Date: 201905
Local time of day: 0001-0600
Location: VNY.Airport, US
Flight conditions: IMC
Light: Daylight
Aircraft: Light Transport
Operator: Air Taxi
Operating under: Part 135
Flight phase: Takeoff / Launch
Airspace: Class C VNY
ATC / advisory: TRACON SCt
Aircraft component: FMS/FMC
Component problem: Malfunctioning
Reporter organization: Fractional
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Confusion; Human-Machine Interface; Time Pressure; Troubleshooting
Anomaly: Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Contributing factors: Aircraft; Human Factors; Procedure
Primary problem: Human Factors

Narrative: We briefed the departure two times. We reviewed the legs against the departure chart with FMS. HARYS2 departure; LAS transition. It called for straight out to PPRRY intersection the left turn 110. We reviewed the departure and procedures two times. Confirmed FMS details. After takeoff at apex 500 AGL; LNAV 1 captured with PPRRY in front of us with left turn 110 depicted on screen and showed on FMS box. The command bars started a small right turn; which I thought was a small turn to PPRRY intersection. The command bars kept going right and picture on MFD still showed PPRRY with left turn. I engaged autopilot and stopped turn at apex a 210 heading. At about that time we were checking in with Socal departure. They gave us and immediate heading to 080 and told us to check procedure. After turning on to heading the box showed PPRRY passing and FMS resequenced itself to next fix. There was a serious issue from apex 500 AGL to apex 1;900 MSL with our FMS. We definitely had the correct procures in the FMS. We briefed and had everything verified and planned perfectly. It really shook my confidence in the FMS and the aircraft operating system. Things happened very quickly at low altitudes and in a high work load area. There was also GPS testing in the area. It's the only thing that I can think of that might have created this issue. It was one of the strangest things I've seen. I have never seen anything like this before. I am disappointed that I followed the command bars with LNAV captured 40 degrees before I stopped the turn. We briefed departure two times and ensured that everything was dialed in. When it started right; I should have recognized it sooner. It took me a few seconds to realize what was happening. My reaction time could have been better. Between 500 AGL and 1;900 feet; things are moving quickly. Add Tower and turning on autopilot; my reaction time to select heading took longer than it should have. There's nothing I could have done better. I wish it was a mistake I did in programming. However; it was all programmed properly. It was almost like the FMS had a momentary meltdown. Possible GPS testing may have been the issue. I reviewed all things we did before issue. My reaction time could have been better.




Synopsis: Air taxi pilot reported experiencing FMS display problems on departure. ATC provided heading vectors; possible GPS testing mentioned as a contributing cause.