CV 580
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Instructor
Flight Crew Last 90 Days 90; Flight Crew Total 5640; Flight Crew Type 300
Aircraft Equipment Problem Critical
Flight Crew Landed in Emergency Condition; Flight Crew Inflight Shutdown; General Declared Emergency
Aircraft
At FL220 we were given descent to 13;000 while on the STAR to destination. PF reduced power for descent and we began descent. During descent we noticed the #2 engine propeller RPM drop to 1200 RPM. (Normal RPM in flight is 1350 RPM). PF increased power to see if any change; no change in prop RPM. We proceeded to perform the Propeller Under Speed abnormal procedure checklist outlined in our aircraft procedures POH. After performing procedure the RPM increased to 1220 RPM which was still below normal operating RPM. We notice oil pressure on reduction gear box for #2 engine dropped to 150 PSI which is bottom of normal operating range and the power section oil pressure had dropped to bottom of normal operating range also. Per the Propeller Under Speed checklist if the RPM remained below 1340 after performing the initial procedures; then the emergency engine shutdown handle for the engine had to be pulled and the engine shutdown. We followed the procedure and shutdown the #2 engine. As the PNF; I informed Approach; as we were on frequency with them; and declared the emergency. We were given clearance direct to destination and landed without incident. We contacted our company maintenance; reported the issue and made the required maintenance logbook write up. Since the propeller RPM is controlled by a governor that keeps the RPM on speed during all flight phases and not by the flight crew; it was assumed that a possible issue with the prop governor caused the issue when the power throttle was reduced during the initial descent.
CV580 had low propeller RPM after descent was initiated. After checklist procedures were accomplished RPM remained low. The engine was shut down.