Gonzo01 Posted May 31, 2010 Share Posted May 31, 2010 (edited) I notice at high altitudes that TAS in the VSD is greater than GND Speed at times, and changes depending on my heading. I thought TAS is CAS corrected for nonstandard temperature and pressure and should never exceed ground speed. I realize at these altitudes Mach speed is a more valid index to the speed of the aircraft. But it seems that TAS seems to be off or even reversed with Ground speed in the VSD. Can someone take a look at this in the F-15's VSD and let me know if I am not understanding this correctly. Thanks, Gonzo Edited May 31, 2010 by Gonzo01 Link to comment Share on other sites More sharing options...
GGTharos Posted May 31, 2010 Share Posted May 31, 2010 What if you have a tail-wind? [sIGPIC][/sIGPIC] Reminder: SAM = Speed Bump :D I used to play flight sims like you, but then I took a slammer to the knee - Yoda Link to comment Share on other sites More sharing options...
Gonzo01 Posted May 31, 2010 Author Share Posted May 31, 2010 Wouldn't that effect your ground speed and not your True Airspeed (TAS)? A tailwind would actually increase your Ground Speed not your True Air speed. Just like a head wind would decrease your ground speed. The aircraft's True airspeed should remain unchanged due to wind. What I don't understand is what would cause True Airspeed to be greater than Ground Speed at times. Maybe acceleration and it's effect on compressibility above 200kts, but only during the acceleration phase not the whole time while cruising at 30,000 ft. Gonzo Link to comment Share on other sites More sharing options...
Robin_Hood Posted May 31, 2010 Share Posted May 31, 2010 (edited) Well, say, you're at 300 knots TAS (relative to the air around you). If you've got a 30 knots headwind, then your ground speed will actually be 300-30 = 270 knots. So you have TAS > GS. (TAS is the speed relative to the air - check http://en.wikipedia.org/wiki/Airspeed) Edited May 31, 2010 by Robin_Hood 1 2nd French Fighter Squadron Link to comment Share on other sites More sharing options...
EtherealN Posted May 31, 2010 Share Posted May 31, 2010 Gonzo, like Robin indicated - nevermind the ground when working on airspeed. It's completely irrelevant as long as you are not about to impact it. (Though obviously when doing navigation by clock-and-compass you will have to work with the wind and thereby pick up your travel relative to the ground since your target or destination is usually defined as on or above a ground point.) A more direct example than Robins: let's take a Fiesler Storch. Nice light thing that can do some nice tricks if you dare take it up in strong wind (don't): Heading 360, TAS 20 knots, wind 360 20 knots. TAS is 20, groundspeed is 0. It's not quite a hover, but... well, yeah, it is a hover. Sort of. :P [sIGPIC][/sIGPIC] Daniel "EtherealN" Agorander | Даниэль "эфирныйн" Агорандер Intel i7 2600K @ 4.4GHz, ASUS Sabertooth P67, 8GB Corsair Vengeance @ 1600MHz, ASUS GTX 560Ti DirectCU II 1GB, Samsung 830series 512GB SSD, Corsair AX850w, two BENQ screens and TM HOTAS Warthog DCS: A-10C Warthog FAQ | DCS: P-51D FAQ | Remember to read the Forum Rules | | | Life of a Game Tester Link to comment Share on other sites More sharing options...
DoctorK Posted June 1, 2010 Share Posted June 1, 2010 (edited) EDIT: Sorry, I was wrong. I assumed it was unfixed like many other bugs of HSI, AOA gauge, Flight director in HUD, Backup speed meter... This is a known bug from 1.1. TAS gauge in VSD shows CAS instead. Edited June 1, 2010 by DoctorK Link to comment Share on other sites More sharing options...
Gonzo01 Posted June 1, 2010 Author Share Posted June 1, 2010 (edited) Thanks guys for the help. I can't believe this has been a bug since 1.1. That means ED has had over four years to fix it. There is not a lot of hardcore sims left in the PC industry, I wish I understood better why ED choose not to fix something so significant like (i.e TAS in VSD, HSI, AOA gauge, Flight director in HUD, Backup speed meter, etc..) Is it just the F-15 or all aircraft? Combined with some of the new bugs like crashing occasionally while trying to select the ILS mode. I really like ED's work, it's just sometimes old bugs drive me away from sim for many years until someone has tried to mod the sim to fix what the the original developers could not. Unfortunally, this has the added benfit of making the sim too unstable to play online. Gonzo Edited June 1, 2010 by Gonzo01 Link to comment Share on other sites More sharing options...
EtherealN Posted June 1, 2010 Share Posted June 1, 2010 (edited) Gonzo, it's not a bug. Read what Robin and I wrote. There is nothing that prohibits TAS from being greater than ground speed. There are still a few unsquashed bugs in it, but this isn't one of them as far as I've been able to see. The TAS/GS stuff works just as expected for me. If you are having crash issues that's a separate matter for separate investigation, since my own experience is that it is extremely stable. I've done 12-hour "shifts" on the 104th server without any crashes or performance degradation, so if you experience such things we might want to look over your system to see what's causing it. DoktorK, could you source your quote for verification? Edited June 1, 2010 by EtherealN [sIGPIC][/sIGPIC] Daniel "EtherealN" Agorander | Даниэль "эфирныйн" Агорандер Intel i7 2600K @ 4.4GHz, ASUS Sabertooth P67, 8GB Corsair Vengeance @ 1600MHz, ASUS GTX 560Ti DirectCU II 1GB, Samsung 830series 512GB SSD, Corsair AX850w, two BENQ screens and TM HOTAS Warthog DCS: A-10C Warthog FAQ | DCS: P-51D FAQ | Remember to read the Forum Rules | | | Life of a Game Tester Link to comment Share on other sites More sharing options...
Robin_Hood Posted June 1, 2010 Share Posted June 1, 2010 It definitely was a bug in 1.1, but it is indeed fixed now :thumbup: By the way, if anyone wonders, the "atmosphere" modeled in FC2 is still the same as in 1.1 in terms of TAS/IAS/Mach relation. I remember the temperature didn't change anything in 1.12, not sure how it is now (but my bet would be it's still the same) 2nd French Fighter Squadron Link to comment Share on other sites More sharing options...
104th_Crunch Posted June 1, 2010 Share Posted June 1, 2010 Is it correct to say that if there is no wind in a FC2 mission that Ground Speed and TAS should be equal in level flight? Link to comment Share on other sites More sharing options...
Robin_Hood Posted June 1, 2010 Share Posted June 1, 2010 Yes it is :) Easy to check with the F-15, which has both TAS and GS indicated on the Radar display 2nd French Fighter Squadron Link to comment Share on other sites More sharing options...
104th_Crunch Posted June 1, 2010 Share Posted June 1, 2010 Yes it is :) Easy to check with the F-15, which has both TAS and GS indicated on the Radar display Yes, but I am pretty sure I have been in FC2, level flight, no wind, and GS and TS displayed different. I'll have to recheck. Link to comment Share on other sites More sharing options...
Recommended Posts