What is the effect of flying into warmer air on the altimeter reading?

When flying into warmer air, the altimeter typically reads lower than the true mean sea level (MSL) altitude. This occurs because the altimeter is calibrated to expect a standard temperature and pressure at sea level. Warmer air is less dense than the standard atmosphere at the same pressure, causing the aircraft to be at a higher altitude than the altimeter indicates.

As an aircraft climbs, the pressure decreases, which is what the altimeter uses to determine altitude. If the surrounding air is warmer than the standard temperature, the pressure at a certain altitude is higher than it would be in standard conditions. Consequently, when the altimeter interprets this higher pressure, it calculates a lower altitude—resulting in a misleading reading. This phenomenon is crucial for pilots to understand, as it can lead to potential safety issues if the actual altitude of an aircraft is misjudged due to incorrect altimeter readings.

Understanding the relationship between temperature, pressure, and altitude is vital for effective flight operations, allowing pilots to make necessary adjustments to ensure accurate altitude awareness while flying in varying atmospheric conditions.