Mountain Flying Safety and Education - Part VI

Weather Conditions that Depend on Seasons

Orographic Lifting

Moist air is always dangerous in flying. When it is lifted it forms cloud bases or worse depending on the season.

If you into weather (and you should be) the Adiabatic Lapse Rate and the Dew Point  is a rough way to predict cloud bases for decision making in flight plans.

Flat-landers see this in the Winter. Keep in mind air loses its moisture when temperatures a low. Using the Adiabatic Lapse Rate of 4.5 degrees F the air will cool each 1,000 feet the air is lifted. There is a relationship between unsaturated air and its dew point. When the air temperature reaches its dew point condensation occurs and clouds begin to form. Now the situation changes, will the dryer air continue to rise to a level where freezing of the water molecules begins. Energy release begins and rapid buildups of clouds starts. Thunderstorms is the ultimate result of lifting air with moisture present.

In mountains the amount of air may contain less moisture than at sea level and the cloud bases form below the peaks. This cuts visibility and, if you fly into them you may meet what ever the cloud is hiding.

In the summer time the air, at high elevations, can contain more moisture. As the lifting of the air, by bumping into mountain slopes, occurs the air not only reaches the point where condensation takes place but continues to rise until the freezing point of water is reached. When a change of state from liquid to a solid (ice) heat is given off. This increase in heat pushes the cloud development to a level where a thunderstorm forms. Weather, weather and more weather. IFR pilots are very cautious about weather. It is an excellent safety lesson.

Temperature inversions

Mountain valleys are places where an inversion can happen. Cold dense air tumbles underneath warmer air that contains more moisture. Cloud formation begins at night to form under the warm air and fog forms.

Your departure and arrival should coincide with a time when the fog layer heats up and dissipates with sunrise. If the weather calls for a cloudy day it will take longer for the fog to clear.

Mountain Flying and Training - Part V

Altitude Effect on Performance - Details

Overall performance:

• Higher density altitudes increase takeoff and landing distances. By a reduction in weight you can regain some of the lost takeoff and landing performance at high density altitudes. Fly the airplane at no more than 90% of maximum gross weight. Take a Republic SeaBee at a maximum gross weight of 3600 pounds. 90% of 3600 pounds is 3240 pounds. Reducing the weight to 3240 pounds you would regain the lost performance.

•  Higher density altitudes decrease the rate of climb and actual service ceiling. Decrease the maximum gross weight of the plane to 90% of maximum will increase the rate of climb and actual service ceiling. Multi-engined  aircraft have good performance increases in takeoff, landing, climb and actual service ceilings. If you expect to fly mountain terrain often an investment in a multi-engined plane is a definite increase in safety margins. Turbocharged aircraft compensate for density altitude therefore their performance increase is less than non-turbo charged planes.

• True airspeed is higher than indicated airspeed. This is a visual illusion discussed earlier in a post about night landings. It can pertain to takeoffs in daylight. When your true airspeed is higher than a given indicated airspeed the pilot responds to the visual cues of higher ground speed he observes and rotates at a lower indicated airspeed than normal. The pilot is actually below his normal rotation speed. Rotating at an airspeed below actual rotation speed increases the takeoff run due to the illusion.

• Turning radius is larger at high altitude at a given indicated airspeed. Turning radius is proportional to the square of the true airspeed of your plane. Increase your true airspeed by 10% your turn radius increases by 20%. In a boxed canyon, in mountain flying, the increase may be too much for you to make the turn. You can decrease the radius of the turn by decreasing you true airspeed. This decrease in true airspeed will cause the plane to descend. If the terrain is too close you could crash. You can prevent the crash by increasing the bank of your turn. Be careful, decreasing your true airspeed and the angle of your bank brings you closer to a stall. Not a good flying decision if you didn't plan for it in the first place . Planning ahead is mandatory. The planes performance limits give you the information to calculate safe flying criteria. Passes, ridges, narrow canyons, weather, high winds and associated turbulence will affect you and your planes performance.

Flying in mountain terrain is great if you know your plane well and plan ahead.

Mountain Flying and Training - Part IV

Mountain Flying Safety 

Microbursts

Microbursts are sudden gusts of unusual strength. They form quickly and catch many pilots by surprise. Microbursts cause  serious aircraft accidents without warning.

There are two types of microbursts. Wet and dry microbursts. 

You associate the wet microburst in Eastern active thunderstorms with intense rain. The cause, in young thunderstorms, occurs because updrafts are formed when water changes to ice at the freezing level in the atmosphere. In moist regions of the East the air is loaded with moisture. When liquid water goes through a change in state (from liquid to a solid) it releases 540 calories per gram of liquid state water.

When you watch a thunderstorm build, over a period of time, suddenly it seems to explode quickly to thousands of feet in a short time span. The energy released, as water changed from a liquid to a solid (ice), it heats the air and the air rises quickly. This is the updraft phase. As the small ice crystals accumulates more liquid, as it tries to fall back, that friction creates a downdraft. Hail is the final product from the oscillation of the small ice crystals back and forth (vertically) in the growing thunderstorm.

