the approach to landing.

  • DON’T be too proud or too vain to check with experienced mountain pilots concerning operations to and from unfamiliar fields.

  • DON’T attempt VFR flight in mountainous terrain unless you have the minimum visibility you have established as a personal safety standard.

  • DON’T become complacent about the horizon when flying with outside visual reference. A gentle upslope terrain may cause an unknown constant climb with the possibility of an inadvertent stall. The horizon is the base of the mountains some six to eight miles away.

  • DO file a flight plan for each leg of your flight. Also, make regular position reports to allow search-and-rescue personnel to narrow down the search area if you are overdue on the flight plan.

  • DO check all aspects of the weather including weather reports and forecasts.

  • DO familiarize yourself with the high-altitude characteristics and performance of your airplane. This includes the takeoff and landing distance and rate of climb under various density altitude conditions.

  • DO spend some time studying the charts to determine the lowest terrain along the proposed route of flight. If possible, route the flight along airways.

  • DO have confidence in the magnetic compass. The compass (unless it has leaked fluid or someone has placed interfering metal near its magnets) is the most reliable instrument. Charts will show the areas of local magnetic disturbance that may affect the accuracy of the compass reading.

  • DO plan the fuel load to allow flight from the departure to the destination airport with a reserve to counter unexpected winds.

  • DO fly a downdraft, that is, maintain speed by lowering the nose of the airplane. Unless the airplane is over a tall stand of trees or near a shear cliff, the downdraft will not extend to the ground (exception: microburst).

  • DO use Sectional Aeronautical Charts instead of World Aeronautical Charts (WAC) because of the greater detail (8 miles per inch).

  • DO approach ridges at an angle. The recommendation is to use a 45-degree angle approach when in a position of one-half to one-quarter mile away. This allows an escape, with less stress on the pilot and airplane, if unexpected downdrafts or turbulence are encountered. Flying perpendicular to the ridge, rather than at a 45-degree angle, does not mean you cannot escape the downdraft or turbulence by making a 180-degree turn. But, it does mean the airplane will be subjected to the effects of the downdraft and turbulence for a greater period of time. Usually, a steeper bank will be required to make the 180-degree turn. This will increase the g-loading stress on the airplane.

  • DO use horse sense (common sense) when performing takeoffs or landings at mountain strips. If you have any doubt about the operation, confirm the aircraft performance using the Pilot’s Operating Handbook or Owner’s Manual. If the physical conditions are adverse and compromise the operation, delay the operation until conditions are better.

  • DO count on the valley breeze (wind blowing upstream during the morning hours) and the mountain breeze (wind blowing downstream during the evening hours). In an otherwise calm wind condition the valley breeze will create an approximate 4-knot tailwind for landing upstream. The mountain breeze will cause an approximate 8-knot to 12-knot tailwind for takeoff downstream.

  • DO make a stabilized approach for landings. Since the late ‘60s the power-off approach has been discouraged because of thermal shock to the engine.

  • DO remember your study of aerodynamics. It is possible to stall the airplane at any airspeed and any attitude (providing you are strong enough and the airplane doesn’t break first). If a stall is entered in the same manner, for example, with a slow deterioration of the airspeed, it will stall at the same indicated airspeed at all altitudes even though the true airspeed is greater at higher altitudes.

By Brian Cruikshank, Oct 2008

You need to be careful flying through the Colorado Rocky Mountains in a small non-turbocharged plane, but it can still be done safely. There are many paths over the Rockies. What path to use depends on each particular situation: clouds, winds, weather, and intended direction. Also what you are comfortable with and your experience. In general, I do not pick straight lines, but instead follow the main valleys and minimize my time flying over the highest mountains. Through my trips west, I have used quite a few paths. Each one is quite beautiful.

Here are the main paths I have taken crossing the divide going from the furthest north to the furthest south. All these routes are not exact, but approximate. The flight path tool I could find could not show the route more exactly.

One interesting item to note is that the section from Grand Junction along the Colorado River to Vail and to Kremmling is very well covered by radar almost to the ground. This makes flight following possible and a good idea. All the other routes (through Gunnison and Alamosa) are not covered well by radar at lower altitudes.

North route into Southern Wyoming and west
Usually only needed if heading somewhere further north. This is the lowest terrain on the North side of the Colorado Rockies.

Over Colorado/Wyoming border, to Kremmling, and along the Colorado River
A nice low spot exists near the CO/WY border. Below is the route, but I would not go all the way to Laramie. This is the closest I could indicate on this flight planning tool.

I hear going over Cameron Pass or the FROGS intersection can be good. I have not had the situation yet where I used it for long trips, but I have gone over it for fun though.

Over Rocky Mountain National Park and along the Colorado River
Going over Rocky Mountain National Park is often less bumpy than over Corona pass.

Over Rollins Pass (Corona Pass) and along Colorado River

Southern Middle Route through Salida then Gunnison
A nice middle route if the norther routes will not work. There are 2 ways to get to Salida:
klmo-larks-kank- through Wilkerson Pass and Salida
klmo-pub-kank- through Pueblo then Salida
Then through Marshall pass (better than Monarch pass since Monarch is a sequence of ridges with downdrafts instead of just one)
- CO11-hbu-kmtj

Southern route through Alamosa and Durango
Another route further south if the main mountain section is bad for weather. There are three ways to get to Alamosa:
klmo-larks-kank-als- through Wilkerson Pass and Salida then Alamosa
klmo-pub-kank-als- through Pueblo then Salida then Alamosa
klmo-pub-gosip-als- through La Veta Pass then Alamosa (La Veta Pass can have some pretty big turbulence for being a low pass)
Then through Durango
- brazo-dro

Very Southern route near Albuquerque
On the way back to Longmont in the past, I have had to wait in Albuquerque for a snow to clear in the Denver area. Then I proceeded the rest of the way when the snow cleared. This is the lowest terrain route on the southern side of the Colorado Rockies.
Another route for the north/south portion that has had less turbulence for me is on the windward side of the Sangre De Cristo mounains.

