Learjet 45
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Other / Unknown
ATC Issue All Types; Aircraft Equipment Problem Less Severe; Deviation - Altitude Crossing Restriction Not Met; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance
General None Reported / Taken
ATC Equipment / Nav Facility / Buildings; Aircraft
Our flight on the XXth of June 2020 originated in ZZZ1 to ZZZ and terminated on ZZZ2. After departing ZZZ1 to ZZZ we received a message (while at cruse altitude) on our FMS that our number one GPS had failed. We did not notice any abnormalities. When we were within 30 miles of ZZZ; we were given vectors for the LOC-DME E approach to Runway 15. Our clearance from ZZZ to ZZZ3 was the ZZZZZ Departure to ZZZZZ to ZZZZZ1 to ZZZZZ2 and the ZZZZZ3 Arrival into ZZZ2. Once airborne and prior to reaching the waypoint we were given a right turn direct to ZZZZZ1. Prior to reaching ZZZZZ1 we were cleared direct to ZZZZZ3 and instructed to descend per the ZZZZZ3. We were to cross ZZZZZ3 at 15;000 per the STAR. Then after ZZZZZ to cross ZZZZZ4 at between 14;000 and 13;000. Our FMS showed us over ZZZZZ3 and the autopilot started a slight right turn over ZZZZZ3 turning towards ZZZZZ4. At this time we started our decent to cross ZZZZZ4 at 14;000 to 13;000. We were then given vectors to Runway XXL. We questioned the controller; we stated that we were landing at ZZZ3. She said that she assumed we were going to ZZZ4 airport because almost everyone coming over ZZZZZ3 normally landed at ZZZ4. She gave us a new vector for ZZZ3. A second person came on the radio and stated that the controllers were working with new software. After landing at ZZZ3 we were asked to call Approach Control on the land line about a possible altitude deviation. He said that we started our decent prior to ZZZZZ3 and I assured him that our FMS showed us over ZZZZZ3 and the autopilot started a right turn toward ZZZZZ4 and we started our descent. He said that their radar showed us level at 15;000 and we started our decent 9.7 miles prior to ZZZZZ3. If this is true and they observed us starting our decent early. Why wasn't we questioned about starting down prior to ZZZZZ3. We have reported this to our radio shop and they said the failed GPS could be the antenna and it will be inspected and also the lack of proper satellite reception could cause a problem. The FMS will be taken out and bench checked.
Lear 45 pilot reported a possible altitude deviation due to GPS failure.