Inflight Engine Shutdown
While in flight, the pilot noticed that the oil pressure indicator for the right engine had dropped to the red line. In response, he shut down the engine and feathered its propeller.
Electrical Failure and Gear Extension
After entering the traffic pattern for landing, the pilot lowered the landing gear. Immediately thereafter, the radar and radios became inoperative, indicating a complete loss of electrical power. The pilot reported that he heard and felt the landing gear extend, but the downlock lights did not illuminate.
Approach and Landing Sequence
To create adequate spacing behind another aircraft, the pilot performed a 360-degree turn. He then continued the approach to land. During the landing rollout, the landing gear collapsed, causing damage to the aircraft.
Post-Accident Investigation
An examination of the right engine found that the low oil pressure condition originated from a piece of carbon debris under the seat of the oil pressure relief valve. Both of the aircraft's alternators were tested and found to be operating satisfactorily. However, both voltage regulators had experienced internal failures, and both alternator circuit breakers were in the tripped (popped) position.