correct as is GPS not updating correctly after air engine loss

[DreamingInfraviolet]

Hi! I ran into an INS issue with the F16.

• Start mission with GPS available
• Start at Las Vegas airport coordinates N36°12 W115°11
• Take off, turn off engines around N 36°07 W115°09 in mid-air
• Land at N36°14 W115°01
• Cycle power, restart engine
• Aircraft displays coordinates in INS DED page: N36°07 W115°09, which are the wrong coordinates. Expected coordinates are N36°14 W115°01. Attempting to change them doesn't work
• Do full INS alignment. HSD coordinates still incorrect
• FIX page shows "SYS ACCUR HIGH, GPS ACCUR HIGH" despite INS coordinates being wrong. Performing an overfly FIX does nothing
• Turn off GPS. Overfly Fix finally works

So it seems like after losing power and landing, the GPS coordinates are stuck to the values when the plane lost power mid-air, instead of correctly updating. This seems like a bug? Turning off GPS and doing a manual FIX seems to be the only way to solve this.

f16ins.trk

[Lord Vader]

Hi @DreamingInfraviolet

I watched your track and must observe several things you need to review.

You try to change coordinates with the INS system in NAV mode. It won't be updated like that. If you want to do this, you need to reset the INS system (off, then one of the align modes) inserting the coordinates in the first two minutes of alignment in NORM mode. 

By design, INS does not know where it is unless you confirm the coordinates. In this case, if you confirm the current ones, you would intentionally have a misalignment. The system will say it's "accurate" because it's assuming your coordinates are correct. 

Remember our model of the F-16 does not include an integrated GPS system, like the A-10C EGI. This is a separate system that generates a position via an algorithm called a Kalman filter. Long story short, GPS is an aid to this equation. 

The Fix feature will only correct INS coords drift if GPS is not available. So it's working correctly in your example.

I was able to take control of your track and do the correct procedures with success. 

Hope this helps.