GLF4 captain experiences slow loss of cabin pressurization at FL430. An emergency descent is initiat...

Attributes
ACN	1183698
Time
Date	201406
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Gulfstream IV / G350 / G450
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Pressurization System
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

An hour and a half into the flight at FL430 we noticed the cabin was ascending and the pressure differential was dropping. We tried to stop the ascent by following the QRH procedure with no success. A few minutes later the 'cabin press low' message illuminated on the cas system. At this point we donned our oxygen masks; declared an emergency; dropped the masks in the cabin and initiated an emergency descent procedure and diverted. At approximately 10;000 feet MSL we cancelled the emergency and made an uneventful landing. Upon further investigation there was no indication of bleed air pressure from the left engine and left bleed air circuit breaker and 28V cabin press circuit breaker's had popped.

Original NASA ASRS Text

Title: GLF4 Captain experiences slow loss of cabin pressurization at FL430. An emergency descent is initiated and the flight diverts to a suitable airport. On post flight it was discovered that the L Bleed air CB and 28V Cabin press CB's had tripped.

Narrative: An hour and a half into the flight at FL430 we noticed the cabin was ascending and the pressure differential was dropping. We tried to stop the ascent by following the QRH procedure with no success. A few minutes later the 'Cabin Press Low' message illuminated on the CAS system. At this point we donned our oxygen masks; declared an emergency; dropped the masks in the cabin and initiated an emergency descent procedure and diverted. At approximately 10;000 feet MSL we cancelled the emergency and made an uneventful landing. Upon further investigation there was no indication of bleed air pressure from the L Engine and L Bleed air CB and 28V cabin press CB's had popped.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

GLF4 captain experiences slow loss of cabin pressurization at FL430. An emergency descent is initiated and the flight diverts to a suitable airport. On post flight it was discovered that the left bleed air circuit breaker and 28V cabin press circuit breaker's had tripped.