TrueHeading
Log inEnrol
DGCA Aviation Meteorology · 103 questions

Pressure & Altimetry: DGCA Aviation Meteorology Questions and Answers

103 practice questions on Pressure & Altimetry with answers and explanations, plus the key concepts and formulas, from the TrueHeading question bank.

Practise all 103 questionsFlashcards

About this topic

Use this page to revise Pressure & Altimetry for the DGCA Aviation Meteorology paper. Below are the key ideas first, then 12 practice questions with answers and explanations, picked from the 103 questions in the TrueHeading bank for this topic.

In short: It depends on the subscale setting:

Open the full set in the student zone to answer every question, track your accuracy and take timed mock tests.

Key concepts: Pressure & Altimetry

9 ideas to know cold.

QNH, QFE and QNE: what does the altimeter read?

It depends on the subscale setting:

  • QNH: altitude above mean sea level (reads aerodrome elevation on the ground)
  • QFE: height above the aerodrome (reads zero on the runway)
  • QNE / 1013.25: pressure altitude, used for flight levels
mean sea levelaerodrome1013.25 → pressure altitudeflight levelsQNH → field elevationaltitude above sea levelQFE → 0 on the runwayheight above aerodrome

Flying from high pressure to low pressure without resetting: what happens?

The altimeter over-reads: the aircraft is lower than indicated. “High to low, look out below.”

  • Each 1 hPa of error ≈ 30 ft
  • Flying from warm to cold air gives the same effect
  • Low to high pressure is the safe way round (altimeter under-reads)

How do you find pressure altitude?

Correct the elevation for the difference between 1013 hPa and the QNH.

PA=elevation+(1013−QNH)×30 ftPA=\text{elevation}+(1013-QNH)\times 30\ \text{ft}
  • QNH 1003 hPa at elevation 500 ft gives PA = 500 + 300 = 800 ft

What temperature correction applies to an altimeter?

True altitude differs from indicated by about 4 ft per 1000 ft per °C of ISA deviation.

Δh≈4×h1000×ΔTISA\Delta h\approx 4\times\frac{h}{1000}\times\Delta T_{ISA}
  • Colder than ISA: true altitude is lower than indicated (dangerous over high ground)
  • Warmer than ISA: true altitude is higher

Transition altitude, transition level and transition layer?

Below the transition altitude use QNH (altitude). Above the transition level use 1013.25 hPa (flight levels).

  • The transition layer lies between the two
  • Vertical position: altitude (QNH), height (QFE), flight level (1013)
  • Set the standard setting when climbing through the transition altitude

What is the difference between QNH and QFF?

QNH is station pressure reduced to mean sea level using ISA temperatures. QFF is reduced using the actual temperature of the air column.

Tip: QFF is used for synoptic charts, QNH for altimeter settings.

How do you convert QNH to QFE?

Subtract the elevation expressed in hPa.

QFE=QNH−elevation (ft)30QFE=QNH-\frac{\text{elevation (ft)}}{30}
  • QNH 1013 at elevation 900 ft gives QFE ≈ 983 hPa

Explain QNH, QFE and QNE.

QNH: sea-level pressure from ISA, altimeter reads elevation on the ground. QFE: station pressure, reads zero on the ground. QNE: 1013.25 hPa, reads pressure altitude.

  • Transition altitude/level: change from QNH to QNE
  • High to low or hot to cold: look out below
  • 1 hPa ≈ 27–30 ft near sea level

How does pressure altitude relate to true altitude?

True altitude = pressure altitude corrected for the actual (non-ISA) temperature.

DA=PA+120 (TOAT−TISA)DA=PA+120\,(T_{OAT}-T_{ISA})
  • Cold air: true altitude below indicated
  • Correction ≈ 4 ft per 1 000 ft per °C of ISA deviation
  • Density altitude = pressure altitude + 120 × (OAT − ISA)

Practice questions: Pressure & Altimetry

Tap “Show answer” after you have tried each one.

Q1An aerodrome is at elevation 1000 ft and the QNH is 1003 hPa. Taking 1 hPa = 30 ft, the pressure altitude of the aerodrome is:

  1. 1 600 ft
  2. 1 000 ft
  3. 700 ft
  4. 1 300 ft
Show answer

Answer: D. 1 300 ft

Pressure altitude = elevation + (1013 − QNH) × 30 = 1000 + (10) × 30 = 1 300 ft.

Q2An aerodrome is at elevation 0 ft and the QNH is 1015 hPa. Taking 1 hPa = 30 ft, the pressure altitude of the aerodrome is:

  1. 60 ft
  2. −120 ft
  3. −60 ft
  4. 0 ft
Show answer

Answer: C. −60 ft

Pressure altitude = elevation + (1013 − QNH) × 30 = 0 + (−2) × 30 = −60 ft.

Q3An aerodrome is at elevation 500 ft and the QNH is 1024 hPa. Taking 1 hPa = 30 ft, the pressure altitude of the aerodrome is:

  1. −160 ft
  2. 170 ft
  3. 830 ft
  4. 500 ft
Show answer

Answer: B. 170 ft

Pressure altitude = elevation + (1013 − QNH) × 30 = 500 + (−11) × 30 = 170 ft.

