Date: 201702
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Light: Daylight
Aircraft: Dash 8-200
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Initial Climb
Aircraft component: Gear Extend/Retract Mechanism
Component problem: Improperly Operated
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Overcame Equipment Problem; Flight Crew Returned To Departure Airport; Flight Crew Landed As Precaution; General Maintenance Action
Contributing factors: Aircraft; Human Factors
Primary problem: Human Factors

Narrative: All operations for preflight and boarding were normal. After starting the Number 2 engine; a ramp agent made hand gestures towards the crew that were interpreted as a signal to shut down the Number 2 engine. The crew preformed the start abort procedure followed by the start abort checklist. After the engine was secured I signaled the FA (Flight Attendant) to open the main cabin door and I opened the flight deck access door and exited the aircraft to speak with the ramp agent. The ramp agent said 'the nose gear was spewing hydraulic fluid and started smoking.' I decided to deplane the passengers and call dispatch/maintenance. I informed them of the situation and made an appropriate entry into the logbook. As a crew we left the airplane and proceeded to the crew room. We stayed in the crew room until we were informed that the aircraft had been fixed.We proceeded to restart our procedures for preparing the aircraft for departure. We started with the originating checklist and continued with normal flight operations. All operations were normal until climb out. After takeoff 'positive rate; gear up' was called The FO (First Officer) placed the gear selector switch in the up position. Upon doing this we noticed a gear unsafe indication on the landing gear annunciator lights. I called for the Gear Unsafe Indication checklist. I engaged the autopilot; informed ATC of the situation; and requested vectors for a return. The FO preformed the checklist while I flew and spoke to ATC. I also made a call to the FA to verify that the gear was in fact not retracted. The FA confirmed this. As we proceeded to accomplish the checklist; it directed us to ensure the Alt Landing Gear Extension door was closed. As we checked this item we made the realization that it was not closed. We then closed the door in accordance with the checklist and the gear immediately retracted. We continued the checklist to conclusion.It was our thought that maintenance had opened the door and left it open while servicing the hydraulic system. We also derived that the reason the gear did not retract as normal was due to the designed operation of this door being open. We decided that the safest course of action would be to return and have maintenance confirm that this was in case the reason for the gear unsafe indication and that there were no other hydraulic/gear issues. We returned and landed with no other abnormal indications or issues. It is my opinion that the crew performed admirably and decisively in dealing with this situation.Our SOPs direct the Flight Deck Pre-flight Inspection checklist be accomplished when accepting the airplane from another crew or for the first flight of the day.  Returning to the aircraft after a lengthy delay and/or a lengthy maintenance procedure should be added to this list.




Synopsis: The Captain of a DHC-8 reported that during climb they were unable to retract the nose gear.