Incident Overview
A pilot reported that approximately ten minutes after departure, the engine exhibited low oil temperature and pressure. The pilot initiated a turn to return to International Falls. About five minutes later, the engine shuddered and lost power. A forced landing was executed in a swampy area.
Investigation Findings
Examination of the aircraft revealed that the crankcase breather tube was completely blocked with ice. This blockage caused oil to be expelled through the front engine seal. Additionally, an airworthiness directive (AD) that addressed this specific issue had not been complied with.
Sequence of Events
The pilot's decision to return to the departure airport was prompted by the abnormal oil readings. Despite the attempt, the engine failure occurred before reaching the destination. The forced landing in the swamp resulted in damage to the aircraft. The pilot's report indicated no other anomalies prior to the incident.
Mechanical Details
The crankcase breather tube, designed to relieve pressure and vent crankcase vapors, became obstructed by ice accumulation. This ice formation prevented proper ventilation, leading to increased internal pressure and subsequent oil loss through the front seal. The AD in question was intended to prevent such blockages, but its non-compliance left the aircraft susceptible to this condition.