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DGCA ATPL Aviation Meteorology study materials
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DGCA ATPL Aviation Meteorology practice questions

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Question 1The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

Which gas forms the largest proportion of the dry atmosphere by volume?

  1. Nitrogen Correct answer.
  2. Carbon dioxide
  3. Oxygen
  4. Argon

Explanation

Dry air is dominated by nitrogen at about 78 percent by volume, with oxygen at about 21 percent. Argon and carbon dioxide are present only in small trace amounts.

Question 2The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

In which atmospheric layer does the temperature generally increase with height?

  1. Mesosphere
  2. Tropopause
  3. Troposphere
  4. Stratosphere Correct answer.

Explanation

The stratosphere contains the ozone layer, which absorbs ultraviolet radiation and causes temperature to rise with height. The troposphere and mesosphere both show temperature decreasing with height.

Question 3The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

What is the standard sea-level pressure used in the ICAO Standard Atmosphere?

  1. 1015.0 hPa
  2. 1013.2 hPa Correct answer.
  3. 1023.2 hPa
  4. 1000.0 hPa

Explanation

The ICAO Standard Atmosphere defines mean sea-level pressure as 1013.25 hPa, usually rounded to 1013.2 hPa. This value is the reference for pressure altitude and QNE settings.

Question 4The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

What is the standard sea-level temperature and mean temperature lapse rate in the ICAO Standard Atmosphere?

  1. 15 °C and 2 °C per 1000 ft
  2. 0 °C and 1.98 °C per 1000 ft
  3. 15 °C and 1.98 °C per 1000 ft Correct answer.
  4. 10 °C and 2 °C per 1000 ft

Explanation

The standard atmosphere assumes 15 °C at mean sea level with a lapse rate of about 6.5 °C per km, equivalent to roughly 1.98 °C per 1000 ft. This lapse rate applies through the troposphere.

Question 5The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

Approximately what proportion of the total mass of the atmosphere lies within the troposphere?

  1. About 75 percent Correct answer.
  2. About 90 percent
  3. About 50 percent
  4. About 25 percent

Explanation

Although the troposphere extends only to about 8–12 km, it contains roughly three-quarters of the atmospheric mass because density decreases rapidly with height.

Question 6The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

A layer of air has a base temperature of 20 °C and a top temperature of 5 °C, with a thickness of 5000 ft. What is the environmental lapse rate?

  1. 2.5 °C per 1000 ft
  2. 1.5 °C per 1000 ft
  3. 2.0 °C per 1000 ft
  4. 3.0 °C per 1000 ft Correct answer.

Explanation

The temperature falls by 15 °C over 5000 ft, giving 15 ÷ 5 = 3 °C per 1000 ft. Lapse rate is the change of temperature with height.

Question 7The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

Why does the tropopause generally occur at a higher altitude over the equator than over the poles?

  1. Coriolis force is zero at the equator and lifts the tropopause
  2. Stronger surface heating produces deeper tropospheric convection and a taller troposphere Correct answer.
  3. The equatorial ozone layer is thicker and pushes the tropopause upward
  4. Equatorial air has a lower mean molecular weight

Explanation

Intense solar heating at the equator drives vigorous convection, so the troposphere is deeper and the tropopause is higher, around 16–18 km. At the poles, weaker heating gives a shallower troposphere with the tropopause near 8 km.

Question 8The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

In which atmospheric layer do most meteorological phenomena such as clouds and precipitation occur?

  1. Stratosphere
  2. Mesosphere
  3. Thermosphere
  4. Troposphere Correct answer.

Explanation

The troposphere holds nearly all water vapour and experiences the vertical mixing that forms weather. Its lapse rate makes it unstable enough for cloud and precipitation development.

Question 9The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

What is the significance of the tropopause for aircraft performance and weather?

  1. It is the altitude at which the ozone concentration is highest
  2. It acts as a lid limiting most vertical motion and marks the top of the weather layer Correct answer.
  3. It marks the level where pressure stops decreasing with height
  4. It is the level at which temperature begins to fall rapidly

Explanation

The tropopause is a stable boundary that suppresses most large-scale vertical motion, so clouds and turbulence are largely confined below it. Jet streams are also found near the tropopause.

