Instrument Flight Rules (IFR) Practice Exam 2025 - Free IFR Questions and Study Guide

When the air temperature is warmer than standard, it causes the altimeter to indicate a lower altitude than the altitude actually flown. This phenomenon occurs because altimeters are calibrated based on the standard atmosphere, which assumes a specific temperature lapse rate. When the temperature increases, the density of the air decreases, leading to a situation where the altimeter reads lower than the actual altitude.

The altimeter operates on the principle that it detects changes in atmospheric pressure, which is affected by altitude. In warmer air, pressure changes occur differently compared to standard air, which leads to inaccuracies in the altimeter's readout. Pilots need to be aware of this relationship to ensure proper altitude reporting and navigation, particularly in conditions where temperature may vary significantly from standard values.

This understanding is crucial for maintaining safe flight operations, as altitude is a critical factor in avoiding terrain or other air traffic. It's important for pilots to adjust their altitude awareness based on temperature deviations to accurately interpret altimeter readings.