Baron 55/Cochise
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Flight Engineer
Flight Crew Last 90 Days 240; Flight Crew Total 11000; Flight Crew Type 119
Situational Awareness
Aircraft Equipment Problem Critical; Airspace Violation All Types
Flight Crew Inflight Shutdown; Flight Crew Landed in Emergency Condition; Flight Crew Diverted; General Maintenance Action
Human Factors; Aircraft
Was flying as pilot-under-instruction on routine training refresher flight. Part of the practice was the controlled shutdown; feather; and re-start of each engine. When attempting to unfeather the right engine; it initially would not unfeather. We remained in the practice area offshore; but became distracted by the procedure and it appeared that we were close to the lateral limits of [the] Class C airspace. Upon recognizing this; we immediately headed east to avoid. We continued to monitor Approach frequency; but did not check in with them; as our intention was to remain clear of their airspace; as we continued to troubleshoot the malfunction; as we proceeded south offshore during this process. After all inflight procedures had become exhausted; it became apparent that the propeller could not be moved out of FEATHER; and thus Tower at the nearest airport [was advised]. We then proceeded to land without incident. Post-flight examination showed that the internal rubber bladder of the unfeathering accumulator had failed internally; without warning or indication; thus preventing the propeller from unfeathering in flight. Although we did not want to 'bother' busy Approach with our (then) non-emergent troubleshooting; perhaps it would have been better to call them when approaching the lateral limits of their airspace.
Beechcraft Baron pilot reported diverting to a nearby suitable airport after an engine that had been intentionally feathered for training would not unfeather.