CEN25LA165

The pilot reported he was about 4 hours and 45 minutes into a survey flight when the engine suddenly lost power. He attempted to troubleshoot and was unable to regain engine power before making an emergency landing. The airplane sustained substantial damage to the fuselage. Postaccident examination of the engine revealed that a B-nut was loose on the fuel line at the fuel flow divider. When the electric boost pump was turned on during the examination, fuel flowed freely out of the loose connection. Additionally, multiple discrepancies were noted throughout the engine compartment, including (but not limited to): cylinder base nuts that were loose, a cylinder temperature probe that was hanging by its wire, and grommets that were missing or in disrepair along the fuel and oil lines. Maintenance performed about a week before the accident included the removal and replacement of three cylinders and the completion of a 100-hour inspection. It is possible that the mechanic performing the maintenance removed the fuel line to facilitate the cylinder replacement. Regardless of whether or not the mechanic removed the fuel line, the loose B-nut and other discrepancies found in the engine compartment indicate that the 100-hour inspection completed on the same day as the cylinder replacements was inadequate.

On March 27, 2025, about 1312 central daylight time, a Cessna T206, N27DV, was substantially damaged when it was involved in an accident near Natchez, Mississippi. The pilot and copilot were not injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 aerial observation flight. The pilot reported that about 4 hours and 45 minutes into a survey flight, the engine suddenly lost power. The pilot pitched for best glide and performed emergency checklists items but was unable to regain engine power. He declared an emergency and diverted toward runway 14 at Hardy-Anders Field/Natchez-Adams County Airport (KHEZ), Natchez, Mississippi. Unable to glide to the runway, the pilot attempted to land the airplane to the side of the runway to avoid hitting the approach lighting system. During the landing, the airplane struck a berm, went airborne, and bounced. The airplane sustained substantial damage to the fuselage. Maintenance records showed that the Nos. 3, 4, and 5 cylinder assemblies were removed and replaced about a week before the accident and that a 100-hour inspection was completed on that same date. Postaccident examination of the airplane revealed that a B-nut was loose on the fuel line at the fuel flow divider. When the electric boost pump was turned on during the examination, fuel flowed out of the loose connection. Additionally, multiple discrepancies were noted throughout the engine compartment, including (but not limited to): cylinder base nuts that were loose on the cylinders that were replaced and one other cylinder, a cylinder temperature probe that was hanging by its wire, and grommets that were missing or in disrepair along the fuel and oil lines.