LittleJP Posted October 23, 2015 Posted October 23, 2015 Hi guys, I'm collecting data for updated speed tests at various altitudes in winter atmosphere (-15c). I'm using the HUD speed and averaging it at various points to get the speed. My question is this IAS or TAS? If it is IAS, how do I calculate TAS in these conditions?
-TBC-AeroAce Posted October 23, 2015 Posted October 23, 2015 (edited) For TAS you need to correct IAS for density/temp/pressure(ideal gas law or u can use ISA tables) that changes in air with height. Basically IAS calculates the airspeed assuming sea level ISA conditions are constant. These figures will not stay constant as you climb hence the reason IAS will be lower than TAS I can't be bothered to type all the necessary maths here but wiki/nasa/plenty of university sites(Princeton is a good one)/youtube will give you much more detail I forgot to say that all the math changes once air compressibility happens which is at a mach number of 0.3 so be careful with that Edited October 23, 2015 by [TBC]AeroACE
coconut Posted October 23, 2015 Posted October 23, 2015 I could be wrong but I think you can choose whether you TAS or IAS. Side question: what is CAS?
-TBC-AeroAce Posted October 23, 2015 Posted October 23, 2015 I don't really get CAS. I never used it in my Aerospace Engineering studies or when training to be a private pilots
JtD Posted October 23, 2015 Posted October 23, 2015 Calibrated air speed - same as IAS, but without position error. Basically when we are talking about IAS in game, we're usually talking about CAS, because we don't care about position error. Or maybe it's not modelled, and the IAS we see is real. 1
Dakpilot Posted October 23, 2015 Posted October 23, 2015 Dev's have said that there is positional error, when at extreme AoA or unusual attitudes the IAS will give unreliable readings It was mentioned when some were complaining of unrealistic slow speeds during a manoeuvre demonstrated in a vid, Han or someone said all was fine (actual airspeed EAS/CAS) because indicated airspeed was wrong due to positional error Cheers Dakpilot
Brano Posted October 24, 2015 Posted October 24, 2015 The best way how to get your TAS in game is to measure the distance flown thru the map grids.Set your altitude,set your engine and start stopwatch.More grids you fly thru,more precise is your measurement.I usually do 3 grids = 3x10km. formula is a primary school stuff: speed = distance/time
Dakpilot Posted October 24, 2015 Posted October 24, 2015 Would that not be Groundspeed...? chuck in a little wind and you will not have TAS Cheers Dakpilot
JtD Posted October 24, 2015 Posted October 24, 2015 Yes, it would, but in game you can set wind to 0 and in real life you would fly in low wind conditions, the same course within a short time span in both directions, thus practically eliminating the influence of wind.
Dakpilot Posted October 24, 2015 Posted October 24, 2015 Use E6B flight computer, authentic WWII every airforce had similar http://www.aviationexplorer.com/Virtual_E6B_Flight_Calculator_Emulator.html Use IAS/TAS fields Cheers Dakpilot
Brano Posted October 24, 2015 Posted October 24, 2015 Would that not be Groundspeed...? chuck in a little wind and you will not have TAS Cheers Dakpilot My bad,I thought I was stating obvious - no wind in mission setting
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