What happened
The pilot reported that while climbing through an altitude of 4,300 feet, he experienced a sudden loss of power from the left turbocharger. Shortly after this mechanical failure, he observed sparks emanating from the engine compartment, which quickly developed into a fire. In response to the emergency, the pilot shut off the fuel supply to the affected engine and waited for the flames to extinguish completely before feathering the propeller.
With the engine secured, the flight was continued to Montgomery, Alabama, where the aircraft was based. Upon arrival, the pilot executed a landing without using flaps. No additional problems were encountered during the remainder of the flight or upon landing.
The investigation
A post-incident inspection of the aircraft revealed that the coupling connecting the exhaust system to the waste gate had failed. This failure allowed hot exhaust gases to escape directly into the engine cowling, which caused the observed sparks and subsequent fire. The damage sustained by the aircraft was significant, including damage to the engine mount beams and the wing spar located within the engine nacelle.
Findings
The investigation determined that the primary cause of the incident was the failure of the exhaust-to-waste-gate coupling. It was noted that Airworthiness Directive 75-23-08, Revision 5, does not apply to this specific fractured component, meaning there was no mandatory regulatory requirement for its replacement or inspection under that specific directive at the time.
Safety message
This incident highlights the critical importance of monitoring engine instruments and exhaust systems during climb phases. Early detection of turbocharger performance issues can allow for timely troubleshooting before catastrophic failures occur.