Combined Picture of Routes

Using the above flyagogo links, then clicking on the little Google earth button on the left side of the web page for each link, I built a Google Earth image with all the routes. (Save the file and load it into Google Earth). If you want you can add the sectionals by clicking on this link to Google Earth Sectional Chart information. If you are zoomed out, I think the sectionals do not look good. But zoomed in, the sectional information is nice. I found these addons for NexRad Information for Google Earth, West Cloud Satellite information for Google Earth, and Eastern Cloud Satellite information for Google Earth.

Some Quick General Thoughts

Take a mountain flying course. Many instructors in Denver area are available for this type of instruction.

Landing in the moutains is different; here are some of the factors:

  • Density altitude is a major factor.
  • Your ground speed will be higher since you are flying the same indicated approach airspeed at a higher altitude.
  • Short field methods are important even on longer strips.
  • Your horizon and determining what is straight and level is sometimes confusing since the sky horizon is much higher than the real horizon.
  • Your approach and pattern is often restricted by high moutains.
  • Many other items that you would cover in a mountain lesson.

Colorado Department of Transportation has a nice book and on-line information for all the different Colorado airports.

Approach ridges at 45 degrees to reduce the amount needed to turn around if needed. Watch out for downdrafts and turbulence. Don't fly over the ridges if the winds aloft are expected to be above 30 knots at 12,000 MSL. Always have an out if something goes wrong. And IFR over the rocky moutains is a bad idea in small planes; don't try.

There are many AWOS stations near passes. Use this information where you can. It can give you an idea of how the winds are doing in different places.

Here are some books to read available at Marv Golden. Sparky Imeson has a good website with lots of mountain flying information.

Once again take instruction if at all possible.


By Ray Preston on April 9, 2014

Mountain Flying

By virtue of learning to fly at Selkirk College you will be much more familiar with mountain flying and its joys and hazards than pilots trained at almost any other school in the  world. All your cross-countries will be mountain flights and of course your local flights will be in the mountains too.

Without doubt mountain flying is challenging, the main factor being the weather, combined with the fact that safe operation requires considerably more altitude than in the  flatlands. There are some advantages to the mountains for example they make it much easier to  identify checkpoints when navigating. All in all mountain flying, like any type of flying, is as  safe as you make it. The purpose of this article is to help you make it as safe as possible. 

Minimum Safe VFR Altitude (in the mountains)

Depending on where you learned to fly you may be in the habit of flying at altitudes little more than circuit altitude at considerable distances from the airport. Many students in the lower mainland for instance think nothing of descending to circuit altitude in the practice area and then  flying 10 or even 20 miles at that altitude back to the airport. You have quite likely also done  practice diversion exercises at 500 agl. In the mountains you MUST not do either of these things.

In flatter parts of the world it is pretty easy to specify a ground level. The defining  characteristic of mountains, as opposed to hills, from an aviation perspective is whether or not  you can fly in the valleys. In the mountains you CAN fly in the valleys, but sometimes you  don’t. Therefore there are two distinct circumstances to mountain flying and you must know  which one applies at a given moment. You may fly “in a valley”, or you may be “crossing a  ridge.” All mountain flying can be divided into these two categories. A given flight may switch  back and forth between these circumstances many times, but you are always doing one or the
other of these.

When flying in a valley experienced mountain pilots establish minimum safe altitudes for each particular VFR valley route. In what follows we will discuss several common VFR routes  and the minimum altitudes for each.

When crossing ridges experienced mountain pilots agree that when wind conditions are  ideal the minimum safe altitude is 1,000’ agl above the ridge tops. When the wind speed rises to more than 20 knots the minimum rises to 2,000’ agl. There is a specific technique for crossing a ridge safely. If you employ the technique and develop some experience in judging where the downdrafts are going to be you may sometimes be able to fly lower safely. We will discuss ridge crossing below.

Most mountain airports are in the bottom of valleys, like Castlegar (or Kelowna, Penticton, Kamloops, Cranbrook, etc.) The only way to approach these airports is along the “corridor” created by the valley. If you are arriving from other directions you must either maintain ridge-crossing altitude (see above) until over the airport or plan your arrival so that you intercept the valley, then descend to the airport. When you do start your descent you should avoid flying for extended periods of time at low altitude. There are fewer good off airport landing sites in the rugged mountainous terrain, so it is prudent to plan your descent so that you reach circuit altitude just prior to reaching the circuit. If you find yourself leveling off at circuit altitude several miles before the airport you are flying too low.

Mountain Cross-countries

While you are at Selkirk College you will be sent on a number of VFR cross-country flights. You can find the details in the AVIA 100 and AVIA 200 sections of this manual.

The instructors tend to describe these trips as either “valley trips”, or “DR trips.” A valley trip is one in which you fly along a valley with very few if any ridge crossings. It is a type of VFR cross-country unique to the mountains. We discuss it extensively below. A “DR trip” is a dead reckoning trip, i.e. one in which you fly directly from one location to another. This is the only type of navigation that students at most flight schools will experience. In the mountains any DR trip will necessarily involve crossing ridges. For example when you fly to Swift Current you will cross the Rocky Mountains, the biggest ridge in North America.

A DR cross-country over the mountains is no big deal when the winds are light and the ceilings high. When you are more than 2,000’ above all the ridges then flying around B.C. is no different than flying across Saskatchewan. The challenge is in the fact that at any time the ceiling could drop and you might have to descend to within 2,000’ of the ridges, or even drop right down into a valley and convert to VFR valley-flying techniques. When this happens your piloting skills will be challenged.

While you are a student at Selkirk College we will take great care not to send you on DR cross-countries when there is a significant probability that they will turn into VFR valley flights. Besides the obvious safety consideration the VFR route usually takes longer, and that means it costs more. Even though we try to avoid it, it is probable that you will have to switch between DR ridge crossing and VFR valley techniques a few times during your flying at Selkirk. Depending on the type of job you get after graduation this sort of thing could become a regular, almost daily, occurrence for you.

