Read accident case studies and aviation stories to help you stay sharp.
By Dan Sobczak
Editor's note: This article first appeared in America's Flyways magazine in June 2005, and Airport Journals in August 2005. This content does not constitute flight instruction. Consult a certified flight instructor in your area for proper flight instruction.
I once sat inside the cockpit of a Cessna L-19, a two-seater with a big engine and a climb rate more than double that of a Cessna 172. The aircraft was being flown in the Colorado Mountains on what appeared to be a perfect flying day: calm conditions and severe clear.
The Cessna's flight ended prematurely, however, going down vertically into gradually rising terrain, fatally injuring the pilot and passenger onboard. But I survived the two-seater's crash.
How is it possible that I could have been onboard this two-seater's flight and survived such a crash in the mountains? Because I was watching the final 20 seconds of this flight on videotape from the perspective of inside the cockpit.
The Rocky Mountains west of Denver, Colorado. Photo by Dan Sobczak.
The souls onboard happened to be capturing their flight on videotape by a cockpit-mounted camera when a rather pleasant scenic flight turned tragic in just a matter of moments. Two years after the crash, a hiker accidentally discovered the Cessna’s wreckage. The videotape onboard captured the entire accident.
On the tape, the pilot and passenger make sundry comments concerning the beautiful scenery, while the terrain below gradually rises. Moments later, the pilot is aware of the steeper terrain, but by now it's too late. All of his escape routes are closed. At nearly treetop level, he attempts an escape from the rising earth. You hear the stall warning go off. You see a wing drop. The aircraft enters a stall. And seconds later, it's all over. It is very chilling to watch this tape.
But it is even more chilling to realize how easily you as a pilot can get into such a situation if you have not prepared in advance, and how difficult it is to get out once all your escape routes have expired. Certainly the best escape route is to avoid getting your airplane into such a situation to begin with.
As a safety-conscious pilot, how do you prepare? There are many good articles and books written on mountain flying techniques, and it would be well worth your time to read a few of these texts to increase your aviation knowledge. But knowledge alone may not be enough to save you. Not one of these books can give you what you really need to fly the mountains: experience.
No matter how many hours you may have logged as a pilot, until you experience mountain flying and the related effects of density altitude on a light aircraft's performance, it is difficult to appreciate how remarkably different it is compared to the performance your airplane achieves at lower elevations.
As a student pilot, my limited knowledge of density altitude may have been slightly better than the average student because I learned about this phenomenon very early on in my training from a meteorologist who is also a pilot. He introduced me to the three H's of density altitude: Height, Heat and Humidity. As altitude (height), temperature (heat), and humidity increase, so does density altitude, or the altitude the airplane thinks it is at, and performs in accordance with. As density altitude increases, your airplane's performance decreases.
But my knowledge alone was not enough. I had an excellent flight instructor during my private pilot training, but one flight we never undertook was that of heading north to the mountains of Arizona for a lesson in density altitude to experience decreased aircraft performance.
As a result of my student training experience, shortly after I passed my check ride I made the decision that the northern half of Arizona, with all its tempting beautiful mountain scenery, was off-limits to my flying until I received mountain flying instruction. I signed up for a local flight school's FAA-sanctioned mountain flying safety course. The one-day course (which was also part of the WINGS pilot proficiency award program) included 2.5 hours of thorough ground instruction and 3.0 hours of flight training to three of northern Arizona's most popular, and potentially dangerous, airports: Flagstaff (KFLG), Sedona (KSEZ), and Payson (KPAN).
At 7,011' MSL, northern Arizona's Flagstaff Pulliam Airport (KFLG) offers pilots rewarding views of the San Francisco Peaks mountain range, while raising significant safety challenges due to high density altitude. Photo by Greg Brown. Used with permission.
After preparing my own flight planning prior to the day of class, I walked into the briefing room where the usual hangar flying conversation transpired among the other five pilots who also enrolled in the course. The ground school began with an introduction which described what mountain flying has to offer pilots: great flying, fantastic scenery, and, as we all discovered upon watching the Cessna L-19 video clip, the tragic consequences of not being prepared for it.
The ground instruction covered a lot of material, including density altitude and related aircraft performance, proper mixture leaning procedures for various phases of flight (emphasizing the use of maximum lean for taxi operations), the importance of flying the same indicated airspeed you would normally fly at lower elevations, the effects of weight and balance on a mountain flight, and of course weather and mountain waves.
After the ground instruction was complete, I teamed up with a flight instructor to begin my mountain flying experience. However, it quickly became apparent we would not be making our flight to the north country due to thunderstorms enroute and snowy conditions at Flagstaff, only 89 nautical miles north, despite the sunny and clear morning weather in Phoenix. It was a good lesson in obtaining detailed weather briefings before venturing into the mountains. Weather can change quickly in the high country, and often has much more localized weather phenomena than do the flatlands, so obtaining a thorough and detailed weather briefing is key in making your go/no-go decision.
