Date: 201704
Local time of day: 1201-1800
Location: ZOA.ARTCC, CA
Flight conditions: VMC
Light: Daylight
Aircraft: Citationjet (C525/C526) - CJ I / II / III / IV
Operator: Corporate
Operating under: Part 91
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZOA
ATC / advisory: Center ZOA
Aircraft component: Pressurization System
Component problem: Malfunctioning
Reporter organization: Corporate
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Flying; Captain
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: The situation occurred approximately 20 miles East of CABAB intersection at an altitude of FL430. Oakland Center advised us to cross CABAB at FL360; we programmed the FMS and enabled VNAV to assist our descent to make the crossing restriction. As we arrived at our Top of Descent point; V-Path captured and the aircraft pitched down to descend. The Pilot Flying decreased power to ensure the aircraft did not accelerate in the descent. Moments after setting power for the descent I physically felt a rapid change in cabin pressurization so I immediately directed my attention to the cabin pressurization controller and indicator to see a cabin climb rate over 5000 feet and increasing; I then cross referenced with the cabin altitude/differential indicator to see differential rapidly descending and cabin altitude rapidly climbing. I then immediately turned to grab my quick donning mask and applied it directly over my headset. When I returned my focus forward I noticed that the Cabin Alt Warning annunciation sounded and visually appeared in the annunciator panel. I immediately switched the microphone switch to mask; advised ATC of our status and explained we had lost cabin pressurization and were commencing a rapid descent. The pilot flying with mask donned commenced the memory items of the rapid descent checklist as we followed ATC's heading and altitude guidance in our initial descent altitude of 17000 feet and nearly 90 degree heading change. As we continued to descend to our initial altitude after we were on assigned heading; I completed the rapid descent checklist. In reference to the checklist I monitored the cabin altitude indicator and verified that it never exceeded 15000 feet. Multiple times in the descent I directed my attention to the passenger to ensure that he had donned his mask and was alert throughout the descent. Upon reaching 17000 feet and leveling off the cabin began to partially re-pressurize. We were then allowed to adjust to a more westerly course and allowed to descend further to 10000 feet. At this time we assessed the condition of our passenger to ensure he was alright and the aircraft showed no physical signs of damage. After ensuring the passengers safety and the aircrafts condition we elected to continue to [destination] as we had already prepared for the airport and the threatening conditions had been mitigated. Another alternate  was discussed as it was roughly twenty miles behind us; however at an altitude of 10;000 feet and that short of a distance we felt compelled to continue to [destination] as we were already familiar with it and prepared for it; and the aircraft and passenger were in good condition to continue. We felt this was the safest plan of action given the circumstances and condition of the passenger and aircraft were suitable to continue that is what we did.  We maintained 10000 feet much of the way to [destination] and the cabin pressurization system actually re-established normal cabin pressure and descended the cabin to near field elevation just like it normally does (at ten thousand feet the differential indicator maintained a roughly 11 o'clock position; and the cabin altitude was slowly descending to near field elevation) The rest of the flight continued without incident as the aircraft systems; performance; and handling were all otherwise normal. After a normal approach and landing we exited the aircraft and completed a thorough post flight examination and found nothing abnormal. There were no injuries of the crew or the single passenger aboard the aircraft during the situation.


Second narrative: [Report narrative contained no additional information.]


Synopsis: C525 flight crew reported a loss of pressurization and rapid descent. Pressurization was reestablished at 10;000 feet and continued to a landing at the original destination.