What happened
On July 11, 2014, a Cessna 170, registration PP-DSZ, departed from Fortaleza (SBFZ) for a repositioning flight to Crateús (SNWZ). The aircraft was carrying a pilot and one passenger. Approximately thirty minutes into the flight, the engine began operating irregularly, characterized by a significant loss of power.
The pilot attempted to return to the airfield, performing magneto tests and switching fuel tanks to restore normal operation. After failing to stabilize the engine, the pilot declared an intention to perform an emergency landing on the CE-455 highway. However, upon noticing vehicles on the roadway, the pilot opted to land in a pasture at Fazenda Vitória, adjacent to the highway. During the final approach, the engine ceased functioning entirely. The aircraft landed successfully without damage to the airframe, and both occupants remained uninjured.
The investigation
CENIPA investigators examined the aircraft's maintenance history and mechanical components. The aircraft had recently undergone a 100-hour inspection and an Annual Inspection (IAM) in April 2014, which included a carburetor overhaul and the replacement of all fuel hoses.
During post-incident testing at a maintenance facility, the engine operated normally when the fuel system was temporarily modified to bypass the fuel selector, tanks, and the fuel strainer (drain cup) by connecting a line directly to the carburetor. While inspecting the fuel strainer, investigators discovered a rubber fragment lodged within the component. Although the current fuel hoses were in good condition and the strainer gasket was intact, the size of the fragment was consistent with the outlet of the strainer. Investigators concluded that the fragment likely originated from the old fuel hose that had been replaced during the previous maintenance cycle.
Findings
- Debris in the fuel system: A rubber fragment found in the fuel strainer caused an obstruction at the outlet, restricting fuel flow to the carburetor.
- Maintenance residue: The fragment was believed to be a remnant of the previous fuel hose replaced during the 100-hour inspection.
- Engine failure: The restricted fuel supply led to the initial power loss and the eventual complete engine shutdown during the approach.
Safety action
- Maintenance personnel at the aircraft's maintenance facility were advised to exercise increased care when servicing fuel system hoses to prevent debris from compromising engine operation.