Hawker 900 flight crew experiences a loss of cabin pressurization at FL410 and declares an emergency...

Attributes
ACN	1194345
Time
Date	201408
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Light	Night
Aircraft 1
Make Model Name	HS 125 Series
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Component
Aircraft Component	Pressurization Control System
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Inflight Event / Encounter Weather / Turbulence

Narrative:

We were on a ferry permit to ZZZ1 at FL410. We were deviating around convective weather and were IMC at night in moderate to heavy rain; and light to moderate turbulence. Sic noticed that the cabin altitude needle showed cabin altitude rising rapidly. He suggested we request a lower altitude to try to arrest the cabin altitude. ATC assigned us FL390. As I started the descent sic said we should put O2 masks on; which we did. A few seconds later the cabin altitude and master warning alarms activated. We initiated an emergency descent. I handled the flying duties while my sic ran the appropriate checklists and dealt with ATC. Once we reached 12;000 MSL we removed our O2 masks and started looking for a suitable airport. We determined that ZZZ was the best option. We began an RNAV approach; but broke out and landed visually. There was no tower or ATC at this airport at the time we landed. Post flight inspection did not indicate any cause for the depressurization.

Original NASA ASRS Text

Title: Hawker 900 flight crew experiences a loss of cabin pressurization at FL410 and declares an emergency before descending to 12;000 FT. The crew elects to divert to a suitable alternate.

Narrative: We were on a ferry permit to ZZZ1 at FL410. We were deviating around convective weather and were IMC at night in moderate to heavy rain; and light to moderate turbulence. SIC noticed that the cabin altitude needle showed cabin altitude rising rapidly. He suggested we request a lower altitude to try to arrest the cabin altitude. ATC assigned us FL390. As I started the descent SIC said we should put O2 masks on; which we did. A few seconds later the CABIN ALT and Master Warning alarms activated. We initiated an emergency descent. I handled the flying duties while my SIC ran the appropriate checklists and dealt with ATC. Once we reached 12;000 MSL we removed our O2 masks and started looking for a suitable airport. We determined that ZZZ was the best option. We began an RNAV approach; but broke out and landed visually. There was no tower or ATC at this airport at the time we landed. Post flight inspection did not indicate any cause for the depressurization.

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.

Hawker 900 flight crew experiences a loss of cabin pressurization at FL410 and declares an emergency before descending to 12;000 ft. The crew elects to divert to a suitable alternate.