Date: 201807
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: VMC
Aircraft: Duchess 76
Operator: FBO
Operating under: Part 91
Mission: Test Flight / Demonstration
Flight phase: Cruise
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Propeller Pitch Change Mechanism
Component problem: Failed
Reporter organization: FBO
Reporter function: Single Pilot
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Commercial
Human factors: Communication Breakdown; Workload
Anomaly: Aircraft Equipment Problem Critical
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Overcame Equipment Problem
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: I was conducting a scheduled test flight for a Duchess Be-76. I performed my preflight actions. The reason for this test flight was that a problem had occurred with the accumulator and governor in the right engine. I was tasked with climbing to altitude shutting down the engine testing the ability of the engine to re-start. I departed the airspace and climbed to 5;500 feet. I remained nearby the airport approximately 5 nm southwest of the field. After conduct of pre-maneuver checklist and clearing turns I proceeded to shut down the right engine. On engine shut down I went through the usual procedure feathered the propeller and isolated the engine.After a period of a few minutes I then began the process of re-starting the engine; by use of the unfeathering accumulator; this did not work. The right propeller moved [less than] a turn. I began troubleshooting by exercising the propeller level and engaging the starter to 'kick start' that is create some momentum on the propeller to re-start the engine. This did not rectify the situation so I proceeded with the next course of action. I shut all on my avionics began to crank start the engine; I pitched up and achieve an airspeed of approximately 70 knots. This also failed to rectify the situation I tried this 4 four times in the space 5 to 10 minutes. During this time I noticed I was now experiencing a loss of oil pressure in my still operating engine (left engine). The throttles and the propeller lever were both in the full forward position. While both sets of levers were in the full forward position the propeller RPM gauge would only indicted a reading of approximately 1;400-1;600 and the oil pressure was reading lower than the lowest posted value on the gauge. I believe the gauge may have been failing because when I exercised the throttle lever I could hear and feel the change in power condition; a yawing force and minor change of heading.Due to this change in situation I elected to return to the airport immediately. I turn my avionics back on and intended to communicate my intentions to the Tower. It was at this time my audio panel had failed and I was unable to use the onboard radios. Fortunately I had brought a handheld VHF radio with me on the test flight and communicated my intentions to Tower. I did not squawk 7700 I was pre-occupied bringing the aircraft back to the runway. Moreover I missed several radio calls due to the fact I needed to fly the aircraft rather than monitor the handheld and I could not monitor the frequency through my headset.Once I was establish on approximately a 4 nm final (I made my approach above the glide path) I moved the landing gear switch to the down and locked position. I was in the process of checking that the landing gear was down and locked I looked and the landing gear lights to see that I did not have 3 solid greens. I instead had three flashing greens and no red lights. I recycled my landing gear and then performed the emergency gear extension procedure to mitigate the risk. I communicated the condition of my landing to the Tower and sort the relevant assistance. The aircraft holding short of the runway stated that the gear appeared down; and the Tower also stated that the gear appeared to be down. I made single engine landing on Runway XXR and exited at taxiway Bravo.I left the aircraft in the condition in which it landed and was met by the airport fire brigade I gave my details to the fire brigade representative. The aviator tug arrive at taxiway Bravo I briefed the maintain crew and returned to the ramp. I then briefed the Chief Pilot and Director of Operations.




Synopsis: BE76 pilot reported several aircraft system malfunctions occurred during a test flight.