Question 10The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

Approximately what is the mean sea-level pressure expressed in inches of mercury?

  1. 29.92 inHg Correct answer.
  2. 30.92 inHg
  3. 28.92 inHg
  4. 27.92 inHg

Explanation

Standard sea-level pressure of 1013.25 hPa converts to about 29.92 inHg. This value is used as the standard altimeter setting reference.

Question 11The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

What is the primary source of atmospheric water vapour?

  1. Evaporation from oceans and transpiration from vegetation Correct answer.
  2. Combustion of fossil fuels
  3. Photodissociation of ozone
  4. Volcanic outgassing

Explanation

Water vapour enters the atmosphere mainly through evaporation from water surfaces and transpiration from plants. These processes supply nearly all atmospheric moisture.

Question 12The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

An aircraft is flying at a pressure altitude of 10,000 ft in an atmosphere where the temperature is 15 °C warmer than ISA. How does the true altitude compare with the indicated altitude?

  1. True altitude is equal to indicated altitude
  2. True altitude cannot be related to indicated altitude
  3. True altitude is lower than indicated altitude
  4. True altitude is higher than indicated altitude Correct answer.

Explanation

Warmer-than-standard air is less dense, so pressure levels are found at greater true heights. When the altimeter is set to standard pressure, the aircraft is actually higher than indicated.

Question 13The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

How does the density of air change with increasing altitude in the standard atmosphere?

  1. It increases linearly with height
  2. It decreases only above the stratopause
  3. It decreases approximately exponentially with height Correct answer.
  4. It remains constant up to the tropopause

Explanation

Because air is compressible, both pressure and density fall off roughly exponentially with height. Density halves at about 18,000 ft.

Question 14The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

Which statement correctly describes the composition of the atmosphere with respect to water vapour and carbon dioxide?

  1. Both vary in concentration and are mainly confined to the troposphere Correct answer.
  2. Both are uniformly distributed with height
  3. Both are chemically inert and play no role in weather
  4. Both are concentrated in the stratosphere

Explanation

Water vapour and carbon dioxide are variable constituents, and their concentrations are highest in the lower atmosphere. Water vapour in particular is almost entirely confined to the troposphere.

Question 15The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

What happens to the environmental lapse rate as an air parcel rises through the stratosphere?

  1. It typically becomes isothermal or weakly positive, indicating a stable layer Correct answer.
  2. It remains exactly equal to the dry adiabatic lapse rate
  3. It becomes irrelevant because pressure no longer changes
  4. It becomes strongly negative, indicating extreme instability

Explanation

In the stratosphere, temperature is nearly constant or rises with height, so the environmental lapse rate is small or negative. This makes the layer very stable and suppresses vertical motion.

Question 16The Atmosphere: Composition, Vertical Structure and Standard Atmosphere

A pressure of 500 hPa is encountered at a certain flight level. In the standard atmosphere, at approximately what altitude does this pressure occur?

  1. About 25,000 ft
  2. About 10,000 ft
  3. About 34,000 ft
  4. About 18,000 ft Correct answer.

Explanation

In the standard atmosphere, pressure halves at about 18,000 ft, where it is roughly 500 hPa. This is a useful reference for flight level and pressure-altitude calculations.

Question 17Temperature, Pressure, Density and the Gas Laws

In the International Standard Atmosphere, what is the sea-level temperature and the standard lapse rate in the troposphere?

  1. 15 °C and 6.5 °C per 1000 ft
  2. 15 °C and 1.98 °C per 1000 ft Correct answer.
  3. 10 °C and 1.98 °C per 1000 ft
  4. 0 °C and 2.0 °C per 1000 ft

Explanation

The ISA fixes sea-level temperature at 15 °C and a mean tropospheric lapse rate of about 1.98 °C per 1000 ft (6.5 °C per km). These are the reference values used for calibrating altimeters and computing density.

Question 18Temperature, Pressure, Density and the Gas Laws

What is the ISA sea-level pressure and the ISA sea-level density?

  1. 1000 hPa and 1.225 kg/m³
  2. 1013.25 hPa and 1.225 kg/m³ Correct answer.
  3. 1013.25 hPa and 1.000 kg/m³
  4. 1013.25 mb and 0.905 kg/m³

Explanation

The ISA defines sea-level pressure as 1013.25 hPa and sea-level density as 1.225 kg/m³. These values anchor all pressure and density computations in the standard atmosphere.

