Incident
A police helicopter engaged in a mission at an altitude of less than 500 feet above ground level experienced a loss of engine power. The pilot was unable to reach a suitable landing area and could not maintain rotor rpm. The helicopter struck trees and a light pole, then landed hard on a road before sliding into a fence.
Examination Findings
Post-incident examination revealed that the #2 connecting rod had separated from the crankshaft. A torque check on the remaining connecting rod bolts found that all were below the minimum specified value.
Manufacturing Context
At the time of engine assembly, a work action (strike) was in effect at the engine manufacturer. Production continued with management and replacement workers. During assembly, the crankshaft had been replaced for an unknown reason. After the crankshaft replacement, new connecting rods were attached but were not properly tightened.
The replacement workers manned the two assembly stations identified as most probable for the replacement of the crankshaft and the failure to tighten the connecting rod bolts. Although long‑time employees knew the correct procedures for documentation of a replaced crankshaft, no specific written instructions were available for the replacement employees.
The engine failed at 45.7 hours total time.