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Flight level and standard pressure. A Flight Level (FL) is the vertical distance of an aircraft above the ISOBARIC SURFACE of 1013.25hPa (hecto Pascal) or 29.92 in Hg (inches of Mercury). An ISOBARIC SURFACE is the invisible landscape that connects all points with the same atmospheric pressure.
With Standard Pressure (1013.2 mb) set, an aircraft altimeter indicates Pressure Altitude (Flight Level), and is used by all aircraft operating above the transition altitude to provide a common datum for vertical measurement.
27 cze 2023 · One flight level is equivalent to 100 ft, i.e. FL 100 is 10 000 ft and FL 320 is 32 000 ft. Since the pressure lapse rate is approximately 1 hPa per 30 ft, the pressure altitude at an airfield can be easily determined if the QNH is known (see here for further details and a calculator).
25 sty 2024 · Image: C. Lomas. Aircraft measure altitude using their altimeter. Traditionally, the altimeter is a pressure-based instrument (i.e. an instrument that measures the air pressure outside) and is either calibrated in Hectopascals ‘Hpa’ or Inches of Mercury ‘InHg’.
Description. The aircraft altimeter barometric sub-scale must be set to the appropriate setting for the phase of flight. These are: Flight level. Standard pressure setting (1013 hPa) is set when flying by reference to flight levels at or above the transition level; Altitude.
EXAMPLE: The minimum safe altitude of a route is 19,000' MSL and the altimeter setting is reported between 29.92 and 29.42 inches of mercury, the lowest usable flight level will be 195, which is the flight level equivalent of 19,500 feet MSL (minimum altitude plus 500 feet)
The flight levels correspond to the altitude in 100-ft increments (hectofeet) above the pressure surface of 1,013.25 hPa calculated according to the standard atmosphere. For example, FL050 is the pressure surface 5,000 ft above the pressure surface 1,013.25 hPa.
