Date: 202102
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Weather elements / visibility: Turbulence
Light: Daylight
Aircraft: Any Unknown or Unlisted Aircraft Manufacturer
Operator: Corporate
Operating under: Part 135
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: INS / IRS / IRU
Component problem: Malfunctioning
Reporter organization: Corporate
Reporter function: Pilot Flying; Captain
Reporter qualification: Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem; Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: After a 2 hour delay for other related maintenance issue we took off from ZZZ on our way to ZZZ1. Right after take off as we were climbing an AMBER CAS message showed indicating IRS 1-2 COOL FAIL we were climbing to 2;000 ft. then we were cleared to 10;000 ft. we kept on climbing with CAS message still showing AMBER at around 8;000 ft. I instructed SIC to get the QRH as we were still climbing; we reached 10;000 ft. then we were cleared to FL230 as we passed 10;000 ft. we started working on the problem QRH indicated to SHUT DOWN IRSs as we kept on climbing to FL230 I was hoping perhaps the cool air would cool IRS and I wouldn't have to shut them off because if I did I will lose automatization and navegation as we were going thru the QRH the IRS 1 and 2 shut themselves OFF at that point I lost all automatization; AP AT; Yaw Damper; Navigation and DUs 1 and 6 showed a RED ATT (no attitude indicators). At that point We manually shut off the IRS and I went to the display controller and selected IRS3 the RED ATT indicator went away I had my attitude indicator back but not any automatization still no AP AT Yaw damper and Navigation then we were cleared to climb to FL320 at that point I made my mind of not more climbing did not want to get to RVSM space without automatization and I instructed my SIC to call ATC and request return ASAP and PRIORITY; ZZZ2 ATC was very busy it took some time for my SIC to get the request in so I stayed at FL230. After communicating with ATC they asked for our intentions I instructed my SIC return to airport but DIVERT to ZZZ4 (ZZZ4 has a longer runway than ZZZ they are closed to one each other and the winds when we took off were very strong) ATC acknowledged the request and were giving some turns and step descents I don't really remember what headings or what altitudes however I was trying no hand fly the airplane and land safely. It was very bumpy we had severe to moderate turbulence I instructed the Captain to go the cabin and tell passengers we are returning to airport fasten their seat belts she went back there and instructed passengers to do that then she came up front and asked if bracing position was necessary I said no but I want you seat in the back with them and make them feel comfortable she said two little girls were crying but they were OK we also had 2 Dogs on board. We started our descent and turns as per ATC instructions preparing for the visual approach latest winds were 08018G23 during the descent at some level off altitudes it was hard to keep the airplane stable or on assign altitude as it was very bumpy it fell like like the trim was working at half rate and without yaw damper I had to use rudder input also. During all the flight from the take off on I couldn't hear my SIC when she was transmitting to ATC when pushing the push to talk button on the yoke; I could hear ATC but not my SIC... I also instructed Captain to call Operations on SAT PHONE but was not working either. I hand flew that airplane for about 40 minutes almost from takeoff to landing we landed safely and exited the runway on our own; Fire trucks were waiting and asked if we needed assistance we said no; then on the ground ATC gave my SIC a phone number for me to call. I also spoke to NAME County fire and rescue they wanted a statement from me as well as my name; I called ZZZ3 ATC on NUMBER they also wanted a statement of the failure and I said we had the NAV computers overheat and the shut off we lost all automatization but I was able to control the airplane however it was very bumpy at some times....they asked for my name; my pilot certificate number; address phone number and said they will write an incident report and I should do the same. After landing I spoke to passengers I explained to them in a way that they could understand why we came back and why we choose ZZZ4 they were fine with it and just wanted a recovery flight. Captain fed them on the plane while I went to FBO I talked to chief pilot I spoke to Operations and Maintenance and I called Center as requested. I came back to plane and right at that time a recovery GV landed we helped the passengers to transfer to other plane and transfer their luggage. After they left SIC and I did a radio check on the ground checked all the buttons in the right position and they were still could not hear her were she pushed the push to talk button not in VHF1 or VHF2. We secured the airplane added some oil helped the Captain with the cleaning and got to our hotel almost 3 hours after we landed.




Synopsis: Captain reported diverting after losing cooling to both Inertial Reference Systems; which caused the failure of numerous systems.