Full formScience
QNHstands forAtmospheric pressure adjusted to mean sea level
Full Form of QNH
What is QNH?
QNH is a Q code used in aviation to denote the barometric pressure at a specific location adjusted to mean sea level (MSL). When a pilot sets the QNH value on the aircraft's altimeter, the instrument displays the altitude above sea level. This adjustment is crucial for maintaining safe vertical separation from terrain and other aircraft, especially during approach and landing. In India, QNH is disseminated by Airports Authority of India (AAI) via ATIS, tower, or approach frequencies. It is used by pilots of all categories—commercial, private, and military—as well as by air traffic controllers. QNH is expressed in hectopascals (hPa) or millibars, and standard pressure is 1013.25 hPa. Understanding QNH is essential for the DGCA and other civil aviation exams in India, as altimeter setting is a core topic. Unlike QFE, which gives height above a specific aerodrome, QNH provides height above sea level, making it universally comparable across different locations.
QNH का फुल फॉर्म
समुद्र तल से ऊँचाई के लिए वायुमंडलीय दबाव समायोजित
Example
Before landing at Delhi airport, the pilot tuned the QNH to 1013 hPa to ensure the altimeter showed correct elevation above sea level.
QNH — frequently asked questions
What is the full form of QNH?
The full form of QNH is 'Atmospheric pressure adjusted to mean sea level'. It is a Q code used in aviation to set altimeters so they indicate altitude above mean sea level.
How is QNH different from QFE?
QNH is the pressure setting that makes the altimeter read altitude above mean sea level (MSL), while QFE is the pressure setting that makes the altimeter read height above a specific aerodrome elevation. QNH is used for en-route flying and standard procedures; QFE is used for local traffic pattern and landing at a specific airport.
Why do Indian pilots need to know QNH?
Indian pilots must know QNH to correctly set their altimeters for safe flight operations. It is essential for obstacle clearance, maintaining assigned flight levels, and passing DGCA exams. Air traffic control in India provides QNH values to ensure uniformity in altitude reporting across the airspace.