Mountain Operations. REFERENCES FM 1-202, Environmental Flight, February 1983 TC 1-218, Aircrew...
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Transcript of Mountain Operations. REFERENCES FM 1-202, Environmental Flight, February 1983 TC 1-218, Aircrew...
Mountain Operations
REFERENCES
FM 1-202, Environmental Flight, February 1983
TC 1-218, Aircrew Training Manual Utility Aircraft, March 1993
Aircraft Operator’s Manual
OUTLINE
• Mountain Weather and Climate• Winds• Density Altitude
• Flight Techniques
Definitions
Prevailing Winds - Upper-level winds; flowing predominantly from West to East.
Local Winds - (Valley Winds) created by convection heating and cooling.
Surface Winds - Winds close to the ground. Less turbulent than both prevailing and local winds.
Demarcation Line - The point which seperates the upflow from the downflow of air.
Types of Mountain Wind Flow
DEMARCATION LINE
Turbulence and Downflow
Prevailing Winds
Surface Winds
Local Winds (Upflow)
Light Winds
WIND DEMARCATION LINE
Light Winds
• 1 to 10 Knots• Gentle updraft as wind accelerate uphill• Wind will follow the slope of the terrain• After the crest the wind will turn into a gentle downdraft
Moderate Winds
WIND DEMARCATIO
N LIN
E
UPDRAFT
Moderate Winds
• 11 to 20 Knots• Increase in the up and downdrafts will create moderate turbulence• There will be an updraft on the leeward side near the crest• The demarcation line will form closer to the crest and will be steeper
Strong Winds
WIND
DEMARCATIO
N LIN
E
Strong Winds
• Above 20 Knots• Demarcation line will move to the forward side of the hillcrest.• Updrafts, Downdrafts and turbulence will increase.
Mountain Wave
WIND
Stable Air
Unstable Air
Mountain WaveConditions
•Stable layer of air above a unstable of air•Wind directoin fairly constant with increasing speed with altitude•Mountain is perpendicular to the airflow
Effects
•Updrafts of 2,000 FPM to 5,000 FPM•Moderate to Severe Turbulence•Altimeter errors as much as 1,000 Ft when penetrating a wave•Icing can be expected in clouds when below freezing
Mountain Wave Cloud Formation
WIND
Stable Air
Unstable AirLenticular Clouds
Rotor Clouds
Cap Cloud
When weather conditions are favorable, the following visual indicators can exist: Cap clouds, Rotor clouds and Lenticular clouds
Mountain Wave Cloud Formation
Lenticular Clouds - Lens shaped clouds normally found between FL250 and FL400. They may form downwind from the mountain ridge. Turbulence will exist below the clouds.
Cap Cloud - Consist primarily of updrafts. They will develop updrafts and downdrafts as it passes over the mountain
Mountain Wave Cloud Formation
Rotor Clouds - Clouds of short duration will a rapid onset and dissapation. They can have updrafts in excess of 5,000 FPM.
- Found downwind of mountain- Bases found below the ridge with tops up to the lenticular
clouds
Mountain Wave Cloud Formation
DENSITY ALTITUDE
• Pressure altitude corrected for non-standard temperature.
• Altitude at which your aircraft will perform at.
• As DA increases-------air density decreases
Effects of DA on aircraft performance?
• Reduced horsepower (Torque) available.– As DA incr. - air molecules spread out - less air
going into the engine = less horsepower (Torque) being produced.
• Reduced wing efficiency– Less air molecules acting on the wings to produce
lift.
RESULTS• Increased takeoff roll
• Reduced climb performance (ft./min.)
• Increased landing distance (higher TAS, higher GS)
• Decrease in the “excess power available”
• Aircraft response----more sluggish
• Deceleration effects (ability to slow down, and not fall through)
Flight Techniques
Preflight. Complete a detailed performance evaluation to determine if any operating limitations will be encountered.
Starting engine(s). Use normal starting procedures.
Taxiing. Use normal taxiing procedures.
Before takeoff. If a takeoff is made from an airport located at a
high elevation--
In Pressurized aircraft. Place the bleed air valves in the ENVIRO-
OFF position to provide more power for the takeoff.
Takeoff. Use normal takeoff procedures. NOTE: Many mountain landing strips or runways are not level. Unless local conditions dictate otherwise, always take off downhill.
Flight Techniques
During flight. Use normal procedures. Be alert for clear air turbulence that may be encountered because of uneven terrain and wind variations.
Landing. Use normal landing procedures. NOTE: Many mountain landing strips or runways are not level. Unless local conditions dictate otherwise, always land uphill.
Before leaving the aircraft. Use normal procedures. Ensure that the aircraft is properly secured. (In mountainous areas, the possibility of severe and rapidly changing weather is greater than normal.)
SUMMARY
• Mountain Weather
• Density Altitude
• Flight Techniques
QUESTIONS?
QUESTIONS?