SW Aviator Magazine - August/September 1999 issue
Back To Basics
Mountain Flying
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.

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The material in this publication is for advisory information only and should not be relied upon for navigation, maintenance or flight techniques. SW Regional Publications and the staff neither assume any responsibilty for the accuracy of this publication's content nor any liability arising out of it. Fly safe.