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?