What happened
On March 21, 2020, a Piper Aztec PA-23-250, registration N14178, was conducting a private flight from North Eleuthera International Airport to New Bight Airport on Cat Island. While climbing through 1,200 feet, the pilot noticed irregularities in the fuel flow of the left engine. This was immediately followed by loud bangs and the appearance of flames emerging from the left engine cowling.
The pilot attempted to return to the airport by joining the right downwind pattern for runway 0 7. However, the fire intensified, making a return to the airfield impossible. Seeking the safest available option, the pilot identified a nearby beach and executed an emergency ditching in shallow waters approximately 250 feet from the shoreline at Lower Bogue, Eleuthera. The aircraft sustained substantial damage from the impact and the fire. The pilot and two passengers successfully exited the aircraft in waist-deep water and were assisted by local residents and police. There were no injuries.
The investigation
The investigation focused on the mechanical failure of the left engine. Investigators examined the engine and various components, including the connecting rod, bearings, and bolts, at facilities in both the United States and the Bahamas. Although saltwater submersion caused significant corrosion to the components, laboratory analysis at Lycoming's Materials Laboratory provided critical insights into the failure sequence.
Technical examination of the #3 cylinder assembly revealed a catastrophic failure of the engine block attaching hardware. The investigation also scrutinized the engine's maintenance history, noting that the engine had undergone a field overhaul in late 2018 and contained several non-Lycoming components, including parts manufactured by Continental and Superior.
Findings
- The primary cause of the accident was a catastrophic failure of the #3 cylinder on the left engine, which severed the fuel line and ignited the in-flight fire.
- The failure was triggered by the structural failure of one connecting rod bolt due to sudden overload.
- The remaining intact connecting rod bolt experienced bending and deformation because it was rocking back and forth within the assembly.
- The engine's recent overhaul involved the installation of various components from different manufacturers, including Superior-manufactured bolts and nuts.
- Weather conditions were clear (VMC) and were not a contributing factor to the event.