N3744F 6 Posted April 16, 2014 Share Posted April 16, 2014 Since installing 1.14 (poss. earlier, but at least since then) the <&TOCISADev> field has given some strange negative values, typically between -20 and -45, that aren't even close to the true deviation according to the TOC temperature. It is worth noting that the TOC for all of my flights is above FL370, so I'm wondering if PFPX has a problem calculating dev when ISA temp becomes static..? For example (all temps degrees Celsius): A flight I planned today has cruise at FL410, a TOC temp of -61 and a TOC ISA Dev of -29! Under ISA, 41000ft temp should be -56.5, so the actual ISA deviation is -4.5 (~ -5). Anyone else having these problems? Link to comment Share on other sites More sharing options...
CaptainTim 11 Posted April 17, 2014 Share Posted April 17, 2014 Have you ever thought this might be down to your individual weather programme? What do you use? Link to comment Share on other sites More sharing options...
N3744F 6 Posted April 17, 2014 Author Share Posted April 17, 2014 I really fail to see how weather program makes a difference, all the values I quoted were from within PFPX itself. It looks as if there is a problem in the internal calculation of this variable. Link to comment Share on other sites More sharing options...
CaptainTim 11 Posted April 17, 2014 Share Posted April 17, 2014 What are you using for your weather in the sim. Whats this difference you talk about?!? Link to comment Share on other sites More sharing options...
N3744F 6 Posted April 17, 2014 Author Share Posted April 17, 2014 In the above example, the PFPX OFP shows that TOC temp is -61 and that the TOC ISA dev is -29. At my TOC (41000ft) ISA states a temperature of -56.5, which means the actual ISA deviation that PFPX should be calculating is -4.5 --> (-61) - (-56.5) = -4.5 Somehow, PFPX is calculating -29, clearly a significant difference from the actual value. Link to comment Share on other sites More sharing options...
B.Fatih KOZ 3 Posted April 18, 2014 Share Posted April 18, 2014 Yes <&TOCISADev> field is giving wrong values ... At FL340 temp is expected to be -53 C but ISA DEV value was -47 So there is a problem with that field , did you checked the latest documents about the template editing/ building fields ? Maybe Christian changed something or added some new functions for ISA DEV ... [ I did not checked them , just tested with an older template ] @CaptainTim ; ISA DEV (ISA Deviation) is not related to the WX software we use and it is not related with the simulator wx you had during flight ... If you are interested please check http://en.wikipedia.org/wiki/International_Standard_Atmosphere for basic details , from that page you can find more links with more info Best wishes Link to comment Share on other sites More sharing options...
N3744F 6 Posted April 18, 2014 Author Share Posted April 18, 2014 Thanks for confirming the problem The latest Flight Plan Template Guide (Rev. 10) shows no change to <&TOCISADev>, however I remember that a change to the field took place within the last few revisions, with the addition of a second formatting parameter (so [0] gives + / - formatting, and [1] gives P / M formatting). I'll have a play with different PFPX version installs this afternoon to find out when the field last worked correctly, and maybe look at the <&AvgISADev> field as a possible interim solution. Link to comment Share on other sites More sharing options...
AALScott 1 Posted April 20, 2014 Share Posted April 20, 2014 Just out of curiousity what does ISA Dev tell you when planning a flight? I know that it means that its warmer or colder than ISA but when you are planning why is that important? Link to comment Share on other sites More sharing options...
N3744F 6 Posted April 20, 2014 Author Share Posted April 20, 2014 Others may be far more qualified to answer that than me, but here's my 2 cents Let's not disregard the fact that ISA dev is just another way of writing outside air temperature for a given altitude. In truth there are probably many dispatch calculations involving temperature although I'm not sure how deep the PFPX calculations or available flight model data go... One example that springs to mind is that outside air temperature directly affects Mach number, and therefore fuel flow is affected. Interestingly, if you use any of the modern Boeing FMCs, you'll notice a field on one of the preflight pages for inputting ISA deviation. I'm led to believe that this is used to calculate the most economic climb profile for the aircraft (with reference to the cost index), among other things. Link to comment Share on other sites More sharing options...
N3744F 6 Posted April 20, 2014 Author Share Posted April 20, 2014 Also, to update my 18th Apr. post, I've sadly not yet had the chance to experiment with past PFPX versions. I'll complete ASAP and report the results. Link to comment Share on other sites More sharing options...
daan_vb 37 Posted May 31, 2014 Share Posted May 31, 2014 Any update to this problem, i'm also trying to inpu this into my flightplan but its coming up with the wrong value Link to comment Share on other sites More sharing options...
N3744F 6 Posted May 31, 2014 Author Share Posted May 31, 2014 My apologies, been very busy with academic work recently and not had the chance to look at previous versions. In my latest OFP template I simply changed the 'TOC ISA Dev' field for the 'Average ISA Dev' field until it is addressed- this is intended to only be a temporary workaround but at least the output is believable! I was very surprised they let the bug persist into 1.15 to be honest. Link to comment Share on other sites More sharing options...
FlightSimSoft.com 283 Posted June 2, 2014 Share Posted June 2, 2014 issue confirmed and fixed for next release. Link to comment Share on other sites More sharing options...
N3744F 6 Posted June 2, 2014 Author Share Posted June 2, 2014 Thank you Christian! Link to comment Share on other sites More sharing options...
Recommended Posts
Archived
This topic is now archived and is closed to further replies.