What happened
On 6 October 2018, a Cessna 182L, registration EI-CDP, was conducting a scheduled parachute operations flight at Clonbullogue Airfield, Co. Offaly. The aircraft was carrying one pilot and four skydivers. During the climb phase at approximately 3,500 feet, the pilot noticed unusual vibrations and a loss of power.
While attempting to return to the airfield, the pilot initially targeted Runway 27, but low sun position obscured visibility. The pilot then attempted to approach the reciprocal runway, Runway 09. During this maneuver, the engine lost all power completely. To avoid trees on the approach, the pilot executed a 180-degree turn, which triggered the aircraft's stall warning.
Upon reaching the runway, the pilot performed an emergency landing. To avoid overshooting the runway and hitting a perimeter fence, the pilot applied heavy rudder and aileron inputs. This caused the aircraft to skid sideways across the grass surface, resulting in a tail strike and the aircraft coming to rest on a tarmac area beyond the runway end. There were no injuries to the crew or passengers, though the aircraft sustained substantial engine damage.
The investigation
The AAIU examined the aircraft's engine and the flight path using CCTV and on-board video. The investigation focused on the mechanical state of the Continental O-470-R engine. Metallurgical analysis of the crankshaft revealed several fatigue cracks. Specifically, researchers found evidence of thermal distress on the No. 2 main journal. The analysis showed that frictional overheating had reached temperatures high enough to alter the steel's microstructure, creating a layer of untempered martensite.
Findings
- The primary cause of the engine failure was a fractured crankshaft.
- This fracture was triggered by localized heat-induced cracking.
- The overheating was likely caused by metal-to-metal contact between the No. 2 main journal and its plain bearing.
- This contact was a result of a loss of lubrication, likely due to a shift in the bearing.