Date: 202106
Location: ZZZ.ARTCC, US
Aircraft: A320
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
ATC / advisory: Center ZZZ
Aircraft component: Air Cycle Machine
Component problem: Malfunctioning; Failed
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Human factors: Troubleshooting; Time Pressure
Second reporter function: First Officer; Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical
Detector: Automation Aircraft Other Automation
When detected: In-flight
Result: Air Traffic Control Issued New Clearance; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; Flight Crew Diverted
Contributing factors: MEL; Aircraft
Primary problem: Aircraft

Narrative: Aircraft was dispatched with an inoperative Pack #2 due to a regulator fault and [the flight] was in full compliance with the MEL at departure. Flight was completely full in the cabin. Due to Pack #2 being inoperative it was difficult to cool the main cabin temp using only Pack #1. Using only Pack #1 at FL370 we were able to maintain 72 degrees in the cabin using max cold and high flow. Approximately 200 nm west of ZZZ at FL370 we received an ECAM AIR PACK 1+2 FAULT. ATC was notified and [priority handling was requested]. Upon checking the pressurization and bleed air page; it appeared that Pack #1 was overheating showing an output temperature in amber yet we never received a Pack 1 OVHT ECAM. The cabin altitude was still under control. A descent to 10;000 ft. was initiated without exceeding the cabin altitude before we complied with the ECAM to turn off Pack #1 leaving us unpressurized. Contact was made with Dispatch and Maintenance Control to discuss the situation resulting in a diversion to ZZZ.


Second narrative: Approximately 240 nm from ZZZ; at a cruise altitude of FL350 and while in communication with Center; an ECAM aural and Master Caution sounded for AIR PACK 1+2 FAULT. The CA (Captain) said he noted a momentary amber overheat temp in Pack 1; but it did not trigger the PACK 1 OVHT caution. I (Pilot Monitoring) did not see this indication that had subsequently returned to a green inlet temperature. Pack 2 was previously secured and turned off per the MEL deferral on our 2nd release. Pack 1 showed a fault light. The AIR PACK 1+2 FAULT ECAM directed us to secure Pack 1; descend to 10;000 ft. MSL or MEA and then turn on the RAM Air when the pressure differential was less than 1.0. Even though Pack 1 had a fault light in the overhead panel; it appeared to be partially functioning; the cabin pressure holding and the cabin altimeter only increasing at a very slight rate. A flight crew decision was made to begin an immediate normal descent to 10;000 ft. without the use of oxygen while closely monitoring the pressurization page to ascertain the true nature of the Pack 1 malfunction. The CA directed me to assume pilot flying duties and ATC responsibilities while he coordinated with Operations; Dispatch; flight attendants and the passengers. We began a coordinated 1500-2000 fpm rate of descent via two ATC-assigned step down altitudes of FL300 and FL200 before ultimately reaching 10;000 ft. The aircraft was lowered in a steady continual descent with no pauses which I believe helped our situation. Cabin pressure held steady around 8;000 ft. during the normal descent. Upon reaching 10;000 ft.; Pack 1 was secured; differential pressure reached less than 1.0; RAM AIR was selected on and the cabin altimeter climbed from approximately 8;000 to 10;000 ft. as expected. We completed all remaining ECAM items until the screens were normal. The rate of fuel burn at 10;000 ft. MSL made reaching our initial destination of ZZZ1 impossible; and it was decided that ZZZ was a suitable diversion while 200nm away and with 11;600 pounds of fuel aboard along with the best Maintenance; aircraft and passenger accommodation options. We informed ATC; Dispatch; Operations; and proceeded accordingly. We switched to the next Center and the Captain [requested priority handling] and returned to the pilot flying role while we coordinated an uneventful arrival via the ZZZZZ to Visual XX approach at ZZZ and ultimately parking at gate XY. We were then met by the ZZZ Chief Pilot at the gate and proceeded to fill out a risk mitigation form following the event. We then accepted a new aircraft and release at gate XZ and ultimately brought the same passengers to ZZZ1 two hours later than originally planned.In totality; I felt the event was handled safely and professionally. The CRM skills taught and utilized allowed both the CA and First Officer to properly divide duties while ensuring sufficient cross checks and communication. At no time did I feel rushed or stressed. I believe the deliberate delay in securing the faulty Pack 1 that appeared to be functioning along with the continual scanning of the pressurization page allowed us to avoid an unnecessary priority descent; use of pilot oxygen; or the deployment of passenger oxygen that might have accompanied a rapid depressurization. All in all; I felt the CA was composed and handled the event in line with Company desires. While I regret the delay the passengers experienced; I believe we handled the event in a safe and caring manner.


Synopsis: Air Carrier Pilot Crew reported departing with one air cycle machine inoperative and during cruise flight the other air cycle machine indicated a fault condition necessitating a diversion.