If the actual temperature at 6,000 feet is 3 degrees Celsius, which equals the standard temperature, what is the relationship between true altitude and indicated altitude?

• A. Lower
• B. Higher
• C. Cannot be Determined
• D. The Same

Answer: (D)

The key idea is that temperature affects how high pressure surfaces sit in the atmosphere. The altimeter reads altitude based on pressure, so when the actual temperature profile matches the standard atmosphere, there’s no thermal error—pressure surfaces line up with true geometric height. Since at 6,000 feet the temperature given (3°C) matches the standard temperature, there’s no discrepancy between what the altimeter indicates and the aircraft’s true height above mean sea level. In this case, true altitude and indicated altitude are the same.

If the air were colder than standard, the true altitude would be lower than indicated; if it were warmer than standard, the true altitude would be higher than indicated.