As you fly around B.C. you should be keeping track in your mind of whether you are in “valley mode” or “ridge-crossing mode”. These are as distinct as VFR and IFR. We will now discuss each.

Ridge Crossing Technique

A ridge is a line of mountains that connect to each other like links in a chain. Mountain chains are also known as mountain ranges. And some individual mountains have names.

The tops of the mountains are called peaks. The lower points, where two mountains touch, are called a passes. Usually highways cross ridges at passes, and when the ceiling is too low to fly over the peaks aviators cross there too (we will discuss that more as we go along).

Most ridges have names; for example just north of Castlegar is the Valhalla range, just to the west are the Rossland and Christina ranges, and just east of us are the Bonnington and Selkirk ranges (for which the college is named).

In B.C. almost all the ranges run north and south; consequently there are extended north south valleys between the ranges. You can fly some of these valleys for many miles. The Columbia river (Arrow Lakes) is one such valley. The famous “Rocky Mountain Trench” is another.

Erosion has created some east west valleys also, although most of those valleys are quite short (the Kootenay River from Crawford Bay to Castlegar for example). Sometimes fairly low passes join these valleys. Remember that when you fly over a pass you are actually crossing a ridge, not flying a valley. For example the Blueberry Paulson pass connects the Kootenay River valley to the Grand Forks valley, crossing the Rossland mountain range (see your Calgary and Vancouver VNCs).

The main hazard in crossing a ridge is either encountering a downdraft of such force that the airplane is pushed down into the ground, or encountering terrain that rises so steeply that the airplane cannot out climb it. The rising terrain hazard is most common when attempting to fly through a pass. Downdrafts are the main hazard when crossing ridges above peak elevation. We will now discuss these two situations in detail.

The easiest situation to make general statements about is when the weather is good enough to fly above the top of the peaks. In this case the pilot does not need to “slip through a pass” to cross a ridge. Instead s/he simply flies directly enroute, just like a flatlander.

The picture to the left shows the situation where the pilot is approaching a ridge, intending to fly across it. If there is no wind there will be little danger. 1,000’ is recommended as the minimum altitude because there is almost always some wind at altitude. 

But if the wind is stronger than 20 knots then a substantial downdraft will form on the lee (downwind) side of the ridge. The downdraft could be well over 1,000 feet per minute. Of course such strong downdrafts don’t always form, but you don’t want to turn your life into a game of Russian roulette, so the first rule when crossing a ridge on a windy day is to stay 2,000’ above the altitude of the peaks. If you can do that you are pretty safe except when mountain waves form. We will get back to mountain waves in a minute; first let’s deal with the situation where you are unable, due to ceiling or airplane performance, to fly 2,000’ above the ridge.

If you must cross a ridge at less than 2,000’ the safest way is to fly a path like the one shown to the left.

As you approach the ridge turn so that you fly across at a 45 angle. That way, if you encounter a downdraft you can quickly turn away from the ridge, back to
the valley where you have lots of terrain clearance (see picture for “escape route”).

Once you reach the center of the ridge turn 90 to the ridge to get away from it as quickly as possible. Make sure you understand and follow this procedure anytime you are crossing a ridge at less than 2,000’ above the peaks. 

Crossing a ridge via a pass presents a whole different set of problems. Downdrafts may still be a problem, but even on calm days you may find that the valley leading to the pass slopes so steeply that you can’t safely out climb it. The results can be disastrous.

In the picture to the left an airplane is climbing up a sloping valley that leads to a pass. You can see that the clouds are well below the height of the peaks, one of which is shown in the background. For clarity the clouds obscuring the peak have been left out of the picture.

If the valley leading to the pass slopes at less than 200 feet per nautical mile most airplanes will be able to out climb it.

But many valleys slope more steeply; in that case the pilot should establish a minimum altitude at which it is safe to begin the flight up the valley toward the pass (see picture to left). Some advice on minimum altitudes when approaching specific passes is provided below, additional advice can be found in the publication Aviation Weather Hazards of British Columbia and the Yukon, copies of which are in the College library. 

An important rule for safe mountain flying is to respect the minimum altitude for entrance to a sloping valley and turn around if the ceiling is below that. Doing so will avoid the need to turn around later, close to the ground.

Sometimes the clouds follow the slope of a valley, as in the diagram above, but not always. Anytime you are approaching a pass you have to be prepared for the possibility of it being shrouded in cloud necessitating a turn around. We discuss the technique for turning around later.

When flying up a sloping valley it is easy to lose track of airspeed and get too slow. This is particularly so when visibility is poor, as it often is. The pilot must monitor the airspeed regularly. If the airspeed is allowed to decay while the ground rises up below, there comes a point when it is no longer possible to turn around safely. A good mountain pilot will never let things get that far (the procedure for turning around in a mountain valley is discussed below).

A very insidious situation is depicted in the picture to the left. An airplane has crossed a pass and is descending along a sloping valley in which the ceiling is getting lower and lower (closer to the ground).

We can see that a few miles ahead this pilot is going to have to turn around – but she doesn’t know that yet. 

When the airplane finally turns around will it be able to climb back up the valley to the pass? If not then this pilot is making a big mistake – and it may be his/her last. The rule in mountain flying is to never descend down a valley that you can’t turn around and climb back up. If you are descending down a steeply sloping valley then you must have sufficient climb performance so that if you turn around you can climb back to the pass. In a steep valley with a low performance airplane (like a C-172) that means cutting off the descent at a minimum altitude, just as described above regarding minimum altitude to enter a valley approaching a pass. It is very easy to be drawn into a mistake in such situations as you may feel you have enough ceiling to continue safely. If you actually make it through (i.e. don’t wind up turning around) you may never realize you risked your life, but if you do have to turn around and then realize you are too low to get back up the slope you will get that sinking feeling in your stomach that tells you that you have made a big mistake. Note: Two examples of such valleys are descending from Nancy Green Lake to CYCG along highway 3, and descending from Manning Park toward Hope Slide along highway 3 (remember that these two “valleys” are really passes that cross ridges).

