Air Carrier Flight Crew reported anomaly with FMS equipment possibly due to 5G interference during climbout.
Synopsis
Air Carrier Flight Crew reported anomaly with FMS equipment possibly due to 5G interference during climbout.
Narrative
Prior to pushback; both crew members verified and LCA in jumpseat (observed) that all fixes in flight plan were verified in the FMS against the Jepp charts and FMS map. Upon departure; while climbing 'via the SID' and upon approaching SPRKY; the white course on the MFD appeared to change into 'two half circles' instead of continuing course on to the next fix on the SID; which was GOALY. Immediately upon realizing this; we disengaged autopilot and hand flew the turn from SPRKY to GOALY. We also rebuilt the fixes in the FMS; placing GOALY ahead of us and SPRKY behind us. ATC didn't note any course deviation and we continued on the remainder of the SID with no further automation issues.We believe the cause of this event was an automation anomaly and/or 5G interference. As we had confirmed and crosschecked the FMS data inputs prior to departure. If this is a recurring problem for 5G interference at this waypoint; it could be briefed as part of the WANT briefing as a potential threat. Mitigation strategy would be to hand fly the departure procedure and be ready to manually input way points
Second reporter narrative
Possible FMS anomaly. After TO on the Zepper SID we are about to fly over a fly over waypoint. The FO's (First Officer) (who was flying) MFD showed a weird figure 8 type pattern to intercept the course; the CA (Captain) MFD showed a 270 turn heading back to PHX. The CA called for the controls and turned off the automation and turned in the direction of the course we should be flying. After putting the course behind us and turning back on the automation; the FMS worked as it should. The box was programmed correctly; we are not sure what caused this issue. The FMS worked for the entire rest of the flight. I was occupying the Jumpseat for a Line Check on the First Officer.FMS Anomaly. The box was programmed correctly on the ground for what we were cleared for by ATC. I believe we could have asked for a heading since we deviated from a clearance; however in light of what occurred I believe the crew did a good job avoiding the aircraft getting into an undesired aircraft state.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.