Date: 201212
Local time of day: 1801-2400
Location: ZZZ.Airport, US
Light: Night
Aircraft: Dash 8-300
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Takeoff / Launch
Airspace: Class B ZZZ
ATC / advisory: Tower ZZZ
Aircraft component: Hydraulic Main System
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Workload; Training / Qualification; Troubleshooting; Situational Awareness
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Returned To Departure Airport; Flight Crew FLC complied w / Automation / Advisory; General Declared Emergency; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: During the turn prior to departure; I noticed the Number 2 hydraulic quantity was low and contacted Maintenance for servicing. Once complete; the flight boarded and prepared for departure. During start up; crew observed that the Number 2 Engine hydraulic pressure took longer than normal to register proper pressure. Pressure eventually came up while the crew was evaluating the situation and all indications were normal thereafter. I contacted Maintenance for guidance. The Controller stated that he instructed the Maintenance Crew to thoroughly examine for leaks and stated that they found none and if all indications were normal that there should be no anticipated irregularities. The First Officer had not observed any leaks during his walk around. There were several other aircraft lined up for departure so I estimated that we would have ample time to monitor for any changes during that time. Due to a runway change; taxiing eventually consumed 30 minutes; during which time the crew closely monitored the hydraulic system. At no point during the taxi was there any abnormal indication on the hydraulic system; the crew felt confident that the system was functioning properly and elected to depart. When landing gear was selected up; gear fully retracted; however the left and nose gear doors remained extended. The Number 2 ENG HYD PUMP caution; LEFT DOOR & NOSE DOOR annunciators were illuminated and Number 2 Hydraulic pressure was below normal. I do not recall exactly what the pressure was; but I do not believe it was zero. I immediately restricted airspeed to 140 knots to prevent damage to the gear doors. Crew declared an emergency with ATC and our return to the departure airport. We requested vectors to contact company and run the appropriate checklists. FO contacted company and advised of the situation and our return to ZZZ. Reception was spotty at the low altitude however Dispatch received the message. Crew advised the Flight Attendant with the Emergency Return Report and began running the emergency checklists. The checklist ultimately directed us to an alternate gear extension. Once all this was accomplished the flight was vectored back and landed on Runway 29 due to the strong winds out of the northwest. Landing was normal and flight cleared the runway at intersection U. Once on the ground; all hydraulic indications were normal. We advised Ramp Control and operation that we would need to be towed to the gate. Operations advised that the tow teams were not authorized to enter the taxiways. Since the gate was a short distance straight ahead of the airplane I called maintenance for clearance to taxi the rest of the way to the gate; which the Controller approved. Once on the ramp the flight shutdown and was towed to the gate.




Synopsis: A DHC-8-300 hydraulic system malfunctioned after takeoff allowing the landing gear to retract but not the left main and nose gear doors so an emergency was declared and the flight returned to the departure airport. All hydraulic indications were normal after landing.