The close proximity of downdrafts and updrafts (microbursts) cause forces that can flip a plane over. Control and recovery are very difficult. The plane may soon exceed its structural limit and come apart in the thunderstorm.

Wet microbursts are phenomenon to avoid.

Out in mountainous country the dry microburst is found. The western states are dry so thunderstorms usually have high ceilings underneath.

Why are they so dangerous? They form underneath the thunderstorm in clear air. You don't see them and, without warning, the gust hits you. Damage is done because you haven't slowed the aircraft down to a speed where gusty conditions won't cause structural damage.

In wet microbursts you don't penetrate the building storm. In dry microbursts a pilot is tempted to fly under the storm because of the relatively high ceiling under the storm. Wind velocities of microbursts can exceed the ability of a plane to climb or prevent a rollover if caught between an updraft and a downdraft simultaneously.

Lesson learned is a safe flight only if you respect any thunderstorm. 

Mountain Flying and Training - Part III

Pressure Patterns

When you live near or in the mountains you learn the positions of high and low pressure areas in your locality.

In the Northern Hemisphere (North of the Equator) high pressure cyclonic motion is "clockwise" (looking down on the rotation it moves from left to right.) 

A low pressure cyclonic motion is "counter "clock-wise" (looking down on the rotation it moves from right to left.

For example, if a high pressure area is moving in from the NW to the SE and a low pressure area is leaving from the SE and moving E what could happen if you flew from the SW to the NE between the two fronts?

As the two fronts proceed on their respective paths, the "clock-wise" rotation of the winds from the high pressure moving in merges with the "counter-clockwise" rotation of winds from the low pressure area moving eastward.

They combine to produce very high, turbulent winds. If you are flying between  them you will experience strong head winds and experience a very bumpy ride over the Appalachian Mountains.. (The West doesn't have all the mountain ranges to themselves, only the youngest)

Where I live, south of the Smokey Mountains in the Up State area of South Carolina (Near Clemson University) the wind patterns are affected by the mountainous terrain) Our weather has a mind of its own when compared to the state.

Make it a point to know your own flying location. You need to make plans based on that knowledge.

Mountain Waves and Lenticular Clouds 

When winds aloft reach 30  to 35 MPH and flow at right angles to ridges the wind is deflected, in such a way, to form clouds that appear to look like water rushing over a trout stream. These are mountain waves. These waves form downwind from the ridge and are formed from very strong updrafts and downdrafts. Without enough moisture to form clouds this is called CAT. (Clear Air Turbulence) Running into CAT can stress a plane beyond its limits and a possible breakup of the plane may occur.

If enough  moisture is in the air the mountain waves are visible. This gives you early warning to avoid the area until conditions change or subside.

In the flatlands the formation of visible air waves look like the lens in a glass lens. The flow could be laminar (smooth) or turbulent. (rough) They form quite high an the flatlanders don't worry about their effect on their planes.

Roll Clouds in front of a thunderstorm are different. If caught in one your plane, regardless of power, will crash into the ground from the very strong rotating air.

Flight planning will help you sort out the best route to fly to accomplish your goal.

Winds in Passes

Winds speed up when passing through a pass. Any time wind speeds up obstacles will create turbulent flow of air. The turbulence will produce very powerful updrafts and downdrafts. The climbing power of an aircraft may not out-perform the downdrafts. Stay away from turbulence in mountainous terrain.

Learning mountain flying is hard. Take one little bite each time  and soon the task is done.

Mountain Flying Safety and Training Part II

We covered the worst case scenario in Mountain Flying. A crash. Now, heres the rest of the story in pieces.

Before you consider mountain terrain think about requirements.

Your Requirements as a Pilot

• Experience

• Your Background - it is essential to attend a certified mountain flying course to give you the knowledge and skills you need for your safety and prevent damage to your plane

• Mountain flying is no place for a low-time pilot still in training and practicing what he/she was taught. Hours of logged time should, at a minimum, be 150 to 200 hours. you need the extra training for the more extensive trip planning, navigation and what to look for in weather reports keyed for mountains

Aircraft Requirements

• No horse power lower than 160 HP to 170 HP. Density altitude plays a major role in reducing the effectiveness of an airplanes engine

• Watch and know what your gross weight limits are. Gross weight will affect take off, climb and altitude performance. The weight and horsepower combine to make mountain flying dangerous if you fly with marginal power and too much weight.

• Add 60 HP to the minimum horsepower for each passenger you carry. If you have a four place plane add 180 HP to the 160 HP. A minimum power requirement is 340 HP to safely fly mountain terrain.

Ceiling and Weather Requirements

• If you intend to fly over mountain passes plan on giving you, your plane and passengers the benefit of a long enough distance and rate of climb to clear the top of the pass. 1,000 feet is the requirement taught in courses. Most passes are over 10,000 feet mean sea level and require a clearance 1,000 feet below the clouds. Adding this requirement to the 1,000 feet just to clear the ridge makes a 2,000 foot factor in your flight planning.

