WTG1000 TAS inaccurate

MrTommymxr · June 2, 2026, 6:07pm

Frequency: Consistently
Severity: Low

Noticed the TAS not matching anymore on the WTG1000. I think this is new.

MattNischan · June 8, 2026, 10:51pm

The sim allows you to configure an error to be applied to indicated airspeed for your indicators. However, it does not carry those errors along to the true airspeed and mach. So, in the Garmin units, we compute those values using the current IAS, pressure and temperature. As such, it may not exactly match the simvar (but will be accurate to the IAS displayed and conditions, where the simvar may not).

Hope that helps,
Matt

MrTommymxr · June 9, 2026, 7:50am

Im pretty sure the G1000 computes CAS to convert to TAS. If it didn’t do that, then the wind vector would not be accurate.

Like here when the OAT sensor started to die. Actual OAT was ~10°C

MrTommymxr · June 9, 2026, 8:59am

speaking of the wind vectors, are you guys ever going to compute the wind or just use the vars?

MattNischan · June 9, 2026, 2:50pm

The real one does, yes, but like the TAS simvar, the CAS simvar does not track the IAS error. So, math-wise, we effectively back into CAS and then compute out to TAS.

I don’t believe we have computing the wind presently on our roadmap.

Thanks,
Matt

MrTommymxr · June 9, 2026, 5:05pm

Can we have the option to define the values in the panel.xml?
we just copy paste the values from the cockpit.cfg

MattNischan · June 9, 2026, 6:51pm

Maybe I’m not totally understanding the use case here. Since the IAS error can be defined already in cockpit.cfg, what would be the benefit of also being able to define these values in the panel.xml?

Thanks,
Matt

MrTommymxr · June 9, 2026, 7:58pm

Define the inverse, so CAS/TAS can be calculated correctly

falcon71 · June 10, 2026, 5:40am

Maybe this will help, it’s actually not difficult to compute:

github.com/falcon71/kln90b

kln90b/data/Wind.ts

main


      
          * @param windDirection
          * @param heading
          */
          export function calculateGroundspeed(tas: Knots, heading: Degrees, windspeed: Knots, windDirection: Degrees) {
             return Math.sqrt((windspeed ** 2) + (tas ** 2) - 2 * windspeed * tas * Math.cos(heading * Avionics.Utils.DEG2RAD - windDirection * Avionics.Utils.DEG2RAD));
          }
          
          /**
          * https://edwilliams.org/avform147.htm#Wind
          */
          export function calculateWindspeed(tas: Knots, gs: Knots, heading: Degrees, track: Degrees): Knots {
             return Math.sqrt((tas - gs) ** 2 + 4 * tas * gs * (Math.sin(((heading - track) * Avionics.Utils.DEG2RAD) / 2)) ** 2);
          }
          
          export function calculateWindDirection(tas: Knots, gs: Knots, heading: Degrees, track: Degrees): Degrees {
             return NavMath.normalizeHeading((track * Avionics.Utils.DEG2RAD + Math.atan2(tas * Math.sin((heading - track) * Avionics.Utils.DEG2RAD), tas * Math.cos((heading - track) * Avionics.Utils.DEG2RAD) - gs)) * Avionics.Utils.RAD2DEG);
          }
          
          export function calculateHeadwind(windSpeed: Knots, windDirection: Degrees, heading: Degrees): Knots {
             return windSpeed * Math.cos((windDirection - heading) * Avionics.Utils.DEG2RAD);
          }