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OFP shows altimeter setting in hectopascals, not inHg

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Hi, I posted on this before but now I have more information. The issue is that PFPX calls TOPCAT for the takeoff and landing data, and then brings the altimeter setting back in hectopascals, which gets passed to the OFP, even when the airport is located in a region in which inches of mercury would be preferred.


Attached is a screenshot of PFPX calling TOPCAT for takeoff information from Chicago O'Hare. You can see that PFPX/TOPCAT is fetching the altimeter setting in inches of mercury, and interpreting the METAR correctly - you'll see that under "Pressure," the correct numbers 30.06 are displayed. 


However, when you look at the results window (this is the information that TOPCAT will append to the OFP), you'll see that the altimeter setting is in hectopascals ("QNH 1018"). You'll see it in the line that reads:


TEMP +2C QNH 1018 WIND 130/12 (09KT HW) (emphasis added)


That line is brought into the PFPX flight plan verbatim.


I'm guessing that TOPCAT is looking at a config setting somewhere that requests results be given in hPa, but for the life of me I can't see where that would be. The PFPX file for the aircraft I'm using has the units set at feet and pounds. Under TOPCAT performance module, the file that is called is Boeing 747-400 RB211-524H, but I'm not sure what that links to or even if it's the problem. Within TOPCAT, I have only one aircraft in the aircraft database, and under "Aircraft Details," the pressure units are listed as inches of mercury.


Inside the TOPCAT "Aircraft" folder, the files are unreadable to me (i.e., not readable by a standard text editor). Inside the TOPCAT "Configurations" folder,  I can see some readable configurations but I can't see a line for setting a preference for the altimeter setting.


That's all I can think of. Can anyone help me get TOPCAT to send inHg to PFPX? Thanks!


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I don't believe you can change the pressure configuration within Topcat.


Using the main program you can see hPa as the main function with the inHg equivalent displayed:


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If you call up the results table you'll also see the hPa figure in use which is relayed back to PFPX:


TAKE-OFF KORD/ORD  RWY 10L  TORA 3962M            
G-ZESA  BOEING 747-400 RB211-524H
CHICAGO OHARE INTL                                

TEMP +2C   QNH 1018   WIND 110/09 (08KT HW)

------------------  CONDITIONS  -------------------

------------------  FULL THRUST -------------------
   +2C 271020 OBS(B) 114-121 121 141   2221M   1.57

----------------  REDUCED THRUST  -----------------
  +69C 234034 OBS(B) 127-129 129 139   1054M   1.37
  +70C 231976 CLIMB    129   129 139    980M   1.37
  +71C 227989 CLIMB    129   129 139    902M   1.37
  +72C 224001 CLIMB    129   129 139    823M   1.37
//+73C 220102 CLIMB    129   129 139    740M   1.37


------------------  ENGINE OUT  -------------------
"AT 2200' LT TO HP 'OBK' 113.0" (092 INBD RT)

---------------------- END  -----------------------



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  • 1 year later...

Lo and behold, after a year and a half, I found a solution. If anyone would like to have inHg on the OFP, then just go to the window seen on the very first post in this thread. Then, FIRST enter and check all your performance data and hit Calculate (but not Apply) until you have your final results. Once you are through with the Calculate feature, then go down to the Pressure field and re-enter your pressure in inHg. (Just type over the existing entry, even if it's the same, but don't Return or Tab out of that field.) Now, Calculate one final time, hit Apply, and the pressure will show up on your OFP as an altimeter setting, with an "A" preceding it (as in "A30.06"). A minor thing, but if someone wants the feature, that's how to use it.


Note that this may only work for airports where the METAR reports InHg in the first place. If the METAR is in hectopascals, this may not work.


[Edited because I made a mistake in describing the process; it works as written now.]

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