Flying in the mountains

By BILL SCHROEDER, For General Aviation News

While departing a high-density-altitude airport, a Cessna 177RG, with four people on board, climbed about 50 feet but did not accelerate. The airplane was observed descending before hitting trees about ½ mile off the departure end of the runway.

MountainFlyingWeight and balance computations placed the airplane over maximum allowable gross weight. Density altitude was computed at 8,493 above mean sea level. The airport, at 6,264 feet msl, is known for its high-density altitude and downdrafts at the end of the departure runway.

Probable cause of the accident, according to the NTSB, was the pilot’s decision to take off, over maximum allowable gross weight, from a high-density-altitude airport. Other factors? The high-density altitude, down drafts and the pilot’s lack of familiarity operating from high density altitude airports.

The pilot’s logbook revealed that his only experience operating at an airport with a field elevation over 3,000 feet above sea level was one takeoff and landing at an airport with a field elevation of 3,996 feet. As a result of this pilot’s actions — and inexperience — he and his three passengers were killed.

When it comes to high-density altitude training, one takeoff and one landing does not meet any acceptable standard of performance. That’s why all pilots planning to fly in mountainous regions should go through a comprehensive training program. The checkout should consist of a combination of ground and flight training that takes at least eight hours to complete.

During ground training, the aircraft’s operations manual should be used to review performance for takeoff, climb, cruise and landings. Compare the sea level performance with performance at higher density altitudes. Also compare gross weight performance with weights less than gross. It is recommended that a plane taking off from a high density altitude airfield weigh at least 10% less than gross weight for better performance.

Most takeoff and climb performance figures are determined during test flights at airfields that are close to sea level elevations, which means that much of the higher altitude performance figures are interpolated, especially takeoff distances and climb rates. Be aware of the importance of using the “red knob” (mixture control) to obtain maximum performance from the engine.

Become familiar with the KOCH Chart, which is used to show what percentages a pilot should add to the sea level takeoff distance and sea level rate of climb based upon temperature and pressure altitude. (You can download a KOCH Chart at FlightSafetyCounselor.com.) Follow the directions at the bottom of the chart and compare the KOCH Chart performance figures to those in the aircraft operating handbook.

Next look at terrain along planned routes and in the vicinity of airfields. Keep in mind that the “direct to” route is not always the safest route when flying in the mountains. Plan routes that do not exceed the capabilities of the aircraft or the pilot and, of course, provide adequate mountain top clearances. Also become familiar with oxygen requirements.

Your instructor should take some time to talk about weather in the mountains and how to obtain information where weather reporting stations are non-existent. Calling a local radio station, an FBO or even a local law enforcement agency can provide weather information that can be useful in planning a flight if ASOS or AWOS information is not available. The Area Forecast should be included in the pre-flight weather briefing, as it will provide information needed to safely conduct the flight over the entire route. Your instructor also should explain how winds can funnel through mountain passes, increasing speed dramatically (venturi effect), causing turbulence and downdrafts.

Always carry extra water and other provisions when flying in the mountains. A basic survival kit is also recommended. Take some warm clothing for those cool mountain nights should you have to make an off-field landing in high terrain.

Always file a flight plan. Radar service for flight following may be impossible to obtain due to mountainous terrain. It is nice to know that 30 minutes after the expected closure time of the flight plan, the FSS will start the process of looking for overdue aircraft.

The flight portion of your training should consist of cross-country flying to each of the airfields identified during the flight planning phase and then doing several takeoffs and landings at each field. Compare performance calculations with actual performance at each of the fields. If an FBO is located at the field, stop and talk with them about specific operations at their field and some of the problems faced by pilots flying into and out of their airport.

Once it’s complete, your instructor should review the flight and answer any questions you might have concerning the entire day of training.

One last thing: Select a nice VFR day for training. If the weather is forecast to be marginal, cancel and reschedule.

Bill Schroeder is a Master CFI who gives mountain flying training in the Reno-Lake Tahoe area. For more information: FlightSafetyCounselor.com.

