Date: 201508
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: Dash 8-100
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Cruise
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Turbine Engine
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Flying; First Officer
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Landed in Emergency Condition; Flight Crew Landed As Precaution; Flight Crew Inflight Shutdown; Flight Crew Diverted
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: The crew had just swapped into the plane; and pushed back from [the] gate on time. After single-engine taxi to runway for departure; the #1 engine was started. All indications were normal after the start; and during the take-off roll. During initial climb-out around 300 feet; the CA noticed a brief flicker of the Master Warning Light; but did not catch which warning light triggered the Master Warning. All gauge indications were normal at that time.About 15 minutes into the flight; in cruise flight at 12;000 feet; navigating direct; the crew noticed fluctuation of the #1 engine oil pressure. It fell to the 45-55 range and began intermittently triggering the #1 ENG OIL PRESS warning light and the Master Warning light. The crew referenced the emergency checklist; then conferred with the FA; telling her of the problem and that an engine shut-down was likely. CA then spoke to dispatch and maintenance control. It was decided to divert to ZZZ; company's maintenance base; which was equidistant to the destination at that time (75 nm). After notifying ATC of the need to divert; turning on course to ZZZ; the CA spoke to the FA again; then made an announcement to the passengers (16 on board) about the need to shut down the engine.The crew then followed the engine shut-down procedure; and feathered the #1 engine; per the emergency checklist. At that time the oil pressure was still fluctuating between 45-55 PSI with intermittent flashing of the #1 ENG OIL PRESS warning light. The engine appeared to feather normally; with NP about 250 RPM; but there was a strong vibration felt throughout the plane from the feathered engine. The oil pressure dropped lower with near continuous illumination of the #1 ENG OIL PRESS warning light. The crew then decided to shut-down and secure the engine.The FO was the pilot flying; and continued an admirable job of piloting the plane; single engine; to landing in ZZZ. All appropriate checklist were accomplished and the flight was otherwise comfortable and uneventful to completion at the gate in ZZZ. The crew had asked for emergency vehicles to be standing by at touchdown in ZZZ to look for possible damage; smoke; or leaks. None were observed; nor were any leaks or abnormalities noted by the crew or maintenance at the gate in ZZZ. Maintenance indicated that the engine was very low on oil (about 6 quarts); though the plane had an airworthiness sign-off the day before.Following the incident; the FA elected to go home; and the pilots elected to continue flying. A reserve FA and spare plane were obtained in ZZZ; then all the same passengers boarded and were flown to the original destination. Upon arrival; the crew was praised and thanked by many passengers; and all seemed calm and happy.


Second narrative: [Report narrative contained no additional information].


Synopsis: Dash 8 flight crew reported they shut down the #1 engine in flight because of low oil pressure. Flight diverted to a suitable nearby alternate.