Certified Flight Instructor - Flight Instructor Airplane Practice Exam

What happens to the indicated altitude of a sensitive altimeter in colder-than-standard temperatures?

1. It indicates lower than the true altitude.

2. It indicates higher than the true altitude.

3. It remains unchanged.

4. It provides erratic readings.

The correct answer is: It indicates lower than the true altitude.

When a sensitive altimeter is exposed to colder-than-standard temperatures, it indicates a lower altitude than the actual true altitude. This phenomenon arises from the principles of atmospheric pressure and temperature. Altimeters measure the atmospheric pressure and use that measurement, along with a standard lapse rate, to determine altitude. Standard atmospheric conditions assume a specific temperature and pressure relationship. When the temperature is colder than standard, the air density increases, which results in the altimeter reading lower than it should for a given pressure level. This effect occurs because colder air is denser than warmer air at the same pressure level. Therefore, if you are flying in an area where the temperature is below the standard atmosphere, the altimeter will not accurately reflect altitude, leading to potential altitude discrepancies. This is particularly important for pilots to understand, as flying at a lower indicated altitude than true altitude could lead to terrain and obstacle clearance issues.