Date: 202101
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Gulfstream IV / G350 / G450
Operator: Corporate
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Aircraft component: Air Conditioning and Pressurization Pack
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew; Person Flight Attendant
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Aircraft Equipment Problem Dissipated; Flight Crew Diverted; Flight Crew Landed in Emergency Condition; Flight Crew Overcame Equipment Problem; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: On [Date]; an in-flight [problem] occurred regarding a Gulfstream GIV-SP. The details are as follows:On [Date]; [Aircraft X] was on a FAA Part 135 flight from ZZZZ to ZZZ1. There were a total of XX occupants on board of which included 3 crew members. The Pilot Flying (PF) was [Name]; the Pilot Monitoring (PM) was [Name]; and the third crew member; [Name]; was the Cabin Server (CS).The aircraft departed ZZZZ at approximately XA:00 on an IFR flight plan. The aircraft climbed uneventfully to an initial altitude of FL430. After about 20 minutes at altitude; a passenger came to the flight deck and asked if we could cool down the cabin. The PM set the cabin temperature controller to a cooler temperature. After about 5 minutes; the R COOL TURBINE HOT CAS message displayed. The crew performed the appropriate checklist and after a minute the message went out.At this point; the cabin was at a higher temperature than before and the passengers complained again. The PF decided to go back into the cabin to verify that all the gasper vents were open and to check if there were any other indications of potential issues. It was apparent that there was a significant temperature difference from the forward portion of the cabin compared to the aft. The forward cabin was at least 10 degrees warmer than the aft. Additionally; the PF noticed some warm air coming out of the vents. After checking the upper cabin gasper vents; the PF returned to his seat. After a short discussion on possible issues; the crew elected to descend to FL390.When the aircraft leveled at FL390; the CS came up to the flight deck and asked the PF if he noticed any haze in the cabin. The PF looked back and saw no smoke or haze. The CS went about her duties.After a few more minutes; the PF noticed smoke coming from the PM's vent and the crew received another R COOL TURBINE HOT CAS message. The PF immediately donned his O2 mask and requested to the PM that we ask for an immediate descent and to pull out the checklist. At this time; the cabin started to fill up with visible smoke and the Cabin Server came up to the flight deck to respond. The Cabin Server donned her O2 mask. After O2 masks were on; the appropriate checklists were performed. The cabin started to depressurize immediately after the right pack was turned off (as required by the R COOL TURBINE HOT checklist). At this point; a rapid descent was performed and [ATC was advised]. During the descent; smoke remained in the cabin. Due to the smoke in the cabin and loss of pressurization; the crew elected for vectors to the nearest suitable airport ZZZ2. While the aircraft was descending; the passenger O2 masks deployed and the CS instructed the passenger to put their O2 masks on. At about 15;000 ft.; the smoke started to dissipate. The crew continued their descent to 6;000 ft. and accepted vectors to the ILS XXR at ZZZ2. At this time; the cabin was completely free from smoke. The crew took off their O2 masks and completed all remainder checklists for landing. At XB:00 the aircraft landed uneventfully.On the landing roll out Fire and Rescue was approved on the runway to follow the aircraft to its parking spot. After shutting down the engines; the crew assessed the situation and verified that all passengers were OK and that no one was injured. At this point; the PM notified the airport that the crew and passengers will need to clear customs. After the crew and passengers were cleared from customs; the airplane was written up for multiple system failures including an abnormal cabin depressurization; the left pack unable to provide appropriate cabin pressurization under the above conditions; a malfunction within the right air cycle machine; and the aft [lavatory] O2 mask failing to deploy.




Synopsis: Gulfstream-IV Captain reported a fumes event during cruise resulting in a diversion.