Air start tanker flight path and airspeed issues

[Nealius]

In the attached track there are two issues with air start tanker flight pathing and airspeed. 

1. On mission start the tanker does not fly straight to its first waypoint. Instead it does a 180 turn away, followed by another 180 turn back to the waypoint, which takes it 12+ miles off course. In previous versions of DCS tankers would spawn flying in a straight line to their first waypoint.

2. Airspeed/Groundspeed/Mach seems to be off. No wind in mission so TAS and GS are effectively the same. According to online calculators like this one, 270KCAS at 20,000ft is 361.7KTAS or 0.588M. Inputting 362kts at 20,000ft in the ME gives 0.54M instead of calculated 0.588M. Furthermore, in the game the F2 info bar says IAS is 264kts, which is 354KTAS/0.576M. Getting the tanker to fly exactly 270kts indicated is trial-and-error because neither the ME calculations nor the actual speed in-game appear consistent. In previous versions of DCS tanker speeds only varied by +/- 2kts. Now it's +/- 6kts or more (I've seen KC-130s doing 234kts when set to do 250kts at altitude).

EDIT for point 2: Changing mission temp to 15C gives 0.59M so the ME calculations seem to be correct and account for temp changes, but the tanker is still flying 6kts slower than it should be.

tanker-s-turn.trk

Edited March 5 by Nealius

[razo+r]

2. I think your online converter is wrong. I've used three different online calculators and all those showed 264 KIAS is 361 KTAS. The one you linked showed indeed 270 KCAS equals 361 KTAS. To be fair, it doesn't make sense that yours calculates CAS, as it is a bit different for each aircraft, while IAS should theoretically be the same for all.

So there is a chance you found the single one website who does something different/wrong.

Will try and report back to make sure.

[razo+r]

1) I know what you mean and the behaviour by the tanker is indeed weird and should be looked at.

However, a workaround would be, add a waypoint just infront of the tanker and move the "Circle/Hold" action from the DP waypoint to the first waypoint. That would remove the weird behaviour.

[Nealius]

It looks like the calculator I was using assumed 15C. I've found another calculator that allows OAT delta in the calculation.

The tanker speeds are an issue when Warthogs and fast jets are operating in the same area. A 10kt variance with temperature changes frome real weather injecting on a persistent server aren't an issue for fighters with excess power, but for an A-10 it could mean the difference between tanking and not tanking at all. We really need the AI to auto-adjust to a standard speed depending on the recipient aircraft. Mission builders can do a workaround with the AI task push to set different speeds but that can clutter the F10 menu or whatever flag triggers are in the mission, and on a server it could be abused by users who aren't tanking.

Edited March 5 by Nealius

[777coletrain]

On 3/5/2025 at 12:46 AM, razo+r said:

To be fair, it doesn't make sense that yours calculates CAS, as it is a bit different for each aircraft, while IAS should theoretically be the same for all.

Just FYI, it's the other way around. CAS should be the same across all aircraft because it's corrected for instrument and position errors. IAS is just what is shown to the pilot without any of those errors being fixed. You may notice some aircraft (the viper comes to mind) show a "C" next to the airspeed to show that it's CAS not IAS.