IRL Pilot here. I would argue that the Baro altimeter should generally always be set to sea level pressure (QNH). You then reference your known field elevation for whatever field you're landing at. For Al Ain here, you would know that the field elevation was about 814ft. Same difference for the Island you started at. Neither way is necessarily wrong. But referencing known elevations, rather than setting the Balt to 0 on the ground is a more common practice. The transition level you talked about in Civil Aviation in North America at least is when you go into the Flight Levels, generally 18000 feet MSL. ATC references Flight Levels instead of altitudes and in that space you reset your altimeter to 29.92. ATC might say "Climb FL 250" Which the layman will think means 25000 feet, but it really could be 24500 feet because of pressure differences, But because we've reset the altimeter, those altitude reading are now uniform for all aircraft operating in What we call "Class A Airspace" aka the airspace above 18000 feet stretching to about 60000 feet. In DCS I'd say its a matter of using what your aircraft has available, and also doing what you prefer as a pilot. I prefer to set sea level pressure at all times and then just reference known field elevations as well as use my Radar Altimeter below 5000 feet if so equipped.
@@grimreapers It's far easier to use QFE in a basic aircraft (e.g. No charts and definitely no rad.alt.). The altimeter reads zero at touch-down; how simple is that?
Simple way to remember: QFE: Question Field Elevation, used for local training. QNH: Question No Height, used for transit to other areas. So set QFE for take-off, then to 29.92 during transit and ask for QFE at destination. In real life you set regional QNH with continous updates during transit and approach phase and must know altitude of destination to substract from your height.
The phrase QNH came about because the Admiralty Datum for tides is at Newlyn Harbour, Cornwall, hence QNH. QFE or Field Elevation is always zero when you are on the ground at any particular airfield. Your example of Al Ain airfield at 814ft would therefore read zero ft for QFE and 814ft for QNH when you were sat on the runway. SPS is always 1013hPa/Mb or 29.92inHg. This is used for aircraft separation where there is no risk of hitting the ground, i.e. above the transition altitude.
Now let's talk dynamic weather. In the dynamic weather settings, notice how you select the pressure differential in that spot, thus creating a low or high pressure zone. That means QNH will vary depending on where you are in relation to these areas. In this case, the online calculator is useless because you don't know the correct values to enter - except by asking.
IFR charts altitudes are ment to be used with QNH set. QFE alt only for minimums. Most locations utilize the QNH altitude that provides altitude above mean sea level. However QFE altitude may be used in some locations (e.g. Russian Federation, People's Republic of China and some UK airports for VFR patterns) - Thats why DCS ATC in Caucasus map is giving us QFE.
Good stuff. I had to figure all this out on the DCS forums when I couldn't get my altimeter to read zero at any airfields in Nevada and didn't understand why...
Thanks Cap that was really interesting and more importantly extremely useful. Funny thing is that watching this gave me a bit of a flashback. My Dad is a yahtsman and years ago (when I was 10 or 11) he made me learn a lot of the Q Codes associated with maritime navigation and communicarion. He also made me learn Morse Code. I had entirely forgotten about this until I watched this video! Sadly, I cannot remember any of the Q Codes or Morse Code. Anyway, I now have enough knowledge to understand this and correctly apply it to DCS, so thanks again, your efforts are much appreciated!
Hi GR You are really thorough and do a really good job with all these nerdy things that I (and probaly other youtubers) want to become aware of. Thank you for your helpful efforts. Enjoy many of your videos, especially about DCS :)
So if one is landing at an airfield then QFE = The barometric altitude of the airfield and QNH = The barometric altitude of that airfield relative to sea level?
IRL Pilot here. I would argue that the Baro altimeter should generally always be set to sea level pressure (QNH). You then reference your known field elevation for whatever field you're landing at. For Al Ain here, you would know that the field elevation was about 814ft. Same difference for the Island you started at. Neither way is necessarily wrong. But referencing known elevations, rather than setting the Balt to 0 on the ground is a more common practice. The transition level you talked about in Civil Aviation in North America at least is when you go into the Flight Levels, generally 18000 feet MSL. ATC references Flight Levels instead of altitudes and in that space you reset your altimeter to 29.92. ATC might say "Climb FL 250" Which the layman will think means 25000 feet, but it really could be 24500 feet because of pressure differences, But because we've reset the altimeter, those altitude reading are now uniform for all aircraft operating in What we call "Class A Airspace" aka the airspace above 18000 feet stretching to about 60000 feet. In DCS I'd say its a matter of using what your aircraft has available, and also doing what you prefer as a pilot. I prefer to set sea level pressure at all times and then just reference known field elevations as well as use my Radar Altimeter below 5000 feet if so equipped.
