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Guest KathyPilot

ASA provides incorrect ISA - Lapse Rate Problem

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Although I posted this question to the bottom of another thread, that thread was not ASA specific, I'll post it here as new because you have not addressed it during the past week - perhaps you missed it. I'm a new customer (3 weeks) so if I am missing something in my settings I'm all ears. Or, If I can provide you with logs and such I am willing to help.As other have posted, I am experiencing a large delta from ISA. For instance, at 34000 I would expect no more than +/- 10 or 15 on average from ISA, but I sometimes have a delta from ISA in the range of +40. Additionally, data as presenta in the ASA briefing page is quite different from the surrounding Winds Aloft reports from http://aviationweather.gov/products/nws/fdwinds/. For RW flying I use this site for flight planning (along with AOPA) and most times they are very close. I cannot use ASA for proper flight with these large deltas from ISA because the complex aircraft I use in FSX depend on ISA to compute engine performance. I'm not going to ask about the wind issue because even Pete and his FSUIPC can't get a perfect handle on that and I see you are working it anyway.I've tried using a simple aircraft with the Latest version of ASA, nothing else running except FSUIPC4 with no wx settings. Also, I have tried the various settings in ASA (smoothing, pseudo stations, etc) to no effect for this problem. How are you computing ISA?Thanks for your time.Katherine

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Hello,We are aware of an issue of temperature being temporarily depicted incorrectly in some cases. We are working on this.As to how we compute "ISA" I am not sure I understand. ISA meaning standard atmosphere is not a computation but a given 15C and 29.92 pressure at sea level. Lapse rate of 2.2C per 1000ft is assumed in "ISA" but we don't make any assumptions and use actual forecast data. Of course nearing the upper altitudes this standard lapse rate is not appriopriate anyhow.We use the WFS global forecast model data to come up with our aloft data. This has traditionally been very accurate as it is the same data that is used to plot real life winds aloft forecast charts. If you are noting discrepancies, could I ask you to please email me an example to damianc AT hifisim.com so I can investigate?Thanks!

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