When flying a non-precision instrument final, how should MDA be determined?

Determining the Minimum Descent Altitude (MDA) during a non-precision instrument approach is essential for ensuring a safe landing. The correct method is to reference the barometric altimeter. The barometric altimeter measures atmospheric pressure, allowing pilots to maintain altitude above the ground or obstacles during the final approach phase when visibility may be limited.

Using the barometric altimeter provides a standardized reference that pilots can rely upon to adhere to safe altitude requirements as defined by the specific approach procedure for their flight. This is crucial since non-precision approaches do not have electronic guidance like ILS, instead relying solely on visual cues once the MDA is reached and the required runway environment is in sight.

In contrast, using visual sighting is not appropriate for determining MDA, as pilots may not have enough visibility to safely judge altitude. Radar altimeter readings are generally more applicable for precision approaches where actual height above ground level is crucial, while a pressure altimeter focuses on altitude relative to mean sea level. Thus, riferimento to the barometric altimeter is critical for ensuring safe descent and final approach altitudes during non-precision instrument approaches.