#### Pilot12345

##### Member

- Joined
- Oct 24, 2004

- Posts
- 20

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- Adding

I know to determine the approximate pressure altitude at your departure or destination airport for performance charts, etc. you add 1,000 feet to field elevation for each 1.00 in. Hg that the reported altimeter setting value is below 29.92 in. Hg,

__and subtract 1,000 feet for each 1.00 in Hg above 29.92 in Hg__., and that you always subtract the reported altimeter setting from 29.92 in. Hg., then multiply the answer by 1,000 to find the difference in feet between field elevation and pressure altitude....

Example:

29.92

__- 30.07__

0.15

0.15 X 1,000 feet = -150 feet

Ok so let's say the field elevation is: 3,750

Subtract the pressure altitude correction: -150 feet

= a field pressure altitude of 3,600

Here is my question.....

If the field elevation was 50 ft instead of 3,750

and using the same #'s above of 29.92 and 30.07

My pressure altitude would be -100 feet, that dosen't sound right. What am I doing wrong?

Thank's for your help!!!