I rescheduled my flight, and two weeks later, it was time to fly. This day, the weather was cooperating nicely despite gusty winds up north, so my flight instructor and I strapped into the school's Cessna 172S and took off for the high country. Launching from Deer Valley Airport (KDVT) at an elevation of 1,478' MSL, I took note of our C-172's familiar 500 fpm climb rate and we flew direct to Flagstaff Pulliam (KFLG), elevation 7,011' MSL, about a 50-minute flight. As our flight progressed, we discussed each topic we had gone over in class as it came up during the flight: route selection, proper methods of crossing ridge lines, determining the effects of wind against terrain, and engine performance.
As I quickly learned during my flight, one of many keys to successful mountain flying is knowing the winds aloft. Knowing how the wind is affected by the mountainous terrain below and visualizing what the wind is doing when it comes in contact with terrain is paramount. As my instructor illustrated, to help visualize this a pilot should think of the wind as water flowing over rocks. Flowing water is smooth when running over a flat, even surface. Once the water flows over jagged rocks, it flows like rapids in a raging river where turbulent waves are created, often lasting far downstream. Similarly, as airflow passes over a ridge, mountain waves form, while underneath and often invisible to the pilot are severe rotor waves, which frequently have downdrafts in excess of 1,000 fpm, far exceeding the climb ability of any normally-aspirated light aircraft.
But how do you determine winds aloft during your flight? Often while flying over the mountains, you may be out of communication range and unable to obtain enroute weather briefings from a nearby flight service station or an air traffic control center. If this is the case, then your next best tool is the weather itself. Remember the old standby see and avoid for traffic avoidance? In this case, it's see and observe. If there is visible moisture in the air in the form of clouds, then you have another source of information about winds aloft right at your disposal. All you need to do is decipher the message. Every cloud tells a story about its adjacent wind patterns. And it's up to you as the pilot to read what the clouds are telling you about potential winds that may affect your flight.
As we made our approach into Flagstaff, a perfect example of a lenticular cloud, resulting from the mountain wave over the peaks that day, appeared to rest comfortably over the tip of Humphrey's Peak, the highest point in Arizona at 12,633' MSL (just five miles northwest of the Flagstaff runway). Of course, we knew the wind currents running through and below that lenticular cloud were anything but restful.
The beautiful red rock vistas of Sedona, Arizona (KSEZ) lure pilots from around the country. Photo by Greg Brown. Used with permission.
We flew a low-pass over the Flagstaff runway to experience what a go-around would feel like at our now-diminished and sluggish climb rate of 200 fpm, flew the traffic pattern, performed a full-stop taxi back, then launched for Sedona Airport (KSEZ), elevation 4,827' MSL, about 10 minutes to the southwest. After a brief stop at Sedona Airport to stretch our legs and check in with Prescott Flight Service once more for an updated weather briefing, we launched for Payson (KPAN), elevation 5,157' MSL where we performed another full-stop taxi back, and then launched for home. Three hours exactly had ticked off on the Hobbs meter when we shut down back at Deer Valley Airport (KDVT), after which we discussed the flight in detail in our debriefing.
There are, however, plenty of other aspects about mountain flying pilots must understand than simply density altitude and weather patterns. Many mountain airports have their own visual illusions due to varying circumstances, such as sloping terrain, or nightfall, which cause the headlights of cars on nearby highways to appear as a false horizon. Interstate-17 just a few miles off the departure end of runway 21 in Flagstaff can be a dangerous false horizon if conditions are just right, especially with the fast-rising terrain just a few short miles beyond the interstate.
In addition, each mountain airport has its own unique weather phenomena due to surrounding terrain, as I learned at Sedona with its cliffs and jagged rock formations all around the immediate vicinity of the runway. Don't forget that some mountain airports have obstructions at the end of a runway which may be impossible to clear in a single engine light aircraft, such as the 7,903' MSL peak just 12 nautical miles southwest of Payson. A thorough pre-flight before launching is key to knowing the complexities of your route over the mountains and the conditions at your destination airport.
No flight should end tragically like the Cessna L-19 crash video. It's up to you as the pilot in command to determine the outcome of your mountain flight. Mountain flying offers pilots rewarding flying experiences and fantastic views, but it also raises significant safety challenges. As one flight instructor who has years of instruction experience told me, mountain flying and related density altitude topics may be the most consistently under-trained and poorly understood operations in general aviation. You owe it to yourself, your family and your friends to receive the proper training experience before flying the mountains.
The Flight Chain App team
Dan Sobczak is the founder of www.FlightChainApp.com, a mobile app that helps pilots learn from accident chains by making NTSB reports more convenient and easier to digest. Dan received his private pilot certificate in 2003.
Flight Chain App and its companion blog www.AheadOfThePowerCurve.com are committed to reducing general aviation accidents, helping improve aviation safety, and growing the pilot population.
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Flight Chain App and its blog Ahead of the Power Curve are committed to reducing general aviation accidents, helping improve aviation safety, and growing the pilot population.