Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Situational Awareness
ATC Issue All Types; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert
Human Factors; Chart Or Publication; Procedure
ATC expects flyover and the FMC reads flyby (SID depicts flyby)We were issued an obscure clearance out of San Jose which read SJC 2 departure to the MOONY intersection back to the SJC VOR and onward to the BMRNG intersection. The MOONY intersection is not a fly over way point so the FMS turned back to the north towards the SJC VOR well short of the way point. This brought the attention of the Controller who explained to us that we were off course turning 20 miles north of this 180 degree turn as the FMS is designed to do since it is not a fly over waypoint. He advised us this is a nav deviation and he would be filing paper work on it and advised us to do the same. I called NorCal once we were en route and had a constructive conversation about what went wrong. [The NCT representative] explained that this has happened before and I explained why the FMS turned when it did. [My First Officer] pulled up an article explaining how the FMC/FMS works which depicts a very similar scenario. I asked [the NCT representative] if he had seen this publication. Whether he has seen it or not; I did suggest that a track needs to be published depicting a fly over waypoint for the MOONY intersection or realistically a point closer to the VOR than the MOONY intersection. By the time we turn downwind on this departure we were at 7500 feet well clear of inbound traffic as well as the terrain.
The easy fix to this issue would be to assign a valid transition on the SJC2; either PXN or AVE which would allow the FMS to proceed all the way to MOONY instead of smart turn to SJC. ATC could issue a radar vector to to SJC as time permits.Another solution would be to revise the SID to modify MOONY to a fly-over waypoint.A third possibility is to add MOONY as a valid transition with a manual sequence heading after MOONY.The primary issue is that the personnel designing the SID do not consider fly-by vs fly-over.
CE-680 flight crew reported ATC indentified a track deviation when the FMC performed a fly-by rather than a fly-over departing SJC.