high altitude operations. introduction far 61.31 high altitude aerodynamics and meteorology...

High Altitude Operations High Altitude Operations

IntroductionIntroductionFAR 61.31

• High altitude Aerodynamics and meteorology

• Respiration

• Effects, symptoms and causes of hypoxia and other high altitude sicknesses

• Duration of consciousness without supplemental oxygen

• Causes and effects of gas expansion and gas bubble formation

• Preventative measures for eliminating gas expansion, gas bubble formation and high-altitude sickness

• Physical phenomena of decompression

• To act as P.I.C. of an airplane with a service ceiling or maximum operating altitude greater than 25,000 ft, the following ground training is required:

OverviewOverview

High Altitude Weather

High Altitude Physiology

High Altitude Aerodynamics

• To accomplish the training, we will look at these topics

ObjectivesObjectives

• By the end of this course, you will be able to:

• Define atmospheric divisions and discuss their significance with respect to jetstreams, C.A.T. and thunderstorms.

• Identify C.A.T. and thunderstorm avoidance strategies.

• Identify causes of jet upset and how to manage them.

• Discuss the importance of oxygen and nitrogen partial pressure.

• Identify the cause, effects and remedies of hypoxia, hyperventilation and decompression sicknesses.

• State the various oxygen requirements needed to safely and legally operate above 10,000 feet.

• Discuss the aerodynamic characteristics of transonic flight, including undesirable aspects.

High Altitude MeteorologyHigh Altitude Meteorology

● In this section we will look at atmospheric divisions and their characteristics, in particular those divisions concerned with high altitudes. We will examine Jet streams and look at weather phenomena associated with high altitudes, specifically clear air turbulence and thunderstorms.

● In this section we will look at atmospheric divisions and their characteristics, in particular those divisions concerned with high altitudes. We will examine Jet streams and look at weather phenomena associated with high altitudes, specifically clear air turbulence and thunderstorms.

• Atmosphere

• Jet Stream

• Clear Air Turbulence

• Thunderstorms

The AtmosphereThe Atmosphere

● The two atmospheric divisions that we will concern ourselves with are the troposphere and the stratosphere. As well, we will look closely at the division line between these two spheres called the tropopause.

● The two atmospheric divisions that we will concern ourselves with are the troposphere and the stratosphere. As well, we will look closely at the division line between these two spheres called the tropopause.

Troposphere

TropopauseTropopause

Stratosphere

The TroposphereThe Troposphere● The troposphere is the lowest layer where most of the weather occurs. Its height

varies considerably from poles to equator. The troposphere can be as high as 65,000ft at the equator and 20,000ft or lower at the poles.

● Atmospheric temperatures decrease rather steadily in the troposphere. Generally there is a 3 to 4º F (2ºC) loss per 1000 feet. An important note to keep in mind is that the height of the troposphere changes seasonally where it is higher in the summer than in the winter.

● The troposphere is the lowest layer where most of the weather occurs. Its height varies considerably from poles to equator. The troposphere can be as high as 65,000ft at the equator and 20,000ft or lower at the poles.

● Atmospheric temperatures decrease rather steadily in the troposphere. Generally there is a 3 to 4º F (2ºC) loss per 1000 feet. An important note to keep in mind is that the height of the troposphere changes seasonally where it is higher in the summer than in the winter.

• 0-20,000’ at Poles• 0-65,000’ at Equator• 3 to 4°F (2°C) loss

per 1,000’

Troposphere

StratosphereStratosphere● The stratosphere is the next layer of atmosphere, which is located

directly over the troposphere. This layer is typified by relatively small changes in temperature with height except for a warming trend near the top.

● The stratosphere temperature remains fairly constant at -67ºF (-55ºC).

● The stratosphere is the next layer of atmosphere, which is located directly over the troposphere. This layer is typified by relatively small changes in temperature with height except for a warming trend near the top.

● The stratosphere temperature remains fairly constant at -67ºF (-55ºC).

Troposphere

• Fairly constanttemperature of -67 °F(-55 °C)

Stratosphere

TropopauseTropopause● The tropopause is the transitional line or boundary between the

Troposphere and the Stratosphere and is found at average altitudes of 65,000ft over the equator and 20,000 feet over the poles. The average height of the tropopause over the United States is about 36,000 feet.

● The tropopause is the transitional line or boundary between the Troposphere and the Stratosphere and is found at average altitudes of 65,000ft over the equator and 20,000 feet over the poles. The average height of the tropopause over the United States is about 36,000 feet.

TropopauseTropopause• 20,000’ at Poles• 36,000’ over USA• 65,000’ at Equator• Varies daily and

seasonally

Troposphere

Stratosphere

TropopauseTropopause● The height of the tropopause varies daily, as well as seasonally, and can

change from 20,000 to over 45,000 ft. In general the height of the tropopause is affected by the temperature of air. Heights will be greater over warm air than over cold air.

● The tropopause is of particular interest to pilots because temperature and wind vary greatly in this vicinity. In fact, the tropopause is where maximum windspeeds are found. These high winds create the strongest wind shears, creating zones of clear air turbulence.

● These variations affect the efficiency, comfort, and safety of flight.

● The height of the tropopause varies daily, as well as seasonally, and can change from 20,000 to over 45,000 ft. In general the height of the tropopause is affected by the temperature of air. Heights will be greater over warm air than over cold air.

● The tropopause is of particular interest to pilots because temperature and wind vary greatly in this vicinity. In fact, the tropopause is where maximum windspeeds are found. These high winds create the strongest wind shears, creating zones of clear air turbulence.

● These variations affect the efficiency, comfort, and safety of flight.

20,000’ - Winter

45,000’ - Summer • Tropopause height varies daily and seasonally

• Temperature and winds vary greatly

• Location of maximum wind speeds

ScenarioScenario● Looking at a profile of a flight from Vancouver, Canada to Cali, Columbia we

can easily see the impact of the atmospheric make-up and position of the tropopause in relation to the flight path depending on the season.

● In this example, Given that most all weather occurs within the troposphere, a summer flight could result in more off-track course changes to avoid weather. Flight would often be in ISA+ conditions resulting in higher fuel burns and lower altitude capabilities. Conversely, a flight in winter in the stratosphere would put the flight above most of the weather, in ISA conditions or lower and higher altitude capabilities resulting in lower fuel burns.

● Looking at a profile of a flight from Vancouver, Canada to Cali, Columbia we can easily see the impact of the atmospheric make-up and position of the tropopause in relation to the flight path depending on the season.

● In this example, Given that most all weather occurs within the troposphere, a summer flight could result in more off-track course changes to avoid weather. Flight would often be in ISA+ conditions resulting in higher fuel burns and lower altitude capabilities. Conversely, a flight in winter in the stratosphere would put the flight above most of the weather, in ISA conditions or lower and higher altitude capabilities resulting in lower fuel burns.

20,000’ - Winter

45,000’ - Summer • Tropopause height varies daily and seasonally

• Temperature and winds vary greatly

• Location of maximum wind speeds

Jet StreamsJet Streams● Sometimes the tropopause extends unbroken from the equator to the poles,

but a break in it at mid- latitudes is more the usual situation. Both the polar and tropical portions of the tropopause lie in gradual slopes and sometimes overlap a considerable distance.

● Intensified temperature gradients (lapse rates) usually increase where the tropopause breaks or overlaps. This is where we see the maximum wind speeds and the formation of the jet stream.

● Turbulence/chop indicates proximity to the jet core.

● Sometimes the tropopause extends unbroken from the equator to the poles, but a break in it at mid- latitudes is more the usual situation. Both the polar and tropical portions of the tropopause lie in gradual slopes and sometimes overlap a considerable distance.

● Intensified temperature gradients (lapse rates) usually increase where the tropopause breaks or overlaps. This is where we see the maximum wind speeds and the formation of the jet stream.

● Turbulence/chop indicates proximity to the jet core.

• Occurs in areas of intensified temperature gradients (Lapse rate)

• Lapse rate usually increases where tropopause breaks/overlaps (mid latitudes)

• Maximum winds

• Turbulence/chop indicates proximity

Tropical Tropopause

Polar Tropopause

60,OOO

40,OOO

20,OOO

Jet Stream

Jet StreamsJet Streams● Jet streams are relatively narrow, rapidly flowing, ribbon-like streams of air

embedded within the main airflow. A jet stream may be 1,000 to 3,000 miles long, 100-400 miles wide and a 3,000-7,000 thousand feet thick.

● The jet stream forms just below the tropopause and moves south in the winter and low pressure areas usually follow along the jet stream.

● Jet streams are relatively narrow, rapidly flowing, ribbon-like streams of air embedded within the main airflow. A jet stream may be 1,000 to 3,000 miles long, 100-400 miles wide and a 3,000-7,000 thousand feet thick.

● The jet stream forms just below the tropopause and moves south in the winter and low pressure areas usually follow along the jet stream.

1000 - 3000 miles long

100 - 400 miles wide

3000 to 7000 feet thick

Jet StreamsJet Streams

● Jet stream winds are, by definition, at least 50 knots in strength and can be in excess of 200 knots. Wind speeds drop off abruptly outside the jet core.

● Jet streams are at their strongest around mid latitudes. Time of year also plays an important role in wind speeds and latitudinal location.

● Looking downwind, the air in the jet-core slowly rotates in counter- clockwise fashion. If the air is moist, the jet stream cirrus takes very characteristic forms of hooked shaped cirrus lying under the warm air tropopause.

● Jet stream winds are, by definition, at least 50 knots in strength and can be in excess of 200 knots. Wind speeds drop off abruptly outside the jet core.

● Jet streams are at their strongest around mid latitudes. Time of year also plays an important role in wind speeds and latitudinal location.

● Looking downwind, the air in the jet-core slowly rotates in counter- clockwise fashion. If the air is moist, the jet stream cirrus takes very characteristic forms of hooked shaped cirrus lying under the warm air tropopause.

50 kts50 kts100 kts100 kts

Jet Core150 kts

Jet Core150 kts

Jet Core

Jet StreamsJet Streams● Generally, jet streams are much stronger at more southerly latitudes in the

winter than they are in the summer. A second jet stream is not uncommon, and three at one time are not unknown. The arctic stratospheric jet is caused by the development of a strong westerly thermal wind component during the winter months. This jet stream normally occurs at 70-75 degrees north from 60,000-80,000 feet.

● Generally, jet streams are much stronger at more southerly latitudes in the winter than they are in the summer. A second jet stream is not uncommon, and three at one time are not unknown. The arctic stratospheric jet is caused by the development of a strong westerly thermal wind component during the winter months. This jet stream normally occurs at 70-75 degrees north from 60,000-80,000 feet.

Locations

ARCTIC JET

SUB-TROPICAL JET

POLAR JET

ARCTIC JET

SUB-TROPICAL JET

POLAR JET

Jet StreamsJet Streams● The Sub-tropical jet stream is not associated with fronts. A very strong solar

heating in equatorial regions produces a belt of ascending air. This air turns polward at very high levels. The coriolis force then turns it to the right into a strong westerly jet. The sub-tropical jet predominates in the winter and lies near 25 degrees north at around 45,000 feet. If the polar front moves exceptionally far south the polar front jet stream may merge with the sub-tropical jet stream.

● The Sub-tropical jet stream is not associated with fronts. A very strong solar heating in equatorial regions produces a belt of ascending air. This air turns polward at very high levels. The coriolis force then turns it to the right into a strong westerly jet. The sub-tropical jet predominates in the winter and lies near 25 degrees north at around 45,000 feet. If the polar front moves exceptionally far south the polar front jet stream may merge with the sub-tropical jet stream.

