Post
by Hedgehog » Sat Oct 01, 2022 11:42 am
Also, for some of us who don't have PPLs or real world ground school at some point, something important to understand (though my description will be somewhat simplified). In many cases, I think DCS Hornet pilots just select RDR ALT on deck before take-off and just leave it that way, which is typically fine, and maybe even safer for missions over 'indian territory.' However, to use the approach plates, you must be using BAROMETRIC ALTIMETER.
Which means you need to understand the difference between QFE and QNH.
For QFE, think "Field Elevation." It's the barometric pressure you dial in to your altimeter so that it will read '0' on the runway, even if you're in Denver and a mile above sea level. That's what ATC gives you when you request take-off. Seems like a good setting. I mean, when my wheels are on the runway, I'm at 0 feet, right?
Except the approach plate presents you with altitude requirements above sea level (ASL)!
So, yeah, you could probably fly an approach safely with radar altimeter to avoid hitting the ground, but it won't keep you from hitting obstructions and such. The approach plate altitudes keep everyone on standard approach patterns as well as keeping everyone safe from hitting things.
So to set your altimeter for ASL, you need QNH. Think "Nautical Height." (Above sea level. Nautical Height. Get it?) And we get the QNH from ATIS radio. And don't forget to set your ALT switch back to BARO.