Question 19Temperature, Pressure, Density and the Gas Laws

As an aircraft climbs in the troposphere, how do pressure and density change with increasing altitude?

  1. Pressure decreases while density remains constant
  2. Both decrease, but pressure falls proportionally faster than density Correct answer.
  3. Both increase steadily with altitude
  4. Both decrease at exactly the same proportional rate

Explanation

Pressure equals the weight of the overlying air and falls rapidly with height. Density also falls but less steeply, because temperature decreases with height and cold air is denser, partly offsetting the pressure loss. Hence pressure decreases proportionally faster than density.

Question 20Temperature, Pressure, Density and the Gas Laws

What does the term 'pressure altitude' mean?

  1. The true height of the aircraft above the surface
  2. The altitude indicated when the subscale is set to 1013.25 hPa Correct answer.
  3. The altitude corrected for non-standard temperature
  4. The altitude read when the subscale is set to the local QNH

Explanation

Pressure altitude is the altitude shown on the altimeter when 1013.25 hPa is set on the subscale. It is the reference used for flight levels and for computing density altitude.

Question 21Temperature, Pressure, Density and the Gas Laws

Density altitude is best described as which of the following?

  1. The altitude shown with the local QNH set
  2. The geometric height above the aerodrome reference point
  3. The altitude at which the aircraft would reach its service ceiling
  4. The pressure altitude corrected for temperature deviation from ISA Correct answer.

Explanation

Density altitude is the pressure altitude adjusted for the actual temperature deviation from ISA. Warmer-than-standard air raises density altitude, degrading performance.

Question 22Temperature, Pressure, Density and the Gas Laws

An aerodrome at 2000 ft pressure altitude reports a temperature of 30 °C. Given ISA temperature at that level is about 11 °C, what is the approximate ISA temperature deviation?

  1. +19 °C Correct answer.
  2. +41 °C
  3. +11 °C
  4. −19 °C

Explanation

The deviation is the actual temperature minus the ISA temperature for that level: 30 − 11 = +19 °C. A positive deviation means the air is warmer than standard, giving a higher density altitude.

Question 23Temperature, Pressure, Density and the Gas Laws

How does increasing humidity affect the density of a given volume of air at constant pressure and temperature?

  1. It decreases density because water vapour is lighter than dry air Correct answer.
  2. It increases density only above the tropopause
  3. It has no effect because water vapour is a gas
  4. It increases density because water vapour is heavier than dry air

Explanation

Water vapour has a lower molecular mass than the average dry-air molecule, so replacing dry air with vapour at the same pressure and temperature lowers the mixture density. Humid air is therefore less dense than dry air.

Question 24Temperature, Pressure, Density and the Gas Laws

Which statement correctly describes the relationship between density, pressure and temperature for a fixed mass of dry air?

  1. Density rises with pressure and falls with temperature Correct answer.
  2. Density rises with both pressure and temperature
  3. Density is independent of pressure and temperature
  4. Density falls with pressure and rises with temperature

Explanation

From the gas equation of state, density is proportional to pressure and inversely proportional to absolute temperature. Raising pressure packs more molecules into the volume, while raising temperature thins the air.

Question 25Temperature, Pressure, Density and the Gas Laws

For a fixed mass of gas at constant temperature, what happens to its volume when the pressure is doubled?

  1. The volume is halved Correct answer.
  2. The volume remains unchanged
  3. The volume is doubled
  4. The volume is reduced to one quarter

Explanation

Boyle's law states that at constant temperature the product of pressure and volume is constant. Doubling the pressure therefore halves the volume.

Question 26Temperature, Pressure, Density and the Gas Laws

A gas at constant pressure is heated so that its absolute temperature doubles. What happens to its volume?

  1. The volume doubles Correct answer.
  2. The volume stays the same
  3. The volume halves
  4. The volume increases by a factor of four

Explanation

Charles's law states that at constant pressure volume is directly proportional to absolute temperature. Doubling the absolute temperature therefore doubles the volume.

