Incident Overview
An airplane experienced an in-flight fire that resulted in substantial damage to the cowling covering the engine turbocharger area and to the firewall. The pilot executed an emergency landing at an alternate airport after an uncommanded extension of the landing gear. No evidence of smoke or fire was observed during the flight; the damage was only discovered during a postflight inspection, which revealed that the cowling around the turbocharger had been consumed by fire.
Examination Findings
Following the incident, an examination of the airplane found that the turbocharger exhaust tailpipe clamp was secured with a multi-segment steel self-locking nut. The required fastener for that application is a single-piece steel self-locking nut. The fire damage was concentrated in the area of the turbocharger and surrounding cowling and firewall.
Emergency Landing Details
The pilot reported an uncommanded landing gear extension, which prompted the decision to land at an alternate destination airport. The landing was completed without further incident, and the extent of the fire damage was not apparent until the aircraft was inspected on the ground.