18 Questions
During a flight over the sea from Marseille to Palma de Mallorca at FL 100, the true altitude is constantly increasing. What could be the reason for this?
The air around Palma is warmer than the air around Marseille
What is the recommended minimum flight altitude when overflying a mountain range with an air mass that is 15° C warmer than the standard atmosphere?
14100 FT
What is the difference between QNH and QFE at an airport dependent on?
The air pressure at the airport
If you change the pressure reference on your altimeter from QNH = 1023 hPa to standard setting (1013hPa) after landing at an airport, what will your altimeter indicate?
1723 FT
What should be taken into account when determining the recommended flight altitude to overfly a mountain range?
Both terrain clearance and altimeter calibration
What can cause variations in altimeter readings during a flight?
Both changes in air temperature and pressure
If the air mass you are flying through is 10° C warmer than ISA, what will be the altitude shown on your altimeter when you have reached the recommended minimum altitude of 12000 feet?
11790 feet
An aircraft flying at an indicated altitude of 2500 ft enters an area of lower pressure without adjusting the subscale setting. What will happen to the aircraft?
The aircraft will gradually descend
An aircraft is flying at FL 90 (9000 ft pressure altitude) over the sea, with a true altitude of 9100 ft. What assumption can be made about the air mass in which the aircraft is flying?
It is warmer than ISA
When an aircraft passes the Transition Altitude and the pilot adjusts the subscale accordingly, what will happen to the indicated altitude?
The indicated altitude will increase
When flying over mountainous terrain, what is the recommended minimum altitude to ensure terrain clearance?
12000 feet
If the air mass through which you are flying is colder than ISA, what will be the altitude shown on your altimeter when you have reached the recommended minimum altitude of 12000 feet?
10980 feet
What is the pressure altitude when the barometric pressure scale is set to 29.92 inHg?
The altitude indicated when the barometric pressure scale is set to 29.92 inHg.
An aircraft descends and lands at an airfield with a QNH of 1013mb set. If the airfield has an elevation of 540ft, what will its altimeter read on landing?
540ft.
An aircraft is to fly at an indicated altitude of 5000 ft from X (elevation 850 ft, QNH 984 hPa) to Y (elevation 2300 ft, QNH 1024 hPa). What is the true height of the aircraft over X and Y?
5.000 ft over X and 4.150 ft over Y.
If the QNH at an airfield is 1009 hPa and the air temperature is 10°C lower than standard, what is the QFF?
Less than 1009 hPa.
Flying at FL135, the radio altimeter indicates a true altitude of 13,500 ft and the local QNH is 1019 hPa. What is the average temperature deviation of the crossed air mass?
Colder than ISA.
What is the recommended flight altitude for VFR flights based on terrain clearance?
At least 500 ft above the highest obstacle within a 3 nm radius.
Study Notes
Altimeter and QNH Settings
- When flying over a mountain range, the recommended minimum flight altitude is 15000 FT/AMSL, and the air mass is 15°C warmer than the standard atmosphere, with an altimeter set to QNH (1023 hPa), the altimeter reading would be approximately 13830 FT.
Flight Planning and Navigation
- When flying over the sea from Marseille to Palma de Mallorca, the true altitude increases due to warmer air around Palma de Mallorca.
Altimeter Readings and QNH
- The difference between QNH and QFE is dependent on the air pressure at the airport.
- When landing at an airport, setting QNH = 1023 hPa as reference pressure on the altimeter, and the altimeter indicates 1200 ft, changing the pressure reference to standard setting (1013hPa) would show a different reading.
Mountain Flight Planning
- When flying over a mountain range, the chart recommends a minimum altitude of 12000 feet above mean sea level, with an air mass 10°C warmer than ISA, and an altimeter set to 1023 hPa (QNH), the altimeter would show approximately 11520 feet.
Air Mass Temperature
- When flying over the sea at FL 90, the true altitude is 9100 feet, and the local QNH is unknown, it can be assumed that the air mass is colder than ISA.
Altimeter Settings and Indications
- When an aircraft is flying towards an area of lower pressure and fails to revise the subscale setting, it will gradually climb.
- When an aircraft descends and lands at an airfield with a different QNH setting, the altimeter reading will be affected.
- On takeoff, setting the altimeter to the local QNH of 1023 hPa, and adjusting the subscale accordingly, the indicated altitude may increase or decrease depending on the air mass temperature.
Pressure Altitude and QFF
- Pressure altitude is the indicated altitude corrected for non-standard temperature and pressure.
- QFF is the altimeter setting that makes the altimeter read zero at sea level.
Test your knowledge on calculating altimeter reading based on altitude recommendations, air temperature deviation from ISA, and QNH setting. Determine the altitude shown on the altimeter when reaching the recommended minimum altitude for mountain flying.
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