Date: 201204
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: B717 (Formerly MD-95)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Airspace: Class C ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Cargo Door
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Distraction; Situational Awareness; Training / Qualification; Troubleshooting
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; General Maintenance Action
Contributing factors: Aircraft; Procedure
Primary problem: Procedure

Narrative: I arrived at the aircraft and began the cockpit safety inspection and applied ground power after reviewing the aircraft logbook. I noticed one MEL that was for the Standby Avionics Cooling Fan INOP and circuit breaker collared. I proceeded outside and did a normal walk-around finding no defects. Boarding was normal and un-rushed. The Captain and I completed all the checklists; pushed back and taxied for departure after 2 successful engine starts. We lined up on the runway and I assumed the controls as pilot flying. We were cleared for takeoff and I applied takeoff power and executed a normal takeoff. Just after takeoff I noticed my ear pressure equalization was unusual and within a matter of minutes we got a CABIN RATE alert on the EAD. We both noticed that the cabin was climbing at roughly the same rate as the aircraft. The Captain said we may have a problem with pressurization and gave me the aircraft and radio control. The Captain attempted switching pressurization controllers to no effect and then tried manual pressurization and could not control the cabin altitude. He then stated we need to level off below 10;000 FT so we amended our clearance with ATC and informed them of pressurization problems. After the Captain tried trouble shooting the pressurization and not getting an adequate response from the system he decided to return to the departure airport. We got an amended clearance from ATC and returned to the departure airport for a visual approach. During the descent we remained in manual pressurization with the outflow valve full open and I executed a slow descent to ease pressure issues for the passengers. During the descent we received a CABIN INFLOW LO alert momentarily then quickly went out. We made a normal landing and returned to the gate. As the Captain conferred with Maintenance I went outside to inspect the outflow valve and noticed nothing unusual. I then went to the aft cargo door suspecting a door had not been closed even though we never had an indication of a door open. I noticed that the aft cargo door was latched but the door was slightly twisted in the frame allowing the forward part of the door to latch but the aft portion had a large gap. I believe this was our problem and upon testing the outflow valve and pressurizing the aircraft found that everything worked fine once the aft cargo door had been sealed properly. One of the ground crew observed the door ajar as I did and was the one who reseated the door properly. Training the ground crew to recognize a properly seated and locked cargo door would prevent future errors.




Synopsis: A B717 Aft Cargo Door was partially closed ajar so that the Door Warning System indicated proper closure but after takeoff the aircraft would not pressurized. The crew returned to the departure airport where door was discovered.