Gulfstream V / G500 / G550
Flight Crew Air Transport Pilot (ATP)
Troubleshooting; Human-Machine Interface
Aircraft Equipment Problem Critical
Flight Crew Diverted
Aircraft
During enroute climb; eight minutes after takeoff passing FL220 while hand flying; we received an amber CAS 'FGC 1 FAIL'. System 'auto' switched to FGC 2. While I (pilot flying) continued to trim for climb; PIC (pilot not flying; in right seat) pulled QRH and requested a level off at FL270 & slowed to 250kts with ATC. Within a few seconds of trimming thru trim switch; CAS 'FGC 2 FAIL' illuminated. Manually switched back to FGC 1 thru Sensor panel and noticed that electric trimming moved trim wheel very slowly and immediately CAS 'FGC 1 FAIL' re-illuminated...auto switching back to FGC 2 and selecting electric trim off. Attempted to reset electric trim but unable and started using manual trim wheel. It was noticed that the manual trim was extremely difficult to operate and had spring back when moved. Referring to QRH it lead us to recovering FGC; however would require us to pull CBs that would fail; FMS; auto throttles; FGC; bus controller and Eng instruments. We felt that the FGC FAILING may be due to trim being hard to move from possible water frozen on cables (plane sat overnight in rain on ramp) or possible trim cable off a pulley and did not want to aggravate a plane we could control manually.We contacted the chief pilot on duty of issue and for divert suggestions. It was decided to divert to a suitable airport and after getting ATC clearance; proceeded there and landed without further issues hand flying using manual trim.[Although the] preflight trim check and control check; completed prior to flight; did not reveal any issue; I would continue to do these [while] noting if any binding is accruing in trim wheel. However; checking these on ground without any air loads is not the same as we experienced in flight. During this event we worked with ATC informing them of our progress and complied with all routing and clearances issued.
A GLF5 flight crew experienced seriously compromised pitch trim capability during climb through FL220; ultimately generating FGC 1 and then 2 FAIL CAS messages which alternately went away when they switched between them. They diverted to a nearby airport utilizing manual pitch trim; the use of which also required excessive effort. The reporter speculated that a cable off its pulley or ice on a cable restricting passage may have been the culprit.