Mission Aircrew Course Chapter 7: High Altitude and Terrain Considerations (Jul 2005)

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Mission Aircrew CourseChapter 7 High Altitude
and Terrain Considerations(Jul 2005)
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Aircrew Tasks

• P-2011 DISCUSS THE EFFECTS OF DENSITY ALTITUDE ON
  AIRCRAFT PERFORMANCE (O)
• P-2024 DISCUSS STRATEGIES TO COMBAT HIGH ALTITUDE
  EFFECTS (S)

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Objectives

• Discuss the symptoms and dangers of dehydration,
  and strategies used to combat its effects. S
  7.3
• Discuss the symptoms and dangers of ear block,
  sinus block and hypoxia, and strategies used to
  combat their effects. S 7.3.1 7.3.3

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Objectives

• Review the effects of high altitude on aircraft
  performance
• Concerning atmospheric pressure O 7.1
• State the pressure at sea level, and describe how
  to compensate for other-than-sea level
  pressures when setting the altimeter
• Discuss the three factors that affect the density
  of an air mass.
• Define density altitude
• State the phases of flight affected by a decrease
  in atmospheric pressure, and how aircraft
  performance is affected. O 7.2
• Discuss strategies to compensate for high DA
  during searches. O 7.2.1
• Discuss mountainous terrain precautions and
  strategies. O 7.4

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Human Performance Dehydration

• The loss of water through the skin, lungs and
  kidneys never ceases
• Loss increases as the humidity drops with
  increasing altitude
• Symptoms are dryness of the tissues and resulting
  irritation of the eyes, nose and throat
• Minimize intake of coffee, tea, cola or cocoa
  since they contain caffeine and other chemicals
• Prevention Strategies
• Drink plenty of hydrating fluids WATER!
• Increase air flow (vents and windows)
• If the search objective allows, reduce
  temperature by climbing to higher altitude

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Other Effects of Altitude

• Ear Block
• Congestion around the Eustachian tube makes
  pressure equalization difficult
• Can produce severe pain and a loss of hearing
  that can last from several hours to several days
  (can rupture eardrum)
• Sinus Block
• Sinus congestion makes pressure equalization
  difficult, particularly during descent
• Can produce severe pain
• Hypoxia
• Normally not a concern for non-mountainous CAP
  operations (usually below 12,000 MSL)
• Can have loss of night vision as low as 5,000
  feet
• Body has no built-in warning system against
  hypoxia
• Everyone s symptoms are different
• Onset altitude will vary depending upon individual

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Prevention Strategies

• Ear Block
• Yawn, swallow, tense muscles in throat
• Valsalva maneuver
• Sinus Block
• Dont fly if youre not well
• Medication usually not effective and has side
  effects
• Hypoxia
• Avoid smoking, alcohol and depressants
• Supplemental oxygen

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Atmospheric Pressure

• A barometer is used to register changes in
  pressure measured in inches of mercury
• Standard sea-level pressure and temperature
• 29.92 inches of mercury
• 59 degrees F (15 degrees C)
• A change of 1000 feet in elevation makes a change
  of about one inch
• To correct for local elevation, set altimeter to
  latest reading (ATIS/AWOS/ASOS/FSS) or enter
  field elevation

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Density Altitude

• Three factors
• Pressure
• Temperature
• Humidity
• Altitude and pressure combined to determine
  pressure altitude
• Add non-standard temperature to get density
  altitude
• Remember Drag, lift, power available and true
  airspeed are all affected by density altitude

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TAS vs. DA
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Density Altitude
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Flight Computer

• Circular slide rule
• Density altitude
• Nautical to statute miles
• True airspeed
• Other stuff

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Aircraft Performance

• Density altitude and aircraft weight have a
  tremendous effect on aircraft performance
• Both must be accurately calculated, especially
  for mountain flying missions

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Pressure vs. Performance

• As altitude increases pressure decreases this
  decrease can have a pronounced effect on flight
• Engine (hp) and prop are less efficient
• Take off distance, climb rate, and landing
  distance effected
• Take off distance almost doubles with a 5000 foot
  elevation increase
• Rate of climb slows with higher elevation
• Landing distance increases with higher elevation
• Higher Humidity, Heat or Height result in reduced
  aircraft performance

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DA ROC
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Reduced Performance
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Strategies

• Dont fly at high elevation during the hottest
  part of the day
• Carefully calculate DA and weight
• Reduce load
• Less fuel
• Crew of three instead of four
• Less baggage
• Remember High to Low, Look out Below (update
  altimeter setting hourly)
• If you fly in the mountains, take the Mountain
  Fury Course

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Flight Near Mountainous Terrain

• Crews must be constantly careful that the search
  never takes them over terrain that rises faster
  than the airplane can climb. Narrow valleys or
  canyons that have rising floors must be avoided,
  unless the aircraft can be flown from the end of
  higher elevation to the lower end, or the pilot
  is certain that the aircraft can climb faster
  than the terrain rises. Careful chart study by
  the crew prior to flight will help identify this
  dangerous terrain.
• If you fly in the mountains, take the Mountain
  Fury Course

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Flight Near Mountainous Terrain
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Flight Near Mountainous Terrain
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Flight Near Mountainous Terrain
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• QUESTIONS?