WPR23LA341 · Bellanca 7ECA

The flight instructor and pilot receiving instruction were on final approach for landing about 700 ft above ground level (agl) when the engine suddenly lost total power. The flight instructor accomplished a forced landing short of the runway, and the airplane struck two fences, resulting in substantial damage to both wings. The flight instructor and mechanic recovered the airplane to a hangar. The mechanic started the engine uneventfully, ran it briefly at a low power setting, and noted no issues. During a second engine run attempt following additional examination of the airplane, the engine would not operate continuously or at a high power setting. Fuel flow was verified to the engine. The carburetor was removed for examination, and the examination revealed no anomalies with the carburetor. The carburetor was subsequently reattached, another engine run was accomplished, and the engine operated for several minutes at various power settings with no anomalies noted. The investigation identified no evidence of preimpact mechanical failure or malfunction that would have precluded normal engine operation. It is possible evidence of an anomaly in the carburetor or engine may have existed but was compromised during the first engine run or during the subsequent removal and examination of the carburetor. Although the airplane was operated in conditions that an FAA carburetor icing probability chart identified as conductive to the formation of carburetor icing at glide and cruise power, the conditions did not fall within the “serious icing” region of the chart, and the pilot receiving instruction reported that the carburetor heat was used intermittently during the approach. Based on the available evidence, the investigation was unable to determine the cause of the loss of engine power.

Verbatim NTSB analysis and probable cause from the NTSB dataset