G-iv flight crew reported diverting to a nearby alternate after a malfunctioning cargo door seal led...

Attributes
ACN	1336883
Time
Date	201602
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
Route In Use	Vectors
Flight Plan	IFR
Component
Aircraft Component	Cargo Door
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 120 Flight Crew Total 5500 Flight Crew Type 1100
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Commercial Flight Crew Flight Instructor Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 90 Flight Crew Total 6400 Flight Crew Type 180
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

The first officer was the pilot flying. Prior to climbing through FL410 the first officer donned his oxygen mask and was using supplemental oxygen. Approximately 20 minutes after departure at FL450 we received a cabin pressure low message on the crew alerting system. The captain immediately donned his oxygen mask and started using supplemental oxygen and then took over the flight controls from the first officer. We confirmed the validity of the message by looking at the increasingly high cabin altitude on the cabin pressure controller and initiated a rapid emergency descent with engines at idle thrust and speed brakes deployed while monitoring for other aircraft visually and on TCAS.we [advised ATC] and requested a diversion to [a nearby alternate]. We completed the checklist and QRH items. We landed without further incident.aircraft maintenance discovered that the baggage door seal would not fully inflate; and led to cabin pressure loss.

Original NASA ASRS Text

Title: G-IV flight crew reported diverting to a nearby alternate after a malfunctioning cargo door seal led to a loss of cabin pressure.

Narrative: The First Officer was the pilot flying. Prior to climbing through FL410 the First Officer donned his oxygen mask and was using supplemental oxygen. Approximately 20 minutes after departure at FL450 we received a CABIN PRESSURE LOW message on the crew alerting system. The Captain immediately donned his oxygen mask and started using supplemental oxygen and then took over the flight controls from the First Officer. We confirmed the validity of the message by looking at the increasingly high Cabin Altitude on the CABIN PRESSURE CONTROLLER and initiated a rapid emergency descent with engines at idle thrust and speed brakes deployed while monitoring for other aircraft visually and on TCAS.We [advised ATC] and requested a diversion to [a nearby alternate]. We completed the checklist and QRH items. We landed without further incident.Aircraft Maintenance discovered that the baggage door seal would not fully inflate; and led to cabin pressure loss.

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.

G-iv flight crew reported diverting to a nearby alternate after a malfunctioning cargo door seal led to a loss of cabin pressure.