Phenom 300 flight crew reported the Garmin 3000 system malfunctioned and caused various settings to change erratically. Communication with ATC was difficult and the transponder code would also randomly change. The flight crew diverted to an alternate airport. On the ground; the same conditions reoccurred when the flight crew was applying power to the aircraft.
Synopsis
Phenom 300 flight crew reported the Garmin 3000 system malfunctioned and caused various settings to change erratically. Communication with ATC was difficult and the transponder code would also randomly change. The flight crew diverted to an alternate airport. On the ground; the same conditions reoccurred when the flight crew was applying power to the aircraft.
Narrative
On our planned ferry flight from ZZZ1 to ZZZ2 to deliver the airplane to a pre-purchase inspection; we were climbing through 40;000 ft. in IMC when we heard the autopilot disconnect aural warning. When we checked the PFD (Primary Flight Display) it showed the autopilot engaged but then it disconnected again with the aural and visual warnings going off. At this point we were being handed off from ZZZ1 Center to ZZZ Center and I pressed and held the autopilot quick disconnect button to prevent the autopilot from reengaging and began to hand-fly. I briefly continued the climb as our last clearance was to climb to 43;000 ft. when all of a sudden the Garmin 3000 went haywire. It seemed as though any setting or mode that could be changed by the pilot was being changed randomly; as if someone was pushing every button at the same time.Due to the baro setting being changed randomly; our altitude became unreliable so I initiated a descent and a turn back to the east; away from the weather and towards known VMC conditions; and the pilot not flying [requested priority handling] with ZZZ Center. The GTCs (Garmin) that contain the radio controls began to behave erratically and the radios began swapping between emergency mode and our previously input frequency so at that point we became concerned our transponder was also not reporting properly so we squawked XXXX. I then continued the descent and turn eastbound while the pilot not flying continued to attempt to contact ZZZ Center. We broke out of the cloud layer at about 20;000 ft. and I initiated a turn towards ZZZ as I could see the ground in that direction. Passing through about 17;000 ft. the radios began to stabilize and contact was regained with ZZZ Center; signaling the beginning of the total stabilization of the G3000 system.I continued to hand-fly as I did not want to risk engaging the autopilot and having another issue and we squawked normal and were handed off to ZZZ Approach for a safe landing on Runway XXR. We taxied in with no assistance and shut down normally. After shutdown; plugged in a ground power unit to perform a central maintenance computer download to send to Maintenance and after about 15 minutes on ground power; the same symptoms occurred and lasted for roughly twenty minutes. The aircraft will remain on the ground in ZZZ until maintenance personnel can travel to and inspect the airplane.
Second reporter narrative
Flight was a planned reposition from ZZZ1 to ZZZ2 to a maintenance facility for pre-buy inspection. Crew consisted of 2 Phenom 300 pilots; both single pilot typed; with significant experience in type. I was the pilot not flying for this flight as insurance had mandated a 2-pilot; typed; and current crew. We arrived at ZZZ1 to begin preflight prep. We re-evaluated weather and discussed an appropriate flight plan before filing and planning to depart. We completed preflight actions and taxied to Runway XX for a VFR departure to the west. We picked up our IFR clearance shortly after takeoff and were initially cleared to 23;000 ft. and on course as filed over ZZZ. We were eventually cleared to our filed altitude of 43;000 ft. Conditions in the climb were VMC until above 12;000 ft. and then solid IMC in fairly smooth air until nearing 39;000 ft. where we began to intermittently break out on top. As ZZZ1 Center was handing us off to ZZZ [Center] while we were in between ZZZ and ZZZ3; the autopilot disconnected and re-engaged multiple times in a short time span. We also noticed multiple changes rapidly occur on the avionics displays and settings. As we checked in with ZZZ Center; we informed them of the avionics issues and our decision to turn back to ZZZ and made the decision to [request priority handling]. Due to the unreliability of our avionics; questionable navigation capability; and the pilot flying having to hand-fly and continuously hold the quick disconnect button to prevent the autopilot from re-engaging in an unknown state; I requested headings and a descent towards VMC conditions. At this point; every setting that could possible be changed; i.e.; altimeter setting; altimeter units; nav source; radio frequencies; autopilot modes; yaw damper engagement; and pitch trim movement; were all in question. The best way to describe it afterwards was it was like someone was pushing every soft key on the Garmin G3000 displays repeatedly. The baro setting repeatedly cycled through all units it can be set to and at a couple of points the altimeters displayed meters.During all this; communications with ATC and internally between the pilots was very difficult. The radios would switch frequencies uncommanded; switch to an emergency mode; and turn to maximum volume randomly. We would have intermittent contact with ATC and other aircraft over XXX.X during our initial turns and descent. As transponder code would also randomly change; we were extremely concerned as to whether our transponder was actually providing an accurate position. The AHRS held pretty stable and when comparing PFD (Primary Flight Display) 1; PFD 2; and standby source airspeed; we never felt there was a question of if it was correct. We were initially turned north and given a descent to FL270 and then a further descent to FL200 as ZZZ turned us east. Nearing 20;000 ft. we noticed that we were VMC and could see ZZZ and began a turn towards the airport. We were cleared further descent to 13;000 ft. and switched over to ZZZ Approach. Once we were around 17;000 ft.; the conditions began to subside and happen at a much less frequent rate. Radio communications became stable and we were able to continue descent and be vectored for a visual approach to Runway XXR. The pilot flying continued to hand-fly the aircraft and I directed checklists to complete all normal actions; including approach brief and computation of landing data leading up to our approach and landing.We landed after a total duration of 0.7 hours and taxied into the FBO with no further assistance required. Prior to leaving the aircraft; we contacted our maintenance facility and conducted some troubleshooting and avionics downloads. Approximately 15 minutes after applying power to the aircraft; we noticed the same conditions we observed inflight re-occur on the ground. The autopilot would engage un-commanded; in random modes; change nav sources; and at times would not disengage via the quick disconnect button or autopilot button on the control panel. It would run the pitch trim to the nose up and down limits unless interrupted with the quick disconnect switch. We also observed the altimeter units and barometric unit settings rapidly change on their own and the radios enter emergency mode as we had seen inflight. The aircraft is currently grounded until further maintenance investigation takes place.
NASA callback
Reporter stated the anomaly was determined to be spurious signals emitted by the Garmin Primary Flight Display #2. Reporter further stated this was a known issue and has happened in the past.
Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.