mission aircrew course chapter 7: high altitude and terrain considerations (jul 2005)
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Mission Aircrew Mission Aircrew CourseCourse
Chapter 7: High Chapter 7: High Altitude and Terrain Altitude and Terrain
ConsiderationsConsiderations(Jul 2005)(Jul 2005)
P-2011 DISCUSS THE EFFECTS OF DENSITY ALTITUDE ON AIRCRAFT PERFORMANCE (O)
P-2024 DISCUSS STRATEGIES TO COMBAT HIGH ALTITUDE EFFECTS (S)
Aircrew TasksAircrew Tasks
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}
ObjectivesObjectives
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}
ObjectivesObjectives
Human Performance: Human Performance: DehydrationDehydration
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
Other Effects of Other Effects of AltitudeAltitude
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
Prevention StrategiesPrevention Strategies
Ear Block• Yawn, swallow, tense muscles in throat• Valsalva maneuver
Sinus Block• Don’t fly if you’re not well• Medication usually not effective and has side
effects
Hypoxia• Avoid smoking, alcohol and depressants• Supplemental oxygen
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
Atmospheric Atmospheric PressurePressure
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
Density Density AltitudeAltitude
TAS vs. TAS vs. DADA
Density Density AltitudeAltitude
Flight Flight ComputerComputer
Circular slide rule• Density altitude• Nautical to statute
miles• True airspeed• Other stuff
Density altitude and aircraft weight have a tremendous effect on aircraft performance
Both must be accurately calculated, especially for mountain flying missions
Aircraft Aircraft PerformancePerformance
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
Pressure vs. Pressure vs. PerformancePerformance
DA & DA & ROCROC
Reduced Reduced PerformancePerformance
Don’t 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
StrategiStrategieses
Flight Near Flight Near Mountainous TerrainMountainous 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
Flight Near Flight Near Mountainous TerrainMountainous Terrain
Flight Near Flight Near Mountainous TerrainMountainous Terrain
Flight Near Flight Near Mountainous TerrainMountainous Terrain
Wind
Flight Path
2000 ft.
QUESTIONS?
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