=475FG= Dawger Posted June 22, 2021 Posted June 22, 2021 The true air speed in external view appears to be absent the correction of indicated air speed to calibrated air speed, resulting in a lower than expected true airspeed reading in external view.
Nealius Posted June 24, 2021 Posted June 24, 2021 The "TS" in external view infobar and on the F10 map is actually GS, not TAS. With a headwind you would see a lower than expected reading.
grafspee Posted June 25, 2021 Posted June 25, 2021 Exactly map speed is ground speed, external is TAS System specs: I7 14700KF, Gigabyte Z790 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor
Nealius Posted June 27, 2021 Posted June 27, 2021 External is also GS, last I checked. You can see it fluctuate when AI are doing racetrack orbits on their upwind and downwind legs. 1
grafspee Posted June 27, 2021 Posted June 27, 2021 Maybe you are right System specs: I7 14700KF, Gigabyte Z790 Aorus Elite, 64GB DDR4 3600MHz, Gigabyte RTX 4090,Win 11, 48" OLED LG TV + 42" LG LED monitor
=475FG= Dawger Posted June 28, 2021 Author Posted June 28, 2021 On 6/24/2021 at 6:24 PM, Nealius said: The "TS" in external view infobar and on the F10 map is actually GS, not TAS. With a headwind you would see a lower than expected reading. Ground speed is true air speed corrected for wind. With no wind, the conditions I tested this under, TAS and GS are the same. So if the external view speed labeled as true air speed is actually ground speed, it is still in error as it is off in the manner described in the original post.
Frederf Posted June 28, 2021 Posted June 28, 2021 Ground speed is not true airspeed corrected for wind. If you fly 200 knots straight up your TAS is 200 your groundspeed is 0. "TS" is neither true airspeed nor ground speed. TS is true speed or your velocity through the XYZ coordinate system. In flight around a round planet GS and TS aren't the same at all heights even horizontal. For example flying the Earth's circumference of 40,000km in 20 hours is 2000km/h ground speed. However at 30km altitude the same feat requires a true velocity of 2009.375km/h to have the same 2000 km/h ground speed. DCS does not have a curved planet and doesn't have this difference. So in DCS horizontal motion does have the property of TS = GS. IAS, CAS, EAS, TAS, GS, TS are six different speed measurements. Up until recently the infobar was labeled IAS/TS which displayed the actual values of EAS/TS. I think that's still the case but some modules had their IAS/CAS cockpit instruments updated to display IAS/CAS instead of EAS.
=475FG= Dawger Posted June 28, 2021 Author Posted June 28, 2021 42 minutes ago, Frederf said: Ground speed is not true airspeed corrected for wind. If you fly 200 knots straight up your TAS is 200 your groundspeed is 0. "TS" is neither true airspeed nor ground speed. TS is true speed or your velocity through the XYZ coordinate system. In flight around a round planet GS and TS aren't the same at all heights even horizontal. For example flying the Earth's circumference of 40,000km in 20 hours is 2000km/h ground speed. However at 30km altitude the same feat requires a true velocity of 2009.375km/h to have the same 2000 km/h ground speed. DCS does not have a curved planet and doesn't have this difference. So in DCS horizontal motion does have the property of TS = GS. IAS, CAS, EAS, TAS, GS, TS are six different speed measurements. Up until recently the infobar was labeled IAS/TS which displayed the actual values of EAS/TS. I think that's still the case but some modules had their IAS/CAS cockpit instruments updated to display IAS/CAS instead of EAS. You are over thinking this far too much but that was mildly entertaining.
iFoxRomeo Posted June 28, 2021 Posted June 28, 2021 5 hours ago, pmiceli said: You are over thinking this far too much but that was mildly entertaining. No, he is right. DCS doesn't show True Air Speed, only True Speed, as @Frederf explained. There is a thread buried in the forums, where it is explained. If I find it, I'll post the link. Fox Spoiler PC Specs: Ryzen 9 5900X, 3080ti, 64GB RAM, Oculus Quest 3
=475FG= Dawger Posted June 28, 2021 Author Posted June 28, 2021 5 hours ago, iFoxRomeo said: No, he is right. DCS doesn't show True Air Speed, only True Speed, as @Frederf explained. There is a thread buried in the forums, where it is explained. If I find it, I'll post the link. Fox It is not relevant whether he is correct or not. The speed labeled TS in external view is not calculated properly for the P-51 or the P-51 is displaying CAS to the pilot. My bet is on the former versus the latter.
Frederf Posted June 28, 2021 Posted June 28, 2021 The speed labeled "TS" is not incorrect. That's just how fast the airplane is going. If you flew from two locations 500km apart at 500km/h "TS" then it would take one hour to arrive regardless of wind, altitude, temperature, etc. "TS" is not true airspeed. I just flew a TF-51 as precisely as I could 450km/h TS and recorded F2 "IAS" figure. From TS and known wind it is possible to calculate TAS. Because temperature, altitude, air density are the same the ratio of IAS/TAS should be the same for both. 00 m/s (00 km/h) headwind, 2000m, IAS 408 km/h, TS 450 km/h calculated TAS 450, IAS is 90.7% of TAS 20 m/s (72 km/h) headwind, 2000m, IAS 474 km/h, TS 450 km/h calculated TAS 522, IAS is 90.8% of TAS The separate question of what the cockpit instrument shows is worth investigating. Recently the F2 "IAS" which is EAS was shown directly on pitot-static airspeed indicators in almost all airplanes without conversion. High profile modules like F-16, F-18 were updated to new calculation. It could be other modules like TF-51/P-51 were not. So we test this... At 10,000m 600km/h TS I press active pause immediately so speed is frozen. I check F2 "IAS" is 348 km/h (216.2 mph). I look at cockpit airspeed gauge and it reads at least 220 mph. Later I unpause and fly 700 km/h TS, F2-IAS-EAS 418 km/h (259.7 mph) and cockpit airspeed gauge shows about 267 mph (430 km/h). So even in TF-51 the cockpit gauge is not using the F2 IAS value directly. The source of the difference could be a subject of some study. IAS-CAS conversion is airplane dependent so it would be a question of finding the calibration difference between IAS and CAS for the P-51. There are documented conversions available. Life gets more complicated if I go to https://aerotoolbox.com/airspeed-conversions/ and set 10000m, +5C, TAS 700km/h. It says CAS is 416.8 km/h, EAS 401.8 km/h. Looks like even the F2 IAS has been changed over to IAS/CAS (no difference for an infobar) instead of EAS.
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