Question 27Temperature, Pressure, Density and the Gas Laws

Which of the following is a correct statement of the ideal gas equation of state?

  1. ρ = P R T
  2. P V = ρ R T
  3. P = ρ R T Correct answer.
  4. P V = m R / T

Explanation

For a unit mass the equation of state is P = ρ R T, where R is the specific gas constant. The alternative form P V = m R T follows from multiplying by volume.

Question 28Temperature, Pressure, Density and the Gas Laws

Two air masses have the same pressure but one is colder than the other. How do their densities compare?

  1. Both have equal density because pressure is equal
  2. The colder air mass is denser Correct answer.
  3. The comparison cannot be made without knowing humidity
  4. The warmer air mass is denser

Explanation

At equal pressure, density is inversely proportional to absolute temperature. The colder air mass therefore has the higher density. This is why cold air gives better aircraft and engine performance.

Question 29Temperature, Pressure, Density and the Gas Laws

An aircraft departs from a hot, high-elevation aerodrome. Compared with a cold, sea-level aerodrome, how will its take-off performance be affected?

  1. Longer take-off run and reduced rate of climb Correct answer.
  2. Shorter take-off run and improved climb
  3. Shorter take-off run and reduced climb
  4. Unchanged take-off run but reduced climb

Explanation

Hot, high conditions give low air density, which reduces engine power (for piston engines), propeller thrust and wing lift. The aircraft needs a higher true airspeed and a longer ground run, and the climb rate is reduced.

Question 30Temperature, Pressure, Density and the Gas Laws

In the ISA, at what approximate altitude does the pressure fall to about half of its sea-level value?

  1. About 5 000 ft
  2. About 18 000 ft Correct answer.
  3. About 10 000 ft
  4. About 36 000 ft

Explanation

Pressure decreases roughly exponentially with height and reaches about half of the sea-level value near 18 000 ft in the ISA. This reflects the rapid early fall of pressure with altitude.

Question 31Temperature, Pressure, Density and the Gas Laws

Why does the tropopause mark the upper limit of the troposphere in terms of temperature behaviour?

  1. Temperature begins to fall more rapidly above it
  2. Density becomes constant above it
  3. The lapse rate becomes approximately isothermal above it Correct answer.
  4. Pressure stops decreasing above it

Explanation

Within the troposphere temperature falls with height, but at the tropopause the lapse rate becomes near-isothermal or reverses in the stratosphere. This change in temperature gradient defines the boundary.

Question 32Temperature, Pressure, Density and the Gas Laws

An altimeter with 1013.25 hPa set reads 5000 ft while flying in air colder than ISA. How does the true altitude compare with the indicated altitude?

  1. True altitude is lower than indicated altitude Correct answer.
  2. True altitude equals indicated altitude
  3. True altitude is higher only above the tropopause
  4. True altitude is higher than indicated altitude

Explanation

Cold air is denser, so pressure levels are compressed toward the surface and the altimeter over-reads. With a fixed subscale setting the aircraft is therefore lower than the altimeter suggests, which is a terrain-clearance hazard.

Question 33Atmospheric Pressure, Altimetry and Pressure Systems

In the ICAO Standard Atmosphere, what are the sea-level pressure and temperature values on which altimetry is based?

  1. 1013.25 hPa and 0 °C
  2. 1000 hPa and 15 °C
  3. 1000 hPa and 0 °C
  4. 1013.25 hPa and 15 °C Correct answer.

Explanation

The ICAO Standard Atmosphere fixes mean sea-level pressure at 1013.25 hPa and mean sea-level temperature at 15 °C, with a standard lapse rate of 1.98 °C per 1000 ft. These reference values underpin pressure altitude and the calibration of altimeters.

Question 34Atmospheric Pressure, Altimetry and Pressure Systems

An aircraft on the ground at an aerodrome sets 1013 hPa on its altimeter subscale. The altimeter then indicates:

  1. Height above the aerodrome
  2. Pressure altitude Correct answer.
  3. True altitude
  4. Aerodrome elevation

Explanation

When the subscale is set to the standard pressure 1013.25 hPa, the altimeter displays pressure altitude, the altitude corresponding to the ambient pressure in the standard atmosphere. Elevation and true altitude require QNH or QFE settings respectively.

