What happened
On October 27, 2014, a Robinson R22 Beta helicopter, registration PP-JRL, was conducting a local flight training mission for a Private Pilot Helicopter course. The aircraft departed from the Piraquara Aerodrome in Paraná, Brazil, carrying an instructor and a student.
While performing straight and level flight training, the aircraft experienced a sudden loss of engine power and rotor RPM. The instructor took control of the aircraft after observing the low rotor RPM warning light and hearing the low RPM horn. The instructor subsequently performed a forced landing in a marshy area characterized by tall grass. Although the aircraft sustained substantial damage, both occupants escaped the crash without injury.
The investigation
CENIPA investigators, accompanied by representatives from the Department of Science and Technology of the Air Force (DCTA), examined the engine to determine the cause of the power loss. The investigation established that the engine failure was caused by the displacement of the air filter seal. This seal was sucked into the carburetor and became lodged in the venturi, partially obstructing the airflow to the engine.
The investigation also reviewed the manufacturer's Service Bulletin SB-110, issued on October 14, 2014. This bulletin addressed a manufacturing issue where the adhesive used to bond the seal to the B771-1 revision C air filter reacted poorly to aviation gasoline, causing the seal to lose adhesion. The bulletin mandated the replacement of these filters with a newer revision or required a daily inspection of the seal prior to flight. While the aircraft was equipped with the older revision C filter, there was no record indicating that the operator had been performing the daily inspections required by the bulletin.
Findings
- Maintenance of the aircraft