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Aircraft general knowledge
8.12.5.2 Speed designations
There are different designations for speed:
- Indicated airspeed, IAS, is what is read on the instrument.
- Calibrated airspeed, CAS, is the indicated airspeed corrected for instrument
error and position error on the pitot tube (at high angles of attack).
On newer airspeed indicators, CAS = IAS
- The true airspeed, TAS, (True Air Speed) changes with altitude, as the air
becomes thinner the higher we go, the airspeed indicator will show too little.
This can be corrected by 2% per 1000 feet or according to the table.
8.12.5.3 Instrument error
At low speeds, position errors can occur due to the position of the pitot tube
with the high angle of incidence.
Simulator showing the pitot-static system
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8.12.6 Altimeter
You can say that the altimeter is in reality just a barometer, where instead of
pressure in hPa or millibar, the unit of feet are set on the scale.
Since 1 hPa is approximately 30 feet, this means that for every 30 feet you move
up in the air, the pressure drops by
1 hPa.
Here you can see a schematic
diagram of the altimeter.
Flyveteori PPL(A)(UL)/LAPL Henning Andersen, Midtjysk Flyveskole© 2025 769