Comments

  1. says

    Jack,

    You make a valid point. When describing high density altitude operations we should probably be saying high elevation airport operations and the effect of temperature on that field elevation. And, of course its impact on aircraft performance. Remember, an airport at 6000 feet is still, regardless of temperature, a high elevation airport. Those of us who regularly fly in the high country sometimes get used to describing our environment in our terms only. Thanks for the comment. The FAA still describes density altitude as pressure altitude adjusted for temperature.

  2. says

    Recently I’ve seen a number of articles on High-density Altitude operations and I find the terminology being used as one that can be confusing. In each case, the writer has been talking about high-altitude operations which are also low-density (air) altitudes. In Death Valley we would have a high-densitiy situation. I am not sure what the official FAA position is on the terminology in use.

  3. Charles C says

    Very well written article by Bill Schroeder. Its unfortunate that flight training not conducted in mountainous terrain unsually only gives enough knowledge about mountain flying to make the pilot dangerous to self and others. The pilots license when given does not restrict a pilot from flying in the mountains. The FAA needs to adjust the required pilot training to include a course on mountain flying, instead of relying on the aircraft insurance companies to request it. Excellent job by the writer. Hopefully we will see more articles by Bill Schroeder.

  4. Doug Rodrigues says

    There is more to Mountain Flying than to just be concerned about density altitude. There is the movement of air mass. When air moves, it moves up and down slopes, creating areas of lift and sink. Throw in a hot day with rising thermals, that moving air mass can become a real mess to deal with. Any new pilot wanting to experiment with mountain flying should first do it with a lightly loaded plane. That would give you some advantage with the performance envelope, but still give you the experience of flying in thinner air, or worse yet, thinner air in motion. Learn about ridge lift, thermals, areas of lift and sink, mountain waves, and then imagine them all combined into one big mess of air that you could potentially launch yourself (and your passengers) into through pure ignorance. Book learning is fine, but when it comes to actually knowing how to fly in the mountains safely, you have to take small steps first until reaching that moment where you discover what your personal limits are, and what the limits of the aircraft you fly are.

    During the takeoff roll, if your gut feeling is hinting that something may not be right, then STOP, taxi back and recalculate the aircraft’s performance. Something definitely isn’t right if at full throttle, the aircraft isn’t accelerating like you think it should. Either the plane is too heavy, the air is too thin for what you want the plane to do, or there could be a mechanical problem. “Listen” to that gut feeling. If you continue with the takeoff and actually get off the ground, but find that the plane won‘t climb, what would you do? First, you DON”T want to raise the noise any higher! That would put your behind the power curve and you’ll mush into the ground. All you can do in that predicament is keep your flying speed up and forget about doing an impossible climb. Lean your mixture for maximum power and maintain full throttle. You may have to fly around obstacles that you’re unable to climb over! Just make sure that your bank angles don’t go beyond 10 degrees or so, or you’ll increase the centrifugal load on the plane and lose altitude. That last thing you want to do is chop the power. A heavily loaded plane flying on “the edge” will drop like a rock if you chop the power. Ask any Ag Pilot? Try flying toward lower elevation,if available, to put more AGL between you and the ground.

    All of the above risky situations could have been avoided simply by calculating the aircraft’s performance before taking off. That would have been a simpler way to keep out of trouble. Landing at a high elevation airport with low fuel is nothing like taking off later with the tanks topped off. If your load is heavy, then why top the tanks off? Why have 4 hours of fuel in the tanks if you have enough gas to get you to a lower elevation airport plus one hour reserve? All of that extra un-needed fuel weight makes a BIG difference in performance on a hot day at high altitude. Also, how many people look beyond a strange runway’s end and ask themselves what they’d do in case of an engine failure, or lack of climb ability? Where are the obstructions? Where is the lower terrain? A conscience effort has to be made to think about these things before you takeoff.

    Just my two cents.

  5. Paul Peterson says

    How nice to see an article on Mountain Flying. I hope to see more articles like this from Bill Schroeder.

    It would be great to see a series of articles on backcountry flying.
    WIth the expertise available to General Aviation News in the west (Idaho Aviation Association, Montana Pilots Association, Utah Backcountry Pilots, Recreational Aviation Foundation, Oregon Pilots Association, Lori MacNichol, etc), there could be a regular series of columns and articles on backcountry flying. With the snow disappearing and backcountry airstrips beginning to open up, this would be an area of interest to many pilots.

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