Locations

Slowdown or Stall at High AltitudesSlowdown or Stall at High Altitudes

● Know performance limits of the airplane

● The jet-stream – upper air currents - significant

– Velocities – can be very high

– Windshear can cause severe turbulence

– Windshear – Substantial airspeed decay

● Know performance limits of the airplane

● The jet-stream – upper air currents - significant

– Velocities – can be very high

– Windshear can cause severe turbulence

– Windshear – Substantial airspeed decay

Pilot TipWith upper air currents of decreasing velocity wind shear – the backside of the power curve may be encountered.

Pilot TipWith upper air currents of decreasing velocity wind shear – the backside of the power curve may be encountered.

Pilot Tip: The pilot will have to either increase thrust or decrease angle of attack to allow the airspeed to build back to normal climb/cruise speeds. This may require trading altitude for airspeed to accelerate out. Failure to accelerate out of the backside of the power curve may result in the aircraft stalling.

Pilot Tip: The pilot will have to either increase thrust or decrease angle of attack to allow the airspeed to build back to normal climb/cruise speeds. This may require trading altitude for airspeed to accelerate out. Failure to accelerate out of the backside of the power curve may result in the aircraft stalling.

Weather EffectsWeather Effects

High Altitude ThreatsHigh Altitude Threats

● Airplane Icing

● Clear air turbulence

● Convective turbulence

● Wake turbulence

● Mountain wave

● High Level windshear

● Thunderstorms

● Airplane Icing

● Clear air turbulence

● Convective turbulence

● Wake turbulence

● Mountain wave

● High Level windshear

● Thunderstorms

Pilot TipHigh altitude weather can cause favorable conditions for upsets. Thorough route analysis is key to avoiding conditions that could lead to an upset.

Pilot TipHigh altitude weather can cause favorable conditions for upsets. Thorough route analysis is key to avoiding conditions that could lead to an upset.

Operating Near Maximum AltitudeOperating Near Maximum Altitude

Clear Air TurbulenceClear Air Turbulence● As discussed, maximum wind speeds are found at the boundary layer

between the troposphere and stratosphere known as the tropopause. Jet streams stronger than 110 knots (at the core) are apt to have areas of significant turbulence near them in the sloping tropopause above the core, in the jet stream front below the core, and on the low-pressure side of the core.

● As discussed, maximum wind speeds are found at the boundary layer between the troposphere and stratosphere known as the tropopause. Jet streams stronger than 110 knots (at the core) are apt to have areas of significant turbulence near them in the sloping tropopause above the core, in the jet stream front below the core, and on the low-pressure side of the core.

Jet Core110 kts +Jet Core

110 kts +

TropicalTropopause

PolarTropopause

Area of MaximumSevere Turbulence

Areas of Possible Severe Turbulence

Clear Air TurbulenceClear Air Turbulence● Because of the frequent presence of strong wind shears in the vicinity of the

tropopause, this boundary zone often is a region of turbulence. Since this zone is often devoid of clouds, this turbulence is known as clear air turbulence. Although CAT can be present at any altitude, CAT experienced at high altitude can cause aircraft control problems.

● Because of the frequent presence of strong wind shears in the vicinity of the tropopause, this boundary zone often is a region of turbulence. Since this zone is often devoid of clouds, this turbulence is known as clear air turbulence. Although CAT can be present at any altitude, CAT experienced at high altitude can cause aircraft control problems.

Jet Core110 kts +Jet Core

110 kts +

TropicalTropopause

PolarTropopause

Area of MaximumSevere Turbulence

Areas of Possible Severe Turbulence

Significant Weather ChartSignificant Weather Chart● CAT on a significant weather chart, turbulence is highlighted by the area

surrounded by dashed lines.

● In example 1, over the north eastern United States, moderate turbulence is present between FL300 and F400 feet.

● In example 2, north east of the British Isles, moderate turbulence is present between FL320 and FL370.

● CAT on a significant weather chart, turbulence is highlighted by the area surrounded by dashed lines.

● In example 1, over the north eastern United States, moderate turbulence is present between FL300 and F400 feet.

● In example 2, north east of the British Isles, moderate turbulence is present between FL320 and FL370.

Example 1Example 1

Example 2Example 2

200 mb chart200 mb chart● On charts for standard isobaric surfaces, such as 300 millibars, if 20-knot

isotachs are spaced closer than 150 nautical miles (2.5 degrees latitude), there is sufficient horizontal shear for CAT. This area is normally on the poleward (low-pressure) side of the jet stream axis, but in unusual cases may occur on the equatorial side.

● On charts for standard isobaric surfaces, such as 300 millibars, if 20-knot isotachs are spaced closer than 150 nautical miles (2.5 degrees latitude), there is sufficient horizontal shear for CAT. This area is normally on the poleward (low-pressure) side of the jet stream axis, but in unusual cases may occur on the equatorial side.

Area of possible CAT due to close proximity of isotachs

200 mb chart200 mb chart● Please note the area highlighted on this 200mb chart is the same area as

seen in example 1 on the Significant Weather chart (previous slide). Note also that this area of turbulence is mostly on the poleward (low pressure) side of the jet stream. Turbulence is also related to vertical shear. From the tropopause height/vertical windshear chart, determine the vertical shear in knots-per-thousand feet. If it is greater than 5 knots per 1,000 feet, turbulence is likely.

● Please note the area highlighted on this 200mb chart is the same area as seen in example 1 on the Significant Weather chart (previous slide). Note also that this area of turbulence is mostly on the poleward (low pressure) side of the jet stream. Turbulence is also related to vertical shear. From the tropopause height/vertical windshear chart, determine the vertical shear in knots-per-thousand feet. If it is greater than 5 knots per 1,000 feet, turbulence is likely.

Area of possible CAT due to close proximity of isotachs

Satellite ImagesSatellite Images● Weather satellite pictures are useful in identifying jet streams associated

with cirrus cloud bands. CAT is normally expected in the vicinity of jet streams. Satellite imagery showing wave-like or herringbone cloud patterns are often associated with mountain wave turbulence. Pilots should avail themselves of briefings on satellite data whenever possible.

● Weather satellite pictures are useful in identifying jet streams associated with cirrus cloud bands. CAT is normally expected in the vicinity of jet streams. Satellite imagery showing wave-like or herringbone cloud patterns are often associated with mountain wave turbulence. Pilots should avail themselves of briefings on satellite data whenever possible.

Jet Stre

am Cirrus

Jet Stre

am Cirrus

Satellite ImagesSatellite Images● If turbulence is expected because of penetration of a sloping tropopause,

watch the temperature gauge. The point of coldest temperature along the flight path will be the tropopause penetration.

● Turbulence will be most pronounced in the temperature-change zone on the stratospheric (upper) side of the sloping tropopause.

● If turbulence is expected because of penetration of a sloping tropopause, watch the temperature gauge. The point of coldest temperature along the flight path will be the tropopause penetration.

● Turbulence will be most pronounced in the temperature-change zone on the stratospheric (upper) side of the sloping tropopause.

MountainsMountains● Windshear and its accompanying CAT in jet streams is more intensive above

and to the lee of mountain ranges. CAT should be anticipated whenever the flight path traverses a strong jet stream in the vicinity of mountainous terrain.

● Both vertical and horizontal windshear are, of course, greatly intensified in mountain wave conditions. Therefore, when the flight path traverses a mountain wave type of flow, it is desirable to fly at turbulence-penetration speed to avoid flight over areas where the terrain drops abruptly, even though there may be no lenticular clouds to identify the condition.

● Windshear and its accompanying CAT in jet streams is more intensive above and to the lee of mountain ranges. CAT should be anticipated whenever the flight path traverses a strong jet stream in the vicinity of mountainous terrain.

● Both vertical and horizontal windshear are, of course, greatly intensified in mountain wave conditions. Therefore, when the flight path traverses a mountain wave type of flow, it is desirable to fly at turbulence-penetration speed to avoid flight over areas where the terrain drops abruptly, even though there may be no lenticular clouds to identify the condition.

RotorsRotors

WindsWinds● High pressure ridges & fronts are often turbulent.

● If turbulence is encountered with a direct head wind or tail wind, change course or flight level.

● If jetstream turbulence is encountered in a crosswind don’t change course

● If turbulence is encountered in an abrupt wind shift associated with a sharp pressure trough line, establish a course across the trough rather than parallel to it.

● Monitor radio and file PIREPs

● High pressure ridges & fronts are often turbulent.

● If turbulence is encountered with a direct head wind or tail wind, change course or flight level.

● If jetstream turbulence is encountered in a crosswind don’t change course

● If turbulence is encountered in an abrupt wind shift associated with a sharp pressure trough line, establish a course across the trough rather than parallel to it.

● Monitor radio and file PIREPs

ThunderstormsThunderstorms● The vertical growth of thunderstorms is generally no higher than the

tropopause. The anvil tops or cirrus blow-off is capped at or below the tropopause height. Keeping in mind that the tropopause height varies daily and seasonally, the tops of thunderstorms can range from 20,000 to over 45,000 feet.

● In some cases thunderstorms can push through to the stratosphere. Meteorologists refer to this as an overshooting thunderstorm. These storms are known to produce severe weather at both the surface and high altitude of the storm.

● The vertical growth of thunderstorms is generally no higher than the tropopause. The anvil tops or cirrus blow-off is capped at or below the tropopause height. Keeping in mind that the tropopause height varies daily and seasonally, the tops of thunderstorms can range from 20,000 to over 45,000 feet.

● In some cases thunderstorms can push through to the stratosphere. Meteorologists refer to this as an overshooting thunderstorm. These storms are known to produce severe weather at both the surface and high altitude of the storm.

Tropopause

Thunderstorm HazardsThunderstorm Hazards● Under no circumstance should an aircraft be flown into a thunderstorm at

any altitude, regardless of how benign the storm appears. Even the smallest and most innocent looking storm can contain air motions significant enough to destroy an aircraft.

Thunderstorm avoidance requires you to circumnavigate the storm. There are three prevalent hazards to consider when circumnavigating a thunderstorm:• Hail• Airflow Disruption• Flight Over Storm

● Under no circumstance should an aircraft be flown into a thunderstorm at any altitude, regardless of how benign the storm appears. Even the smallest and most innocent looking storm can contain air motions significant enough to destroy an aircraft.

Thunderstorm avoidance requires you to circumnavigate the storm. There are three prevalent hazards to consider when circumnavigating a thunderstorm:• Hail• Airflow Disruption• Flight Over Storm

Tropopause

?

HailHail● The first major hazard is hail. Although radar can detect the storm, hail can

go undetected. Hail can be encountered when circumnavigating a thunderstorm at an altitude below the anvil or blow-off. Even if the pilot is maintaining the recommended distance from the storm (20 to 25 NM), passage beneath the downwind extending cloud can produce a hail encounter, sometimes up to 10 miles or more downwind of the storm.

● Other precipitation that can be encountered from the storm is water from heavy rain falling from the outward bulge near or below the anvil base. This water can erode acrylic windshields or strip paint from the aircraft. Most recommended turbulence penetration speeds will reduce this type of damage.

● The first major hazard is hail. Although radar can detect the storm, hail can go undetected. Hail can be encountered when circumnavigating a thunderstorm at an altitude below the anvil or blow-off. Even if the pilot is maintaining the recommended distance from the storm (20 to 25 NM), passage beneath the downwind extending cloud can produce a hail encounter, sometimes up to 10 miles or more downwind of the storm.

● Other precipitation that can be encountered from the storm is water from heavy rain falling from the outward bulge near or below the anvil base. This water can erode acrylic windshields or strip paint from the aircraft. Most recommended turbulence penetration speeds will reduce this type of damage.

