Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 60; Flight Crew Total 7850; Flight Crew Type 2900
Aircraft Equipment Problem Critical
General Declared Emergency
Aircraft
While in cruise; the cabin altitude began climbing at an uncontrollable rate. The 'Emergency Descent' checklist appeared on the Crew Alert System. We donned our masks; advised ATC and followed the 'Emergency Descent' checklist. The cabin regained pressurization and we leveled off at FL240. The QRH led us to check the bleed air pressures from both engines. We noted that the left bleed air valve had shut off. We completed the 'Bleed Air System Failure' checklist. Normal flight was then continued to our destination.
A G-IV flight crew initiated and emergency descent when the cabin altitude began to climb uncontrollably. Upon stabilizing the cabin while maintaining FL240 they determined the cause to be the left engine pneumatic bleed valve that had shut off.