Duchess 76
Flight Crew Commercial; Flight Crew Flight Instructor
Aircraft Equipment Problem Critical
Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition; General Maintenance Action
Aircraft
As per [procedure]; we had to shut down the engine and restart it in the air. When trying to unfeather the left propeller; blade angle did not move at all so the left propeller did not unfeather. Tried to restart the left engine using the 'without unfeathering accumulator' checklist and the left engine did not move; we cranked the engine 4 times up in the air with no success. Decided to come back to land single engine. We requested priority but did not declare emergency. On the ground we tried to restart the engine with no success; we tried 3 times. On the ramp with the Chief Instructor and a mechanic we tried to figure what the issue was; apparently the accumulator does not have enough pressure to unfeather the propeller; showed about 35 PSI when the aircraft's manual says it should have approximately 300PSI.Airplane went down for the same reason one day before this incident happened. Mechanics should double check that the airplane systems are working properly before putting the airplane back on line. Probably a second opinion of how the squawk was resolved could help to prevent this scenario.
BE-76 instructor pilot reported the left engine did not unfeather following a test flight shutdown.