Flying in the Mountains
IFR Means I Follow Roads
By Alan Smith
Flying light aircraft in the mountains, especially during the winter months, has its own set of rules. Some are fairly obvious while others are a bit more subtle.
Flying a light plane through rugged mountain territory is done without some of the emergency options a pilot has while crossing the flatlands or wide valleys below. It should be clear, for example, to any pilot as he or she moves through the high peaks and canyons of a mountain range that fields in which he could safely put the airplane in the event of engine failure are few and far between.
In fact, they are so rare that a sensible pilot should just assume there are none. What does this mean? It’s best, especially in any single-engine aircraft, to keep a road within gliding distance. Not just any road, but, if possible, one that one could fly out of again once the problem is solved. Freeways look nice but have heavy traffic and overpasses. You could probably safely land in the freeway median. But you could very probably not fly out of there. You and your airplane would have to leave expensively on a flatbed truck.
Long ago, while in rough country in a Citabria, I noticed that my windshield was slowly being covered with oil and that the oil temperature was rising. A definite “uh oh.” No airport was in reach. I had been trained to look for an alternative should it be needed.
I was to the right of a paved two lane county road I had been keeping in reach. I reduced power a bit, slowed, and moved over the road. First, I looked for traffic. It was light. Then I looked to see on which side of the road telegraph poles were installed. I looked for any chimney smoke that would give me a wind direction. Even the exhaust smoke of a diesel truck would tell me that. To be sure, I made an “S” turn over the road and looked for drift. I had been heading east in a prevailing west tailwind, so I made a teardrop turn back over the road and started a long final approach, watching for traffic, and hoping the engine wouldn’t seize.
I didn’t want to land just ahead of a car that was speeding along. The driver might be daydreaming or listening to music and, in any case, wasn’t ready for a slowing airplane to come out of nowhere in front of him. In a few minutes I saw a good hole, closed the throttle and dropped to the road with a bounce, staying well to the right because of the utility poles on the left. I was almost able to pivot off the road on the right as I pulled the mixture to shut down. So far so good.
People drove around me staring as I set the brake and got out. Finally a man stopped in his pickup and asked what (the hell) was going on. Then a state police car arrived and at first, the officer was hoping to write somebody a citation for something. Then he calmed down and joined the pickup driver in watching me check the engine. I found a loose oil cap that had allowed oil to siphon out of the crankcase. It was half gone and all over the belly of the Citabria. The three of us picked up the tail and got the airplane pretty well out of the road. Now, what to do?
The pickup man offered to drive me to a gas station, and the officer said he would watch the airplane. I obtained 40-weight oil that would get me home, and the police (two of them now) held up traffic while I made a downhill, slightly downwind takeoff. I climbed out and turned back to rock my wing in thanks for their help.
That’s the way these things are supposed to go. First of all, I knew I had a problem well before actual engine failure. Engines usually don’t just fall silent unless you’re dumb enough to run out of fuel. They do a lot of complaining before giving up. You should know enough about your power plant to be able to see and hear the symptoms of coming failure. Secondly, I had a partial emergency plan in mind throughout the flight in mountainous terrain and, therefore, had no tendency to panic. Whatever happens, do not panic and keep flying the airplane. Panic will kill you.
It’s important to learn what the other hazards inherent in mountain flying are, and get good advice on the best way to deal with them. When you know your route and destination, other pilots that know the area can give you some local info about things to look for or avoid, such as the built-in downdraft at the east end of the east-west runway at Truckee, Calif., but there are some mountain hazards that are everywhere.
No. 1: Density Altitude
A good example is the field elevation at South Lake Tahoe. The runway there is at 6,000 feet. Sure, you say, you know that a takeoff run in a Cessna 172 will be a lot longer in the thinner air. But what if it is a summer day? Thin air thins out even more in warm temperatures. That is the “density altitude.” On a July day at Lake Tahoe the effective or density altitude could be 9,000 feet or even more. With an effective service ceiling of about 11,000 feet, what will a Cessna 172 do on takeoff at 9,000 feet? Not much.
It’s even more dangerous than that because of the deception of high ground speed, versus low airspeed. Remember that at a high DA, your indicated airspeed will be less than your groundspeed. Don’t be fooled. We all know about ground effect, right? It’s a high-pressure area between the wing and the ground that will extend up to about equal the airplane’s wingspan. The airplane gets off the ground at Tahoe on a summer day and flies a few feet off the ground in ground effect but it’s not ready to climb. Use the whole runway and when the airplane lifts off into ground effect, keep the nose down and accelerate in ground effect to a safe climb speed. If you try to force it into a climb, you’ll be out of ground effect and will stall. I hate to think how many light aircraft are on the bottom of that lake. I’ve been told there are many.
