Narrative:

On a multi-engine training flight (during which I was the student) the left engine (#1) was failed intentionally; and secured as per procedure set forth by the manufacturer. Upon beginning restart procedure; it was observed that the unfeathering accumulator was inoperable; and that it alone would not restart the engine. An air start was attempted and the engine would not start. Being south of ZZZ as the closest airport; we declared an emergency and landed ZZZ on 1 engine. ZZZ1 had an emergency vehicle on-site. After landing and securing the airplane; we attempted a restart of the inoperable engine and it did start. After a trip to maintenance and a successful run-up; we returned to ZZZ with both engines operable. There were no injuries; and we 'waived off' the emergency shortly after landing ZZZ and getting the other engine running. Maintenance believes the issue to be worn main bearings letting oil pressure escape through the crank and bearings rather than being properly directed from the accumulator directly to the propeller hub. The accumulator tested fine; with full pressure as per the manufacturer's specification. The engine would not restart in the air; due most likely to the large amounts of drag associated with attempting to start an engine with a fully feathered propeller. It did start successfully on the ground; and did operate properly afterward. Another engine shutdown the next day showed the same problem to be occurring; but this time the shutdown was accomplished in the pattern at ZZZ with ATC advised. There was no emergency declared during that flight. Callback conversation with reporter revealed the following information: reporter stated these engines have two-bladed propellers with variable pitch propeller and hydraulic governor. This aircraft has after market accumulators. Most be-95 travelairs do not have propeller unfeathering assist accumulators. They are replacing all rayjay flex hoses (4) each per engine due to an airworthiness directive that just recently terminated; requiring all rayjay flex hoses be replaced within five years. These hoses also connect to the unfeathering accumulator. The fall back procedure to unfeather a propeller with an inoperative accumulator system is to add extra fuel mixture and use starter in flight to 'quick' start the engine and get oil pressure up to unfeather the propeller.

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Original NASA ASRS Text

Title: A BE95 ACFT DECLARED EMER AND RETURNED TO DEP ARPT WHEN #1 ENG FAILED TO UNFEATHER FOR AIR START DURING MULTI-ENGINE TRAINING. UNFEATHERING ACCUMULATOR SUSPECT.

Narrative: ON A MULTI-ENG TRAINING FLT (DURING WHICH I WAS THE STUDENT) THE L ENG (#1) WAS FAILED INTENTIONALLY; AND SECURED AS PER PROC SET FORTH BY THE MANUFACTURER. UPON BEGINNING RESTART PROC; IT WAS OBSERVED THAT THE UNFEATHERING ACCUMULATOR WAS INOPERABLE; AND THAT IT ALONE WOULD NOT RESTART THE ENG. AN AIR START WAS ATTEMPTED AND THE ENG WOULD NOT START. BEING SOUTH OF ZZZ AS THE CLOSEST ARPT; WE DECLARED AN EMER AND LANDED ZZZ ON 1 ENG. ZZZ1 HAD AN EMER VEHICLE ON-SITE. AFTER LNDG AND SECURING THE AIRPLANE; WE ATTEMPTED A RESTART OF THE INOPERABLE ENG AND IT DID START. AFTER A TRIP TO MAINT AND A SUCCESSFUL RUN-UP; WE RETURNED TO ZZZ WITH BOTH ENGS OPERABLE. THERE WERE NO INJURIES; AND WE 'WAIVED OFF' THE EMER SHORTLY AFTER LNDG ZZZ AND GETTING THE OTHER ENG RUNNING. MAINT BELIEVES THE ISSUE TO BE WORN MAIN BEARINGS LETTING OIL PRESSURE ESCAPE THROUGH THE CRANK AND BEARINGS RATHER THAN BEING PROPERLY DIRECTED FROM THE ACCUMULATOR DIRECTLY TO THE PROP HUB. THE ACCUMULATOR TESTED FINE; WITH FULL PRESSURE AS PER THE MANUFACTURER'S SPEC. THE ENG WOULD NOT RESTART IN THE AIR; DUE MOST LIKELY TO THE LARGE AMOUNTS OF DRAG ASSOCIATED WITH ATTEMPTING TO START AN ENG WITH A FULLY FEATHERED PROP. IT DID START SUCCESSFULLY ON THE GND; AND DID OPERATE PROPERLY AFTERWARD. ANOTHER ENG SHUTDOWN THE NEXT DAY SHOWED THE SAME PROB TO BE OCCURRING; BUT THIS TIME THE SHUTDOWN WAS ACCOMPLISHED IN THE PATTERN AT ZZZ WITH ATC ADVISED. THERE WAS NO EMER DECLARED DURING THAT FLT. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THESE ENGINES HAVE TWO-BLADED PROPS WITH VARIABLE PITCH PROP AND HYD GOVERNOR. THIS ACFT HAS AFTER MARKET ACCUMULATORS. MOST BE-95 TRAVELAIRS DO NOT HAVE PROP UNFEATHERING ASSIST ACCUMULATORS. THEY ARE REPLACING ALL RAYJAY FLEX HOSES (4) EACH PER ENGINE DUE TO AN AIRWORTHINESS DIRECTIVE THAT JUST RECENTLY TERMINATED; REQUIRING ALL RAYJAY FLEX HOSES BE REPLACED WITHIN FIVE YEARS. THESE HOSES ALSO CONNECT TO THE UNFEATHERING ACCUMULATOR. THE FALL BACK PROCEDURE TO UNFEATHER A PROP WITH AN INOP ACCUMULATOR SYS IS TO ADD EXTRA FUEL MIXTURE AND USE STARTER IN FLIGHT TO 'QUICK' START THE ENGINE AND GET OIL PRESSURE UP TO UNFEATHER THE PROP.

Data retrieved from NASA's ASRS site as of January 2009 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.