Circumnavigate Upwind

WIND

WINDWIND

Hail 10 or more miles ahead of storm

Airflow DisruptionAirflow Disruption● The second major hazard with the tops of thunderstorms is the airflow

disruption produced by the upper portion of the storm.

● Placing the upper portion of the storm in a moving stream of air blocks the flow and diverts the air around the storm. This change in flow pattern results in extreme to severe turbulence around the edges of the storm and further downwind from the storm as that flow comes back together.

● This turbulent flow can upset the aircraft as well as produce structural damage.

● The second major hazard with the tops of thunderstorms is the airflow disruption produced by the upper portion of the storm.

● Placing the upper portion of the storm in a moving stream of air blocks the flow and diverts the air around the storm. This change in flow pattern results in extreme to severe turbulence around the edges of the storm and further downwind from the storm as that flow comes back together.

● This turbulent flow can upset the aircraft as well as produce structural damage.

Eddy currents around top of storm can result in severe turbulence


Airflow DisruptionAirflow Disruption● Turbulent airflow around a thunderstorm's upper portions can extent as far

as 20 nautical miles. As indicated below, the proper distance to circumnavigate from the edge of cloud can be determined by wind speeds. Please note these wind speeds and distances for future reference.

● Turbulent airflow around a thunderstorm's upper portions can extent as far as 20 nautical miles. As indicated below, the proper distance to circumnavigate from the edge of cloud can be determined by wind speeds. Please note these wind speeds and distances for future reference.



Circumnavigate 20-25 NM

< 30 knots

30-50 knots

> 50 knots



Airflow DisruptionAirflow Disruption● In addition, the storm should be circumnavigated on the upwind side rather

than the downwind side for two reasons:● Turbulent airflow can be considerably stronger on the downwind side ● The risk of encountering hail or water from the anvil or blow-off. ● Even when circumnavigating around the upwind side, the pilot should be

aware of other disturbances in the area. It is recommended to check on-board radar or PIREPS. If thunderstorms are in a line and less than 40 NM separate the individual storms, penetration through a gap should not be attempted. If the gap between storms is not sufficient, the flight could end in disaster.

● In addition, the storm should be circumnavigated on the upwind side rather than the downwind side for two reasons:

● Turbulent airflow can be considerably stronger on the downwind side ● The risk of encountering hail or water from the anvil or blow-off. ● Even when circumnavigating around the upwind side, the pilot should be

aware of other disturbances in the area. It is recommended to check on-board radar or PIREPS. If thunderstorms are in a line and less than 40 NM separate the individual storms, penetration through a gap should not be attempted. If the gap between storms is not sufficient, the flight could end in disaster.




< 30 knots

30-50 knots

> 50 knots



Flight Over StormFlight Over Storm● The third major hazard is flight over storm.Turbulent air can be encountered

when an aircraft is flying at an altitude higher than the thunderstorm tops. This turbulence can also upset or cause structural damage to an aircraft.

● Sufficient vertical clearance above the physical top of the storm must be maintained. A rule of thumb to use is to over-fly the top of the storm by 5,000 feet for any windspeed up to 50 knots.

● Add an additional 1,000 feet of clearance for each 10 knots above a windspeed of 50 knots

● The third major hazard is flight over storm.Turbulent air can be encountered when an aircraft is flying at an altitude higher than the thunderstorm tops. This turbulence can also upset or cause structural damage to an aircraft.

● Sufficient vertical clearance above the physical top of the storm must be maintained. A rule of thumb to use is to over-fly the top of the storm by 5,000 feet for any windspeed up to 50 knots.

● Add an additional 1,000 feet of clearance for each 10 knots above a windspeed of 50 knots

• Up to 50 knots windspeed, clear tops by 5,000 ft

• Add 1,000 ft per additional 10 knots windspeed

60 knots6,000 ft clearance

IcingIcingHigh Altitude Aerodynamics – Flight TechniquesHigh Altitude Aerodynamics – Flight Techniques

● Icing ConditionsKnow anti-ice equipment limitations (flight manual requirements)

– Temperature limitations

– SAT (Static Air Temperature)

– Changing environmental conditions

● Thermal anti-ice – bleed penaltyNegative effect on the ability to recover from decaying airspeed

– Airplane may not maintain cruise speed or cruise altitude

Pilot TipThe bleed penalty for anti-ice results in a reduction of available thrust - increase in specific fuel consumption.

Pilot TipThe bleed penalty for anti-ice results in a reduction of available thrust - increase in specific fuel consumption.

Use of Anti-Ice on PerformanceUse of Anti-Ice on Performance

In-Flight Icing Stall MarginsIn-Flight Icing Stall MarginsHigh Altitude Aerodynamics – Flight TechniquesHigh Altitude Aerodynamics – Flight Techniques

● Ice accumulation increases aircraft weight / drag

● Airplane may exhibit stall onset characteristics before stick shaker activation

● Automation during icing encounters– Autopilot and Auto-throttles can mask

the effects of airframe icing – Autopilot can trim the airplane up to a stall

thus masking heavy control forces– Pilots have been surprised when the

autopilot disconnected just prior to a stall

Pilot Tip In-flight icing - Serious Hazard - stalls at much higher speeds and lower angles of attack. If stalled, the airplane can roll / pitch uncontrollably.

Pilot Tip In-flight icing - Serious Hazard - stalls at much higher speeds and lower angles of attack. If stalled, the airplane can roll / pitch uncontrollably.

In-Flight Icing Stall Margins (continued)In-Flight Icing Stall Margins (continued)● Adverse Weather Conditions: Stay Alert – Avoidance/Monitor

● Thunderstorm, clear air turbulence, and icing

Avoid potential upset conditions

– Monitor significant weather

– Update weather information

– Important - Trend monitoring of turbulence

– Review turbulence charts

● Adverse Weather Conditions: Stay Alert – Avoidance/Monitor

● Thunderstorm, clear air turbulence, and icing

Avoid potential upset conditions

– Monitor significant weather

– Update weather information

– Important - Trend monitoring of turbulence

– Review turbulence charts

Pilot Tip Adverse weather avoidance is crucial. It is most important that proper airspeed is maintained. Keep an adequate margin above stall, remember that indicated stall speed is increasing and stall alpha is lowering. There are no reliable rules of thumb for icing speeds.

Pilot Tip Adverse weather avoidance is crucial. It is most important that proper airspeed is maintained. Keep an adequate margin above stall, remember that indicated stall speed is increasing and stall alpha is lowering. There are no reliable rules of thumb for icing speeds.

High Altitude Aerodynamics – Flight TechniquesHigh Altitude Aerodynamics – Flight Techniques

Pilot ConsiderationsPilot ConsiderationsHigh altitude weather can cause favorable conditions for upsets. Thunderstorm, clear air turbulence, and icing are examples of significant weather that pilots should take into consideration in flight planning. Careful review of forecasts, significant weather charts, turbulence plots are key elements to avoiding conditions that could lead to an upset.

There have been other recent accidents where for various reasons (trying to top thunderstorms, icing equipment performance degradation, unfamiliarity with high altitude performance, etc.) crews have gotten into a high altitude slowdown situation that resulted in a stalled condition from which they did not recover. There have been situations where for many reasons (complacency, inappropriate automation modes, atmospheric changes, etc.) crews got into situations where they received an approach to stall warning.

Once established in cruise flight, the prudent crew will update weather information for the destination and en-route. By comparing the updated information to the preflight briefing, the crew can more accurately determine if the forecast charts are accurate. Areas of expected turbulence should be carefully plotted and avoided if reports of severe turbulence are received. Trend monitoring of turbulence areas is also important. Trends of increasing turbulence should be noted and if possible avoided. Avoiding areas of potential turbulence will reduce the risk of an upset.

High Altitude Weather High Altitude Weather

● In this section we have looked at atmospheric divisions and their characteristics, in particular we have examined the tropopause and the phenomena which occur at this division, such as jet streams, clear air turbulence and thunderstorms.

● We discussed C.A.T. and thunderstorm avoidance strategies.

● We also looked at ice effects on the airplane

● In this section we have looked at atmospheric divisions and their characteristics, in particular we have examined the tropopause and the phenomena which occur at this division, such as jet streams, clear air turbulence and thunderstorms.

● We discussed C.A.T. and thunderstorm avoidance strategies.

● We also looked at ice effects on the airplane

Summary

• Atmosphere

• Jet Stream

• Clear Air Turbulence

• Thunderstorms

• Icing

• Atmospheric composition

• Respiration

• Hypoxia/hyperventilation

• Decompression sickness

• Oxygen requirements

Flight PhysiologyFlight Physiology

● When operating turbine powered aircraft much higher altitudes are attainable. This can create physiological problems for the human body; therefore, it is extremely important that anyone piloting these aircraft be able to recognize the symptoms of these difficulties and take corrective actions when necessary.

● In this section we will discuss atmospheric composition, respiration, hypoxia/hyperventilation, decompression sickness and oxygen requirements.

● When operating turbine powered aircraft much higher altitudes are attainable. This can create physiological problems for the human body; therefore, it is extremely important that anyone piloting these aircraft be able to recognize the symptoms of these difficulties and take corrective actions when necessary.

● In this section we will discuss atmospheric composition, respiration, hypoxia/hyperventilation, decompression sickness and oxygen requirements.

Atmospheric CompositionAtmospheric Composition● The atmosphere is made up of oxygen, nitrogen, and smaller amounts of

other gases.

● The percentage of these gases is fairly constant in the atmosphere up to an altitude of 70,000 feet.

● What is of concern are changes in pressure and temperature of the air during ascent. These two factors are the cause of all physiological problems encountered by pilots.

● The atmosphere is made up of oxygen, nitrogen, and smaller amounts of other gases.

● The percentage of these gases is fairly constant in the atmosphere up to an altitude of 70,000 feet.

● What is of concern are changes in pressure and temperature of the air during ascent. These two factors are the cause of all physiological problems encountered by pilots.

78% nitrogen 78% nitrogen

21% oxygen21% oxygen

1% other 1% other

up to

70,000 feet

up to

70,000 feet

Physiological Divisions of the AtmospherePhysiological Divisions of the Atmosphere

● There are several divisions of the atmosphere. The two of most concern to the pilot flying modern turbine airplanes are:

• Physiological Zone

• Physiological Deficient Zone

● There are several divisions of the atmosphere. The two of most concern to the pilot flying modern turbine airplanes are:

• Physiological Zone

• Physiological Deficient Zone

Physiologically Deficient Zone

Physiological Zone

Physiological ZonePhysiological Zone

● The physiological zone extends from sea level to approximately 10,000 feet. Within this zone only minor problem may exist in pilots who operate in this area for long periods of time. These problems include:

• Shortage of breath

• Headache

• Sinus and middle ear problems

• Dizziness

● The physiological zone extends from sea level to approximately 10,000 feet. Within this zone only minor problem may exist in pilots who operate in this area for long periods of time. These problems include:

• Shortage of breath

• Headache

• Sinus and middle ear problems

• Dizziness

Physiological Zone0-10,000 ft. MSL

Physiological Deficient ZonePhysiological Deficient Zone● The physiological deficient zone extends from approximately 10,000 feet to

around 50,000 feet. Within this zone serious problems may exist in pilots who are exposed to this area even for short periods of time. These problems include:


• Hypoxia

● The physiological deficient zone extends from approximately 10,000 feet to around 50,000 feet. Within this zone serious problems may exist in pilots who are exposed to this area even for short periods of time. These problems include:


• Hypoxia

Physiologically Deficient Zone

10,000 - 50,000 ft. MSL

Partial PressurePartial Pressure

● As stated earlier, the percentage of oxygen, nitrogen and other gases in the atmosphere is fairly constant below 70,000 feet. What we must concern ourselves with is the partial pressures of each gas not the percentage of gas in the total mixture.

