I'm having some trouble making my calculations of pressure altitude match those in apps and text books.
I'm using the formula from Wikipedia:
(29.92 - altimeter setting) * 1000 + airport elevation
In the app I'm using, the altimeter setting is currently reported as 29.70 with an airport elevation of 22. Using the above formula I would assume:
(29.92 - 29.70) * 1000 + 22 = 242
Yet the app is telling me it is 229
Even more confusing, when looking at the Airman Knowledge Testing Supplement for Sport Pilot, Recreational Pilot, Remote Pilot, and Private Pilot (FAA-CT-8080-2H), figure 8, page 2-8, the pressure altitude for altimeter 29.7 is listed as 205. I assume this is using an airport elevation of 0, but then I would expect the answer to be:
(29.92 - 29.7) * 1000 + 0 = 220
So my questions are:
- Which answer is correct? Wikipedia, the app or appendix 2?
- Why are there 3 different answers?