FAA Helicopter Flying Handbook Practice Test

Altitude is shown by an altimeter, an instrument that senses atmospheric pressure through the static system and converts that pressure into a readout of height above a reference level. As air pressure decreases with altitude, sealed pressure chambers inside the altimeter move the instrument’s hands or a digital display to indicate altitude in feet or meters. The pilot sets the local barometric pressure (QNH or QFE) so the readout matches the intended reference, letting you fly at the correct vertical position relative to sea level or a field. This is different from an Attitude Indicator, which simply shows the aircraft’s orientation (pitch and bank); Air Density is not an instrument display of altitude, and the Agonic Line is a magnetic variation concept, not a tool for reading altitude.