● Note in the table below that while the percentage of each gas in the atmosphere remains constant, the partial pressure of each gas decreases as we increase in altitude. From sea level to 18,000 feet, partial pressures are reduced by nearly half. It is this decrease in the partial pressure of each gas that causes concern. In the next section on respiration, we will examine the effects of this reduction in partial pressure on the human body.

● As stated earlier, the percentage of oxygen, nitrogen and other gases in the atmosphere is fairly constant below 70,000 feet. What we must concern ourselves with is the partial pressures of each gas not the percentage of gas in the total mixture.

● Note in the table below that while the percentage of each gas in the atmosphere remains constant, the partial pressure of each gas decreases as we increase in altitude. From sea level to 18,000 feet, partial pressures are reduced by nearly half. It is this decrease in the partial pressure of each gas that causes concern. In the next section on respiration, we will examine the effects of this reduction in partial pressure on the human body.

Altitude Total AtmosphericPressure(mm HG)

Composition of Gas PartialPressure(mm Hg)

Percentage ofAtmosphere(to 70,000’)

RATIO(Atmosphere)

Sea Level760

NitrogenOxygenOther

593160

7

78%21%

1%

1

14.7 psi

10,000 feet522

NitrogenOxygenOther

407110

5

78%21%

1%18,000 feet

380NitrogenOxygenOther

29680

4

78%21%1%

1/27.3 psi

27,000 feet252

NitrogenOxygenOther

19753

2

78%21%

1%

1/34.9 psi

35,000 feet 179NitrogenOxygenOther

13939

1

78%21%

1%

¼3.5 psi

RespirationRespiration

● As Respiration includes the two-directional exchange of gases between the body and the environment. The body inhales oxygen and exhales carbon dioxide. The body has a dual regulation system to ensure proper levels of both oxygen and carbon dioxide.

● The first regulatory system is controlled by the brain, which responds to carbon dioxide partial pressure. If the carbon dioxide level is too high the brain increases the respiration rate, causing more carbon dioxide to be exhaled. If the carbon dioxide rate is too low, the opposite occurs; breathing rate decreases to allow a build up of carbon dioxide.

● The second system is a back-up respiratory control system, which monitors oxygen partial pressure. This system, located in the large arteries close to the heart, adjusts respiratory rate to ensure the proper oxygen supply.

● As Respiration includes the two-directional exchange of gases between the body and the environment. The body inhales oxygen and exhales carbon dioxide. The body has a dual regulation system to ensure proper levels of both oxygen and carbon dioxide.

● The first regulatory system is controlled by the brain, which responds to carbon dioxide partial pressure. If the carbon dioxide level is too high the brain increases the respiration rate, causing more carbon dioxide to be exhaled. If the carbon dioxide rate is too low, the opposite occurs; breathing rate decreases to allow a build up of carbon dioxide.

● The second system is a back-up respiratory control system, which monitors oxygen partial pressure. This system, located in the large arteries close to the heart, adjusts respiratory rate to ensure the proper oxygen supply.

Dual Regulation system

• Brain• controls CO2 partial pressure

• Arteries (backup)• controls oxygen partial pressure

Lungs

Heart

Brain

Arteries

Respiration AbnormalitiesRespiration Abnormalities

● Should either of these systems detect abnormalities beyond its regulatory controls, the body would enter either of the following states:

• Hyperventilation, associated with an excessive loss of carbon dioxide partial pressure.

• Hypoxia associated with a deficiency of oxygen partial pressure.

● Let's look at each of these states and discuss how we may avoid or prevent them.

● Should either of these systems detect abnormalities beyond its regulatory controls, the body would enter either of the following states:

• Hyperventilation, associated with an excessive loss of carbon dioxide partial pressure.

• Hypoxia associated with a deficiency of oxygen partial pressure.

● Let's look at each of these states and discuss how we may avoid or prevent them.

Hyperventilation SymptomsHyperventilation Symptoms

● As stated, hyperventilation is caused when the body loses a disproportionate amount of carbon dioxide, causing a chemical imbalance in the body.

● Symptoms of hyperventilation include blurring of vision,nausea, lightheadedness, dizziness, increased sensation of body heat and/or a tingling in fingers and toes.

● As stated, hyperventilation is caused when the body loses a disproportionate amount of carbon dioxide, causing a chemical imbalance in the body.

● Symptoms of hyperventilation include blurring of vision,nausea, lightheadedness, dizziness, increased sensation of body heat and/or a tingling in fingers and toes.

Heart

ArteriesLungs

Brain

• Blurring of vision

• Nausea

• Lightheadedness

• Increased sensation of body heat

• Tingling in fingers and toes

Combating HyperventilationCombating Hyperventilation

● To compensate for this imbalance, a decrease in the rate and volume of respiration is needed, allowing the body to build up a normal carbon dioxide level. In extreme cases breathing in a paper bag will accelerate a return to normal carbon dioxide levels.

● If no action is taken nausea and loss of consciousness may occur.

● To compensate for this imbalance, a decrease in the rate and volume of respiration is needed, allowing the body to build up a normal carbon dioxide level. In extreme cases breathing in a paper bag will accelerate a return to normal carbon dioxide levels.

● If no action is taken nausea and loss of consciousness may occur.

Lungs

Heart

Brain

Arteries

• Decrease rate and volume of respiration

• In extreme cases, breath into paper bag

• If no action is taken, nausea and loss of consciousness may occur

HypoxiaHypoxia

● Hypoxia is the greatest single danger to pilots and passengers at high altitude.

● Hypoxia occurs when there is a lack of sufficient oxygen to the body tissue caused by either an inadequate supply of oxygen, an inadequate transport of oxygen or the inability of the body tissue to use oxygen.

● There are four forms of Hypoxia:

• Hypoxic (altitude) Hypoxia

• Hypemic (anemic) Hypoxia

• Stagnate Hypoxia

• Histotoxic hypoxia

● Hypoxia is the greatest single danger to pilots and passengers at high altitude.

● Hypoxia occurs when there is a lack of sufficient oxygen to the body tissue caused by either an inadequate supply of oxygen, an inadequate transport of oxygen or the inability of the body tissue to use oxygen.

● There are four forms of Hypoxia:

• Hypoxic (altitude) Hypoxia

• Hypemic (anemic) Hypoxia

• Stagnate Hypoxia

• Histotoxic hypoxia

Hypoxic HypoxiaHypoxic Hypoxia

● This form of hypoxia is caused by insufficient oxygen partial pressure. For example, when we ascend through 10,000 feet oxygen partial pressure drops considerably, creating a situation where hypoxic hypoxia becomes a reality.

● This form of hypoxia is caused by insufficient oxygen partial pressure. For example, when we ascend through 10,000 feet oxygen partial pressure drops considerably, creating a situation where hypoxic hypoxia becomes a reality.

Lungs

Heart

Brain

Arteries

• Hypoxic (altitude) hypoxia– insufficient oxygen partial pressure

Hypemic HypoxiaHypemic Hypoxia

● Hypemic hypoxia is caused by an inability of the blood to carry proper amounts of oxygen. Excessive smoking or exhaust fumes can cause hypemic hypoxia.

● Hypemic hypoxia is caused by an inability of the blood to carry proper amounts of oxygen. Excessive smoking or exhaust fumes can cause hypemic hypoxia.

Lungs

Heart

Brain

Arteries

• Hypemic (anemic) hypoxia– reduction in the oxygen carrying

capacity of the blood

Stagnant HypoxiaStagnant Hypoxia

● Stagnate hypoxia is defined as an oxygen deficiency in the body due to poor circulation of blood. This type of hypoxia can be caused by positive pressure breathing for long periods and excessive head to toe G-forces.

● Stagnate hypoxia is defined as an oxygen deficiency in the body due to poor circulation of blood. This type of hypoxia can be caused by positive pressure breathing for long periods and excessive head to toe G-forces.

Lungs

Heart

Brain

Arteries

• Stagnate hypoxia– oxygen deficiency in the body due to

poor circulation

Histotoxic HypoxiaHistotoxic Hypoxia

● Histotoxic Hypoxia is defined as the inability of the body cells to utilize oxygen due to the impairment of cell respiration. Alcohol consumption among other things, is responsible for impairment of cell respiration.

● Histotoxic Hypoxia is defined as the inability of the body cells to utilize oxygen due to the impairment of cell respiration. Alcohol consumption among other things, is responsible for impairment of cell respiration.

Lungs

Heart

Brain

Arteries

• Histotoxic hypoxia– impairment of cellular respiration

circulation

Symptoms of HypoxiaSymptoms of Hypoxia

● The first symptoms of hypoxia resemble those affects associated with mild intoxication from alcohol. Other symptoms are listed below.

● The first symptoms of hypoxia resemble those affects associated with mild intoxication from alcohol. Other symptoms are listed below.

Lungs

Heart

Brain

Arteries

• Increased rate of breathing

• Headache

• Fatigue

• Light headed or dizzy sensations, listlessness

• Tingling or warm sensations, sweating

• Poor coordination, impairment of judgment

• Loss of vision or reduced vision

• sleepiness

• Cyanosis: discoloration at the fingernail beds

• Behavior changes, feeling of well being, euphoria

Symptoms of Hypoxia – Exposure TimeSymptoms of Hypoxia – Exposure Time

● Regardless of the type of hypoxia, the symptoms are always the same. The table below highlights hypoxia symptoms in relation to time of exposure and altitude.

● Regardless of the type of hypoxia, the symptoms are always the same. The table below highlights hypoxia symptoms in relation to time of exposure and altitude.

Altitude (Feet) Time of Exposure Symptoms

10,000 to 14,000 Several Hours Headache, fatigue, listlessness, non-specificdeterioration of physical and mental performance.

15,000 to 18,000 30 minutes Impairment of judgement and vision, high self-confidence, euphoria, disregard for sensoryperceptions, poor coordination, sleepiness,dizziness, personality changes as if intoxicated,cyanosis (bluing).

20,000 to 35,000 5 minutes Same symptoms as a t 15,000 to 18,000 feet exceptmore pronounced with eventual unconsciousness.

35,000 to 40,000 15 to 45 seconds Immediate unconsciousness (with little or nowarning).

Symptoms of Hypoxia – Exposure TimeSymptoms of Hypoxia – Exposure Time

● Effective Performance Time (EPT) or Time of Useful Consciousness (TUC) is the amount of time in which the pilot is able to effectively fly an airplane with an insufficient supply of oxygen. As the table below indicates, as altitude increases time decrease.

● Hypoxia, by its nature, is a grim deceiver and makes its victims feel confident that they are doing a better job of flying than they really are. Pilots who are older, overweight, out of condition, or smoke heavily should limit themselves to flight ceilings of 8,000 to 10,000 feet unless supplemental oxygen is available.

● Effective Performance Time (EPT) or Time of Useful Consciousness (TUC) is the amount of time in which the pilot is able to effectively fly an airplane with an insufficient supply of oxygen. As the table below indicates, as altitude increases time decrease.

● Hypoxia, by its nature, is a grim deceiver and makes its victims feel confident that they are doing a better job of flying than they really are. Pilots who are older, overweight, out of condition, or smoke heavily should limit themselves to flight ceilings of 8,000 to 10,000 feet unless supplemental oxygen is available.

Combating HypoxiaCombating Hypoxia

● When combating hypoxia, apply supplemental oxygen, descend below 10,000 MSL, try to determine cause and if unable to correct condition (clear your head), land as soon as possible

● A realization or recognition of hypoxia symptoms should be followed by the immediate use of supplemental oxygen in order to combat hypoxia successfully. In most cases, all faculties are regained within 15 seconds after oxygen is administered.

