Nealius Posted February 18, 2020 Posted February 18, 2020 I'm seeing discrepancies in TAS/Mach in the ME vs. those in an aviation calculator. For reference, I am still on the last 2.5.5 OB and using this aviation calculator for conversions: http://www.hochwarth.com/misc/AviationCalculator.html According to the calculator, I get the following. 275KCAS at 9,000ft is 312.5KTAS at M0.488 However, in the ME if I program 312~313KTAS, it tells me M0.478. If I program M0.488 it tells me 318KTAS. Mission weather is 25C at 29.92. Is the TAS/Mach computation altered with pressure/temp changes? Few of the CAS-->TAS calculators I see ask for any weather info to crunch their numbers.
randomTOTEN Posted February 18, 2020 Posted February 18, 2020 (edited) You're probably reading it wrong. Temperature/pressure is absolutely essential for solving these problems. If the calculator isn't asking for these values then it's already assuming you're inputting density altitude (MSL corrected for non-standard atmosphere) or else it's just not built correctly. 25C at 9,000ft Pressure Altitude (MSL@29.92inHg) is HOT My metal E6-B finds that to be a density altitude of 12,000ft That's ISA+28. 275KIAS under these conditions is 330KTAS M0.49 when I spin the wheel... Edited February 18, 2020 by randomTOTEN
Nealius Posted February 18, 2020 Author Posted February 18, 2020 25C in the ME refers to temp at sea level, from what I can tell. I have no way of telling what the temp is at altitude. How would I find it?
randomTOTEN Posted February 18, 2020 Posted February 18, 2020 Oh, yeah... that's right. Comes out to ISA+10. Not nearly as bad. DA now 10,400ft, OAT= 9C. 275KIAS=322KTAS M0.49
Nealius Posted February 18, 2020 Author Posted February 18, 2020 Hmm, still about a 4~5kt difference, guess it doesn't matter at that point. Does your EA6B automatically calculate DA/OAT? It's been ages since I touched one of those things.
randomTOTEN Posted February 18, 2020 Posted February 18, 2020 yeah there's a window with a pointer. Flight sims are the only things which give me a chance to practice using it!
Nealius Posted February 18, 2020 Author Posted February 18, 2020 Huh, I need to buy another one then. I thought I brought mine with me when I moved to Japan but lost it somewhere along the way.
AG-51_Razor Posted February 18, 2020 Posted February 18, 2020 25C in the ME refers to temp at sea level, from what I can tell. I have no way of telling what the temp is at altitude. How would I find it? Figure on the temperature dropping 2 degrees C per thousand feet of altitude as a standard. :thumbup: [sIGPIC][/sIGPIC]
Nealius Posted February 21, 2020 Author Posted February 21, 2020 (edited) Wait, 9,000ft would be an 18C change, 25-18=7C. How did the E6B get 9C? I'm messing around with a digital E6B app on my phone but something must not be right with it. Mach/Airspeed conversion for 275KIAS at 9C is M0.42 DA/TAS conversion for 275KIAS at 9C and 9,000ft is giving me a DA range of 9,900~10,900 and a TAS range of 319~324 This online E6B (https://e6bx.com/tas/) gives the same values randomTOTEN got, but I'm still confused where the 9C came from. But here's more confusion 29.92, 25C at sea level, no wind. Assuming -2C every 1,000ft OAT at 9,000ft is 7C. 275KIAS should be 321KTAS. However, the info bar in-game is showing 279KIAS and 321KTAS. Edited February 21, 2020 by Nealius
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