Aero-Terms!

Aero-Terms are designed to be a daily reminder of the terms, names, acronyms and explanations of the unique language that populates the aviation world. Aerospace, sport aviation, fixed wing, helo, you name it... it's all fair game.

Aero-Terms should serve as a quick but intriguing reminder of the terms you may use every day, or an introduction to an aspects of the Aero-World you may not yet be familiar with. ANN also encourages readers to go beyond the FMI link, and further research any intriguing terms.

Suggestions for future Aero-Terms are ALWAYS welcome, as are additions or discussion of the explanations given for each Aero-Term.

QNH

QNH is a Q code. It is a pressure setting used by pilots, air traffic control (ATC) and low frequency weather beacons to refer to the barometric altimeter setting which will cause the altimeter to read altitude above mean sea level within a certain defined region. This region may be fairly widespread, or apply only to the airfield for which the QNH was given. An airfield QNH will cause the altimeter to read field elevation on landing irrespective of the temperature. In the UK the lowest forecast value of QNH for an altimeter setting region is called the "Regional Pressure Setting" and may be used to ensure safe terrain separation when cruising at lower altitudes. In some parts of the world a similar procedure is adopted and this is known as "Regional QNH" however this name has been modified to the above in the UK for reasons of ambiguity.

FMI: www.chemeurope.com/lexikon/e/Atmospheric_pressure