Gulfstream V / G500 / G550
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 90; Flight Crew Total 15500; Flight Crew Type 1200
Troubleshooting; Workload; Confusion; Distraction
Aircraft Equipment Problem Less Severe; Deviation - Altitude Excursion From Assigned Altitude
Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
Our flight was normal and uneventful checklists were accomplished and cruising at FL450 we experienced a Cabin Pressure Low CAS message followed by an EDM (Emergency Descent Maneuver). Unaware just what we had we followed checklist procedures and kept the aircraft under control. ATC was notified of our deviation but apparently the mic switch on the right side stuck open because no further transmissions were getting to us. My Captain was monitoring the cabin altitude as well as the conditions in the aircraft and when we realized the pressurization system was controlling and the cabin altitude stabilized to 8700 ft we disengaged the autopilot and leveled out at FL330. The CAS message was out so reengagement of the autopilot was successful. After regaining ATC contact the controller must have heard our report leaving FL450 he asked our intentions and we informed him all systems were regained and to fly direct to a flight plan fix and complete the flight to the destination. After careful research we concluded that [the high arrival airport] elevation which the FMS should have recognized and made corrections to the pressure controller did not and the trip point of 7500 ft which is the low trip was reached and did not reset to the next point up which is 10000 ft. This caused the Automatic Descent Mode to activate. Our recognition and response to this situation was appropriate the passengers were briefed after the flight that an anomaly had occurred and we would investigate it further.
Gulfstream V First Officer reported a cabin pressurization anomaly that prompted an Emergency Descent Maneuver.