● Although recovery is rapid following the administration of oxygen, a word of caution is necessary. The individual recovering from a moderate to severe hypoxia incident is usually quite fatigued and may suffer a measurable deficiency in mental and physical performance for many hours.

● When combating hypoxia, apply supplemental oxygen, descend below 10,000 MSL, try to determine cause and if unable to correct condition (clear your head), land as soon as possible

● A realization or recognition of hypoxia symptoms should be followed by the immediate use of supplemental oxygen in order to combat hypoxia successfully. In most cases, all faculties are regained within 15 seconds after oxygen is administered.

● Although recovery is rapid following the administration of oxygen, a word of caution is necessary. The individual recovering from a moderate to severe hypoxia incident is usually quite fatigued and may suffer a measurable deficiency in mental and physical performance for many hours.

Apply supplemental oxygenApply supplemental oxygen

Descend to 10,000 feet MSLDescend to 10,000 feet MSL

Determine causeDetermine cause

Cannot correct condition,land as soon as possible

Cannot correct condition,land as soon as possible

DecompressionDecompression

● In any discussion of high altitude operation, the possibility of decompression must be considered.

● Decompression is defined as the inability of the aircraft's pressurization system to maintain its designed pressure schedule. This can be caused by a malfunction in the pressurization system or structural damage to the aircraft.

● The more rapid the decompression, the greater the expansion force of gases contained in the lungs and intestine. Physiological decompression may be expressed as either explosive or rapid.

● In any discussion of high altitude operation, the possibility of decompression must be considered.

● Decompression is defined as the inability of the aircraft's pressurization system to maintain its designed pressure schedule. This can be caused by a malfunction in the pressurization system or structural damage to the aircraft.

● The more rapid the decompression, the greater the expansion force of gases contained in the lungs and intestine. Physiological decompression may be expressed as either explosive or rapid.

• Explosive Decompression• A change in cabin pressure faster than the

lungs can decompress. Therefore, it is possible that lung damage can occur.

• Rapid Decompression• Lungs can decompress faster than the cabin

Decompression RateDecompression Rate

● The effects of decompression depend on Cabin size, size of the hole, differential pressure and flight altitude.

● Cabin size, size of the hole and pressure differential determine the time required for decompression while pressure differential and flight altitude govern the expansion ratio for gases within the cabin and various body cavities.

● Rate of decompression dependent on:

• Cabin size

• Size of hole

• Pressure Differential

• Flight altitude

● The effects of decompression depend on Cabin size, size of the hole, differential pressure and flight altitude.

● Cabin size, size of the hole and pressure differential determine the time required for decompression while pressure differential and flight altitude govern the expansion ratio for gases within the cabin and various body cavities.

● Rate of decompression dependent on:

• Cabin size

• Size of hole

• Pressure Differential

• Flight altitude

Explosive Decompression Cabin EffectsExplosive Decompression Cabin Effects

● If the hole in the aircraft is large enough, explosive decompression can affect the cabin by causing an explosive noise, a sudden rush of air and debris toward the hole, a sudden decrease in cabin temperature and pressure, and a fogging due to moisture condensation in the expanding cabin atmosphere.

● Signs of explosive decompression:

• Explosive noise

• Rush of air toward hole

• Sudden decrease in cabin temperature and pressure

• Fogging

● If the hole in the aircraft is large enough, explosive decompression can affect the cabin by causing an explosive noise, a sudden rush of air and debris toward the hole, a sudden decrease in cabin temperature and pressure, and a fogging due to moisture condensation in the expanding cabin atmosphere.

● Signs of explosive decompression:

• Explosive noise

• Rush of air toward hole

• Sudden decrease in cabin temperature and pressure

• Fogging

Physiological EffectsPhysiological Effects

● The physiological effects of decompression include:

• Rapid chest expansion

• Cheek and lip flutter

• Pain in the ears and sinuses

• Abdominal pain

• Difficulty communicating

• Hypoxia

● The physiological effects of decompression include:

• Rapid chest expansion

• Cheek and lip flutter

• Pain in the ears and sinuses

• Abdominal pain

• Difficulty communicating

• Hypoxia

Decompression SicknessDecompression Sickness

● If decompression does occur, another hazard exists, that of dysbarism or decompression sickness. Decompression sickness is classified into either trapped gas or evolved gas.

● If decompression does occur, another hazard exists, that of dysbarism or decompression sickness. Decompression sickness is classified into either trapped gas or evolved gas.

Trapped Gas

Evolved Gas

Trapped GasTrapped Gas

● Under normal circumstances gas is present in various body cavities, including the middle ear, nasal sinuses, teeth, stomach and intestines.

● Under certain conditions, following a decompression, trapped gas expands. If the pilot or passengers cannot pass this gas out of the containing cavity, severe pain can result.

● Under normal circumstances gas is present in various body cavities, including the middle ear, nasal sinuses, teeth, stomach and intestines.

● Under certain conditions, following a decompression, trapped gas expands. If the pilot or passengers cannot pass this gas out of the containing cavity, severe pain can result.

Trapped Gas

- Gas expansion within a cavity

Trapped Gas DisordersTrapped Gas Disorders

● Trapped gas disorders develop rapidly

● Effects of trapped gas include Ear Block, Sinus block, tooth ache and abdominal pains.

● Trapped gas disorders develop rapidly

● Effects of trapped gas include Ear Block, Sinus block, tooth ache and abdominal pains.

Trapped Gas

- Gas expansion within a cavity

- Develop rapidly

Ear block

Sinus block

Tooth ache

Abdominal pains

Trapped Gas PreventionTrapped Gas Prevention

● To prevent against trapped gas:

• Avoid foods that produce gas

• Don't chew gum

• Eat within 12 hours of flight

• Eat slowly

● To prevent against trapped gas:

• Avoid foods that produce gas

• Don't chew gum

• Eat within 12 hours of flight

• Eat slowly

Evolved GasEvolved Gas

● When the ambient pressure falls, diluted gases (typically nitrogen) tend to come out of solution and form gas bubbles. When these bubbles form in the body, severe pain and bizarre neurological symptoms may result.

● When the ambient pressure falls, diluted gases (typically nitrogen) tend to come out of solution and form gas bubbles. When these bubbles form in the body, severe pain and bizarre neurological symptoms may result.

Evolved Gas

Evolved GasEvolved Gas

● Symptoms related to evolved gas formation do not occur very rapidly and rarely below 20,000 feet.

● At altitudes of 35,000 to 40,000 feet it would take approximately 20 minutes for the average individual to develop severe or incapacitating symptoms.

● Symptoms related to evolved gas formation do not occur very rapidly and rarely below 20,000 feet.

● At altitudes of 35,000 to 40,000 feet it would take approximately 20 minutes for the average individual to develop severe or incapacitating symptoms.

Evolved Gas

Evolved Gas DisordersEvolved Gas Disorders

● Bends - Characterized by pain in and about the joints. If ascent is continued pain will worsen.

● Chokes - Caused by nitrogen bubbles blocking the pulmonary blood vessels. This causes a mild burning sensation beneath the sternum and progresses to an uncontrollable urge to cough. Immediate descent is necessary to recover.

● Paresthesia - Characterized by a tingling of the skin. Itchy and blotchy rashes may appear.

● Central nervous system disorders - May see spots or lines and parts of your field of vision disappear headaches are associated with visual problems. Other effects include partial paralysis and sensory disturbances, both of which are transient.

● Bends - Characterized by pain in and about the joints. If ascent is continued pain will worsen.

● Chokes - Caused by nitrogen bubbles blocking the pulmonary blood vessels. This causes a mild burning sensation beneath the sternum and progresses to an uncontrollable urge to cough. Immediate descent is necessary to recover.

● Paresthesia - Characterized by a tingling of the skin. Itchy and blotchy rashes may appear.

● Central nervous system disorders - May see spots or lines and parts of your field of vision disappear headaches are associated with visual problems. Other effects include partial paralysis and sensory disturbances, both of which are transient.

Evolved Gas

Evolved Gas PreventionEvolved Gas Prevention

● Rapid descent to altitudes lower than FL 200 is the most effective way of combating evolved gas symptoms.

● It is advisable to avoid exercise or strenuous movements as they will only worsen evolved gas symptoms.

● It is highly recommended to avoid scuba diving for at least 24 hours before a flight as this activity increases nitrogen partial pressure in the blood.

● Rapid descent to altitudes lower than FL 200 is the most effective way of combating evolved gas symptoms.

● It is advisable to avoid exercise or strenuous movements as they will only worsen evolved gas symptoms.

● It is highly recommended to avoid scuba diving for at least 24 hours before a flight as this activity increases nitrogen partial pressure in the blood.

Evolved Gas

Effects of AlcoholEffects of Alcohol

● As per FAA regulations, no consumption of alcohol is allowed within 8 hours of flight. Alcohol, smoking and illegal drugs have the following effects on the body and can complicate recovery from hypoxia (especially histotoxic hypoxia) and decompression sickness:

● A dulling of critical judgment and a decreased sense of responsibility

• Diminished skill reactions and coordination, resulting in decreased speed and strength of muscular reflexes

• Slowing of eye movement during reading, resulting in an increase in the frequency of technical and tactical errors

● As per FAA regulations, no consumption of alcohol is allowed within 8 hours of flight. Alcohol, smoking and illegal drugs have the following effects on the body and can complicate recovery from hypoxia (especially histotoxic hypoxia) and decompression sickness:

● A dulling of critical judgment and a decreased sense of responsibility

• Diminished skill reactions and coordination, resulting in decreased speed and strength of muscular reflexes

• Slowing of eye movement during reading, resulting in an increase in the frequency of technical and tactical errors

XXX

OxygenOxygen

● Oxygen systems installed on most high-altitude turbine-powered airplanes today are for use in the unlikely event of a rapid decompression.

● FAR 91.211 requires the use of some type of supplemental oxygen at and above 12,500. Specifically;

● Flight crew:

• 12500’ - 14000’ cabin pressure altitude operation without supplemental oxygen cannot exceed 30 minutes.

• Above 14,000 ft, supplemental oxygen is required at all times

● Oxygen systems installed on most high-altitude turbine-powered airplanes today are for use in the unlikely event of a rapid decompression.

● FAR 91.211 requires the use of some type of supplemental oxygen at and above 12,500. Specifically;

● Flight crew:

• 12500’ - 14000’ cabin pressure altitude operation without supplemental oxygen cannot exceed 30 minutes.

• Above 14,000 ft, supplemental oxygen is required at all times

Flight Crew Requirements

OxygenOxygen

● At cabin pressure altitudes greater than 15,000 ft, passengers are to be provided with supplemental oxygen.

● At cabin pressure altitudes greater than 15,000 ft, passengers are to be provided with supplemental oxygen.

Passenger Requirements

OxygenOxygen

● Above FL250 - A minimum of a 10 minute supply of supplemental oxygen for each occupant is required.

● Above FL350 - One pilot must wear & use a mask that is secured and sealed if cabin pressure altitude exceeds 14,000 ft., except:

• For 2 pilot crews at less than 41,000’ with two quick donning oxygen masks. These masks must be able to be donned using one-hand within 5 seconds.

• If one crew member leaves the controls, the other crew member must don mask.

● Above FL250 - A minimum of a 10 minute supply of supplemental oxygen for each occupant is required.

● Above FL350 - One pilot must wear & use a mask that is secured and sealed if cabin pressure altitude exceeds 14,000 ft., except:

• For 2 pilot crews at less than 41,000’ with two quick donning oxygen masks. These masks must be able to be donned using one-hand within 5 seconds.

• If one crew member leaves the controls, the other crew member must don mask.

Pressurized Cabin

OxygenOxygen

● Cabin pressure altitudes warning systems will indicate when the cabin pressure altitude exceeds 10,000 feet.

