Event Overview
While in cruise flight, the pilot noted a gradual left engine oil pressure drop from the normal 70 psi to 20 psi. The pilot shut down the left engine, feathered the propeller, and diverted to an alternate airport.
En Route Actions
En route to the alternate airport, the pilot attempted to restart the left engine to avoid a single-engine landing. According to the pilot, the aircraft battery was "ground down" by the unsuccessful start attempts.
Arrival and Gear Extension
On arrival at the airport, the landing gear would not lower via the electrical system due to low battery output. The pilot attempted to lower the gear manually but insufficient time and altitude remained to complete the operation before landing.
Go-Around and Forced Landing
The pilot attempted a single-engine go-around with the gear partially extended. The aircraft would not maintain altitude. The pilot executed a forced landing in an open field at an elevation of 5600 feet MSL.