ATSEP-BASIC-METEOROLGY (BAS-MET)
Why is Meteorology important for aviation?
Meteorological service for safety, regularity and efficiency of international air navigation
Does pressure increase or decrease when climbing ?
It decreases because more atmosphere is below us when we climb up.
At sea level: How much weight does 1 cubic metre of air have ?
1 kg
Why does an aeronoid barometer have a vacuum in its vacuum chamber ?
Because air would underly changes in temperature and therefore cause inaccuracy
What is the atmospheric standard pressure ? (ICAO)
1013.25 hPa
What is the atmospheric standard temperature according to ICAO ?
15°C
is the atmospheric standard humidity according to ICAO ?
0%
What is the atmospheric standard lapse rate for temperature according to ICAO?
0.6°C per 100 m
What is the atmospheric standard density according to ICAO ?
At MSL 1.225 kg/m³
Why is it necessary to set the subscale pressure for an altimeter ?
Because the altimeter indicates the vertical distance between measured and the subscale pressure
(pressure differs depending where you are) value. Therefore you have to set it for your location in
order to get the correct height in your area.
Does the altimeter show the height relative to the Mean Sea Level (MSL)?
It depends whether you set it to the pressure on MSL. If you don't it will show the height relative to
the pressure you've set it.
What does MSL mean ?
Mean Sea Level
How does temperature affect the air density and pressure ?
, How does the true altitude change during a flight from high to low pressure when using a constant
subscale setting ?
Altitude will decrease. There's a saying that goes like: From high to low look out below. If you don't
adjust your altimeter you might just hit a mountain.
What is QFE ?
It s the Pressure at Field Elevation (ELEV). If you set your altimeter to QFE it will show 0 ft if you're
standing on the field.
What is the barometric lapse rate at sea level with ISA-conditions ?
30ft/1 hPa
What is QNH ?
It's the estimated sea level pressure based on the measured QFE with 30ft/1hPa under ISA-Conditions
If QNH = 1011 hPa and QFE = 1007 hPa how high is the elevation difference between both locations
under ISA-Conditions ?
120 ft -> 1011 hPa - 1007 hPa = 4 hPa
30ft / 1hPa means 120 ft / 4hPa
Why do we use QNH ?
We use it to be independent from ground pressure.
Whats the indication on Runway (RWY) when you set the altimeter to QFE ?
0
Fill in the table.
Solution:
Subscalesetting, Indication on RWY, Indication on flight
QFE,0,HGT
QNH,ELEV,ALT
1013 hPa,QNE,FL/PL/Press.Alt.
Why do we use FlightLevel if there are different pressure values in different areas and we don't get
the correct altitude by dialing in one fixed value (flightLevel 1013.25 hPa is set)
Because everybody has the same margin of error therefore it's good enough for seperation and
aircraft won't crash, which is a good thing to be honest.
Unit of temperature ?
°C
Unit of pressure ?
hPa
Why is Meteorology important for aviation?
Meteorological service for safety, regularity and efficiency of international air navigation
Does pressure increase or decrease when climbing ?
It decreases because more atmosphere is below us when we climb up.
At sea level: How much weight does 1 cubic metre of air have ?
1 kg
Why does an aeronoid barometer have a vacuum in its vacuum chamber ?
Because air would underly changes in temperature and therefore cause inaccuracy
What is the atmospheric standard pressure ? (ICAO)
1013.25 hPa
What is the atmospheric standard temperature according to ICAO ?
15°C
is the atmospheric standard humidity according to ICAO ?
0%
What is the atmospheric standard lapse rate for temperature according to ICAO?
0.6°C per 100 m
What is the atmospheric standard density according to ICAO ?
At MSL 1.225 kg/m³
Why is it necessary to set the subscale pressure for an altimeter ?
Because the altimeter indicates the vertical distance between measured and the subscale pressure
(pressure differs depending where you are) value. Therefore you have to set it for your location in
order to get the correct height in your area.
Does the altimeter show the height relative to the Mean Sea Level (MSL)?
It depends whether you set it to the pressure on MSL. If you don't it will show the height relative to
the pressure you've set it.
What does MSL mean ?
Mean Sea Level
How does temperature affect the air density and pressure ?
, How does the true altitude change during a flight from high to low pressure when using a constant
subscale setting ?
Altitude will decrease. There's a saying that goes like: From high to low look out below. If you don't
adjust your altimeter you might just hit a mountain.
What is QFE ?
It s the Pressure at Field Elevation (ELEV). If you set your altimeter to QFE it will show 0 ft if you're
standing on the field.
What is the barometric lapse rate at sea level with ISA-conditions ?
30ft/1 hPa
What is QNH ?
It's the estimated sea level pressure based on the measured QFE with 30ft/1hPa under ISA-Conditions
If QNH = 1011 hPa and QFE = 1007 hPa how high is the elevation difference between both locations
under ISA-Conditions ?
120 ft -> 1011 hPa - 1007 hPa = 4 hPa
30ft / 1hPa means 120 ft / 4hPa
Why do we use QNH ?
We use it to be independent from ground pressure.
Whats the indication on Runway (RWY) when you set the altimeter to QFE ?
0
Fill in the table.
Solution:
Subscalesetting, Indication on RWY, Indication on flight
QFE,0,HGT
QNH,ELEV,ALT
1013 hPa,QNE,FL/PL/Press.Alt.
Why do we use FlightLevel if there are different pressure values in different areas and we don't get
the correct altitude by dialing in one fixed value (flightLevel 1013.25 hPa is set)
Because everybody has the same margin of error therefore it's good enough for seperation and
aircraft won't crash, which is a good thing to be honest.
Unit of temperature ?
°C
Unit of pressure ?
hPa
