Gulfstream G280
Flight Crew Air Transport Pilot (ATP)
Troubleshooting
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Track / Heading All Types
Flight Crew Became Reoriented; Flight Crew FLC Overrode Automation
Aircraft
We took off normally; it was a cold; clear morning. We were assigned 3;000 feet and heading 060 after takeoff. At 2;000 feet in the turn; the PF turned on the autopilot. Upon reaching 3;000 feet; the autopilot decreased pitch and the autothrottles came back to maintain 200 knots and 3;000 feet. At the same time; we received further climb to 5;000 feet. During the radio exchange; the aircraft continued to decrease pitch without increasing power and started to descend. Around 2;950 feet; the PF disconnected both autopilot and autothrottles to prevent the autopilot from descending further. By the time the PF was able to return the aircraft to a pitch and power setting that would allow the aircraft to climb; we were down to approximately 2;700 feet. Around 3;500 feet; we reengaged the autopilot and autothrottles and both functioned as intended. We continued our climb to 5;000 as instructed with no remark from ATC.On the subsequent flight; we departed runway heading; with a turn to 230. After takeoff; I set the heading to 230 and turned on the autopilot; and the aircraft immediately started rolling to the right. The PF disconnected the autopilot and turned the aircraft in the correct direction. After reengaging the autopilot; it functioned as intended again.On both flights; the autopilot was programmed correctly beyond a shadow of a doubt.
On the following leg; on takeoff we were cleared to 4000 initially with a 40 degree left turn. HDG; FLCH with alt armed was selected. In attempt to recreate the initial event I turned on the autopilot at 2000. The aircraft immediately began an incorrect right turn; when HDG was selected and clearly targeting 40 degrees left. I selected the SYNC (TCS) button to interrupt the turn immediately. When I let go of the SYNC (TCS) button the aircraft continued its right turn. I disconnected the autopilot and autothrottles and turned left as directed. We only ended up about 5 degrees right; but it was a noticeable uncommanded turn contrary to the flight director's commands. Altitude mode was flown and continued correctly. The flight continued as normal after the Autopilot was selected on again.
G280 flight crew reported autopilot anomalies on two flights. Reporters mentioned the autopilot was set correctly in both situations; but the aircraft did not react appropriately.