Valley Flying

By valley flying we mean specifically valleys that have minimal or no slope to them such as river valleys. In B.C. most of these valleys run north and south – the east/west valleys being mostly short or consisting of sloping valleys traversing passes, as already discussed above.

Flying in a valley with a moderate ceiling and good visibility is no big deal. In such cases your primary concern is navigation. If you don’t know the route well it is easy to branch off into the wrong valley and get lost. To prevent mistakes (getting lost) you should keep your pencil or finger on the map recording where you are in the valley, and use your watch to keep track of distance covered and remaining. Don’t forget that you won’t be able to see the mountain peaks, so you must identify your position based on features visible in the bottom of the valley. If there are towns, highways, railways or other prominent features you will have little trouble. If the valley is featureless it will take a lot more effort. Your fancy GPS will be of minimal assistance; you need good old-fashioned map reading skills.

When the ceiling or visibility starts to deteriorate valley flying becomes trickier. We need rules and limits to guide our decision-making and keep us safe. We turn to the task of developing those rules next.

Normal procedure in valley flying is to stay well to the right hand side of the valley. By regulation (CAR 602.34(2) if you are within 3,000’ agl you are not obligated to maintain the cruising altitude according to the usual cruising altitude orders. On a valley flight you should fly as high as the weather permits, which in most cases means 500’ below the ceiling (or just clear of cloud if below 1,000’ agl (read CAR 602.34(2)). By flying on the right-hand side of the valley you will avoid any airplanes flying in the opposite direction, just like cars passing on the highway. There are some exceptions to the right-hand rule and those will be explained as we
continue our discussion of mountain flying.

The Mountain Maneuvering Speed (1.5 x Vs)

You may recall from your aerodynamics course that in theory the minimum radius of turn for any airplane is achieved by flying at the maneuvering speed while banked so steeply that you experience the maximum amount of “g” the airplane is certified for. Most pilots will blackout at four g’s, and it is almost impossible to maintain orientation in poor visibility in such an aggressive turn – so whatever you do, don’t turn around in a valley using this technique. We need a much safer plan.

At 60 degrees of bank you will experience 2.0g. At 45 degrees of bank you will experience 1.41g.

I recommend that private pilots never (NEVER) go beyond 60o bank – and more realistically don’t go over 45o bank.

To be safe then your mountain maneuvering speed is simply the square-root of 2 times your stall speed. We will round that off an call it 1.5 times your stall speed

Calculate your Mountain Maneuvering speed by multiplying your clean stall speed by 1.5. You should really use the calibrated stall speed rather than the indicated speed for this. Once you have calculated your mountain maneuvering speed memorize it and forget the official maneuvering speed.

For the C-172P the Mountain Maneuvering speed is 75 knots.

Turning Around in a Mountain Valley

If you wait to the last second and try to slow from cruise speed to mountain maneuvering speed when you desperately realize the need to turn around you are at great risk of making a greasy spot on the side of a mountain. Instead you should be flying slowly any time you are in a situation where a turnaround is probable. Slow down to a speed similar to what you would fly on downwind in the circuit. For example, in the C-172 we recommend 80 KIAS with 10 of flaps, in the B95 you would slow to 100KIAS with 20 flaps. At these reduced speeds you would continue along the valley, hoping to get through, but ready to slow down the last few knots and turn around if your hopes are dashed. (NOTE: slowing down as recommended here corresponds to the “marginal” weather category explained next – turning around is done as soon as the “unacceptable” category is reached. These categories are explained in the next section.) When the time comes to actually turn around in a valley the secret is to be calm. An airplane can be turned around in a very small area so by far the greatest danger is that you will lose control of the airplane. If you follow the recommendations in the next section about when to turn around and follow the right hand rule described above you should have lots of room to make the turn.

To make a valley turn-around slow the airplane to Mountain Maneuvering speed (75 in the C-172) with zero to 10 flaps. While you are slowing down check your heading indicator to see what heading you are going to turn to (usually you turn 180, or just slightly more). Next, look over your shoulder to check for traffic and obstructions (if you are on the right side of the valley you are going to turn left). Once you are ready to turn fly instruments, i.e. the turn is an instrument maneuver, because in the poor visibility you won’t be able to see the horizon. Add a small amount of power (100 to 200 rpm) to maintain speed and concentrate on aintaining
altitude and 45 bank. Roll out on the planned heading and resume visual flight back to safety. Return to a speed and configuration appropriate to the weather category (see below).

Minimum Recommended Weather for VFR Mountain Flying

While it is impossible to make absolutely definitive rules regarding the lowest possible ceiling and visibility to fly VFR in the mountains there are some solid guidelines that we can provide.

The first rule is that you MUST work your way up to (that really should be down to) flying in minimum weather; the primary factor being familiarity with the route. If some old-timer tells you that you can get through such-and-such pass with a ceiling at 5,000’ asl claiming, “I have done it hundreds of times” then he is probably right, but it doesn’t mean you should go through with such a low ceiling if you have never been there before.

Another thing to keep in mind is that aviation safety is measured in units of accident rate per 100,000 hours. So just because someone, including yourself, has done some activity 100 times without killing themselves does not make it safe. If you have 1 chance in 1,000 of killing yourself those are NOT good odds they are terrible. If every pilot flew with such odds daily airplanes would be raining from the sky. The bottom line is that you must not delude yourself into thinking that just because you got away with “slipping through” once or twice that you will continue to get away with it in the future.