● If in the event of a decompression and cabin altitude reaches between 13-15,000 feet, in most cases passenger and crew oxygen masks will be activated automatically.

● Auto passenger Oxygen mask dispensing device must present masks before cabin pressure reaches 15,000 feet.

● Cabin pressure altitudes warning systems will indicate when the cabin pressure altitude exceeds 10,000 feet.

● If in the event of a decompression and cabin altitude reaches between 13-15,000 feet, in most cases passenger and crew oxygen masks will be activated automatically.

● Auto passenger Oxygen mask dispensing device must present masks before cabin pressure reaches 15,000 feet.

Pressurized Cabin FAR 25

Oxygen – Pre-flightOxygen – Pre-flight

Oxygen – Pre-flight (cont)Oxygen – Pre-flight (cont)

Where can you find this?

Oxygen – Pre-flight (cont)Oxygen – Pre-flight (cont)

Flight PhysiologyFlight Physiology

● In this section we discussed atmospheric composition, respiration and the importance of oxygen and nitrogen partial pressures, the effects of reduced partial pressures (i.e.: hypoxia/hyperventilation) decompression and decompression sickness and oxygen requirements as per FAR 91.211 and FAR 25.

● In this section we discussed atmospheric composition, respiration and the importance of oxygen and nitrogen partial pressures, the effects of reduced partial pressures (i.e.: hypoxia/hyperventilation) decompression and decompression sickness and oxygen requirements as per FAR 91.211 and FAR 25.

Summary

High Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● High altitude operations require:

1. An understanding of high altitude aerodynamics

2. Translate that knowledge into a skill base that provides a safety margin

3. Techniques - High altitude upset recovery training

OverviewOverviewHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● First we’ll review some basic aerodynamic principles

● Then we’ll look at some operational considerations

● Finally we’ll close with a few flight techniques

Speed of SoundSpeed of Sound● The speed of sound is the rate at which small pressure

disturbances are transmitted through the air. The transmitted speed is solely a function of air temperature, which decreases with altitude in the troposphere.

● The speed of sound is the rate at which small pressure disturbances are transmitted through the air. The transmitted speed is solely a function of air temperature, which decreases with altitude in the troposphere.

AltitudeTemperature

(C)Speed of

Sound (knots)

Sea Level 15 661.7

10,000 -4.8 638.6

20,000 -24.6 614.6

30,000 -44.4 589.6

40,000 -56.5 573.8

50,000 -56.5 573.8


Mach IndicatorMach Indicator● In light of these undesirable characteristics, the question then

arises: How do you accurately identify airspeed relative to the speed of sound, if the speed of sound is a function of temperature, without having to continually correct the indicated airspeed for altitude and temperature?

● In light of these undesirable characteristics, the question then arises: How do you accurately identify airspeed relative to the speed of sound, if the speed of sound is a function of temperature, without having to continually correct the indicated airspeed for altitude and temperature?

• The Mach indicator will perform this task. Mach indicators measure the ratio of the aircraft's true airspeed relative to the speed of sound at flight altitude. Mach numbers do not need to be corrected for altitude and temperature, because the existing temperature at flight level determines the speed of sound at flight level. This speed of sound compared to your indicated airspeed gives us a ratio or a Mach number


Subsonic FlightSubsonic Flight● As an airfoil moves through the air mass, velocity and pressure

changes occur which create disturbances in the airflow surrounding the airfoil.

● These disturbances are transmitted outward at the speed of sound.

● If the airfoil is traveling below the speed of sound, these disturbances are transmitted ahead of the object, and the pressure field of the object influences the airflow immediately ahead of the object.

● As an airfoil moves through the air mass, velocity and pressure changes occur which create disturbances in the airflow surrounding the airfoil.

● These disturbances are transmitted outward at the speed of sound.

● If the airfoil is traveling below the speed of sound, these disturbances are transmitted ahead of the object, and the pressure field of the object influences the airflow immediately ahead of the object.


Transonic FlightTransonic Flight● Transonic Flight (0.75-1.2 MACH)

There is a speed at which the local airflow over the top of the airfoil will reach the speed of sound before the airfoil since the flow over the top is faster than the airfoil. This speed is called the critical mach of the airfoil and it varies from aircraft to aircraft depending on wing design.

● At this speed a local shock wave forms on the top of the wing. The transonic regime is defined as those speeds at which FLOW on the aircraft components are partly supersonic. Pressure disturbances behind this region are still subsonic and cannot travel forward. They “pile up” behind the supersonic region creating a shockwave.

● Transonic Flight (0.75-1.2 MACH)There is a speed at which the local airflow over the top of the airfoil will reach the speed of sound before the airfoil since the flow over the top is faster than the airfoil. This speed is called the critical mach of the airfoil and it varies from aircraft to aircraft depending on wing design.

● At this speed a local shock wave forms on the top of the wing. The transonic regime is defined as those speeds at which FLOW on the aircraft components are partly supersonic. Pressure disturbances behind this region are still subsonic and cannot travel forward. They “pile up” behind the supersonic region creating a shockwave.

Airflow Separation

Shock Wave

Supersonic Flow

MACH 0.82


Transonic FlightTransonic Flight

● It is important to remember that as the airfoil speed is increased the area of supersonic flow is increased, the area of supersonic flow enlarges, airflow separation increases, buffet and drag increase and the shock wave moves aft. When this occurs, several undesirable characteristics, such as control surface buzz, Mach tuck, and drag rise, are manifested.

● It is important to remember that as the airfoil speed is increased the area of supersonic flow is increased, the area of supersonic flow enlarges, airflow separation increases, buffet and drag increase and the shock wave moves aft. When this occurs, several undesirable characteristics, such as control surface buzz, Mach tuck, and drag rise, are manifested.

Shock Wave

Airflow Separation

Shock Wave

Supersonic Flow

MACH 0.95MACH 0.95


Flight CharacteristicsFlight Characteristics

● When an aircraft approaches the speed of sound, shock waves develop on the airfoil. The development of these shock waves can have an effect on the aircraft's controllability.

● Drag rise will occur at approximately the same time that the critical mach number is reached and the shock wave starts to form. As the shock wave gets larger and moves aft, drag increases. The effect of a shock wave is much like the effect of opening a door on top of the wing and can cause drastic increases in fuel requirements

● When an aircraft approaches the speed of sound, shock waves develop on the airfoil. The development of these shock waves can have an effect on the aircraft's controllability.

● Drag rise will occur at approximately the same time that the critical mach number is reached and the shock wave starts to form. As the shock wave gets larger and moves aft, drag increases. The effect of a shock wave is much like the effect of opening a door on top of the wing and can cause drastic increases in fuel requirements

Drag Rise

Increase in Drag

Critical Mach +


Flight CharacteristicsFlight Characteristics● Control surface buzz will occur at high Mach numbers on

airplanes that have reversible or non-powered flight controls.

● The buzz is caused by the interaction of the shock wave and the control surface.

● Powered control surfaces eliminate this buzz by holding the control surface rigid thus eliminating the interactions between the shock waive and the control surface.

● Control surface buzz will occur at high Mach numbers on airplanes that have reversible or non-powered flight controls.

● The buzz is caused by the interaction of the shock wave and the control surface.

● Powered control surfaces eliminate this buzz by holding the control surface rigid thus eliminating the interactions between the shock waive and the control surface.

Control Surface Buzz

Airflow Separation

shock wave moves

Supersonic Flow

High Mach Numbers


Airflow Separation

Shock Wave

Supersonic Flow

MACH 0.95MACH 0.95

Flight CharacteristicsFlight Characteristics

● Mach tuck occurs when the shock wave moves aft with the resultant center of lift moving aft on both the wing and stabilizer, which results in a nose down tendency. this nose down tendency is corrected in modern aircraft by the Mach trim system.

● Mach tuck occurs when the shock wave moves aft with the resultant center of lift moving aft on both the wing and stabilizer, which results in a nose down tendency. this nose down tendency is corrected in modern aircraft by the Mach trim system.

Mach Tuck

Center of lift


Design ImprovementsDesign Improvements

● A thinner airfoil with less camber causes less of an increase in speed of the air over the surface of the wing. This results in a higher speed before supersonic airflow occurs.

● A thinner airfoil with less camber causes less of an increase in speed of the air over the surface of the wing. This results in a higher speed before supersonic airflow occurs.

Thinner Airfoil

Design improvementsDesign improvements

● The swept wing design decreases the effectiveness of camber and increases the critical mach number therefore decreasing drag and allowing the aircraft to fly at a higher speed before getting into the critical mach number.

● The swept wing design decreases the effectiveness of camber and increases the critical mach number therefore decreasing drag and allowing the aircraft to fly at a higher speed before getting into the critical mach number.

Swept Wing


● Vortex generators delay the onset of shock-induced airflow separation by producing higher airflow velocities downstream of the shockwave thus increasing the strength of the boundary layer reducing airflow separation.

● Vortex generators delay the onset of shock-induced airflow separation by producing higher airflow velocities downstream of the shockwave thus increasing the strength of the boundary layer reducing airflow separation.

Vortex Generators


● Wing fences are installed on some aircraft to reduce the span-wise flow and improve control effectiveness at lower speeds. Without a wing fence, span wise flow causes the wing to have a tendency to stall from the tips inboard. This is undesirable since there is less warning of an impending stall and because this is usually the area of the aileron, reductions in lateral control effectiveness can occur.

● Wing fences are installed on some aircraft to reduce the span-wise flow and improve control effectiveness at lower speeds. Without a wing fence, span wise flow causes the wing to have a tendency to stall from the tips inboard. This is undesirable since there is less warning of an impending stall and because this is usually the area of the aileron, reductions in lateral control effectiveness can occur.

Wing Fence


● Since sweptback wings have a tendency to stall from the tips inboard, it would be advantageous to change the stall pattern to a more desirable inboard to outboard pattern. This helps to retain aileron effectiveness during a stall warning phase. To affect this pattern stall strips are placed on the leading edge near the wing root to begin the stall pattern in this area at a higher speed to the tip stall.

● Since sweptback wings have a tendency to stall from the tips inboard, it would be advantageous to change the stall pattern to a more desirable inboard to outboard pattern. This helps to retain aileron effectiveness during a stall warning phase. To affect this pattern stall strips are placed on the leading edge near the wing root to begin the stall pattern in this area at a higher speed to the tip stall.

Stall Strips

L/D MaxL/D MaxHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

The lowest point on the total drag curve – also known as Vmd (minimum drag speed)

Pilot Tip

●Airspeed slower than L/D max known as: The “back side of the power-drag curve” or the “region of reverse command”

●Airspeed faster than L/D max is considered normal flight or the “front side of the power-drag curve”

●Normal flight – Speed stable Stable Flight - Airspeed disturbance (i.e. turbulence) - Airspeed will return to the original airspeed when the total thrust has not changed

L/D Max (continued)L/D Max (continued)High Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

Pilot TipSlower cruising speeds are a concern (approaching L/D max). There will be less time to recognize and respond to speed decay during high altitude cruise.

●Slow flight (slower than L/D max) – Unstable

●Lower speed – Result: increased drag

●Increased drag – Result: decrease in airspeed

Ultimate uncorrected result – stalled flight condition

Pilot Tip Flight slower than L/D max at high altitudes must be avoided. Proper flight profiles and planning will ensure speeds slower than L/D max are avoided

Pilot Tip Flight slower than L/D max at high altitudes must be avoided. Proper flight profiles and planning will ensure speeds slower than L/D max are avoided

Optimum AltitudeOptimum AltitudeHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● Calculated for minimum cost when in the ECON mode

– Optimum Altitude increases when you decrease the cost index

● Calculated for minimum fuel burn when in the Long-range cruise (LRC) or pilot-selected modes

– Optimum Altitude increases when speed decreases

● Aircraft weight affects Optimum altitude

– decrease in weight raises the Optimum Altitude

● Temperature also affects Optimum altitude

– increase in temperature lowers the Optimum Altitude

Pilot TipWhen flying at Optimum Altitude, crews should be aware of temperature to ensure performance capability.

