When may a pilot need to add corrections to their altimeter for obstacle clearance?

• A. Very cold temperatures
• B. Very hot temperatures
• C. Standard temperatures
• D. High humidity

Answer: (A)

In very cold temperatures, corrections to the altimeter may be needed to maintain obstacle clearance because the true altitude can end up lower than what the altimeter indicates. When the air is colder than standard, the vertical spacing of pressure surfaces tightens, so the same indicated altitude corresponds to a lower actual height above the terrain. Relying on the uncorrected reading in cold conditions can leave you closer to obstacles than you expect, especially near minimum altitudes or in mountainous areas. Applying a cold temperature correction raises the altitude you use for clearance calculations, helping ensure you maintain the required obstacle clearance. In contrast, very hot temperatures tend to make true altitude higher than indicated, standard temperatures require no adjustment, and humidity alone doesn’t produce the same need for this specific correction.