What happened
On July 19, 2014, a Cessna 182N departed from Lienz-Nikolsdorf airport for a local flight. After the initial climb, the aircraft reached 4,500 ft msl, at which point the pilot slightly leaned the mixture. Shortly thereafter, the engine experienced a sudden drop in RPM, followed by a subsequent increase in RPM. Although the engine continued to run with residual power, the pilot was unable to maintain sufficient performance to return to the airfield.
Upon realizing that Lienz-Nikoliadorf could not be reached, the pilot notified the airport management and identified a suitable landing site consisting of a meadow adjacent to a cornfield near Irschen. During the turn toward the landing site, the aircraft suffered a significant loss of altitude. The aircraft struck the ground heavily on the meadow and slid into the cornfield. The pilot and three passengers were involved in the accident; the pilot sustained one injury, while the three passengers sustained three minor injuries. The aircraft was a total loss.
The investigation
The SUB examined the engine, fuel system, and propeller components to identify the cause of the power loss. Technical inspections included an analysis of the spark plugs, intake manifold, fuel filters, and carburetor. The investigation also included a chemical analysis of the fuel, which was found to be a mixture of MOGAS and AVGAS 100LL.
Engine monitoring data (EGT and cylinder head temperatures) showed that the exhaust gas temperatures were increasing across all six cylinders, indicating a lean fuel-air mixture. The investigation found no evidence of carburetor icing, as the carburetor temperature remained outside the icing range. Furthermore, no mechanical failures, fuel system blockages, or contamination issues were identified in the fuel, oil, or ignition systems.
Findings
- The engine experienced an unexplained power loss characterized by a fluctuation in RPM.
- Analysis of EGT data suggests the power loss was caused by a transient impairment of fuel delivery or an excessively lean fuel-air mixture.
- The pilot followed the appropriate emergency procedures outlined in the aircraft flight manual, attempting to restore power by adjusting the throttle, propeller pitch, and mixture.
- The aircraft was within weight and balance limits, and all required maintenance and documentation were up to date.
- The fuel contained both MOGAS and AVGAS 100LL, but the chemical composition was within acceptable specifications.