Gulfstream IV / G350 / G450
Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 92; Flight Crew Total 4500; Flight Crew Type 1000
Time Pressure; Situational Awareness; Workload
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Flight Crew Landed in Emergency Condition; Flight Crew Inflight Shutdown; Flight Crew Returned To Departure Airport; General Declared Emergency
Aircraft; Chart Or Publication; Procedure
Preflight was normal.  Completed cockpit checks. There was a Blue CAS L ENG Maint 150. We looked it up in the QRH. The QRH stated; 'Dispatch permitted with this message active.' I believe we discussed doing an engine shut down and restart/reboot; but decided to depart with the message active and complete an aircraft shutdown at our destination. We departed shortly. The takeoff and initial climb was normal. Approximately 2 to 3 minutes into flight passing through 5;000 to 6;000 FT I heard a muffled thump. We experienced an aircraft yaw to the left at the same time. The Copilot stated we lost the left engine. We declared an emergency and started to level off and return to the airport. We decided no to try an engine restart as we were so close to the departure airport. We ran the appropriate checklist and we returned to the airport.
A G450 engine auto shutdown after takeoff for unknown reasons but a Blue CAS message L ENG MAINT 150 was displayed during preflight which the QRH stated was a dispatchable item.