What happened
On February 15, 2014, during a preflight inspection at Gotartowice airport (EPRG), the pilot of a 3X47 Navigator UL 002 ultralight aircraft discovered instability in the engine installation while manually rotating the propeller. Upon removing the engine cowlings to investigate the movement, the crew identified that a right-hand bolt securing the engine to the engine mount had sheared off.
Further inspection revealed secondary damage resulting from the engine's movement within the airframe. The investigation identified a severed carburetor drain line, a dent in the coolant radiator, and a dent in the engine mount tubing. No injuries or damage to persons were reported during this incident.
The investigation
The investigation, conducted by the operator's internal commission, focused on the physical state of the failed hardware and the extent of the collateral damage. The fractured bolt was removed for examination. Analysis of the fracture surface revealed bright areas, which are characteristic of fatigue failure.
Findings
- The primary cause of the incident was the failure of an engine-to-mount mounting bolt due to an undetermined cause.
- The fracture surface characteristics suggested the bolt had likely failed during a previous flight.
- The movement of the engine within the cowling, caused by the loss of the mounting bolt, led to the damage of the radiator, engine mount, and carburetor drain line.
Safety action
Following the investigation, the flight training center conducted refresher training with aviation personnel, emphasizing the importance of performing thorough aircraft inspections after every flight.