Gulfstream G-IV flight crew reported loss of both flight guidance computers on final approach. Reporter stated this is a recurring issue.

ACN 1955247 2022-12 Gulfstream IV / G350 / G450 Multi-Engine Turbojet Aircraft Upsets Incidents

Initial ApproachPart 91

What is ASRS?

The Aviation Safety Reporting System is NASA's voluntary, confidential, non- punitive incident-reporting system, established 1976. Pilots, controllers, dispatchers, and maintenance technicians file reports describing safety- relevant events. NASA de-identifies every report before adding it to the public database. Reports are not investigated by NASA, the FAA, or the NTSB — they represent the reporter's perspective.

Pilot narratives

Verbatim from the de-identified NASA record. First-person account by the reporter. NASA strips identifying details (names, company, specific time); anonymization placeholders are ZZZ, X, Y.

Reporter 1

While on the RNAV (GPS) X Runway XX approach to ZZZ, between waypoints ZZZZZ and ZZZZZ1 and just after completing the before landing check with the aircraft fully configured for landing, we experienced a simultaneous failure of both Flight Guidance Computers (FGCs). Aircraft entered an uncommanded nose-down pitch attitude at which time the "FGC 1-2 FAIL" CAS message appeared along with audible alert. Autopilot, autothrottle, flight director, electric pitch trim and yaw damper all disconnected. PF (Pilot Flying) immediately took control of the airplane and corrected the pitch attitude while remaining on the approach course. We assessed and discussed the situation and decided due to our low altitude and close proximity to the runway that the best course of action was to continue the approach and landing without attempting to troubleshoot the anomalies. PF flew the aircraft while PM (Pilot Monitoring) manipulated the manual trim wheel at the PF's command. Aircraft landed safely without further incident. This was the second simultaneous dual FGC failure in the G-IV fleet (two different aircraft) in the last two weeks. Both failures occurred during the approach phase of flight, and both occurred in cold weather environments (ZZZ1 and ZZZ). Suggest getting Gulfstream and/or Honeywell involved in identifying and remedying the root cause(s) of these failures. The potential for a catastrophic outcome from a similar failure under less optimal weather conditions or with a less experienced crew is rather high.

Reporter 2

On an 8 mile final to Runway XX in ZZZ we experienced a dual flight guidance computer failure while flying the RNAV-GPS X Runway XX. The aircraft experienced an uncommanded pitch down as all automation including auto-throttles disconnected. The pitch trim and yaw dampener also failed. The aircraft was flown manually with no automation, no auto throttles, and manual pitch trim to an uneventful landing using raw data. Please investigate with Gulfstream to fix the problem. Had this occurred in IMC with the slightest distraction the result could have been very different.

NASA classification — Anomalies

Aircraft Equipment Problem
Inflight Event / Encounter

NASA classification — Assessments

Contributing Factors / Situations: Aircraft
Primary Problem: Aircraft

ASRS reports are voluntarily submitted, de-identified by NASA, and represent the reporter's perspective. The presence of reports on a topic cannot be used to infer prevalence in the National Airspace System. The authoritative source is the NASA ASRS Database Online at asrs.arc.nasa.gov ↗.