Citation II/SP (C551)
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Flight Instructor; Flight Crew Instrument
Flight Crew Last 90 Days 150; Flight Crew Total 10000; Flight Crew Type 500
Confusion; Distraction; Human-Machine Interface; Situational Awareness; Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued Advisory / Alert; Aircraft Equipment Problem Dissipated; Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Aircraft
While en route; approximately 440 nautical miles to the southwest of our destination; our GPS appeared to provide erroneous information. While the GPS unit itself displayed an accurate position; the information relayed to the HSI and multifunction display was ultimately erroneous in terms of what information the flight crew received. Ultimately we were queried by Center controllers that we were proceeding 30 degrees off course. At that point we checked our GPS against the on-board VOR's and confirmed that we were proceeding off course. At that point we reset the GPS after which it appeared to function properly. We continued to monitor it against the VOR receivers with no further errors being detected.
A C550 developed a 30 degree track error apparently caused by a faulty GPS which was reset and resulted in normal route tracking.