On May 27, 2024, about 1520 central daylight time, a Cessna 172P, N658NV, was substantially damaged when it was involved in an accident near Citronelle, Alabama. The airline transport pilot was seriously injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 positioning flight. According to the Federal Aviation Administration aviation safety inspector who responded to the accident scene, the owner had arranged for the pilot to recover the airplane from the maintenance facility that had just completed an annual inspection. The owner reported that the airplane had been idle for 25 years before he purchased it and had the annual inspection performed. He said the pilot flew the airplane for about 45 minutes, returned to the airport for fuel, and then departed on the accident flight from Copiah County Airport (M11), Crystal Springs, Mississippi, to Peter Prince Airport (2R4), Milton, Florida. According to local law enforcement, the pilot stated at the scene that he had, “lost his engine” and performed a forced landing to the field, where the airplane came to rest upright but substantially damaged. In a written statement, the pilot said the airplane was in a cruise configuration when the engine, “surged slightly a few times” before it began running “erratically.” The pilot described his remedial actions to restore full engine power as he maneuvered the airplane toward a suitable forced landing site that was “beyond gliding distance.” The engine stopped producing power, and he “stretched” the glide for the desired field, but “lacked the energy for a proper flare” and landed hard. Examination of photographs revealed damage to the underside of the engine compartment, a separated nose landing gear, and damage to the left wingtip. The propeller remained attached, and one blade was bent aft. Examination of the cockpit and cabin area revealed that the copilot and rear seats were not installed. There was no carpeting nor interior trim panels installed, and unsecured insulation was exposed. One blanket of insulation hung free from the ceiling. Instruments and radios were labeled “Inop” across the instrument panel. The airplane was recovered from the accident site to a secure facility for examination. The engine was run using a temporary fuel cell. No anomalies were noted during the engine run. A drop of about 125 to 150 rpm was noted during a magneto check using the airplane’s magneto switch. The magneto P-leads were removed from the magnetos and two separated wires were installed on the magneto P-leads to perform the second engine run, bypassing the airplane’s magneto switch. No anomalies were noted on the second run and the magneto rpm drops were consistent to that observed with the magneto switch. A total of four engine runs were performed. The engine started without delay and ran smoothly from 700 rpm to 2,600 rpm. The fuel pressure was noted at 2 psi and 6 psi with the boost pump engaged. Oil pressure was in the green/normal range. The fuel tank vent tube located near the leading edge of the left wing was found obstructed during a field test with low-pressure air. Further examination of the vent line revealed the obstruction was a compacted organic material consistent with mud dauber nesting. (See figure 1.)

Figure 1: View of occluded fuel vent tube as found. Note organic material (Mud dauber nest). According to the manufacturer’s Model 172 Series Service Manual: 12-11 CHECKING. If stoppage of the either the fuel vent or vent bleed hole occurs, with the engine running, it can lose power, and eventually stop due to fuel starvation, which can lead to collapsing of the fuel tank.