The weather guidelines suggested below are intended for use after graduation. While you are a student higher weather standards apply. As mentioned above you must work your way up/down to these limits, and may even be able to go beyond them on particular routes if you develop enough familiarity with those routes. The speed and climb performance of your airplane are major factors in establishing minimum weather as well. A very fast airplane requires much more weather to operate safely. On routes that involve steeply sloping valleys a very powerful airplane that can out climb the slope may safely operate with a lower ceiling than a low powered
airplane (see the advice above about approaching passes). Keep these things in mind – just because an experienced pilot feels the weather is good enough for him to slip through in a C-180 doesn’t mean you can get through safely in a King Air.

You should categorize weather as follows:

  1. Excellent – no problems, no limitations
  2. Good – no problems, but start getting weather updates and reviewing the map.
  3. Marginal – continue, but if it gets worse divert and land
  4. Unacceptable – divert now BEFORE the situation becomes dangerous
  5. Dangerous – you should already be on the ground
  6. Too late (you are now a statistic)

Keep in mind that we are talking about flight in valleys with minimal slope. In that situation, if the ceiling is high enough for you to maintain 1,000’ agl and the visibility is 15+ the conditions can be classified as excellent. As long as you meet your minimum altitude criteria for any valleys that slope up to passes you will have a pleasant flight.

As soon as the visibility drops to between 10 and 15 miles, but still with 1,000’ agl cruise, you should downgrade your weather assessment to good. There is no reason to change your route and most likely all will go as planned, but if the weather gets any worse you may need to divert so you should be PLANNING now. I.E. just make sure you know what alternate routes are available, what alternate airports are available, and be sure to call FSS and get a weather update for the rest of your route.

Once the visibility drops to between 5 and 10 miles, OR if the ceiling drops so that you are flying between 500 and 1,000’ agl the weather is marginal. Marginal weather does not necessarily cause an experienced mountain pilot to divert (i.e. a pilot who knows the route well) but you should SLOW DOWN - in the case of the C-172 slow to 80 KIAS and drop 10 of flaps.

In lots of cases you won’t have to divert, you might have to work around some fractus clouds, as described later – but you definitely must begin taking each remaining mile of the trip one at a time, i.e. you fly from each bend in the valley to the next then make a conscious decision whether to continue or divert. A specific diversion plan must always be in your mind, and you must establish a visibility and ceiling that you will not go below. (Don’t forget to keep track of what is going on behind you. Don’t let weather close in behind you so that a 180 turn-around is no longer an option.)

If the visibility drops below 5 miles or the ceiling below 500’ agl the weather is classed as unacceptable, and it is time to divert. Such weather is really not good weather at all – it will be quite uncomfortable in fact – but it isn’t fatal if you stay calm. BUT, if it gets any worse it will be fatal so divert and land somewhere safe now, before you regret it. Of course you would divert even sooner (marginal weather) if the weather was deteriorating rapidly, it was reported as below 5 miles (unacceptable) ahead, or you were not highly familiar with the route (remember that the advice being dispensed here is for a licensed commercial pilot who is IFR rated and quite familiar with mountain flying. It is also assumed that the pilot knows the route and airplane being flown well).

If the visibility drops to less than 2 miles in the mountains you are going to need some luck to survive. You should already be on the ground, if you’re not then go down now. If no airport is close by do an off-airport precautionary. There may be some specific situations where this advice doesn’t apply – for you to recognize such a case you would need to be a highly experienced mountain pilot and you wouldn’t be paying attention to this advice anyway. A debate you may find yourself facing someday in mountain flying is whether or not to climb out of the valley and request an emergency IFR clearance. The practicality of this option depends on several factors – but it usually isn’t a good idea. Obviously if you are flying a high performance twin, such as a KingAir, and the valley is wide, and you can ensure yourself of a suitable heading to avoid the valley sides during the climb, then it is a possibility. But if you are deep in a valley in a C-172 or similar airplane then a climb to IFR altitude is definitely a last desperation move to be executed only by a pilot who did not follow all the other advice provided above.

In summary, you should consciously get into the habit of categorizing the weather, as described above, as you fly on valley trips. Know your command responsibilities for each category and fulfill them. If you do this you won’t get into trouble and you won’t scare yourself either.

Dealing With Fractus Clouds, etc.

Sometimes when you fly a mountain valley the ceiling is smooth and the visibility is constant below it. That makes it pretty easy to categorize as suggested above. But often there are bits of clouds that tear off from the main cloud deck and float around in the valley – these are called fractus clouds. There can also be isolated showers in which the prevailing visibility drops for several miles. There can also be isolated shallow fog banks that hug one side of the valley, or completely fill some section of the valley. When you encounter these weather phenomena you need a plan.

Often the fractus clouds block your vision down the valley. If they drop it below 10 miles then you should immediately adjust your category to marginal and start planning a diversion. However, while you are doing that you should try changing your cruising altitude. Move up a few hundred feet, or if that isn’t possible descend a few hundred feet. Often a small change in altitude will give you a completely different perspective on the clouds and you might be able to upgrade your weather category back to good (if not then you haven’t lost anything by trying.) If an altitude change doesn’t help then try moving a bit side to side in the valley - normally you should be on the right-hand side but you can try moving to the center, or even to the left side for a while. If you do move you need to take extra care looking for other airplanes, but it is a reasonable experiment to see if things look better. If they do look better then scan the valley ahead and judge as to whether or not to continue. Seldom will you need to fly the non-standard side of the valley for more than a few minutes – if it looks like you will have to then perhaps it would be wise to cancel the trip, especially if it is a frequently flown route where there is likely to be opposite direction traffic.

It is not uncommon to change altitude several times on a valley trip, in order to maintain the highest possible visibility. It is much better to change altitude than allow flight visibility to deteriorate due to dogged insistence on maintaining a specific altitude. Keep in mind that all the power changes increase your fuel consumption, so you need to keep conservative track of your remaining fuel. Also keep in mind that if you are doing this sort of thing then by definition the
weather is marginal, so you should have a specific diversion plan and cut-off weather in mind.

Don’t forget to keep track of whether you have enough fuel for your diversion plan. We will talk about fuel reserves next.

