Human-Machine Interface
Aircraft Equipment Problem Critical
Flight Crew Diverted; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Inflight Shutdown
Aircraft
First flight of day for crew on a day trip. On time departure. Twenty-five minutes into flight at FL250. After pushing MCT button and adjusting cruise power. 2 minutes later speed was still a little fast so I adjusted power again and noticed that the Number 2 Oil PSI gauge was fluctuating rapidly. It was going high into the yellow and low into the yellow. I advised the Captain and we watched the gauge while checking for other abnormal indications. We decided to call Maintenance Control and get their opinion. While talking to Maintenance the pressure started to fluctuate lower now dipping down into red; and causing the Master Warning to illuminate intermittently and the PTU was turning on and off. We decided to divert. While descending through about FL240 the Master Warning was now illuminated continuously and the PSI was fluctuating but trending lower. We discussed shutting the engine down per the checklist that we had in hand but decided not to think it was an indication problem only. The oil temperature did not increase at all; all other engine indications showed normal. The divert airport was VFR and we got approval for a visual approach. On downwind to base we got our first indication that it was more than an indication problem. The Number 2 RPM was fluctuating. It came back to 1020 and then on base to final it was variable again. We landed and shut down the Number 2 engine once clear of the runway. We taxied to the gate and deplaned normal. We thought it was just an indication problem and should have been more cautious and shut down the engine per the checklist.
A Q400 oil pressure began fluctuating in cruise so the crew diverted assuming an indication issue because other indications were stable. However; they shut the engine down on landing because of RPM fluctuations.