Question 35Atmospheric Pressure, Altimetry and Pressure Systems

As an aircraft climbs, the atmospheric pressure and density:

  1. Pressure decreases while density increases
  2. Both increase
  3. Both decrease Correct answer.
  4. Pressure increases while density decreases

Explanation

Pressure and density both decrease with increasing altitude because the weight and compression of the overlying air diminish upward. Their rates of decrease differ, but the direction is the same for both.

Question 36Atmospheric Pressure, Altimetry and Pressure Systems

Which altimeter setting causes the altimeter to read zero when the aircraft is on the ground at the aerodrome?

  1. QFE Correct answer.
  2. QNE
  3. Regional QNH
  4. QNH

Explanation

QFE is the pressure setting which, when set on the subscale, makes the altimeter read zero (or the height above the reference datum) at aerodrome level. QNH makes it read aerodrome elevation instead.

Question 37Atmospheric Pressure, Altimetry and Pressure Systems

The term 'QNH' refers to the pressure:

  1. At the aerodrome reference point
  2. At the transition level
  3. At the standard datum of 1013.25 hPa
  4. Reduced to mean sea level using standard atmosphere assumptions Correct answer.

Explanation

QNH is the aerodrome pressure reduced to mean sea level assuming standard atmosphere conditions between the station and sea level. Setting QNH makes the altimeter indicate elevation on the ground.

Question 38Atmospheric Pressure, Altimetry and Pressure Systems

In the lower atmosphere, pressure decreases with height at approximately:

  1. 1 hPa per 30 ft Correct answer.
  2. 1 hPa per 1000 ft
  3. 1 hPa per 100 ft
  4. 10 hPa per 100 ft

Explanation

Near sea level pressure falls by roughly 1 hPa for every 30 ft of climb, which is the basis for the 30 ft per hPa rule used in altimetry. This rate decreases at higher altitudes.

Question 39Atmospheric Pressure, Altimetry and Pressure Systems

An aircraft flies from an area of high pressure into an area of low pressure without resetting the altimeter. The altimeter will:

  1. Under-read, so the aircraft is higher than indicated Correct answer.
  2. Under-read, so the aircraft is lower than indicated
  3. Remain correct
  4. Over-read, so the aircraft is lower than indicated

Explanation

If the subscale is left at the higher pressure setting while the aircraft enters lower pressure, the altimeter indicates an altitude higher than the true one (it under-reads relative to actual height). The aircraft is therefore lower than the altimeter suggests, which is the 'high to low, look out below' hazard.

Question 40Atmospheric Pressure, Altimetry and Pressure Systems

An aircraft is flying at a constant indicated altitude from a warm air mass into a cold air mass. Its true altitude will:

  1. Remain constant
  2. Increase
  3. Decrease Correct answer.
  4. Increase then decrease

Explanation

In colder air the pressure surfaces are compressed toward the ground, so a given indicated altitude corresponds to a lower true altitude. Flying from warm to cold air therefore reduces true altitude while indicated altitude stays constant, the 'high to low, look out below' temperature hazard.

Question 41Atmospheric Pressure, Altimetry and Pressure Systems

The transition level is:

  1. The height at which QFE is set
  2. A fixed level at all aerodromes
  3. The lowest flight level available above the transition altitude Correct answer.
  4. The altitude at which the altimeter is changed from QNH to standard pressure

Explanation

The transition level is the lowest flight level that can be used above the transition altitude, and it varies with the QNH. The transition altitude is the fixed altitude at which the change from QNH to standard pressure is made.

Question 42Atmospheric Pressure, Altimetry and Pressure Systems

With QNH 1030 hPa set, an aircraft on the ground at an aerodrome of elevation 500 ft will indicate approximately:

  1. 0 ft
  2. 1030 ft
  3. 500 ft Correct answer.
  4. 1013 ft

Explanation

Setting QNH makes the altimeter read aerodrome elevation on the ground, so it should indicate about 500 ft. The QNH value itself is not displayed as an altitude.