Fuel Reserves on Mountain Valley Trips

When planning flights in the mountains, especially east-west flights where you will be climbing and descending over passes, remember that fuel consumption tables in the aircraft POH are based on properly leaned mixture. Since you will be setting the mixture rich during climbs and may leave it rich during descents your fuel consumption will be higher than on “normal” cross-countries. Plan accordingly; we recommend increasing your planned fuel consumption by 10% (i.e. use 110% or POH fuel flow values. You should record actual fuel consumption figures over several valley flights to determine your actual fuel flow rate before using anything lower
than this recommended value for flight planning purposes).

CAR 602.88 states that VFR flights must carry enough fuel to reach destination plus 30 minutes reserve. This is completely inadequate fuel reserve for most mountain flights, particularly valley mountain flights.

One reason to carry more reserves is that mountainous areas are usually sparsely populated, so airports are further apart. The same applies to some non-mountainous areas also, and you should carry more reserves there too. The reason should be obvious – if you reach your destination only to find the airport closed (perhaps due to an accident on the airfield) 30 minutes reserve is not of much value if the next nearest airport is two hours flying time away. So, always carry extra reserves in sparsely settled areas, especially when the destination airport has only one runway. Some day I guarantee you will arrive at destination only to discover the runway closed – and as we have mentioned many times you will not be remembered for the 1,000 successful flights but for the one accident you had.

There is another reason why extra fuel reserves are needed in the mountains and that is that diversions are common and can often extend the length of a trip by a large amount. The author has many times flown from CYCG to CYVR VFR in a C-172 or similar aircraft. The record shortest trip was 1.4 hours (good tailwinds and direct flight at 8500 asl) the record long flight was 5.0 hours. The long flight started off with a plan to fly the VFR route along highway 3. This crosses two passes, the Rossland (known as the Blueberry Paulson) and the coast range (known as the Allison pass, or Manning park pass). Both passes were crossed with no problem and the airplane was within 30 minutes of destination at the Hope slide right on schedule as per the flight plan, which called for 2.0 flight time to CYVR. Unfortunately low cloud at Hope required a 180 turn-around. From Princeton we then tried following the Coquihalla to Hope. Unfortunately it was necessary to turn around at the tollbooth. The third try was the charm – from Princeton I flew to Lytton then south along the Fraser Canyon to Hope, then on to CYVR. 

Note that fuel is not available in Princeton, so if 6.0 hours of fuel had not been onboard this flight could not have been completed. Of course the airplane could have been landed in Princeton, but it would have been stuck there until fuel was brought in by land vehicle. The air regulations do not prohibit that, but it would be quite undesirable.

The minimum practical requirement for fuel on a mountain flight is to have enough that if diverting at any point along the route you can always find your way to a safe place to land. Usually the greatest consideration must be given to the later part of the route, as that is where your fuel reserves will be lowest. Don’t make the mistake of thinking that if you make it 75% of the way along a route you will make it all the way. It is very common in the mountains to have to retreat within only a few miles of destination. My personal record is making the 180 turn-around on base leg for destination. So – it is really true that you may have to divert at any point on a trip, and should have adequate reserves to make that diversion.

Ideally you should carry enough fuel that you can both divert to a safe place to land and also refuel to continue with the trip.

The only conditions in which you should even consider reducing reserves to less than advocated above is when the weather is excellent, as defined previously. In that case a diversion is very unlikely and you might prudently fly with a 30-minute reserve, IF you have taken the question of sparsely settled (few airports) into consideration.

High Density Altitude Operation

It was mentioned earlier that most airports are in the bottom of valleys. That is quite fortunate because it means that the airports are not at too high density-altitude. In Canada we have far fewer really high altitude airports than in the USA; Calgary being the highest major airport at 3,557’. The Denver airport is famous for being “one mile” above sea level (5,280’). But the Grand Canyon airport is 6,800’, as is the West Yellowstone airport, and there are other small airports that are even higher.

A few years ago two pilots were on a night charter from Winnipeg to California in a Cessna Citation jet. They had to make a night landing in Utah for fuel. The airport was at 5,200’ asl and the temperature was slightly above standard, so the density altitude was 5,500’. Neither pilot had ever taken off at such a high density-altitude before. They looked in the POH and discovered that above 5,000’ the POH recommends taking off with no flaps – neither pilot had ever done that before. Never the less they taxied out for takeoff and set the flaps to zero as per the POH. At Vr they rotated but the airplane did not leap into the air the way a jet usually does.

It was sluggish and “didn’t feel right.” They rejected the takeoff – they ran off the end of the runway – they wrote off a multi-million dollar airplane – and luckily they survived to know better next time.

There was actually nothing wrong with the airplane. Any airplane, from C-172 top B-777 will feel sluggish and climb poorly at a high density-altitude.

You may have experienced a similar sensation to the one described above if you have flown the C-172 many times with only one or two people on board and mostly at moderate temperatures, then one day you get a chance to fly at maximum weight, and the temperature is a bit warmer than you are used to. When you rotated the airplane may not have lifted off, instead the stall horn beeped and the airplane seemed to stay “stuck to the ground” for what seemed like forever. In fact it was only a few seconds before the airplane finally staggered into the air, but it seemed longer. You would then have noticed that the airspeed was lower than it usually is, so
you lowered the nose and finally everything settled down the way is should be, except you were climbing at several hundred feet per minute LESS than you are used to.

If you are taking off from a high density-altitude airport you MUST anticipate that the airplane will be sluggish and the climb after liftoff shallower than you are used to. Be sure that you have used the POH charts to determine that you have sufficient runway before taking off. When you rotate do so a bit slower than you would a sea level and establish a slightly lower pitch attitude (think about the attitude you would use in climb at the altitude in question, that is the attitude you will need to rotate to on takeoff). Remember that if you over rotate airspeed will remain too low and climb performance will be worse than it should be.

