Background
The accident occurred during a maintenance test flight conducted in the traffic pattern. Two days earlier, a different company pilot had made an unscheduled landing due to a rough-running engine accompanied by vibration. Inspection and maintenance records showed that personnel removed and cleaned the fuel injector nozzles, flushed the servo unit screen, and performed a compression check. Four engine ground runs were conducted; the first three exhibited rough running and vibrations, while the fourth run showed no anomalies.
Pre-Flight
Examination of the inspection discrepancy logs revealed two records for the aircraft. These documents were essentially identical except for item number 3. The first document stated that the No. 5 cylinder fuel injector nozzle needed replacement, with a note that none were in stock. The second document indicated that the fuel injector nozzles were cleaned and reinstalled, and that a ground run-up was normal. The company dispatcher instructed the pilot to perform the test flight, as the airplane was scheduled to return to service that same day. The pilot completed the ground checklist, which included checking the magnetos and propeller, and noted no discrepancies.
Flight
After takeoff, no engine performance malfunctions were observed. However, while on base leg, the engine banged three times, and then parts flew through the engine cowling. The cowling separated and struck the empennage. The pilot subsequently ditched the aircraft in the ocean.
Post-Accident
The aircraft sank and was not recovered.