Question 43Atmospheric Pressure, Altimetry and Pressure Systems

A pressure system in which the pressure decreases outward from the centre and the wind blows clockwise in the Southern Hemisphere is a:

  1. Trough
  2. Low
  3. High Correct answer.
  4. Col

Explanation

A high (anticyclone) has pressure decreasing outward from the centre, and its circulation is clockwise in the Southern Hemisphere. A low has pressure increasing outward and counterclockwise circulation in the Southern Hemisphere.

Question 44Atmospheric Pressure, Altimetry and Pressure Systems

Which statement about the geostrophic wind is correct?

  1. It blows parallel to the isobars only in the Southern Hemisphere
  2. It occurs only near the surface where friction dominates
  3. It blows parallel to straight isobars with the Coriolis force balancing the pressure gradient force Correct answer.
  4. It blows across the isobars toward low pressure

Explanation

Geostrophic flow occurs in the free atmosphere where friction is negligible, with the Coriolis force exactly balancing the pressure gradient force. The result is wind parallel to straight isobars, with low pressure to the left in the Northern Hemisphere and to the right in the Southern Hemisphere.

Question 45Atmospheric Pressure, Altimetry and Pressure Systems

Near the surface, friction causes the wind to:

  1. Blow exactly along the isobars
  2. Back and cross the isobars toward low pressure Correct answer.
  3. Increase in speed and align with the isobars
  4. Reverse direction relative to the geostrophic wind

Explanation

Surface friction reduces wind speed, weakening the Coriolis force, so the pressure gradient force turns the wind across the isobars toward low pressure. This also causes the wind to back (turn counterclockwise in the Northern Hemisphere) compared with the geostrophic direction.

Question 46Atmospheric Pressure, Altimetry and Pressure Systems

The pressure gradient force is directed:

  1. From high pressure toward low pressure, perpendicular to the isobars Correct answer.
  2. Parallel to the isobars
  3. From low pressure toward high pressure
  4. Toward the poles

Explanation

The pressure gradient force acts from higher toward lower pressure and is perpendicular to the isobars, with magnitude proportional to the spacing of the isobars. It is the force that initiates air motion.

Question 47Atmospheric Pressure, Altimetry and Pressure Systems

An aircraft descends from a flight level with 1013 hPa set to an aerodrome where QNH is 1013 hPa. If the aerodrome has elevation 1000 ft, the altimeter at touchdown will read approximately:

  1. 1013 ft
  2. 0 ft
  3. 1000 ft Correct answer.
  4. 2000 ft

Explanation

When QNH equals standard pressure 1013 hPa, the aerodrome elevation corresponds directly to the pressure altitude. With QNH equal to 1013 hPa the altimeter will read the aerodrome elevation of about 1000 ft at touchdown.

Question 48Atmospheric Pressure, Altimetry and Pressure Systems

The 30 ft per hPa rule is used primarily to:

  1. Convert indicated altitude to true altitude for temperature
  2. Determine density altitude from humidity
  3. Compute the transition level
  4. Estimate the change in indicated altitude resulting from a change in altimeter setting Correct answer.

Explanation

The 30 ft per hPa rule relates a change in altimeter subscale setting to a change in indicated altitude near the surface. For example, a 1 hPa setting error corresponds to roughly 30 ft of altitude error.

Question 49Atmospheric Pressure, Altimetry and Pressure Systems

An aircraft on approach experiences an unusually high temperature error on a hot day. The indicated altitude compared with true altitude will be:

  1. Higher than true altitude Correct answer.
  2. Lower than true altitude
  3. Unrelated to temperature
  4. Equal to true altitude

Explanation

In air warmer than the standard atmosphere, pressure surfaces are farther apart, so a given indicated altitude corresponds to a greater true altitude. The altimeter therefore under-reads the true height, meaning the indicated altitude is lower than true altitude, which is why hot-day approaches are flown higher.

Question 50Atmospheric Pressure, Altimetry and Pressure Systems

An aircraft flying at FL100 with 1013 hPa set crosses into air colder than standard. If the true altitude is to be maintained, the indicated altitude must be:

  1. Increased Correct answer.
  2. Decreased
  3. Set to QFE
  4. Left unchanged

Explanation

In cold air the pressure surfaces are compressed, so a given indicated altitude corresponds to a lower true altitude. To maintain the same true altitude, the aircraft must climb to a higher indicated altitude, so the indicated altitude must be increased.