First officer reported altitude deviation following loss of cabin pressure.

Attributes
ACN	1675005
Time
Date	201908
Local Time Of Day	0601-1200
Place
Locale Reference	TEB.Airport
State Reference	NJ
Environment
Light	Daylight
Aircraft 1
Make Model Name	Citation II S2/Bravo (C550)
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	Vectors
Flight Plan	IFR
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor Flight Crew Instrument
Experience	Flight Crew Last 90 Days 35 Flight Crew Total 4200 Flight Crew Type 15
Events
Anomaly	Aircraft Equipment Problem Critical Aircraft Equipment Problem Less Severe Deviation - Altitude Crossing Restriction Not Met Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance

Narrative:

Approximately 25 minutes before the altitude deviation occurred; the aircraft suffered loss of cabin altitude from FL330. After completing all checklist and memory items the trip continues normally. Upon reaching teb airspace the crew was still a bit overwhelmed from the events that had previously occurred. Approach gave us a heading and a descent down to 2;000 ft. The aircraft was turned to the proper heading yet the altitude did not properly capture allowing the aircraft to continue decent down to 1500 ft. Before it was fought by the crew. Whilst this decent was occurring the cure was making final adjustments for the aircraft to be set up to cross dandy intersection at 1;500 ft. And it was made apparent that the co-pilot's side HSI had become inoperative. When the altitude deviation was caught by the crew; immediate corrective actions were taken yet approach issued an altitude warning. Contributing factors included crew fatigue from just completing a rapid decent due to loss of cabin pressure. During the course of this action judgment was affected because the crew was still excited from the previous events that transpired.

Original NASA ASRS Text

Title: First Officer reported altitude deviation following loss of cabin pressure.

Narrative: Approximately 25 minutes before the altitude deviation occurred; the aircraft suffered loss of cabin altitude from FL330. After completing all checklist and memory items the trip continues normally. Upon reaching TEB airspace the crew was still a bit overwhelmed from the events that had previously occurred. Approach gave us a heading and a descent down to 2;000 ft. The aircraft was turned to the proper heading yet the altitude did not properly capture allowing the aircraft to continue decent down to 1500 ft. before it was fought by the crew. Whilst this decent was occurring the cure was making final adjustments for the aircraft to be set up to cross DANDY intersection at 1;500 ft. and it was made apparent that the Co-Pilot's side HSI had become inoperative. When the altitude deviation was caught by the crew; immediate corrective actions were taken yet approach issued an altitude warning. Contributing factors included crew fatigue from just completing a rapid decent due to loss of cabin pressure. During the course of this action judgment was affected because the crew was still excited from the previous events that transpired.

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.