ERA24LA016

The flight instructor reported that the flight was intended to review maneuvers. On the return to their home airport, the engine lost power. The instructor performed an emergency landing in a field where the airplane’s right wing sustained substantial damage when it struck a tree. The postaccident examination of the engine revealed that a float bracket within the carburetor fractured due to cyclic fatigue. This failure would have resulted in a restriction of fuel flow, and the loss of engine power described by the flight instructor. The fracture originated at the bracket’s interior edge with no other anomalies noted.

On October 21, 2023, at approximately 1340 EDT, a Cessna 172L, N7716G, was substantially damaged when it was involved in an accident near Richmond, Virginia. The flight instructor, student pilot, and one passenger were not injured. The airplane was operating as a Title 14 Code of Federal Regulations Part 91 instructional flight. The flight instructor reported that the purpose of the flight was to conduct a review of flight maneuvers in a designated practice area. On the return flight to OFP, the engine began to lose power. The power loss progressed until the airplane could no longer maintain level flight. The flight instructor initiated an emergency landing in an open field short of the runway. During the landing rollout the right wing struck a tree, resulting in substantial damage. A Federal Aviation Administration inspector conducted an on-site examination and noted that the right wing exhibited damage consistent with impact with a small tree located at the accident site. The cabin section showed damage at the right-wing root attachment area. The left wing displayed upward bending from the wingtip about 2 feet inboard. An engine examination established valvetrain continuity with crankshaft rotation through 720°. Ignition continuity was confirmed during the examination of the magnetos, ignition wires, and spark plugs. An undetermined amount of fuel sufficient for flight was found in both fuel tanks. The carburetor was partially disassembled. It was observed that the float bracket had fractured into two pieces. The float remained attached to the bracket by the float lever shaft, and the float valve was coupled to the float by a clip mounted on the float lever shaft. The float’s movement along the shaft allowed axial motion of the float valve within the float valve seat, restricting fuel flow into the bowl when the valve sealed against the seat. The carburetor components were submitted to the National Transportation Safety Board (NTSB) Materials Laboratory for further examination. Analysis revealed that one arm of the float bracket had fractured due to cyclic fatigue. The fracture surface was flat with radiating lines and curved crack growth features consistent with fatigue failure. The origin of the fracture was along the interior edge where the bracket arm intersected the base of the bracket. No anomalies were observed at the fracture origin. A review of the logbook excerpts revealed that in 2005 there was an IRAN (Inspect & Repair As Necessary) performed that referred to the replacement of the various original accessories including the carburetor. No other maintenance was noted on carburetor since 2005.