pilot101486

Hi Peterg I came across this discussion and decided to do some research on the topic. I found a brochure from the Australian Government Bureau of Meteorology titled 'AVIATION WEATHER PRODUCTS Area QNH', which I consider to be a reliable source. According to this brochure, the acronym QNH is indeed one of the Q(uestion) code names developed around 1909 for use in Morse code. When an operator transmitted the letters QNH, it was a concise way of asking for atmospheric pressure at mean sea level (MSL). The phrase was understood to mean "I have a question. What is the atmospheric pressure at Nil Height", essentially referring to mean sea level. I use an app called Wings Taking Flight to find information like this, it references back to the original sources, which can be useful.