Falcon 900
Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 50; Flight Crew Total 6000; Flight Crew Type 500
Workload; Troubleshooting; Human-Machine Interface; Distraction; Confusion
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Flight Crew Overcame Equipment Problem; Flight Crew Became Reoriented; Flight Crew FLC complied w / Automation / Advisory
Aircraft
I downloaded our flight plan into the FMS using an uplink service provider. The clearance was different and I entered the changes manually into the FMS. After a departure on 27L; we were radar vectored right turn to 360 then 090. After a few minutes we were cleared on course. We then commanded direct to the next fix in the FMS. It was then noticed by ATC and ourselves that we were proceeding not as cleared but as filed. After reviewing the FMS it became clear that the changes to the flight plan dropped out and the plan reverted to the downloaded flight plan. I am 100% sure we made the changes to the FMS from filed to cleared. We did not change a runway in the FMS that would have caused on a SID to drop out and we were not cleared a SID. On the prior leg the entire flight plan dropped out of the box on the ground prior to departure which was unusual. I have extensive experience with the NZ-2000 in the Citation X and the Falcon combined and am aware of the usual pitfalls and these do not seem to fit into what I would normally expect. Multiple flight crews are noticing that the Honeywell FMS is getting a little more glitchy as more and more features are added.
The Reporter has also flown the CE750 with the same Honeywell NZ-2000 FMS and has had very few problems in the past five years. Recently; with the latest hardware and software in the Falcon 900EX which he is currently flying; the FMS behaves differently and unpredictably. The major issue in this case is that after an automatic  flight plan upload; ATC modified the route so the flight crew entered the data on a single FMS. His Company procedure is; run the FMS's isolated until any change has been entered and verified by both pilots; then the data is transferred to the second FMS. He is 100% certain that the revised flight plan routing was entered and verified. He is not certain at what point the flight plan reverted to the initial [dispatch service] filed routing but it was detected after TRACON vectors. The Reporter stated that another recent behavior involved the PROG Page displaying incorrect distance to the destination calculations.The Reporter talked to his Chief Pilot and other Company pilots about the Falcon FMS issues and was told that a CE750 was having similar issues. It is his belief that this FMS's functionality has become so complex that previously accepted behavior consistency can no longer be expected.
The downloaded flight plan dropped out of a Falcon 900EX Honeywell NZ-2000 FMS after takeoff even though the crew manually entered a revised flight plan was and verified it after entry at the gate.