Date: 202008
Local time of day: 0601-1200
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Commercial Fixed Wing
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Air Conditioning and Pressurization Pack
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural MEL / CDL; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Aircraft Aircraft Damaged; Flight Crew Regained Aircraft Control; Flight Crew Took Evasive Action; Flight Crew Landed in Emergency Condition; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft; MEL; Procedure
Primary problem: Aircraft

Narrative: When on the ground in ZZZ; I noticed the right pack had been blowing hot air and was uncontrollable in both automatic and manual modes. I made an entry into the maintenance log and called maintenance control to defer the right pack. Once we were en-route we proceeded with the MEL procedures for operating on a single pack. Everything went normal and we proceeded up to our cruise altitude of FL240. When we were at cruise for a little bit of time we noticed that there was an interruption in airflow. We looked up and the L pack switchlight was illuminated OFF and under the ECS synoptic page it was showing the right pack had turned off as well. I then tried to press out the switch and repress it in to see if it would come back. It did not. At this point we realized the cabin was depressurizing and we needed to start a decent. We told ATC and they told us to descend and maintain 17;000. We started down at a rapid rate but the cabin altitude was still climbing constantly at 700 feet per minute. I then pulled out the QRH thinking we had the aircraft under control just having to descend. I proceeded with the abnormal X-XX (unpressurized fight Packs off procedure). The first thing I read was airplane altitude...not above 10;000 ft or lowest safe altitude which ever is higher. This meant to me to get the airplane down to 10;000 ft which we were going to request from ATC but they had us go down to 17;000 ft temporarily. Then I proceeded with the QRH procedure which lead us to press the EMER DEPRESS button. At this point we knew we'd be depressurizing the cabin and deploying the oxygen masks however by the time I had reached this step we had already received the Cabin Alt caution message and were about to get the Cabin Alt warning message.The aircraft was close to 17;000 ft and the cabin altitude had reached approximately 9;500 ft when I decided to follow the QRH procedure and press the EMER DEPRESS. This; of course; depressurized the cabin and blew the passenger oxygen masks. We then proceeded to descend to 10;000 ft and stay there. ATC had let us know they had requested priority handling for us and we were heading to ZZZ1. I called the flight attendant and I had given her [preparation briefing] since we were now a priority aircraft as a precaution. Once we were at 10;000 ft for a while I decided that the passengers and flight attendant could remove their masks and let them know of the situation. I told them we had a malfunction with our only operating pack which led to depressurization which is why the masks had fallen but that we were at a safe altitude and had everything under control. I told ATC that we were at a safe altitude and could cancel our priority handling as long as we still head into to ZZZ1 but they decided to keep our priority status as a precaution. We continued to ZZZ1 normally and ran all our normal checklists. We then started an approach which led to a normal landing and taxied off the runway where we taxied to the gate with emergency vehicles following us as a precaution. Everything else went normal.[Cause was] Equipment malfunction while operating on a single pack.Avoid dispatching with a single pack at higher altitudes or at all with passengers onboard.




Synopsis: Captain reported a pack failure at altitude that resulted in loss of cabin pressure followed by a diversion.