• Weather reporting stations are few and far between in the mountains. Contact a high elevation airport for an accurate determination for the ceiling over the pass. You need a full report on winds and turbulence before you leave. Better now than in the air.

Visibility Requirements

• Experienced mountain pilots use 15 miles visibility before any mountain flying. The mountains interfere with NAV aids and navigation by pilotage and dead reckoning are your choices. Illusions are present in mountain flying. Good visibility is one way to combat illusions and keep you on course with the constant  distraction of scenery and geographical marks. Navigation marks are confusing in some situations.

These requirements differ from region to region. They are basic and a good mountain flying course will add more information.

Mountain Flying Safety and Flying Training - Part I

Mountain Flying Safety and Flight Standards

There are numerous articles and books on Mountain Flying. My interest is safe flight and I build background on safety information and let you decide what you want to accomplish.

Declaring an Emergency and What You Should Do!

Lets start with the worst possible event. If an engine fails, you can't turn back because there isn't room enough or your completely boxed in by weather and you know you have to land somewhere - it is time to declare an emergency! 

Once that is done you must land under control - as best you can.

Engine Failure

You can and should, before the above happens, practice sudden engine failure. Do this with an instructor. Try to memorize the items because a real emergency doesn't leave you time to pull out your emergency plastic cards to read in your spare time. 

You need to pick out a place to land. Fly the airplane. Turn the plane, if you can, toward lower terrain. It may allow you a little more time to search for a place to set down. If you can glide a good distance it may be warmer. Weather in mountains is chilly.

In the worst case scenario what if there aren't any roads? With your altitude gain, if possible, try landing uphill. It will reduce rollout and, if the terrain is rugged, prevent you from sliding off a precipice.

If your into Ecology or Forestry your may know what lies below you to crash into the trees. Most forests, if your below the tree line (10,000 to 11,000 feet above sea level.) The tall evergreen trees await you and, possibly, a few Aspen. (the Aspen are beautiful trees that turn golden in the Fall. Always try to crash in the Fall. It is beautiful.:):)

The Aspen is smaller and you can slowly bring the aircraft to a stall just above the tops of the aspen trees. Hauling the nose upward you may have some motion straight ahead but, in a quick stall, slide backward a bit and let the plane settle into the tree tops. It may save you life if you practice this stunt before you really have to perform.

Well, you need something to put under your cup of Joe when you explain your successful landing stunt!

If the flying is too scary above you may try a straight in crash into the more flexible Aspen grove that can absorb the force of the crash without too much damage.

Be sure to tighten your seat belt and open the cabin door a bit. Crashes have a bad habit of jamming the doors.

If you have time switch off fuel tanks and cut the ignition. Fires are not well received after a crash.

Once down get everybody out of the plane as quick as possible. Attend to anyone who is injured right away.

Density Altitude, Partial Pressure of Oxygen, Mountain Flying

DENSITY ALTITUDE, OXYGEN USE AND MOUNTAINS 

All of the above play a role outside of our normal environment.

Density Altitude in Mountains

• In the eastern plains of Colorado, for example, with Denver called "The Mile High City" and normal temperatures may have a Density Altitude of 8,500 feet during the summer. Increases in temperature and humidity cause an increase in density altitude above true altitude at a specific location.

• Flying  underpowered airplanes in mountain areas is not recommended. Density altitude will affect your rate of climb adversely. Leaning your mixture, for full power, is a must at high altitudes with low concentrations of oxygen.

•  Aircraft gross weight will decrease climb rate. Couple this with underpowered aircraft you have a very dangerous situation in high turbulence, strong updrafts and downdrafts found, on occasion, in mountain flying.

• A general rule of thumb, for performance standards, in mountainous areas with low density altitudes, is approximately 55 to 65 HP per passenger. Four occupants requires a plane with at least 250 HP to fly safely. Fuel injected aircraft will eliminate carburetor icing. Turbocharged aircraft will correct the density altitude. Even then, maximum altitude may compromise tour flight.

• Keep in mind the adiabatic lapse rate in degrees Fahrenheight is 4.5 degrees per 1000 feet. Therefore, as you climb, the temperature decreases 4.5 degrees each 1,000 from Sea Level. At an altitude of 10,000 feet the temperature has declined 45 degrees to 24 degrees. If you compare this to a Standard Temperature of 59 degrees at Sea Level the density altitude is above an airport located at 9,000 feet above sea level. Your airplane, at a 9,000 foot airport in the mountains is acting like it is at 10,000 feet at a temperature of 24 degrees. Even though the temperature is dropping the density altitude is 10,000 feet.

• Reduction in air density reduces the force of lift generated by the planes wings when flying through the less dense air.

• The propeller on a plane is like a vertical airfoil and the thrust generated by the propeller is reduced when the air density is reduced.

You must use oxygen at altitudes above 10,000 feet. Why? Density altitude means the partial pressure of oxygen declines with altitude. When the partial pressure of oxygen declines low enough the oxygen reaching your red blood cells declines to a point where you become hypoxic. please see my post on hypoxia. 

Density altitude is a killer if you don't recognize the effect density altitude can exert on you and your plane.