I’ve noticed a discrepancy in the TAS reported on the Garmin G1000 display and the external view with full HUD. The G1000 numbers are always slightly less than what is reported in the external view full HUD. I mostly fly the C127 and the C208 so that is what I’ve noticed it in, however it could be in more aircraft. The attached images are screenshots taken a few seconds from each other. I have 2 zoomed in images for better readability and 2 full screenshots attached.
I suspect that the Garmin is taking into account the 5kt headwind and displaying the TAS accordingly. Shouldn’t the external view show that same number? Is it a bug? I posted it here as I wasn’t sure. I can make a bug report if it is a bug that needs to be addressed.
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On another flight in a C172S G1000. Garmin shows TAS 100kt. External shows 105kt. I’ve got a 2kt headwind and a 3kt crosswind from left to right. Switching to a different wind display I can see I’ve got a wind at 4kt wind bearing 52° CCW from my heading.
EDIT: Unrelated, but this flight CTD about half way through the flight. 
Attempted another flight, it CTD about 25nm away from destination. 
Not a good night/morning for flying I guess.
However during a portion of the flight I had a 3kt tail wind and a 7kt left to right crosswind. I was still seeing a 5kt discrepancy between the G1000 and the external view with the external view being 5kt faster. It seems like the difference between the two displays is always 5kt. Starting to feel more like a bug.
Another night, another flight.
- C172S G1000 TAS 89kt
- External view HUD TAS 95kt
- 12kt headwind with a 21kt left to right crosswind.
No gusts, so at least I’ve got that going for me. Which is nice.
What’s the proper terminology anyway, do I say I’ve got a left crosswind because it is coming from the left?
Attempting a 1 hour 30 minute flight. During climb to FL110 I am seeing:
- C172S G1000 TAS 83kt
- External view TAS 89kt
- 13kt tailwind
