What happened
On May 20, 2015, a Cessna 172RG, registration PR-ATN, was performing a private transport flight from Primavera do Leste, MT, to Brasília, DF. The aircraft was carrying a pilot and two passengers. Approximately two hours and twenty minutes into the flight, near Goiânia, GO, the aircraft experienced a partial loss of engine power.
Following established checklists, the pilot decided to avoid flying over populated areas and sought a safe location to land and inspect the engine. The pilot successfully performed an emergency landing on an uncertified grass runway used for agricultural aviation in Santo Antônio de Goiás, GO. The landing was completed without incident, and all three occupants remained unharmed. The aircraft sustained no damage.
The investigation
CENIPA investigators examined the aircraft's maintenance history and found that a scheduled inspection, which included the removal, cleaning, and inspection of the spark plug assembly, had been completed just one day prior to the flight.
Upon inspection of the engine, investigators discovered that the lower ignition cable for cylinder number two was loose and out of position. Additionally, the other three lower ignition cables were found to be improperly secured and were at risk of becoming detached. While the upper ignition cables were correctly fixed, the investigation established that the maintenance service failed to ensure the proper torque and positioning of the lower cables.
Findings
- Improper maintenance execution: The ignition cables were not correctly secured following the recent spark plug service.
- Inadequate maintenance supervision: The oversight process failed to detect the improperly installed ignition cables.
- The pilot was highly experienced, with approximately 12,000 total flight hours.
- The aircraft was within weight and balance limits and had a valid airworthiness certificate.
- Meteorological conditions were favorable for visual flight rules (VFR).
Safety action
It is recommended that the National Civil Aviation Agency (ANAC) verify the compliance of maintenance procedures performed by the workshop responsible for the aircraft's recent service.