While high density-altitude is most noticeable during takeoffs it is also a factor during enroute flying in the mountains, especially with lower powered airplanes. Recall the discussions above about how critical climb performance is when approaching a pass, or when flying through a downdraft while crossing a ridge, and you can easily see why reduced performance due to high density-altitude is a problem. Many mountain flying accidents have been caused by reduced climb performance when a pilot attempted to out climb rising terrain only to discover that the airplane was not able to climb as steeply as s/he anticipated. The problem is of course exaggerated if the airplane is loaded heavily. Consequently your flying at Selkirk College, where the airplane is normally well below gross weight, might give you a false sense of security for post-graduate flying at higher weights. Keep that in mind for future mountain flights. Also remember that density altitude is substantially affected by air temperature. Your flying at Selkirk College is mostly done in the cooler months, but if you were flying a fire patrol over the same terrain on a hot August day reduced climb performance due to high density altitude could represent a trap waiting for you to fall into it – so be alert to this danger when mountain flying.

One-Way Strips

As mentioned under the topic Precautionary Approach, many strips in British Columbia are one-way due to high terrain on one end of the field. A photo of Crawford Bay airport can be found on page Error! Bookmark not defined., showing the rising terrain north of the field. The CFS advises pilots to land on runway 32 and takeoff on runway 14. You will have an opportunity to land at this airport when you do your CPL preparatory flights in second year.

Prior to landing at any one-way strip you must always determine your airplanes required landing and takeoff distances WITH A TAILWIND. Decide in advance the maximum wind you are willing, or permitted by your company SOPs, to operate with – then calculate the required runway length with that wind applied as a tailwind. Any time you land at a one-way strip you will either have a tailwind on landing or takeoff, so you need to know before you get there whether or not the runway will be long enough. Be sure to remember to allow for grass or gravel runway if applicable. (Most one-way strips are also unpaved.)

When landing on a one-way strip there is a point on final approach where an overshoot is not safe. Consequently you must determine early on the approach that all is well – and if it is not overshoot early while you still have enough altitude to clear the obstruction. To equip yourself with the best possible odds avoid “crowding” the circuit. Make the base leg reasonably wide so you have a long final approach to get setup on the desired glidepath. DO NOT wait until short final to slow down. On such a difficult approach it is important to establish final approach speed early.

This photo shows an extremely difficult to judge runway. It is easy to misjudge the approach to a runway like this. Use your VSI and scan ASI frequently. If you airplane has the ability to generate an artificial glide-slope be sure to use it.

One of my ex-military thousands-of-hours pilot friends told me in discussion: "Oh yeah, high, hot and heavy are the 3 dangers in aviation."

It's a question of density altitude, which is directly related to aircraft performance. If you're too high, or it's too hot, the plane won't fly. If you're heavy, it's worse.

I found an article to backup what he was mentioning.
(Revised for length.)

NOAA’s National Weather Service July 2012
By Jim Reynolds, Meteorologist

Hot, High and Heavy—The Deadly Cocktail of Density Altitude

Density altitude really can only be seen through aircraft performance.

Unfortunately, density altitude can have deadly consequences before a pilot has a chance to sense its presence.

By definition, density altitude is “the pressure altitude adjusted for non-standard temperature.” Simply put, increasing temperature at a given atmospheric pressure will cause the air density at that pressure to appear as though it resides at a higher physical altitude.

Pilots fly through an atmosphere of air made up of invisible gases.

Only when there is an excess of particulate matter or water vapor in the air can anything be seen in the flight environment. Because air is otherwise invisible, it is not possible to tell when it becomes thinner.

Thinning happens due to increased space between molecules when an air mass is either warmed, has water vapor added to it, or is raised in elevation. Increased spacing between air molecules, which causes air to become thinner, has the following three effects on aircraft performance:

  1. Slower acceleration on takeoff because of a power production reduction. 
  2. Higher true airspeed required to produce the same lift associated with a lower temperature, which generally requires a longer takeoff roll to achieve.
  3. Slower climb because of the reduction in power production and lift.

Any mix of the atmospheric conditions that cause aircraft to perform at the minimum range of their operating envelope are “high density altitude” situations, and are usually quite dangerous.

(Worse...) Keep in mind that the greater loading of an aircraft by either people or gear will eat away further at the diminished capabilities of the aircraft in high density altitude situations.

It's easy to miss developing high density altitude situations. You might sense an increase in humidity, or mugginess, in your surroundings or observe hazy conditions. You might also get a sense of being at an increased altitude because you find yourself catching your breath when doing tasks that don’t usually cause you to breathe deeply.

These physical signs, however, are not enough for pilots to gain a true understanding of how their aircraft will perform given current conditions.

The only way to truly ascertain how an aircraft will perform is to first compute density altitude according to a chart or a calculator and then correlate this information with aircraft performance data in the aircraft’s operating handbook.

While most density altitude effects are experienced at higher elevations, extremely high temperatures at lower elevations can lead to equally negative aircraft performance problems.

Case in point: high temperatures across portions of the desert southwest can easily exceed 115oF in the summer months. ...a temperature of 120oF will cause most pilots to choose not to fly into or out of the airport until temperatures cool down some.

While the effects of density altitude can be insidious, there are ways to beat this hidden foe.

  • If at all possible, fly early or late in the day. Any reduction in temperature may add hundreds of feet to the elevation the airplane thinks it is operating at.
  • Fly as light as possible. If you don’t need full fuel tanks to reach your destination, take on a lesser amount of fuel, much less if possible. Leave behind all of the baggage you don’t really need.
  • Bring along only those passengers necessary for the trip. High density altitude situations are bad for those individuals that just want to tag along.

In short, don’t let the cocktail of “hot, high and heavy” be hazardous to your health!

Putting the above into a practical example, if you're in a C172, your max Service Ceiling = 13,500ft. That's not very much margin if you're attempting cross any decent mountains.

By the E6B, let's say your mountain to hop over is 8500ft MSL (not so high really), and it's normal pressure day Altimeter 29.92 (which can drift widely), and it's a pretty hot day of 28°C (about 83° F).
Your Density Altitude is already almost 12,000ft, and your plane is struggling as it is, leaving you with only 1,500ft margin before you got nothing to pull you up or forward.

