Date: 201212
Local time of day: 1201-1800
Location: ZZZ.ARTCC, US
Flight conditions: VMC
Light: Daylight
Aircraft: Q400
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Pressurization System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Communication Breakdown; Confusion; Time Pressure; Troubleshooting; Workload; Distraction
Anomaly: Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Flight Crew Took Evasive Action; Flight Crew Returned To Departure Airport; Flight Crew FLC complied w / Automation / Advisory; General Maintenance Action
Contributing factors: Procedure; Aircraft
Primary problem: Aircraft

Narrative: On takeoff; we immediately noticed that the aircraft was not pressurizing. As a result of that and multiple ATC calls pointing out traffic and weather below acceleration height; I got distracted and missed the callout for acceleration height. As a result; we never raised the flaps on departure; and when we caught the error we saw 195 KIAS with a Flap 10 setting. I immediately raised the flaps; then ran the 'after takeoff checklist' and the 'failure to pressurize' checklist. On takeoff and throughout the initial climb; the cabin was climbing at the same rate as the aircraft; with associated ear pain. Upon reaching the step in the checklist of 'Bleeds MAX'; the cabin rate trend reversed and we began to pressurize; as noted by a negative rate trend and a decreasing cabin pressure. At this point; the Captain contacted Maintenance Control to discuss the pressure issue as well as the flap overspeed. Since our destination was a major maintenance base; we wanted to ensure ample discussion was had prior to getting too far into our route. Maintenance Control told us to continue as the mechanics there could deal with both issues. As we continued the climb ATC had us level at 15;000 feet for a few minutes; then assigned FL230. During this second climb as we passed 18;500 feet we got the 'Cabin Press Warning' and we noted the cabin at 9;800 feet. At this point we donned our masks and initiated an immediate descent with ATC. At the same time; the Captain made the command decision to return to the departure airport and we started heading in that direction. As I ran the checklist for the second time; the pressurization did not respond at all: at 10;000 feet the cabin indicated 8;500 feet or so; then as we descended the cabin matched the aircraft altitude. It should be noted that the cabin pressure never got above 9;800 feet so the pressurization was working to a degree - but not enough to continue flight above 10;000 feet -  unrealistic considering our destination. As we descended to our departure airport; the Captain and I discussed the possibility of an overweight landing; a question he then put to Maintenance Control. Maintenance Control told him to go ahead and land overweight; and to keep the vertical speed at touchdown to a minimum. Neither one of us  realized it at the time; but apparently an overweight landing was to be conducted only in an emergency; and we had not declared one. The Captain and I discussed the possibility of holding for a few minutes and burn off the 500 LBS we needed to reach our max landing weight of 62;000 lbs; but the captain stated that Maintenance Control wanted us to 'just go ahead and land.' We touched down gently at a weight of 62;500 LBS at a  rate of less than 100 FPM. The flight concluded without incident. Note - during our preflight review of the logbook we noted that two days prior the aircraft had similar pressurization failure at 23;000 feet. The actions after that event consisted of replacing the aft outflow valve; and two other work orders that were non-descriptive. We also had performed a thorough preflight; and noted no  abnormal (non-MEL) open circuit breakers. Finally; after the flight; the Captain and I remained on the aircraft and gave a very detailed report of the events to the maintenance personnel that arrived. The issues in the event were: pressurization failure; functionality returned then a subsequent additional failure. Task saturation; confusing instructions at a critical phase of flight. My failure to prioritize tasking. Lack of a flap configuration/speed warning system. Instructions from Maintenance Control that may not have been in line with SOP. Confusing SOP - the requirement about an overweight landing is not intuitive to the flight crew when we might need that information.




Synopsis: A Q400 pressurization malfunctioned during climb after takeoff and then failed climbing through FL185 so the crew descended and returned to the departure airport. While addressing this issue after takeoff the flaps remained at 10 were until 195 KTS.