Q4An aircraft flies at FL40 with the altimeter set to 1013 hPa. The local QNH is 1020 hPa. Assuming ISA and 1 hPa = 30 ft, the altitude (above mean sea level) of the aircraft is approximately:

  1. 4 000 ft
  2. 4 210 ft
  3. 3 790 ft
  4. 4 420 ft
Show answer

Answer: B. 4 210 ft

Altitude = FL height + (QNH − 1013) × 30 = 4000 + (7) × 30 = 4 210 ft. Low QNH means the aircraft is lower than the flight level suggests.

Q5An aircraft flies at FL120 with the altimeter set to 1013 hPa. The local QNH is 996 hPa. Assuming ISA and 1 hPa = 30 ft, the altitude (above mean sea level) of the aircraft is approximately:

  1. 12 510 ft
  2. 10 980 ft
  3. 12 000 ft
  4. 11 490 ft
Show answer

Answer: D. 11 490 ft

Altitude = FL height + (QNH − 1013) × 30 = 12000 + (−17) × 30 = 11 490 ft. Low QNH means the aircraft is lower than the flight level suggests.

Q6An aircraft flies at a constant indicated altitude with the altimeter on QNH 1030 hPa and then enters an area with a QNH of 1006 hPa, without resetting the altimeter. Assuming 1 hPa = 30 ft, the aircraft is now actually:

  1. at the same height above the ground
  2. higher above the ground by about 720 ft
  3. lower above the ground by about 720 ft
  4. lower above the ground by about 1440 ft
Show answer

Answer: C. lower above the ground by about 720 ft

Pressure change = 1006 − 1030 = −24 hPa. 720 ft error. Moving into higher pressure with an unchanged setting makes the aircraft higher than indicated ("high to low, look out below": the reverse case).

Q7An aircraft flies at a constant indicated altitude with the altimeter on QNH 1006 hPa and then enters an area with a QNH of 1016 hPa, without resetting the altimeter. Assuming 1 hPa = 30 ft, the aircraft is now actually:

  1. lower above the ground by about 300 ft
  2. at the same height above the ground
  3. higher above the ground by about 600 ft
  4. higher above the ground by about 300 ft
Show answer

Answer: D. higher above the ground by about 300 ft

Pressure change = 1016 − 1006 = 10 hPa. 300 ft error. Moving into higher pressure with an unchanged setting makes the aircraft higher than indicated ("high to low, look out below": the reverse case).

Q8An aircraft flies at an indicated altitude of 14000 ft (altimeter on QNH) in air that is ISA −30. Using 4 ft per 1 000 ft per °C of deviation, the true altitude is about:

  1. 14 000 ft
  2. 15 680 ft
  3. 12 320 ft
  4. 10 640 ft
Show answer

Answer: C. 12 320 ft

Error = 4 × −30 × 14 = −1680 ft. Cold air: true altitude is lower than indicated so 12 320 ft.

Q9An aircraft flies at an indicated altitude of 5000 ft (altimeter on QNH) in air that is ISA +20. Using 4 ft per 1 000 ft per °C of deviation, the true altitude is about:

  1. 5 000 ft
  2. 4 600 ft
  3. 5 800 ft
  4. 5 400 ft
Show answer

Answer: D. 5 400 ft

Error = 4 × 20 × 5 = 400 ft. Warm air: true altitude is higher than indicated so 5 400 ft.

Q10The transition altitude is the altitude at or below which the vertical position of an aircraft is controlled by reference to:

  1. flight level (1013)
  2. radio altitude
  3. altitude (QNH)
  4. height (QFE only)
Show answer

Answer: C. altitude (QNH)

At or below transition altitude → altitude on QNH; at or above transition level → flight levels on 1013.

Q11The pressure altitude is read on the altimeter when the sub-scale is set to:

  1. QFE
  2. QNH
  3. the local pressure at 0 °C
  4. 1013.25 hPa
Show answer

Answer: D. 1013.25 hPa

Pressure altitude is the altitude in ISA corresponding to the pressure.

Q12The 500 hPa constant pressure surface is at about:

  1. FL390 (11 800 m)
  2. FL300 (9 000 m)
  3. FL100 (3 000 m)
  4. FL180 (5 500 m)
Show answer

Answer: D. FL180 (5 500 m)

500 hPa ≈ 5 500 m ≈ 18 000 ft.

Practise all 103 questionsTake a Meteorology mock test

More DGCA Aviation Meteorology topics

Atmosphere & ISA125 QTemperature, Humidity & Cloud Base94 QStability & Adiabatics71 QPressure Systems & Depressions27 QWinds & Upper Winds71 QJet Streams27 QClouds, Fog & Precipitation92 QFronts & Air Masses48 QThunderstorms, Turbulence & Windshear66 QIcing42 QTropical Cyclones15 QClimatology & Monsoon32 QWeather Reports & Charts113 QMeteorological Calculations174 Q
All DGCA questionsCPL exam syllabusHow to prepareAviation Meteorology formulas

Learn Aviation Meteorology one-on-one with Nikunj

Unlimited personal sessions, weekly subject tests and lifetime access to the student website. First-attempt pass guarantee, or your money back.

Enquire & enrolDGCA Aviation Meteorology classes
Call WhatsApp