Aircraft Owners and Pilots Association Protecting Your Freedom to Fly

Safety Publications/Articles

Simulated mountains

Even flatlanders should know how to fly the hills

Years ago, I worked as the full-time "aviation safety guy" for the state of New Mexico, working to encourage safe flying in the aptly named Land of Enchantment. It was a great job, but there was one discouraging part: seeing the number of "flatlander" pilots who would arrive without realizing how different flight operations can be when field elevations are 5,000 or 6,000 feet or more, and - in the summer, at least - density altitudes can be close to 10,000 feet.

With unfortunate regularity, these visiting pilots would wipe out, littering the beautiful landscape with their airplanes and themselves. More often than not, the root problem was lack of respect for (or lack of true understanding of) density altitude.

My predecessor in that job had once suggested, facetiously, that we erect an 18,000-foot-high fence along the eastern border of the state, stopping flatlanders to ensure that they knew at least the basics of mountain flying. Like all pilots who learned to fly in high terrain, he considered true understanding of density altitude to be fundamental aviation knowledge. He said, "If only primary instructors in the East would teach the basics! What is their problem?"

Well, unlike my well-loved predecessor, I hadn't learned to fly in high terrain. In fact, the bulk of my primary training was at an East Coast airport all of 186 feet above sea level. And even though there were mountains (albeit small mountains by Western standards) just a few miles to the west, I don't recall ever receiving practical instruction in density altitude. Perhaps my instructors at the time considered those relatively small mountains unworthy of any special consideration. Maybe.

I think it's more likely that my instructors at the time had not had any practical experience in mountain flying themselves, and so did not consider it part of the curriculum. Later, after earning my CFI and moving to the Midwest, I gave a thousand or more hours of dual instruction over pancake-flat terrain, only 700 or 800 feet above sea level, with nary a thought about teaching the effects of density altitude. It wasn't until I moved to New Mexico and had the good sense to get a very thorough mountain-flying checkout that I saw the problem.

Obviously, it's not practical to teach a full mountain-flying course if you don't have mountains. But one of the basic reasons that flatlanders come to grief on vertical terrain is lack of a true understanding of density altitude - something that's easy to teach, no matter what the field elevation of your airport. From what I've seen, however, not all instructors at lower-elevation airports do so effectively.

Oh, sure, we always cover density altitude, usually while tracing lines on performance charts. "And notice the extra 50 feet of runway required for takeoff when the temperature rises by 20 degrees in this example," we might say, stifling a yawn. "Of course this official FAA chart, which you will see again in the knowledge test, makes it awfully hard to calculate exact numbers."

So our neophyte pilot dutifully traces lines on the takeoff or climb performance chart, and if the number looks halfway reasonable, it will be entered as another keystroke on the way to a glorious 70 percent or better on the FAA knowledge examination. But is that true understanding? Not on your life!

True understanding of such things is the result of an "ah-hah!" experience, such as staggering off a high-elevation runway in midsummer, praying for a thermal that will allow you to climb out of ground effect before reaching the end of the runway. Or departing an airport in a wide valley and then realizing the only way you'll ever get out of that valley is to climb in slow circles until clearing the surrounding terrain.

It's entirely possible to effectively simulate that "ah-hah" experience, even at low elevations, simply by limiting throttle travel until airplane performance is the equivalent of that caused by high density altitude. Think of it as simulated mountains.

Simulating cumulogranite

When I moved back to low country and first started using the "limited throttle travel" method of teaching density altitude, it was obvious that something was awry. The airplane behaved much better than I knew it should at our simulated density altitude, even though I'd limited engine power to the amount that should have been available. It didn't take much reflection to realize that I'd failed to account for the aerodynamic effects of density altitude on the wings, rather than just on engine power.

But a realistic demonstration can be done without advanced mathematics: simply limit power so that the rate of climb at VY approximates that of the density altitude situation you're simulating. A rate of climb of, say, 200 or 300 feet per minute will give a wide-eyed student a realistic look at one of the main reasons why mountain flying is different. Of course, for safety's sake, caution your student that this is a "dual instruction only" exercise.

