Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Communication Breakdown; Troubleshooting
Aircraft Equipment Problem Critical
Air Traffic Control Provided Assistance; Flight Crew Took Evasive Action; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
During cruise check PM noticed an Abnormal Cabin Pressurization indication at 16;000 feet based on Cabin Altitude versus differential pressure chart; MEL BOOK (Section X; Page X). At the moment Cabin Altitude was indicating 4;400 feet; Cabin Rate 700; Delta P 7.1 crew observed for about 1 minute and noticed that cabin altitude continued to rise up to 5;900 feet. Captain immediately requested lower (10;000 feet) and informed ATC about the situation. At 10;000 feet the cabin altitude remained steady 5;500 feet and Cabin Rate indicated 0. Crew followed QRH procedure (PRESSURIZATION AUTO SYSTEM FAILURE/CABIN DEPRESSURIZATION/CABIN RATE ABNORMAL FLUCTUATIONS). ACARS was INOP. Captain contacted Dispatcher through AIRINC notified about the issue. Crew and Dispatcher agreed to stay at 10;000 feet. Crew had terrain mode selected all time for situational awareness. Also; FA was notified about the problem.  The entire flight we were VMC. Crew landed in ZZZ. At the gate Captain wrote up the problem; and contacted Maintenance.
EMB-145 First Officer reported cabin altitude was uncontrollable and the flight crew elected to request an immediate descent. The flight continued to destination airport at a reduced altitude.