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MOUNTAIN PowerPoint PPT Presentation


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MOUNTAIN. OPERATIONS. REFERENCES : FM 3-04.202 (1-202) ENVIRONMENTAL FLIGHT AERONAUTICAL INFORMATION MANUAL (AIM). OVERVIEW. The mountain environment requires special flying techniques due to: Its severe and rapidly changing weather Impacts on aircraft performance capabilities

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MOUNTAIN

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MOUNTAIN

OPERATIONS


  • REFERENCES:

  • FM 3-04.202 (1-202) ENVIRONMENTAL FLIGHT

  • AERONAUTICAL INFORMATION MANUAL

  • (AIM)


OVERVIEW

  • The mountain environment requires special flying techniques due to:

    • Its severe and rapidly changing weather

    • Impacts on aircraft performance capabilities

    • Acceleration of crew fatigue


WINDS

  • Winds associated with mountains can be broken down into three main categories.

    • Prevailing winds: upper-level winds flowing predominately from west to east in the continental US.

    • Local winds: also called valley winds, are created by convection heating & cooling. They flow parallel to larger valleys. During the day, these winds tend to flow up valley; at night, they flow down valley.

    • Surface wind: the layer of air which lies close to the ground. It is less turbulent than prevailing & local winds.


DEMARCATION LINE

  • Demarcation line: the point which separates the up flow from the down flow of air.

    • It forms from the highest point of the mountain & extends diagonally upward.

    • The velocity of the wind and the steepness of the uplift slope will determine the position of the demarcation line.

    • Generally, the higher the wind speed, & steeper the terrain, the steeper the demarcation line.


TURBULENCE

&

DOWNFLOW

PREVAILING WINDS

DEMARCATION LINE

LOCAL WIND

(UPFLOW)

SURFACE WINDS


LIGHT WINDS

  • Light winds: 1-10 knots

    • Accelerates slightly on the upslope, giving rise to a gentle updraft.

    • Follows the contour of the terrain feature over the crest

    • At some point past the crest, turns into a gentle downdraft.


PREVAILING WINDS

DEMARCATION LINE

LIGHT WINDS


MODERATE WINDS

  • Moderate wind: 11 to 20 knots

    • Will increase the strength of the up drafts and downdrafts and create moderate turbulence.

    • An updraft will be experienced on the lee (the side sheltered from the wind) slope near the crest of the mountain.

    • The demarcation line forms closer to the hill crest and is steeper


PREVAILING WINDS

DEMARCATION LINE

MODERATE WINDS


STRONG WINDS

  • Strong winds: above 20 knots

    • The demarcation line will move forward to the leading edge of the hill crest

    • Becomes progressively steeper and the severity of updrafts, downdrafts, and turbulence will also increase.

    • Under these conditions, the best landing spot is close to the forward edge of the terrain feature.


PREVAILING WINDS

DEMARCATION LINE

STRONG WINDS


MOUNTAIN WAVE

  • A phenomenon that occurs when the airflow over mountainous terrain meets certain criteria:

    • Low-level layer of unstable air

    • Stable layer of air above the lower levels

    • Wind direction fairly constant with altitude

    • Wind speed increasing w/ altitude

    • Mountain lying perpendicular to the airflow


MOUNTAIN WAVE

  • The following conditions can exist in a Mountain Wave:

    • Vertical currents of 2,000fpm are common, 5,000fpm possible

    • Moderate to severe turbulence

    • Wind gusts up to 22 knots

    • Altimeters errors up to 1,000 feet

    • Icing can be expected


STABLE LAYER

WIND

MOUNTAIN WAVE


CLOUD FORMATIONS ASSSOCIATED WITH MOUNTAIN WAVE

  • When proper conditions exist, clouds will form that provide visible indications of the existence of a mountain wave. Three types of clouds may form as a result of a mountain wave.

    • Lenticular Clouds

    • Rotor Clouds

    • Cap Clouds


CLOUD FORMATIONS ASSSOCIATED WITH MOUNTAIN WAVE

  • Lenticular Clouds:

    • lens shaped, high altitudes, 25,000-40,000’. Form in bands or as single clouds, located above and slightly downwind from the ridge of the mountain, turbulence may be encountered under the cloud

  • Rotor Clouds:

    • downwind from the ridge, several rows lying parallel to the ridge, bases at or below ridge level, up/down drafts in excess of 5,000fpm. Short duration & tend to disappear rapidly.

  • Cap Clouds:

    • formed primarily from vertical updrafts, up/down as they pass over the mountain. Part of the cloud extends upwind, with finger-like extensions running down the slope on downwind side of the ridge.


LENTICULAR

CLOUDS

CAP CLOUD

ROTOR

CLOUDS

CLOUD FORMATIONS

ASSSOCIATED W/

MOUNTAIN WAVE


SLACK WINDS

STABLE LAYER

STRONG

GRADIENT

WINDS

WIND

SHEAR

30K

ROTOR

CLOUD

25K

20K

STRONG

WINDS

UNSTABLE AIR

ROTOR STREAMING

TURBULENCE


WIND ACROSS A RIDGE

  • Smooth air and updrafts will be experienced on the windward side of the ridge and downdrafts on the lee side.

  • The steeper the updraft slope & the higher the wind velocity, the more severe the updrafts.

  • As the air flows over the crest, a venturi effect is created. An area of low pressure develops on the lee side of the mountain.

  • Where the ridge line is irregular, a funneling of air through the gaps will occur, causing a mixing of air on the lee side. This condition tends to increase the turbulence.

