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Interactive Simulator

Altimeter Errors Simulator

Make temperature and pressure errors tangible. This trainer visually demonstrates how flying from high to low pressure, or warm to cold air, leaves the altimeter over-reading — the classic "look out below" adage.

Temperature errorPressure errorTrue vs indicated
High to low, hot to cold — look out below. Flying into lower pressure or colder air, without resetting, leaves the altimeter over-reading: you are lower than it shows.
Indicated 6,000 ftTrue 5,520 ft480 ft
0123456789101329.91"6,000WHAT YOU READ

You are LOWER than the altimeter shows — look out below.

Caution: the behaviour of the instruments and information shown is approximate, for illustration and study only, and may not reflect the exact readings of a real aircraft.

Instructions for use

The altimeter is calibrated for the International Standard Atmosphere. When the real atmosphere is colder, or the pressure is lower than what you have set, the altimeter over-reads — your true altitude is lower than indicated. Hence the adage: high to low, hot to cold, look out below.

The numbers

  • Temperature: roughly 4 ft per 1,000 ft per °C of ISA deviation (≈ 4% per 10°C).
  • Pressure: about 27 ft per hPa — fly into lower pressure without resetting and you sit lower than indicated.

Try this

  • Set a high indicated altitude, then drag the temperature to Cold −20°C and watch true altitude drop below indicated.
  • Add a negative ΔQNH to stack the pressure error on top — the gap to the terrain shrinks.
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