How do I find pressure altitude?
Find pressure altitude using rule of thumb for 1498 feet when the altimeter setting is 27.83" Hg.
I did (29.92-27.83)*1000+1498=3588
Did I do this correctly?
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2 Answers
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You are 1498ft above the place where the pressure is 27.83InHg. So how high are you above the place where the pressure is 29.92InHg?
27.83 is 2.09InHg higher than 29.92, ie roughly 2090ft higher. So you are 1498 + 2090 above the place where the pressure is 29.92InHg, ie your Pressure Altitude is ~3588ft.
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This calculator is coming up with 3488 ft
http://imageserver.fltplan.com/PressureAndDensityAltitudeCalc.htm?USER=PILOT
But your formula looks correct to me and you did the math correctly.
Not sure why the 100 ft difference.
answered Mar 11, 2019 at 2:23
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1$\begingroup$ The 100ft difference is due to the fact that "(29.92 - QNH) * 1000 + h" is just an approximation. The website uses the exact equation to compute the pressure altitude. $\endgroup$– fabCommented Feb 4, 2022 at 6:27