A barometric altimeter indicates pressure altitude when the barometric scale is set at

A barometric altimeter indicates pressure altitude when the barometric scale is set at

• A. 29.80 inHg
• B. 29.92 inHg
• C. 30.00 inHg
• D. 29.50 inHg

Answer: (B)

The main idea is that pressure altitude is shown when the altimeter is set to the standard pressure value. Setting the barometric scale to 29.92 inHg calibrates the instrument to the standard atmosphere's sea-level pressure (1013.25 hPa). With this reference, the altimeter displays the altitude corresponding to the ambient pressure in the standard atmosphere—i.e., the pressure altitude. If you set the scale lower than 29.92, the altimeter indicates a higher altitude; if you set it higher, it indicates a lower altitude. The other pressures are nonstandard local settings, which would shift the reading away from the true pressure altitude.

The main idea is that pressure altitude is shown when the altimeter is set to the standard pressure value. Setting the barometric scale to 29.92 inHg calibrates the instrument to the standard atmosphere's sea-level pressure (1013.25 hPa). With this reference, the altimeter displays the altitude corresponding to the ambient pressure in the standard atmosphere—i.e., the pressure altitude. If you set the scale lower than 29.92, the altimeter indicates a higher altitude; if you set it higher, it indicates a lower altitude. The other pressures are nonstandard local settings, which would shift the reading away from the true pressure altitude.