In aviation, the terms QNH, QFE, and STANDART refer to different types of pressure settings that pilots use to calibrate the altimeters in their aircraft. Here are the main differences between them:
1. QNH
- Definition: QNH is a pressure setting used to set an aircraft's altimeter to indicate altitude above sea level. In other words, when the altimeter is set to the QNH value, the reading will show the true altitude above sea level.
- Usage: QNH is used on most flights when the aircraft is in flight at low and medium levels. This value is obtained from local weather reports and adjusted so that the altimeter shows the actual altitude above sea level at that specific location.
- How it is obtained: The QNH value is reported in METARs (aviation weather reports) and is adjusted for local atmospheric pressure.
2. QFE
- Definition: QFE is a less common term that also refers to the atmospheric pressure used for altimeter calibration, but specifically in the setting to display altitude above ground level. It is a term used primarily in some European countries.
- Usage: QFE is used in aviation to adjust the altimeter so that it indicates altitude above the ground below the aircraft, rather than above sea level. It is important in situations where the aircraft is flying at low altitudes and accuracy relative to the terrain is required.
- How it is obtained: Similar to QNH, QFE is based on local atmospheric pressure, but the adjustment is made to reflect altitude above ground rather than sea level.
3. STANDART
- Definition: The STANDART setting refers to a standard altimeter setting that uses a fixed reference pressure. On most aviation systems, this value is 1013.25 hPa (hectopascals) or 29.92 inHg (inches of mercury).
- Usage: The STANDART setting is used in flight levels at higher altitudes, where a uniform setting is necessary for navigation and separation between aircraft. Using STANDART helps maintain consistency in flight altitude across different regions and weather conditions.
- How to get it: This setting does not change and is used when flying at high altitudes or in transit between different areas with different atmospheric pressures. In airspace under the STANDART setting, aircraft are leveled at "flight levels," which are based on this standard pressure.
Summary of differences:
- QNH: Sets the altimeter to indicate altitude above sea level, based on local pressure.
- QFE: Sets the altimeter to indicate altitude above ground, based on local pressure. This is a less common term used in some regions.
- STANDART: Sets the altimeter to a standard fixed pressure of 1013.25 hPa (29.92 inHg), used in flight levels to maintain uniformity in altitude.
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Each type of setting has a specific purpose in aviation and helps ensure accuracy in altitude measurement for navigation and aircraft safety.
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