How is altimeter setting selected and what does it influence?

How is altimeter setting selected and what does it influence?

• A. Based on field elevation/ATC instruction; it affects indicated altitude during flight.
• B. Based on outside air temperature; it affects fuel consumption.
• C. Based on time of day; it affects cockpit lighting.
• D. Based on flight plan; it affects magnetic heading.

Answer: (A)

The essential idea is that the altimeter setting is the local pressure reference you dial in so the instrument shows your true altitude. You select this setting from the field’s pressure (the local QNH) or from ATC instructions. In practice, you set the local field elevation pressure before taxi and then adjust as ATC or the situation requires; above the transition altitude you’ll use the standard setting (29.92) when appropriate. When the setting matches the actual local pressure, the altimeter indicates your true altitude relative to the surface, which is critical for staying at assigned altitudes and ensuring terrain and airspace separation. If the setting is too high, your indicated altitude will be higher than your actual altitude; if it’s too low, you’ll appear lower than you are. Temperature changes affect true altitude, not the altimeter setting itself, and time of day or flight plan don’t determine what the altimeter reads.

The essential idea is that the altimeter setting is the local pressure reference you dial in so the instrument shows your true altitude. You select this setting from the field’s pressure (the local QNH) or from ATC instructions. In practice, you set the local field elevation pressure before taxi and then adjust as ATC or the situation requires; above the transition altitude you’ll use the standard setting (29.92) when appropriate. When the setting matches the actual local pressure, the altimeter indicates your true altitude relative to the surface, which is critical for staying at assigned altitudes and ensuring terrain and airspace separation. If the setting is too high, your indicated altitude will be higher than your actual altitude; if it’s too low, you’ll appear lower than you are. Temperature changes affect true altitude, not the altimeter setting itself, and time of day or flight plan don’t determine what the altimeter reads.