Regional Jet 900 (CRJ900)
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Troubleshooting
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Requested ATC Assistance / Clarification; General Flight Cancelled / Delayed; General Maintenance Action
Aircraft
On date; Aircraft X; while descending on the ZZZZZ3 arrival to ZZZ with both engines power set at about 70% we noticed the engine one oil temperature increasing to about 160 degrees C.  Captain was the pilot flying and first officer was the pilot monitoring. I took the radio from the PM and called for the QRH. We reduced the power to idle and we noticed the temperature slowly getting back into the green arc. Then while still at idle the temperature started to rise again; but this time at a faster rate and as it reached 205 degrees C and in accordance with the QRH we proceeded with an engine shut down procedure of engine number one.We discontinued the approach; requested priority handling; and requested  vectors towards ZZZ2; where the longer runways are more suitable for a single engine; flaps 20; approach.After running our single engine procedures we got cleared for the ILS X at ZZZ2; where we landed without further problems.The emergency vehicles where precautionary positioned by the RWY; and once cleared of the RWY they conducted a visual inspection of the aircraft.No visual damages were noticed so we continued to the gate and disembarked all the passengers.
Captain reported engine #1 over temperature on descent and elected to perform an in flight shut down of the affected engine. The Captain requested priority handling and was vectored to a new approach and a precautionary landing.