744 FORUM (vertical frame)

Pressure diff

Posted By: Adrian (dsl-082-082-238-113.arcor-ip.net)
Date: 13 DEC 2004 - 19:16z

Hi guys

I've been wondering about the pressure differential between cabin and "outside" pressure.
It is my understanding, that "delta" p is cabin pressure - outside pressure.

Let's take an example from a saved PS1.3 flight: "approach VNAV step climb with UAL"

Here's the data: aircraft altitude: 35000 ft, cabin altitude: 5760 ft.
Cabin differential according to PS1.3 is 6.5 PSI.

If I try to calculate it manually, I get a different value:
pressure in 35000 ft is around 265 hPa. Pressure at 5760 is around 812 hPa. Difference is 547 hPa. 547 hPa equals 7.94 psi.

6.5 PSI vs. 7.94 PSI

Where's my fault?

Cheers,

Adrian

Messages In This Thread

• Pressure diff
  Adrian (dsl-082-082-238-113.arcor-ip.net) -- 13 DEC 2004 - 19:16z
  • Re: Pressure diff
    Adrian (dsl-082-082-226-202.arcor-ip.net) -- 11 JAN 2005 - 14:48z
  • Re: Pressure diff
    Markus Vitzethum (EDDN) (dialin.212.114.188.59.nefkom.net) -- 11 JAN 2005 - 15:15z
    • Re: Pressure diff
      Adrian (dsl-082-082-226-202.arcor-ip.net) -- 11 JAN 2005 - 15:21z
      • Re: Pressure diff
        AndreaBuono (host194-38.pool82186.interbusiness.it) -- 20 JAN 2005 - 14:04z
        • Re: Pressure diff
          Adrian (212.117.79.242) -- 20 JAN 2005 - 16:43z
          • Re: Pressure diff
            AndreaBuono (host194-38.pool82186.interbusiness.it) -- 21 JAN 2005 - 11:58z
  • Re: Pressure diff
    Joerg Loehnig (EDDF) (panoramix.lhsystems.com) -- 15 JAN 2005 - 11:04z
    • Re: Pressure diff
      Jan Uitdenhage (mc-scan.tno.nl) -- 17 JAN 2005 - 11:05z
    • Re: Pressure diff
      Adrian (dsl-213-023-250-137.arcor-ip.net) -- 17 JAN 2005 - 17:21z
      • Re: Pressure diff
        h. Miersch (host217-42-248-161.range217-42.btcentralplus.com) -- 17 JAN 2005 - 23:34z
        • Re: Pressure diff
          Adrian (dsl-082-082-232-059.arcor-ip.net) -- 18 JAN 2005 - 09:49z