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09-28-2021, 12:37 AM #1Nxi VNAV bug example
At the Miami weekend, someone asked about the Nxi VNAV software glitch. Basically the situation is that Nxi will sometimes insert bogus altitudes into the VNAV flight plan.
This happened to me again last weekend and took the opportunity to snap a picture of what it looks like when it occurs.
In this case, I got cleared to the BTY VOR, and upon adding it to my flight plan, Nxi also added in 20000ft as a blue VNAV altitude target, presumably copying that value from the FL200 value at BIFFY in the STAR.
I took this picture, then I cleared BTY and did it again and then it didn't happen the second time. So I still haven't figured out exactly what triggers the glitch, but this is at least what it looks like when it happens. -
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10-28-2021, 04:23 PM #4I may have a solution for you, but I'll have to run it past Garmin.
I entered your flight plan into ForeFlight and then evaluated the flight plan, arrival, and the data shown on your MFD. Since it's only 93nm from KHND to BTY (19 minutes), and you're still 70.7nm from BTY, you were in the air for less than 5 minutes and at an altitude below 10,000 feet. But the arrival, which you already entered into the flight plan, has a mandatory crossing altitude of 20,000ft at BIFFY. Since VNAV only works for descents, and you were below the mandatory crossing altitude when entering a new fix, the flight director needed some way of placing you at or above 20,000ft prior to BIFFY, otherwise the flight plan would have been invalid. Ergo, it entered 20,000ft to avoid an invalid flight plan. I suspect that when you reentered the fix, some time had passed, and you were either above 20,000 or you had been cleared to 20,000ft. At that point, the flight director did not need to enter a minimum altitude at the new fix to avoid an error.
Try entering the new fix before adding the arrival or entering the new fix after your cleared to an altitude above the highest mandatory crossing altitude in the arrival. I bet that will fix it. As with most programs - it's a feature. -
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11-03-2021, 09:36 AM #5This is not just an issue with Nxi. I had it on my G1000 before I did the upgrade to Nxi. It started a couple revs back. For me, a downstream waypoint in my FMS likes to hard code itself to an intermediate altitude assigned by ATC during climb out (and after I enter it into the Autopilot). Yesterday, I ran into this on decent when the plane leveled off early due to the same issue. I've not been able to figure out the steps to reliably reproduce. Bizzarre.
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10-03-2022, 01:42 PM #6FYI I checked in with Garmin today about a resolution for the VNAV issue and they are still in the investigation phase. I recently emailed a video of it occurring in flight. Will keep checking in with them once a quarter until we get a resolution.
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10-05-2022, 01:45 PM #8Does anyone have VNAV issues with G3000 ? I do - but it is a different issue than being discussed on the G1000 VNAV above - more related to intermittent - improper FD VNAV calculation and autopilot capture of VNAV descents. If anyone else has seen this type issue we could start a new thread.
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