Setting the barometric scale to 29.92 inHg will cause the altimeter to display

Setting the barometric scale to 29.92 inHg will cause the altimeter to display

• A. Indicated altitude
• B. Density altitude
• C. True altitude
• D. Pressure altitude

Answer: (D)

Setting the barometric scale to 29.92 inches of mercury makes the altimeter reference the standard atmosphere. The instrument then reads pressure altitude—the height above the standard datum plane where the pressure equals 29.92 inHg. This value is a standardized altitude used for flight levels and is not the same as your true altitude above mean sea level or the indicated altitude at local pressure. If you were to set the local QNH, you’d get indicated altitude; if you needed true or density altitude, those depend on temperature and actual pressure conditions. So the display becomes pressure altitude.

Setting the barometric scale to 29.92 inches of mercury makes the altimeter reference the standard atmosphere. The instrument then reads pressure altitude—the height above the standard datum plane where the pressure equals 29.92 inHg. This value is a standardized altitude used for flight levels and is not the same as your true altitude above mean sea level or the indicated altitude at local pressure. If you were to set the local QNH, you’d get indicated altitude; if you needed true or density altitude, those depend on temperature and actual pressure conditions. So the display becomes pressure altitude.