What happened
On November 17, 2013, a Cessna 152, registration N555UF, was conducting a night instructional flight at David Wayne Hooks Memorial Airport (DWH) in Spring, Texas. The purpose of the flight was to practice night takeoffs and touch-and-go landings in the airport traffic pattern.
During the flight, the aircraft completed one touch-and-go landing. While on the initial climb following a second touch-and-go landing, the flight instructor notified air traffic control that the aircraft was experiencing "engine problems" and requested a 180-degree turn to return to the airport. Witnesses reported that the engine had sounded abnormal during the downwind leg and continued to run roughly during the climb.
Following the report of engine issues, the tower controller observed the aircraft enter a steep left bank and descend nose-down into the terrain on the east side of the airport. Witnesses described seeing the aircraft enter a near-vertical descent. The impact caused substantial damage to the aircraft, and both the flight instructor and the student pilot sustained 2 fatal injuries.
The investigation
Investigators examined the wreckage and the engine components. While the carburetor heat control was found in the "off" position, impact damage to the carburetor air box prevented investigators from determining if the heat had been activated during the flight. The weather conditions were noted as being conducive to carburetor ice formation at reduced power settings.
Disassembly of the carburetor revealed that one of the two hollow polymer floats was flooded with fuel. This condition can reduce float buoyancy, leading to poor idle power or carburetor flooding. Maintenance records indicated that the manufacturer had issued several service bulletins over the preceding years recommending the replacement of these hollow polymer floats with a solid-epoxy design to prevent such issues. There was no documentation showing that the carburetor in N555UF had been inspected or updated in accordance with these bulletins.
Findings
- The engine's power loss could not be definitively attributed to a single source, as investigators could not determine the exact extent of carburetor icing versus the impact of the flooded float.
- The flight instructor failed to maintain sufficient airspeed during the 180-degree turn following the partial loss of engine power, leading to an aerodynamic stall and loss of control.