Date: 201503
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Daylight
Aircraft: SF 340B
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent
Airspace: Class B ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Propeller Assembly
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; Captain
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness
Anomaly: Aircraft Equipment Problem Less Severe; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: Pre-flight
Result: General Maintenance Action
Contributing factors: Aircraft; Procedure
Primary problem: Aircraft

Narrative: After landing; the captain conducted a post-flight of the aircraft. On the post flight he noticed that there was oil leaking on the #2 engine below the oil cooler and was sprayed over the main landing gear strut and door. Captain brought the attention of the matter to the first officer who also confirmed it was an oil leak. Maintenance control was contacted and the aircraft was written up to be inspected for the oil leak. The contract maintenance came out looked at the plane. He could not find any leak. He serviced the #2 engine propeller gear box (PGB). Captain ran the engine per the maintenance instruction. The maintenance personnel confirmed that oil was leaking however after engine shutdown could not locate where the leak was coming from. He contacted maintenance control and told them about the situation. The maintenance personnel advised the captain that maintenance control had told him that a maintenance crew had changed seal on the oil cooler and it could be the residual oil that was left over from over servicing either the engine oil or prop oil. Maintenance personnel waited to see if the oil would return to the PGB viewing window. After about 10 minutes the oil that was serviced into the PGB never returned to the viewing window. He again contacted maintenance control and they advised him to service the engine oil and prop oil. Once these were serviced we ran the engine again and the maintenance personnel could not locate any leak. He signed off the logbook describing the oil leak as over servicing from previous station and that maintenance control had said that was the probable cause. Dispatcher contacted the captain; and gave him a new valid time for the flight. Dispatcher also told the captain that maintenance control had reviewed the sign off from contract maintenance and the aircraft was released back to service. On the flight all the engine gauges were within limits and no discrepancy was noted. This could've been due to the nature of the flight time between these two airports being about 10 minutes. Once again on the post flight there was oil on the gear door and struts. The crew reviewed the sign off from previous leg as the oil leak from over servicing of oil and departed without any trouble. During the descent phase of the flight the crew noticed that the #2 engine prop oil pressure was fluctuating between 50-100 psi. We reviewed the QRH just in case we needed to secure the engine which was not needed. The crew also contacted approach and advised them of the problem and requested priority handling to the runway. Engine and prop gauge were monitored through rest of the flight. Captain called in-range and requested maintenance meet the aircraft at the gate. On final approach crew noticed the #2 engine prop oil pressure was at 50 psi. The landing and exiting the runway was uneventful. Once parked at the gate; captain wrote up the discrepancy noticed in-flight. Upon talking with maintenance they said the prop oil gearbox oil was at the bottom of the viewing window and that since it was serviced recently the oil level should not have dropped this low for 2 legs. Captain notified the maintenance control of the write up.I think the suggestion I would give from events like this recurring is that maintenance control request photos or videos that can be texted or emailed to get a full understanding of the problem. I believe that maintenance control did not grasp the whole event and what contract maintenance personnel explained to them on the phone. This could've turned into an in-flight engine shutdown. Also they need to review the maintenance work that had been performed previously and not tell contract maintenance that such and such is normal for this aircraft. This could've also put the contract maintenance license in jeopardy for signing off an aircraft based on what maintenance control told them.




Synopsis: SF340B Captain reports discovering an oil leak during post flight at an out station. Contract Maintenance is called and after consultation with Maintenance Control; agree that the oil is residual oil from an oil cooler repair. After a short leg; the leak still seems to be present but the maintenance sign off in the logbook still seems to be germane so the crew departs. Enroute; low propeller oil pressure is noted but the flight is able to land without shutting down the engine.