Golden Eagle 421
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Flight Crew Last 90 Days 33; Flight Crew Total 1765; Flight Crew Type 25
Human-Machine Interface
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 Returned To Clearance
ATC Equipment / Nav Facility / Buildings; Aircraft; Human Factors
I was given direct to MLB and selected that on my Garmin 530 and then selected NAV on the autopilot. After about 5 mins; I noticed I was right of course and getting worse. I then selected back on course and used HDG mode to keep it back on course. I was called by ATC and asked what happened and I explained to controller and his supervisor. He said they had another incident just before mine with an airliner going opposite direction and he was off course in the opposite direction and so they seemed to think there was an abnormality with the GPS system going on. Within a few miles I was able to place the autopilot back in the NAV mode and it tracked fine with no problems.
After being cleared direct to MLB; a C421 pilot discovers that the autopilot has not maintained the direct course as selected on the Garmin 530 and turns to intercept course. ATC takes note and states that an airliner had been off course in the opposite direction moments before.