Flight Crew Air Transport Pilot (ATP)
Flight Crew Total 8200
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew Landed in Emergency Condition
Aircraft
I was performing an Operational Evaluation and after reaching our initial cruise altitude; we received a HYD 3 LO QTY EICAS message. My First Officer (FO) was flying and I read the QRH. I noted the time and quantity of System 3; it was 18%. I alerted maintenance via ACARS. Approximately 10 minutes later; it was 16%. I alerted Dispatch via ACARS Free Text. Approximately another 10 minutes later; it was now down to 14%. I sourced weather for diversion airports along our route and advised dispatch that a divert might be necessary if we have a leak. Losing one of three hydraulic system completely would reduce Flight Control functionality and redundancy. Approximately another 10 minutes later it was now down to 12%. Approximately another 10 minutes later it was now down to 10%. My FO and I agreed that an immediate divert and an Overweight Landing was necessary before we lost Hydraulic System 3 completely. I alerted Dispatch that a divert was necessary and suggested ZZZ. The dispatcher agreed. I [alerted] the Cabin Crew; advised ATC and the passengers. We performed the Emergency Landing Checklist and the Overweight Landing Checklist. I landed normally in ZZZ and Airport Rescue and Fire Fighting gave us the all clear to taxi to the gate. Overweight Landing vertical speed tolerances were not exceeded on landing. Appropriate write-ups in the AML were made. System 3 was determined to have a leak by Maintenance Personnel.
ERJ190 Captain reported a low hydraulic system quantity and successful divert. Captain reported post maintenance inspection determined system had a leak.