  • Wind striking the ridge at less than 90° produces fewer updrafts and downdrafts.


WIND

WIND ACROSS A RIDGE


WIND ACROSS A SNAKE RIDGE

  • Down drafts and turbulent air may be encountered on the windward slope of succeeding ridges.

  • The severity will be determined by the distance between the ridges, the depth of the valley, and the angle the wind strikes the slope.

  • The closer the ridges are together and the closer the wind is to 90° to the slope, the updrafts and turbulence will be more severe.

  • Greater turbulence will be experienced on the downdraft slope of succeeding ridges due to turbulent air flowing over the ridge.


WIND

SNAKE RIDGE


WIND ACROSS A CROWN

  • Airflow in the vicinity of a crown is normally lateral around its outer edges and over the top.

  • Turbulence will develop on the lee side of the hill, but will not extend too far out from the ground.


WIND

WIND ACROSS A CROWN


SHOULDER WIND

  • The airflow around a shoulder is extremely turbulent regardless of the wind direction.

  • Extreme downdrafts may be experienced if the shoulder is located on the lee side of the mountain.

  • Rotary turbulence may be experienced on the uplift side of the shoulder.


WIND BACKLASH

SHOULDER WIND


WIND ACROSS A CANYON

  • Usually the lower winds flow parallel to the canyon floor. The degree of turbulence in the low areas of a canyon depends on the width & depth of the canyon and the wind speed.

  • In a narrow canyon, the most severe turbulence is in the low area

  • In a wide canyon, the low area may be turbulent free.


STRONG WINDS

WIND ACROSS A CANYON


TECHNIQUES

FLYING


FLYING TECHNIQUES

  • During Mountain Flying the aviator’s senses are sometimes unreliable.

  • A natural tendency is to judge airspeed as too slow and altitude too high.

  • Difficulty may be experienced in maintaining the proper flight altitude.

  • Frequent reference should be made to the flight instruments.

  • Update the PPC to compensate for gross weight changes and center of gravity.


MOUNTAIN TAKEOFF

  • Hover power check should be conducted.

  • PPC: as a minimum: max torque available, go/no-go torques, predicted hover torque

  • When performing a mountain takeoff, apply torque as necessary to gain forward airspeed while maintaining sufficient altitude to clear any obstacles until climb airspeed is reached.

  • Where drop-offs are located along the takeoff path, the aircraft may be maneuvered downslope to gain airspeed.


NORMAL TAKEOFF

AIRSPEED OVER ALTITUDE

MOUNTAIN TAKEOFF


FLIGHT ALONG A VALLEY

  • Aircraft should be flown in the smoother upflowing air on the lifting side of the valley.

  • Requires less power and gives the aircraft a safe flight path.

  • The velocity of the wind will determine how close you will fly to the lifting side.

  • In strong winds, it is advisable to avoid flying close to the slope because of turbulence caused by irregular projections may be encountered.

  • In light winds, aircraft should be flown closer to the side of the valley to allow for maximum horizontal clearance for a 180° turn


WIND

DOWNDRAFT

& TURBULENCE

UPDRAFT

FLIGHT ALONG A VALLEY


RIDGE CROSSING

  • Crossing at a 45° angle facilitates turning away from the ridge should the helicopter be carried below the crest by a downdraft.


RIDGE CROSSING

45° ANGLE


180° TURN OR EARLY CLIMB


APPROACH

&

LANDING


FACTORS IN THE CONSIDERATION OF AN APPROACH PATH

  • Wind direction and velocity

  • Vertical air currents

  • Escape routes

  • Terrain contour & obstacles

  • Position of the sun

  • Approach paths and areas to be avoided


TYPE OF APPROACH

  • There is no standard type of mountain approach.

  • Light wind/when demarcation line is shallow:

    • A relatively low angle of descent or flat approach should be used- requires less power & control movement. If downdrafts are encountered insufficient altitude may be available to continue the approach.

  • Stronger wind/steeper demarcation line:

    • Steeper approach angle. Higher rate of descent & requires more power to terminate the approach. Provides more terrain clearance if downdrafts are encountered.

  • Running landing:

    • Used if insufficient torque to make a normal or shallow approach and landing area is suitable. Effective translational lift is maintained until contact with the ground.


LZ

FIGURE EIGHT

CIRCULAR

LZ

LZ

RACETRACK

LZ RECONNAISSANCE


After Reconnaissance

  • Avoid descents greater than 700fpm

  • Normally, pattern altitude will not exceed 500 feet above the touchdown point.

  • Mountain approach:

  • When 50’ above the touchdown point begin losing effective translational lift. Do not hover OGE. Prior to reaching the near edge of the landing area, the descent should be stopped & forward airspeed reduced to a brisk walk.


WIND

AREA TO BE AVOIDED


AREA

TO BE

AVOIDED

WIND


WIND

AREA

TO BE

AVOIDED


OTHER CONSIDERATIONS


  • SETTLING WITH POWER

  • Vertical / Near Vertical Descent

  • at least 300fpm

  • Low Forward Airspeed

  • Using some of available Engine Power

  • 20%-100%

HOVER OGE

-Large blade-tip vortexes

-High velocity of induced airflow

HOVER IGE

-Reduced rotor tip vortex

-Reduced velocity of induced airflow


QUIZ

Click on the link below to access the

Mountain Flying Techniques Quiz

http://ang.quizstarpro.com

Log-in and Click “Search” Tab

Class Name = Mountain Flying Techniques


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