Regional Jet 900 (CRJ900)
Flight Crew Air Transport Pilot (ATP)
Training / Qualification; Time Pressure; Confusion
Aircraft Equipment Problem Critical
Flight Crew FLC complied w / Automation / Advisory; Flight Crew Took Evasive Action; General Declared Emergency; General Maintenance Action
Aircraft; Chart Or Publication
While enroute approximately 50 miles north east of our departure airport at approximately 17;000 FT; we received a left bleed duct warning. I immediately displayed the ECS synoptic page while the First Officer pulled out the Pilot Operating Manual Abnormal Checklist. We were about to try and change the bleed source due to a MEL L DUCT MON and the right bleed closed; leaving us in an unpressurized aircraft. We then donned our masks as a precautionary; declared an emergency and requested a descent to 10;000 FT. While the First Officer accomplished the checklists I requested direct to the airport. Once at 10;000 FT; we removed our masks and proceeded unpressurized. Flight attendants and passengers were briefed of the situation when we had time and continued uneventful to a landing to our departure airport. After arrival at the gate passengers were sent to the gate next to us with a plane ready. I stayed and filled out the maintenance log and talked to; Dispatch; Maintenance; Tower; and Approach. I then went to the other aircraft and departed about 30 minutes later.Possible memory item for a quick switch of bleed source; although I am not really in favor of flipping switches without following a checklist.
A CRJ-900 CAS alerted L BLEED DUCT with the L DUCT MON MEL'ed and simultaneously the right bleed closed. So with a depressurizing aircraft an emergency was declared; a descent commenced and at 10;000 FT the flight returned to their departure airport.