Optimum Climb Speed DeviationsOptimum Climb Speed DeviationsHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● Optimum climb speed charts and speeds – AFM, FCOM, and FMS

● For increased rates of climb:

– ensure speed is not decreased below L/D max

(Incident Data: Primary reason for slow speed events. Improper use of vertical speed modes during climb)

Pilot Tip Enroute climb speed is automatically computed by FMC:

• Displayed - Climb and progress pages

• Displayed - Command speed when VNAV is engaged

Pilot Tip Enroute climb speed is automatically computed by FMC:

• Displayed - Climb and progress pages

• Displayed - Command speed when VNAV is engaged

Thrust Limited Condition and RecoveryThrust Limited Condition and RecoveryHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● Be aware of outside temperature and thrust available

● Most jet transport aircraft are thrust limited, rather than slow speed buffet limited - especially in a turn

● Use Flight Management Systems/reduced bank angle– Real-time bank angle protection– Routine bank angle limit (10°-15°) for cruise flight

Pilot Tip If a condition or airspeed decay occurs, take immediate action to recover: • Reduce bank angle• Increase thrust – select maximum continuous thrust (MCT) if the

aircraft is controlling to a lower limit• Descend

Pilot Tip If a condition or airspeed decay occurs, take immediate action to recover: • Reduce bank angle• Increase thrust – select maximum continuous thrust (MCT) if the

aircraft is controlling to a lower limit• Descend

Maximum AltitudeMaximum AltitudeHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● Highest altitude at which an airplane can be operated - Lowest of:

– Maximum certified altitude (Structural) - Determined during certification and is usually set by the pressurization load limits on the fuselage

– Thrust Limited Altitude (Thrust) – Altitude at which sufficient thrust is available to provide a specific minimum rate of climb

Note: Depending on the thrust rating of the engines – Thrust Limited altitude may be above or below the maneuver altitude capability. This altitude also changes with changing temp.

– Buffet or Maneuver Limited Altitude (Aerodynamic) – Altitude at which a specific maneuver margin exists prior to buffet onset

(FAA operations: 1.2g 33° Bank) (CAA/JAA operations: 1.3g 40° Bank)

Next Slide: Figure 2 – Optimum vs. Maximum Altitude

Figure 2Typical Optimum vs. Maximum AltitudeFigure 2Typical Optimum vs. Maximum Altitude

AltitudeAltitude

43000

41000

39000

37000

35000

33000

31000

Maximum certified altitude (Structural)

Optimum altitude (Min Cost @ ECON )

Gross weightGross weight

Thrust-limited maximum altitude (100 FPM)

ISA Temp change (Increasing)

Buffet limited maximum altitude (1.3g) (Aerodynamic)

Note: As ISA Temp increases – Altitude capability is reduced. This is a situation where maneuver buffet margins are ok but temperature is

affecting thrust capability to sustain airspeed at the higher altitudes.

Note: As ISA Temp increases – Altitude capability is reduced. This is a situation where maneuver buffet margins are ok but temperature is

affecting thrust capability to sustain airspeed at the higher altitudes.

(Increasing)(Increasing)

Maneuvering StabilityManeuvering StabilityHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● Flight Characteristics:Constant Airspeed – same control surface movement

High altitude Low altitude

● Higher pitch rate ● Lower pitch rate

● Less aerodynamic damping ● More aerodynamic damping

● Greater angle of attack ● Less angle of attack

Pilot TipHigh altitude flight normally has adequate maneuver margin at optimum altitude. Maneuver margin decreases significantly approaching maximum altitude.

Pilot Tip Do not over control airplane with large control movements – use small control inputs. Be smooth with pitch and power to correct speed deviations.

Pilot Tip Do not over control airplane with large control movements – use small control inputs. Be smooth with pitch and power to correct speed deviations.

Maneuvering Stability (cont)Maneuvering Stability (cont)High Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● Flight Characteristics:

● For the same control surface movement at constant airspeed, an airplane at 35,000 ft experiences a higher pitch rate than an airplane at 5,000 ft because there is less aerodynamic damping.

● Therefore, the change in angle of attack is greater, creating more lift and a higher load factor. If the control system is designed to provide a fixed ratio of control force to elevator deflection, it takes less force to generate the same load factor as altitude increases.

● An additional effect is that for a given attitude change, the change in rate of climb is proportional to the true airspeed. Thus, for an attitude change for 500 ft per minute (fpm) at 290 knots indicated air speed (KIAS) at sea level, the same change in attitude at 290 KIAS (490 knots true air speed) at 35,000 ft would be almost 900 fpm. This characteristic is essentially true for small attitude changes, such as the kind used to hold altitude. It is also why smooth and small control inputs are required at high altitude, particularly when disconnecting the autopilot.

Buffet-Limited Maximum AltitudeBuffet-Limited Maximum Altitude

● Two kinds of buffet to consider in flight:

1. Low speed buffet

2. High speed buffet

● As altitude increases:

– Indicated airspeed (IAS) for low speed buffet increases

– High speed buffet speed decreases

Result: Margin between high speed and low speed buffet decreases

● Two kinds of buffet to consider in flight:

1. Low speed buffet

2. High speed buffet

● As altitude increases:

– Indicated airspeed (IAS) for low speed buffet increases

– High speed buffet speed decreases

Result: Margin between high speed and low speed buffet decreases

Pilot TipRespect buffet margins - Proper use of buffet boundary charts or maneuver capability charts and FMC calculations allows the crew to determine the maximum altitude.

Pilot TipRespect buffet margins - Proper use of buffet boundary charts or maneuver capability charts and FMC calculations allows the crew to determine the maximum altitude.



Buffet-Limited Maximum AltitudeBuffet-Limited Maximum Altitude

● High altitudes - excess thrust is limited

– If needed - Select maximum available/continuous thrust at any time

Important: If speed is decaying (airplane getting slow)

– Select Max Available Thrust

Pilot TipSelect MCT to provide additional thrust. To prevent further airspeed decay into an approach to stall condition a descent may be necessary. Use proper descent techniques.

Pilot Tip Selecting MCT may be insufficient in extreme airspeed decay conditions.

Pilot Tip Selecting MCT may be insufficient in extreme airspeed decay conditions.


Early Turbo-Jet Airplanes – “Coffin corner”

● As the altitude increases - pilot is always trying to maintain a safe airspeed above the stall and a safe airspeed below the Vmo/Mmo

● Difference between the stall and the max speed narrows– Coffin corner

● Stall Warning Systems

– “Stick Shakers”, “Pushers”, “Audio Alarms”

– Know your airplane - systems installed and function

Early Turbo-Jet Airplanes – “Coffin corner”

● As the altitude increases - pilot is always trying to maintain a safe airspeed above the stall and a safe airspeed below the Vmo/Mmo

● Difference between the stall and the max speed narrows– Coffin corner

● Stall Warning Systems

– “Stick Shakers”, “Pushers”, “Audio Alarms”

– Know your airplane - systems installed and function

Operating Near Maximum Altitude Operating Near Maximum Altitude

Pilot Tip Airplane Buffet is often a first indicator – Stay Alert!!Pilot Tip Airplane Buffet is often a first indicator – Stay Alert!!



Although limits are checked by FMC:● Available thrust may limit ability to maneuver

● The amber band limits do not provide an indication of sufficient thrust to maintain the current altitude and airspeed

Although limits are checked by FMC:● Available thrust may limit ability to maneuver

● The amber band limits do not provide an indication of sufficient thrust to maintain the current altitude and airspeed


Operating Near Maximum Altitude (continued) Operating Near Maximum Altitude (continued)

High Altitude ThreatsHigh Altitude ThreatsHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

Operating Near Maximum Altitude (continued) Operating Near Maximum Altitude (continued)

The danger in operating near maximum altitude is the potential for the speed and angle of attack to change due to turbulence or environmental factors that could lead to a slowdown or stall and subsequent high altitude upset.

Pilot Tip Decelerating the airplane to the amber band may create a situation where it is impossible to maintain speed and/or altitude. When speed decreases, the airplane drag may exceed available thrust – especially in a turn.

Pilot Tip Decelerating the airplane to the amber band may create a situation where it is impossible to maintain speed and/or altitude. When speed decreases, the airplane drag may exceed available thrust – especially in a turn.


Amber BandAmber Band

● Displays the range of reduced maneuver capability

● Provides 1.3g/40° of bank angle (default) margin to buffet

● Constant regardless of ambient temperature

Pilot TipThe amber band does not give any indication of thrust limits.

Pilot Tip The minimum maneuver speed indication does not guarantee the ability to maintain level flight at that speed.

Pilot Tip The minimum maneuver speed indication does not guarantee the ability to maintain level flight at that speed.

Amber bandsAmber bands

Figure 3Drag vs. Mach NumberFigure 3Drag vs. Mach Number

Dra

gD

rag

Mach NumberMach Number

Drag - 300 Bank

Current Airspeed

Cruise Thrust

Max Continuous Thrust (MCT)

Drag produced at 300 Bank - exceeds Cruise Thrust

.60.60 .85.85.80.80.75.75.70.70.65.65

Thrust Capability

Drag – Level Flight

(Inc

reas

ing)

(Inc

reas

ing)

For normal cruise speeds there is excess thrust available at this fixed weight and altitude. When trying to turn at 30 degrees of bank the drag exceeds the normal cruise thrust limit. If the pilot selects MCT then there is enough thrust.


Weight & Balance Effects on Handling CharacteristicsWeight & Balance Effects on Handling Characteristics

Pilot Tip: Airplane that is loaded outside the weight and balance envelope will result in aircraft handling that is unpredictable. Stall recovery may be severely impeded. This problem may be magnified at high altitude.

Pilot Tip: Airplane that is loaded outside the weight and balance envelope will result in aircraft handling that is unpredictable. Stall recovery may be severely impeded. This problem may be magnified at high altitude.

• Airplane Handling - Airplanes loaded with an aft CG improves en-route performance. The further aft an airplane is loaded, the less effort is required by the tail to counteract the nose down pitching moment of the wing. The less effort required by the tail results in less induced drag on the entire airplane which results in the most efficient flight.

• But, Aft loading - controls are more sensitive and the airplane has less longitudinal stability.

• At high altitude, an aft loaded airplane is more susceptible to upset since it is less stable than a forward loading. Some airline load planning computers attempt to load airplane as far aft as possible to achieve efficiency. Some advanced airplanes use electronic controls to help improve airplane handling with aft loading.

• Loading toward nose –CG moves forward and Longitudinal stability increases

StallsStallsHigh Altitude Aerodynamics - PrinciplesHigh Altitude Aerodynamics - Principles

● An airplane wing can be stalled– Any airspeed, any altitude, any attitude

Pilot TipIf the angle of attack is greater than the stall angle, the surface will stall. Attitude has no relationship to the aerodynamic stall. Even if the airplane is in a descent with what appears like ample airspeed - the surface can be stalled.

Effective stall recovery requires a deliberate and smooth reduction in wing angle of attack.

The elevator is the primary pitch control in all flight conditions, not thrust.

