What happened
On June 19, 2023, a Cessna 170A, registration PT-KUM, was performing a private ferry flight from an unregistered aerodrome in Santiago, Rio Grande do Sul, to Tupanciretã. Shortly after takeoff, the pilot noticed fluctuations in the engine oil pressure accompanied by a loss of engine power.
In response to the power loss, the pilot executed an emergency landing in a nearby crop field. During the landing maneuver, the aircraft overturned and came to rest in an upside-down position. The aircraft sustained substantial damage to the fuselage, tail cone, vertical stabilizer, and powerplant system. The pilot sustained minor injuries.
The investigation
CENIPA investigators examined the aircraft's engine cooling system and discovered that a heat exchanger (radiator) had been installed at the front of the engine. This component differed from the original manufacturer's design, which utilized a different ram-air cooling method. The investigation revealed that this modification was performed without proper documentation, and the component lacked any identification markings or records regarding its manufacture, installation, or maintenance.
Furthermore, investigators found that the aircraft's maintenance logs were out of date, specifically regarding the required 50-hour inspection. A visual inspection of the unauthorized heat exchanger revealed a hole in its structure, which had caused an oil leak. Evidence of an oil stain at the takeoff site suggested the leak was active prior to the flight. The investigation also noted that the use of an unregistered aerodrome for the departure was a violation of Brazilian civil aviation regulations.
Findings
- The primary cause of the engine power loss was a hole in the unauthorized heat exchanger, which led to significant oil leakage and compromised engine lubrication.
- The pilot's decision to continue the flight despite observing oil pressure fluctuations during a previous flight demonstrated poor judgment and complacency.
- Maintenance failures were evident in the lack of records for the 50-hour inspection and the failure to properly document a major airframe alteration.
- The installation of the uncertified cooling component violated regulatory requirements for major alterations (RBAC-43) and part identification (RBAC-45).