Problem with displayed winds

[cbretana]

I have an HDX screen, and the calculated in-flight winds displayed onscreen are (intermittently), way off. I am often getting 40 to 50 knots crosswind displayed, when the actual winds are nowhere near that strong.
What could be causing this?
I have my remote magnetometer mounted under the rear cockpit seat cushion,, and some time ago, I had a similar problem due to carrying something made of steel in the back seat, but that is definitely not what's going on now. Can a faulty OAT sensor cause this? As an aside, I also noticed something today that seems anomalous. At 9500 MSL, although the OAT was reading 34 degrees F, the carburetor Temp sensor was reading 41F. That should not be possible.

 

[Marc_J._Zeitlin]

I have an HDX screen, and the calculated in-flight winds displayed onscreen are (intermittently), way off. I am often getting 40 to 50 knots crosswind displayed, when the actual winds are nowhere near that strong.
What could be causing this?
I have my remote magnetometer mounted under the rear cockpit seat cushion,, and some time ago, I had a similar problem dye to carrying something made of steel in the back seat, but that is definitely not what's going on now. Can a faulty OAT sensor cause this? As an aside, I also noticed something today that seems anomalous. At 9500 MSL, although the OAT was reading 34 degrees F, the carburetor Temp sensor was reading 41F. That should not be possible.

Charlie - the magnetometer is the most likely culprit - if it's off by 10 degrees, at the speeds we fly in our canards, that'll give wildly inaccurate wind indications. I'd try both the on-ground and in-air calibrations again. While it's possible that an OAT sender that's off a few degrees will be a contributor to wrong TAS and wind indications, generally it'll only affect the TAS by a few kts, so the wind vector won't be changed much. But a magnetometer being off by a few degrees CAN give VERY wrong winds. The magnetometer error can also be highly dependent on which direction you're going, so in one direction, it's spot on, and in others, it's off by 20 degrees.

WRT the carb temp, if your carb heat is leaking a bit, the carb intake can be higher than ambient, particularly if you're at WOT. It may also depend on exactly where your CT sensor is mounted and what type it is - you may be getting conducted heat down from the sump.

 

[Dynon]

OAT has a relatively small effect, but if it's WAY off, it could be a factor. Most likely, as Marc says above, magnetic heading is the culprit.

 

[cbretana]

Re-Did a Ground Compass Calibration and that seems to have corrected the problem. Will repeat the In-flight Compass Cal as well tomorrow.