What happened
On November 9, 2002, an AB-115, registration PP-FGU, operated by Aeroclube de Macaé, was performing a ferry flight from Macaé, RJ, to Conselheiro Lafaiete, MG. The flight included a planned refueling stop in Juiz de Fora, MG. The crew consisted of an instructor and a student pilot.
Approximately 44 minutes after takeoff, while cruising at 6,500 feet near Friburgo, RJ, the engine experienced a significant power loss accompanied by loud friction noises and airframe vibrations. The instructor took control of the aircraft and attempted an emergency landing on a highway (the Teresópolis–Friburgo road). However, due to an improper approach profile regarding altitude and airspeed, the aircraft struck medium-voltage power lines and ultimately came to rest at the base of a mountain. The aircraft sustained severe damage, but both crew members escaped uninjured.
The investigation
CENIPA's investigation focused on the mechanical failure and the organizational environment of the operator. Investigators discovered that a maintenance service performed on the number 3 cylinder had not been recorded in the engine logbook, and the identity of the technician responsible was unknown.
Technical analysis revealed that an improper brass adapter had been used to connect the spark plug to the cylinder. This material was not approved by the manufacturer's manual, which specifies steel. The brass alloy could not withstand the operating temperatures, causing the component to fail in flight. Furthermore, the investigation examined the operational management of the Aeroclube de Macaé, noting a lack of formal supervision and a culture of informality.
Findings
- Improper maintenance: The primary cause of the engine failure was the use of an unauthorized brass adapter on the number 3 cylinder spark plug, which failed due to thermal stress.
- Lack of supervision: The aeroclube lacked adequate oversight of maintenance activities, allowing unrecorded and improper repairs to occur.
- Operational errors: The instructor failed to execute a proper emergency approach pattern, leading to an inability to land on the intended roadway.
- Organizational culture: The operator's management was characterized by informality, including a lack of professionalized personnel selection and a lack of formal maintenance records.
- Management overload: The high workload of the organization's Vice-President, who managed multiple professional roles, may have compromised effective oversight.