What happened
On December 3, 2016, a CAP-4 aircraft, registration PP-RTO, was conducting a flight training mission departing from the Caruaru aerodrome in Pernambuco, Brazil. The crew consisted of an instructor and a student pilot. After completing takeoff and landing practice maneuvers, the aircraft proceeded to the northeast sector of the aerodrome. Approximately ten minutes into the flight in that sector, the Continental A-65-8 engine experienced a loss of power. The instructor subsequently executed a precautionary landing at the Caruaru racetrack.
The investigation
CENIPA investigators examined the aircraft and the fuel system to determine the cause of the power loss. An inspection of the fuel quantity indicator showed approximately 18 liters remaining in the lower tank, ruling out fuel exhaustion. Further examination of the carburetor and fuel filter revealed no impurities, obstructions in the fuel lines, or abnormalities in the carburetor itself.
During the investigation, the engine was restarted. The same failure was observed during the ground run; however, upon further inspection, investigators discovered that the mixture control cable was disconnected. Once this connection was restored, the engine functioned normally. The investigation also noted that while the aircraft's maintenance logs were up to date, the aircraft was equipped with a RUPERT propeller model that was not listed as approved for the CAP-4 in the official ANAC specifications.