If you need to get any higher, or if that gets any warmer, or the barometer changes much, you're done for.

Or perhaps you gotta jettison your girlfriend out the window.

by Cordell Akin

My early years were spent in the Midwest, and I vividly remember seeing mountains for the first time when driving west through New Mexico. I was fascinated by them at the time, and that fascination still remains. I love living in the mountains and mountain flying.
Mountains are usually described in terms of panoramic views, snow-capped peaks, green valleys, or the place where one can find a bubbling stream beside a trail that makes the perfect camping spot. I think of these things as well, but I also think of mountains with a mind to aviation: unpredictable winds, high density altitude, steeply rising terrain and box canyons, mountain waves, rotor clouds, turbulence, and clouds covering high ground. This list may sound foreboding, but awareness and knowledge of such things is what makes mountain flying a pleasure, rather than an uncomfortable encounter with the unexpected.

Route Planning
Route planning becomes very important when flying in the mountains, as a straight line between two points may not be the best way to go. Pick a route that avoids the rugged areas and highest peaks where an emergency landing could not be made. It usually takes very little extra time to bypass the most mountainous areas and follow major roads through more populated areas and lower terrain

After choosing the safest route, file a flight plan. It is extremely difficult to locate an aircraft that has a forced landing in rugged, tree covered mountains. I have flown search and rescue missions with the Civil Air Patrol that lasted days—sometimes even weeks—because the route of flight was not known.

The Little Plane That Couldn't
As I wrote in the last article, density altitude (pressure altitude corrected for non-standard temperature) is an important consideration for take-off and landings.

It must also be considered should you fly over high mountains. The rising terrain will often out climb non-turbocharged aircraft. If your aircraft has a service ceiling of 14,500 ft., that is based on standard atmospheric temperature which is 59&Mac251;F at sea level and decreases an average of 3.5&Mac251;F per thousand feet. If the surface temperature at 5000 ft. is 100 degrees, the density altitude on the ground is about 9,000 ft. When you climb to an indicated altitude of 9,500 feet you have reached the service ceiling of you aircraft. I departed with an instrument student on such a day, and we could have eaten lunch during the time it took us to climb from the field elevation of 5,000 feet to an indicated altitude of 9,000 feet. Even if your aircraft makes it to 9,000 or 10,000 feet, the rate of climb will be painfully slow.

If you are flying toward higher ground in a climb and the terrain is going down in your windscreen, your plane will clear it—provided there are no downdrafts. If the terrain is rising in your windscreen, you won't make it, no matter how hard your little airplane tries.

Two pilots from Dallas, TX, were flying in New Mexico in a C-I 72 and decided to cross a ridge just south of Truchas peak (13,102 ft.). The ridge is 11,500 ft. and the aircraft crashed at about the 11,000 ft. level. An aircraft that is trying to climb near its service ceiling will be flying at an angle of attack near the stall. A steep turn away from rising terrain can quickly bring a stall, because the stalling speed increases in a turn.

If you wish to fly in a canyon, climb to the top and fly down the canyon towards lower terrain so as not to get "boxed in." Should you find yourself trapped in a dead-end canyon that is too narrow to make a normal turn, the best option is to apply full flaps to slow down and lower your stalling speed and make a 180&Mac251; turn . The slow speed will decrease the radius of the turn. The best plan for flying in mountainous terrain is to always be in a position where a turn can be made toward lower ground.

Here Come The Winds
Believe it or not, there are calm days in the mountains, but it's most likely than not you will meet the wind if you do much flying over the nation's rooftop. In a light aircraft, it is best to stay on the ground if the winds are greater than 35 miles per hour. Due to the venturi effect, winds will be much greater in the vicinity of mountain passes. Cross passes as high as possible, as downdrafts up to 2,000 feet per minute can occur on the leeward side.

When strong winds of 40 to 50 miles per hour are blowing perpendicular to a mountain range, expect mountain waves and strong downdrafts for many miles on the leeward side. The presence of mountain waves can be identified by lenticular (lens shaped) clouds on the downwind side of the mountains. Rotor winds are also associated with this wind condition. These are strong winds rotating in a wheel like fashion on the immediate leeward side of mountains.

On windy days, always expect turbulence and keep your seat belt and shoulder harness fastened snugly. A sharp jolt of turbulence can slam your head into the cockpit roof and it only takes one time to make you a believer in snug seat belts.

Where Have All The Mountains Gone?
The situation you don't want to enter is to be flying in the mountains and not see them because they are covered with clouds. The combination of rising ground and lowering ceiling can be deadly. I flew a search mission looking for a Long E-Z that crashed in the trees east of Clines Corners, NM and just a few hundred yards north of I-40. The pilot was following the interstate under a low cloud deck, and the ground rose until he ran out of room.

Mountains disappear not only in clouds, but also at night. You should not fly over high territory after sunset unless you are at the minimum en route IFR altitude which provides a 2,000 ft. clearance along airways. When flying after dark, closely monitor your altitude and when in a turn, your rate of descent.

When approaching towns or airports, watch the lights to see if anything rises between you and them. Anything blocking your view of the lights will be higher ground. Also remember that at night you cannot see clouds; a combination of being in the clouds and the dark will really make you wonder where the mountains have gone—and how close they may be.

Mountain flying calls for extra precautions and preparation, but the extra effort is well worth the time. Don't miss the opportunity to fly over the high world, should it come. There is nothing quite like looking out the window at a 10,000 foot peak that appears pleased you have come up for a visit. I think you, too, will find the mountains fascinating and will be lured back many times by their beauty and grandeur.

* * *

Cordell Akin is a CFII, MEI with a total of 10,000 hours and 3,000 hours as a flight instructor. He spent 15 years in East Africa flying a C-185 and a P-210. He is the owner of Akin Air at Coronado Airport in Albuquerque.