Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Confusion; Distraction; Situational Awareness; Workload
Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter CFTT / CFIT; Inflight Event / Encounter Unstabilized Approach
Flight Crew Became Reoriented; Flight Crew FLC complied w / Automation / Advisory
Aircraft; Human Factors
On the ILS for 28R in ZZZ; as we intercepted the localizer and were establishing on the glideslope soon after; we had FGC (Flight Guidance Computer) 1 FAIL; FGC 2 FAIL; Yaw Damp disconnect; Electric Trim Disconnect; Autopilot Disconnect; Auto Throttle Disconnect. All this while we were descending caused us to shoot below the glideslope and apparently trigger a ground proximity warning at Approach. We immediately corrected and climbed as ATC told us to; we were in VMC and had all terrain in sight. No GPWS (Ground Proximity Warning System) alerts occurred. We did not do much troubleshooting as we had the field in sight and were on approach; quick glance to see if the any circuit breakers were popped. Upon landing; we were told [Approach] wanted to have us call them; I did immediately after clearing customs and deplaning passengers. I told them we had equipment issues as we were intercepting; they took notes and I advised I'd file an [ASRS Report]. I also called both the Chief Pilot and Director of Safety to let them know what happened. Maintenance was informed of the write-up and MEL.We could have arrested the descent to make sure everything was ok; the momentary confusion of what exactly was happening probably caused us to dip too low. I'm not sure what else we could have done in the situation; we did not declare an emergency or get into detail with ATC of what was going on as we were on the approach and our attention was needed elsewhere. Maybe a quick declaration of the emergency would have helped?
G-IV Captain reported having multiple equipment issues on approach causing the aircraft to veer below the glideslope resulting in a terrain warning from ATC.