● Understand the difference between:

1. “Approach” to stall recovery

2. Stall recoveryDramatic difference in recovery techniqueKnow the Difference

Flight TechniquesFlight TechniquesHigh Altitude AerodynamicsHigh Altitude Aerodynamics

Remember the High Altitude BasicsRemember the High Altitude Basics

At altitudes where the operational envelope is reduced:

● Be alert!! No time for complacency

● Recognize and confirm the situation

● Do not over control…Do not use largecontrol movements – use small control pressures

● Be smooth with pitch and power to correct speed deviations




● Do not over control…Do not use largecontrol movements – use small control pressures



Altitude Exchange for EnergyAltitude Exchange for EnergyHigh Altitude Aerodynamics – Flight TechniquesHigh Altitude Aerodynamics – Flight Techniques

● Stall Recovery is the Priority – Altitude recovery is secondary to stall recovery

● Characteristics of stall:– Buffeting, which could be heavy at times– A lack of pitch authority – A lack of roll control – Inability to arrest descent rate– These characteristics are usually accompanied

by a continuous stall warning

Pilot Tip: Stall recovery is the priority. Only after positive stall recovery, can altitude recovery be initiated. At high altitudes swept wing turbojet airplanes may stall at a reduced angle of attack due to Mach effects.

Pilot Tip: Stall recovery is the priority. Only after positive stall recovery, can altitude recovery be initiated. At high altitudes swept wing turbojet airplanes may stall at a reduced angle of attack due to Mach effects.

Stall RecoveryStall Recovery


Altitude Exchange for EnergyAltitude Exchange for Energy

At High Altitude, recovery requires reducing the angle of attack

● The elevator is the primary control to recover from a stalled condition– Loss of altitude (regardless of close proximity to the ground)– Thrust vector may supplement the recovery - not the

primary control– Stall angles of attack - drag is very high – Thrust available may be marginal, the acceleration could

be slow

Stall Recovery (continued)Stall Recovery (continued)

Pilot Tip Stall recovery requires that the angle of attack must be reduced below the stalling angle of attack. The elevator is the primary pitch control in all flight conditions… not thrust.

Pilot Tip Stall recovery requires that the angle of attack must be reduced below the stalling angle of attack. The elevator is the primary pitch control in all flight conditions… not thrust.


Altitude Exchange for EnergyAltitude Exchange for Energy

Although stall angle of attack is normally constant for a given configuration, at high altitudes swept wing turbojet airplanes may stall at a reduced angle of attack due to Mach effects.

The pitch attitude will also be significantly lower than what is experienced at lower altitudes. Low speed buffet will likely precede an impending stall. Thrust available to supplement the recovery will be dramatically reduced and the pitch control through elevator must be used.

The goal of minimizing altitude loss must be secondary to recovering from the stall. Flight crews must exchange altitude for airspeed. Only after positive stall recovery has been achieved, can altitude recovery be prioritized.

Stall Recovery (continued)Stall Recovery (continued)


Primary Flight Display Airspeed IndicationsPrimary Flight Display Airspeed Indications

● Modern aircraft are equipped with speedtape

– Help you maintain a safe airspeed margins

– Airspeed trending

ImportantThese displays do not indicate if adequate thrust is available to maintain the current airspeed and altitude

ImportantThese displays do not indicate if adequate thrust is available to maintain the current airspeed and altitude


Flight Techniques of Jet AircraftFlight Techniques of Jet Aircraft

● Automation during cruise– Attempts to maintain altitude and airspeed– Thrust will increase to selected cruise limit – Select MCT (Max Cont Thrust) - to increase available thrust

and stop airspeed decay

● Airspeed continues to deteriorate - the only option is to descend

Pilot Tip Pilot must take action before excessive airspeed loss

● The pilot’s action - pitch down - increase the airspeed while being in an automation mode that keeps the throttles at maximum thrust

● Autopilot engaged - select a lower altitude - use an appropriate mode to descend

● If the aircraft is not responding quickly enough you must take over manually

● Re-engage autopilot once in a stable descent and the commanded speed has been reestablished

Pilot Tip Pilot must take action before excessive airspeed loss

● The pilot’s action - pitch down - increase the airspeed while being in an automation mode that keeps the throttles at maximum thrust

● Autopilot engaged - select a lower altitude - use an appropriate mode to descend

● If the aircraft is not responding quickly enough you must take over manually

● Re-engage autopilot once in a stable descent and the commanded speed has been reestablished

Automation During High Altitude FlightAutomation During High Altitude Flight

Flight Techniques of Jet AircraftFlight Techniques of Jet Aircraft

● Vertical Speed Mode (VS) at high altitude - must be clearly understood

– Energy management, available thrust is reduced at high altitude

– Fundamental to energy management is to control speed either on elevator or with thrust

– VS mode, airplane speed controlled by thrust

– Use of VS has considerable risk during high altitude climb

– VS mode prioritizes the commanded VS rate

– Speed can decay, thrust available is less than thrust required

– Improper use of VS can result in speed loss

● Vertical Speed Mode (VS) at high altitude - must be clearly understood

– Energy management, available thrust is reduced at high altitude

– Fundamental to energy management is to control speed either on elevator or with thrust

– VS mode, airplane speed controlled by thrust

– Use of VS has considerable risk during high altitude climb

– VS mode prioritizes the commanded VS rate

– Speed can decay, thrust available is less than thrust required

– Improper use of VS can result in speed loss


Automation During High Altitude Flight (continued)Automation During High Altitude Flight (continued)

Flight Techniques of Jet AircraftFlight Techniques of Jet AircraftHigh Altitude Aerodynamics – Flight TechniquesHigh Altitude Aerodynamics – Flight Techniques

Automation During High Altitude Flight (continued)Automation During High Altitude Flight (continued)

Pilot Tip General guideline - VS mode should not be used for climbing at high altitudes

Pilot Tip VS can be used for descent - selecting excessive vertical speeds can result in airspeed increases into an overspeed condition

Pilot Tip Using a mode that normally reduces thrust, when the need arises to descend immediately, may not be appropriate for a low speed situation

Pilot Tip General guideline - VS mode should not be used for climbing at high altitudes

Pilot Tip VS can be used for descent - selecting excessive vertical speeds can result in airspeed increases into an overspeed condition

Pilot Tip Using a mode that normally reduces thrust, when the need arises to descend immediately, may not be appropriate for a low speed situation


Human Factors and High Altitude UpsetsHuman Factors and High Altitude Upsets● The Startle Factor

– Dynamic buffeting and large changes in airplane attitude

● When not properly avoided, managed, or flown

– Assures a self-induced upset

Human Factors and High Altitude UpsetsHuman Factors and High Altitude Upsets

● Pilot training – conventional– Typical crew training

– Trained to respond to stall warnings – “Approach to Stall”– Usually limited to low altitude recovery

● High altitude - stalls – Low speed buffet mistaken

for high speed buffet – Actual full “Stall Recovery” – Higher altitudes

Available thrust is insufficient

Reduce the angle of attack

Trade altitude for airspeed.

● Recognition for recovery is sometimes delayed

● Pilot training – conventional– Typical crew training

– Trained to respond to stall warnings – “Approach to Stall”– Usually limited to low altitude recovery

● High altitude - stalls – Low speed buffet mistaken

for high speed buffet – Actual full “Stall Recovery” – Higher altitudes

Available thrust is insufficient

Reduce the angle of attack

Trade altitude for airspeed.

● Recognition for recovery is sometimes delayed


(continued)(continued)


Human Factors and High Altitude UpsetsHuman Factors and High Altitude Upsets

Reasons for delayed recovery

1. Concern for passenger and crew safety following large control movements

2. Previous training emphasized altitude loss

3. Anxiety associated altitude violations and other ATC concerns

4. Less experience with manual flight control at high speed / altitude

5. Lack of understanding - Unaware of the magnitude of altitude loss as it relates to the recovery from the upset condition

6. On the other side there is the concern of accelerating into high speed buffet during the recovery if the airplane is allowed to accelerate too much.

(continued)(continued)

Further InformationFurther Information

For further information on upset recovery, see the FAA Airplane upset recovery aid

For further information on upset recovery, see the FAA Airplane upset recovery aid

High Altitude OperationsAdditional ConsiderationsHigh Altitude OperationsAdditional Considerations

High Altitude Operations – Additional ConsiderationsHigh Altitude Operations – Additional Considerations

Multi-Engine Flame OutMulti-Engine Flame Out

● Prompt recognition of the engine failures – utmost importance

● Immediately accomplishment of the recall items and/or checklist associated with loss of all engines– Establish the appropriate airspeed (requires a manual pitch

down) to attempt a windmill relight– Driftdown will be required to improve windmill starting

capability– Inflight start envelope is provided to identify proper windmill

start parameters

Pilot Tip Regardless of the conditions and status of the airplane - strict adherence to the checklist is essential to maximize the probability of a successful relight.

Pilot Tip Regardless of the conditions and status of the airplane - strict adherence to the checklist is essential to maximize the probability of a successful relight.

Pilot Tip Recognition tip – autopilots and A/T may disconnect or indications of electrical problems may exist with a multi-engine flameout.

Pilot Tip Recognition tip – autopilots and A/T may disconnect or indications of electrical problems may exist with a multi-engine flameout.

Demands Immediate ActionDemands Immediate Action


CorelockCorelock

● Turbine engine – abnormal thermal event (e.g flameout at low airspeed)Result - the “core” of the engine stops or seizes

● Insufficient airspeed - insufficient airflow through the engine

● Engine – restart capability only when seized engine spools begin to rotatePilot Tip After all engine flameouts

• The first critical consideration is to obtain safe descent speed• Determine engine status • If engine spools indicate zero - core lock may exist/mechanical

engine damage• Crews must obtain best L/DMax airspeed instead of accelerating

to windmill speed

Pilot Tip After all engine flameouts • The first critical consideration is to obtain safe descent speed• Determine engine status • If engine spools indicate zero - core lock may exist/mechanical

engine damage• Crews must obtain best L/DMax airspeed instead of accelerating

to windmill speed

● Critical: The crew must follow the approved flight manual procedures, maintain sufficient airspeed to maintain core rotation

● Critical: The crew must follow the approved flight manual procedures, maintain sufficient airspeed to maintain core rotation


RollbackRollback

● Turbine engine rollback - uncommanded loss of thrust

– Reduced N1 RPM - increase in EGT

– Many causal factors:

– Moisture

– Icing

– Fuel control issues

– High angle of attack disrupted airflow

– Mechanical failure

Pilot Tip If airspeed stagnation occurs, check appropriate thrust level. This is important as well as increasing airspeed in the case of an engine has rollback.

Pilot Tip If airspeed stagnation occurs, check appropriate thrust level. This is important as well as increasing airspeed in the case of an engine has rollback.

High Altitude BasicsHigh Altitude Basics




● Do not over control…Do not use large control movements – use small control pressures





● Do not over control…Do not use large control movements – use small control pressures


High Altitude AerodynamicsHigh Altitude Aerodynamics

● In this section we discussed the speed of sound and its relation to temperature, aerodynamics of subsonic and transonic flight, flight characteristics of transonic flight, including undesirable aspects associated with transonic flight and some of the aircraft design improvements that have increased efficiency, comfort and safety of flight at high altitudes and high speeds.

● We also looked at flight handling characteristics and techniques

● In this section we discussed the speed of sound and its relation to temperature, aerodynamics of subsonic and transonic flight, flight characteristics of transonic flight, including undesirable aspects associated with transonic flight and some of the aircraft design improvements that have increased efficiency, comfort and safety of flight at high altitudes and high speeds.

● We also looked at flight handling characteristics and techniques

Summary

• Speed of sound

• Aerodynamics of subsonic flight

• Aerodynamics of transonic flight

• Flight characteristics of transonic flight

• Aircraft design improvements

• Aircraft handling techniques

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high altitude operations. introduction far 61.31 high altitude aerodynamics and meteorology...

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