Additional resources

For flatland students who want to delve even more deeply into the joy of mountain flying, there are numerous resources. If you're an AOPA member (and any instructor who isn't is missing out on an incredible wealth of resources), simply point your computer mouse to www.aopa.org/members/files/guides/mntfly.html. Resources there include my own Flight Amid Vertical Terrain, a four-part series written from my standpoint as a former flatlander, as well as:

  • "Mountain Ways - Coping With Mountain Weather," by Thomas A. Horne. This article provides an informative analysis on how mountainous weather systems work, and more importantly, how to avoid them.
  • Mountain Flying, compiled by the AOPA Air Safety Foundation. ASF presents a thorough coverage of mountain flying from preflight to landing, including weather, mountain airflow, density altitude and aircraft performance, and techniques for flight operations in mountainous terrain.
  • "Part-time Pilots, Full-time Mountains," by Thelma Bullinger, FAA Aviation News. Particularly if you're headed for the great Northwest, there are some things for which you need to be prepared. This article vividly demonstrates the importance of knowing how to calculate density altitude, reviews winds and wind flow patterns as they travel over the changing contours of a mountain range, and teaches the signs of a rapidly building weather system that could put you and your airplane in trouble.
  • Suggested Western Mountain Routes, compiled by AOPA Aviation Services. A table of suggested routes both east to west and west to east across the Rocky Mountains. Includes mileage information and MEA and lists the appropriate charts to use.
  • "Wx Watch: Appalachian Weathermakers - The East Coast's Geography Lesson," by Thomas A. Horne, AOPA Pilot. Sage advice on flying the Appalachian mountain chain - and on the weather it generates. While the Appalachians are dwarfs compared to the loftier Rockies, they still pack a meteorological punch.
  • "California Flying: Big Bear Valley Beckons," by Steven W. Ells, AOPA Pilot. A story on flying to Big Bear City Airport, 6,750 feet above sea level. In addition to the mountain flying education, the article lists plenty of accommodations, and the list of activities runs off the bottom of the page.
  • "Never Again: Caught by the Wave," by Crista Worthy, AOPA Pilot. A first-hand account of a wild ride in a mountain wave.
  • "Safety Pilot: High-flight Hazards," by Bruce Landsberg, AOPA Pilot. An eminently readable article on how to stay safe even though flying out of the livable portion of the atmosphere. It includes the warning signs of hypoxia.
  • "The Ins and Outs of Canyon Flying: A Unique Course Offers Hands-on Flying in Idaho's Backcountry," by Michael P. Collins, AOPA Pilot. A report on a course in Idaho that takes mountain flying to the next level.
  • "Wx Watch: Riding the Waves: Flying in Lee Airflows," by Thomas A. Horne, AOPA Pilot. Wind in mountainous areas behaves in ways not always comprehensible to the average flatlander. This article takes much of the mystery out of the subject.
  • "Postcards: Exploring Jackson Hole - Be Sure to Bring Your Mountain Flying Skills," by Alton K. Marsh, AOPA Pilot. Pilots who enjoy mountain flying can see elk and bison in their natural habitat by day, then enjoy an evening meal of New Zealand elk and farm-raised bison meat.
  • "Wx Watch: Ill Winds: Riding Waves, Shears, Rotors, Bumps, and Jumps," by Thomas A. Horne, AOPA Pilot. A rundown on some of the common problems in dealing with mountain wind shear and turbulence.
  • "O2 Issues: The Whys and Hows of Oxygen Use," by Thomas A. Horne, AOPA Pilot. A comprehensive look at the use of oxygen, often a consideration in mountain flying.
  • "Mountain Flying: The Right Touch, Making Short Work of Small Strips," by Peter A. Bedell, AOPA Pilot. Many ingredients can sour the mixture of mountains and airplanes, with terrain and altitude being the most obvious. Handling small airstrips common throughout the western United States is the subject of this article.
  • "Mapping the States: Getting from Here to There More Colorfully," by Alton K. Marsh, AOPA Pilot. A look at cross-country trips in mountainous areas.
  • "FAA Aeromedical Training Programs for Civil Aviation Pilots." Information on a one-day training course that includes exposure to high-altitude conditions in an altitude chamber. A list of training locations is included.

Kevin D. Murphy, vice president of safety education for the AOPA Air Safety Foundation, has accumulated 5,000 hours in 30-plus years of flying, more than half as an instructor. He holds CFII, MEI, and ground instructor certificates, and flies his wife's 1981 Cessna 172 from their home base near Harpers Ferry, West Virginia.

By Kevin D. Murphy

Back to the Index of Instructor Reports