Date: 201603
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: B767 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb; Takeoff / Launch
Airspace: Class E ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Pressurization System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Troubleshooting
Anomaly: Aircraft Equipment Problem Critical; Aircraft Equipment Problem Less Severe; Flight Deck / Cabin / Aircraft Event Other / Unknown
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; Flight Crew FLC complied w / Automation / Advisory
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: We left this morning on a re-assigned flight. Into takeoff roll both utility buses tripped. I was not going to do a high speed abort for such a small problem per procedure. After takeoff at a safe altitude; we followed QRH procedures; but they wouldn't reset. We decided to continue.Sometime later; after being cleared from 10;000 to 17;000 feet; we had a double auto cabin pressurization failure. Once again we followed the QRH procedures. The only problem is that manual control would not work. After a little trouble shooting we elected to return to [our departure airport]. Thinking that we had lost the cabin; I decided to descend at only 500 feet per minute to minimize the effect on everyone ears. (Good news-the masks did not drop!) In reality the cabin wasn't descending; it was jumping around and uncontrollable; basically frozen where it was; but we didn't discover that until we were on the ground.Then in the descent we got a smoke alarm. Noticed an exhaust fan status message; but there was no procedure for that. Then we decided to [advise ATC of the situation]. After some time; we came around and landed uneventfully and Fire Rescue checked us out with no indication of smoke or fire. We then taxied to the gate.It was at the gate we learned that we were still pressurized. Unable to open windows or doors we turned off the packs to slowly depressurize. I turned the manual knob several times to no avail. Finally; I slammed it in both directions and something finally gave. Heard a hissing noise; we de-pressurized and then were able to open the windows and doors.Smoke alarms stopped and once again; Fire Rescue verified no smoke in the cabin.During this whole event I tried to keep the passengers informed about what was going on; giving somewhere between 5-7 PAs. The flight attendants did an excellent job keeping everyone calm.There was the normal apprehension; and a few passengers did have ear issues; but most took it quite well. Aircraft went out of service and we got another aircraft.After some consultation with maintenance; it appears that we had several totally unrelated problems. The utility bus failure was a total coincidence; not related to our problem. The smoke alarm was explained by the mechanics. As far as the manual control problem; they had no real explanation; but said that were going to change all of the components.




Synopsis: A B767 Captain reported a flight with multiple system failures; the worst one being the pressurization control. Flight returned to departure airport. Aircraft landed pressurized and could not be de-pressurized until parked at the gate.