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Some SID turns do not load correctly


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Departing from San Jose to the north on the TECKY3 departure and the FMS draws the SID in a weird way, creating a near 180 degree turn as it should, but then draws the next line from the first waypoint straight to the second, not counting the turn. The red on the chart is what the plane actually flies, compared to what is shown as the correct procedure and what is on the FMS.

 

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IMO there is nothing wrong with the FMS route.

 

MLPTS is a fly-over waypoint - the turn must not be started until the a/c is overhead. The FMS indicates this with a curved arrow showing the turn direction. After the right turn the a/c would re-intercept the course to SPTNS.

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But shouldn't it just go straight from the end of the turn to SPTNS? It turns like 230 degrees and tries to rejoin the path it drew instead of going straight to SPTNS after the turn, like on the chart.

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I missed the part with the red lines. Indeed, such an excessive turn for re-interception is overdone and therefore likely another FMS issue. Still, re-interception of the course line is necessary, because the aircraft position after completing the turn depends on performance, airspeed and wind. I believe the FMS can not handle ambiguous situations like this. However, on completing the turn you could simply cut the corner with a direct to SPTNS.

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Thanks for the insight. I am tempted to just let the aircraft fly it, though I am worried some of the Vatsim controllers might not like this, so I might fly it in heading mode after the turn.

 

Update: I flew the departure again on nav mode, but quite a bit slower, closer to 200 knots instead of straight to 250, and it made the turn quite a bit tighter so the overcompensation is a bit less. It is still not great but I could probably get away with just leaving it alone, though I am still worried that some controllers would not like it

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