No. 2: Mountain Tight Spots
The profile of the Sierra Nevada range is not unlike an isosceles triangle. The western slope is the long leg of the triangle and the eastern slope is a steep drop into high desert and wide valleys. At some points the eastern flatlands are at 4,000- to 5,000-feet above MSL. The western slope has many steep ridges and canyons along rivers and their tributaries. The prevailing west wind coming out of the central valley pours over this terrain creating updrafts on the windward side of ridges and sharp downdrafts on the leeward or eastern side.
Trying to climb against a downdraft can result in a stall. Keep the nose level and turn downwind to fly out of it. And stay out of canyons on windy days. If you must go in there, stay on the side downwind of the prevailing wind. You’ll find some updrafts there near the canyon wall. Don’t fly down the center. Turbulence from air flowing in downdrafts from the windward side and mixing into updrafts on the other side causes wind shear that could stall you in the middle.
Canyons can also narrow suddenly or end as a “box” canyon with not enough room for a 180-degree turn. Tight turns in tight places are not a good idea. You effectively increase your load in a tight turn and the stall speed jumps up at you by as much as 40 percent. A standard rate turn only increases it by 7 or 8 percent. Don’t go past the last spot where you could turn and above all, don’t be indecisive about that.
Overall, when flying in rough country, it’s best to first get acquainted with your airplane. Practice slow flight out in the open. Put in a notch of flap, reduce power and bring the nose up. Then start adding power back in to maintain your altitude as the airplane slows down. Then, with power, altitude and speed stabilized make some gentle turns and maintain your altitude with power adjustments. Experiment until you have the whole slow flight envelope in mind. Do slow climbing and descending turns. In other words, know your airplane throughout its performance spectrum. You don’t want to start learning what your airplane can and can’t do when you’re in a tight spot. Using this reduced speed in mountainous terrain will also give you more time to make decisions and lessen the impact of air turbulence you will definitely encounter.
No. 3: Mountains Have Their Own Weather
Before leaving on a cross country flight, I know you get the most current weather forecasts available for your route and your destination. However, if there is a mountain range like the Sierra Nevada between your points A and B, bear in mind that the weather forecast may not hold. Factors like the humidity level or ambient temperature of the air mass moving across and pushing up through the mountains may produce local conditions in the rugged terrain. For example, a fairly low overcast drifting across the California central valley will be pushed up the long western slope of the Sierra, cooling sharply as it rises. The result could be a local but heavy snowfall in the upper reaches of the western slope.
I had an experience with that a few years ago. I left a city in the north San Francisco Bay Area for Reno one afternoon. The weather seemed mild enough and VFR conditions under an overcast sky were forecast all the way. Yet, before I reached Donner Pass, I found myself east of Auburn in blizzard conditions. Already icing up, I made a quick turnaround and headed a bit south to land at Placerville. Conditions got worse and Reno now reported snow. I spent the night and went on the next day in a crystal clear morning. I found a hole in the cloud wall, and went on to a now sunny Reno.
There are also heating and cooling differentials where valleys are next to mountains. During the day, the valley will heat and send rising warm air up the mountain slopes to create updrafts. Late in the day, the mountains will cool faster and produce downdrafts of cooling air flowing back down the mountainsides into the valley. Those are just a couple of reasons why mountains can create their own extremely local conditions much different from those forecast for the region.
Finally treat the mountains with respect. If you simply want to get across a mountain range, maintain plenty of altitude. Stay 2,000-feet above the mountains while enroute. Thus means lighter loads. For example, a Cessna 172 essentially becomes a two-seater in the mountains. I prefer to rent a 182 (or equivalent) with its increased horsepower and constant speed prop when going into high country. Don’t attempt a mountain crossing in an airplane not capable of cruising at 11,000 feet MSL. Consult AOPA online for the best mountain crossing routes and MEA altitudes.
It’s also wise to rent or buy two-person oxygen equipment for use during the trip. Some time ago, while crossing the Rockies at Corona Pass in my Piper Tripacer with one passenger, I found myself pushed almost to 13,000 feet in a western slope updraft. My fingernails turned blue and I could see the instruments, but was very slow to understand them. Needless to say that, as soon as I’d crossed the Pass, I got back down to 9,000 feet ASAP.
The mountains are beautiful and spectacular from the air. Just be sure you know your airplane, know yourself, don’t fly into mountain weather, and remember that, in the mountains with single-engine airplanes, IFR means I Follow Roads.
