What happened
On January 26, 2000, an EMB-711 ST Corisco, registration PT-NVM, was performing a domestic flight from São José, SC, to Carazinho, RS, transporting the aircraft owner and family. Approximately 35 minutes into the flight, while cruising at FL 085 near Bom Retiro, the aircraft experienced a sudden propeller overspeed, with the tachometer jumping from 2,400 to 3,300 RPM.
Immediately following the overspeed, the pilot observed oil pressure dropping to zero and noticed oil spraying over the engine cowling and onto the windshield. Faced with a critical loss of lubrication, the pilot decided to perform an emergency landing on the BR-2 and highway. The pilot notified Curitiba ACC and executed an emergency traffic pattern, cutting the engine during the downwind leg. The aircraft performed a belly landing on the asphalt with the landing gear and flaps retracted. The impact caused the left wing to strike a pine tree and the tail to strike an embankment, resulting in severe damage to the aircraft, including the loss of the tail section. All four occupants—the pilot and three passengers—were uninjured.
The investigation
CENIPA investigators examined the engine and propeller assembly, discovering that the failure originated in the propeller governor section. The investigation established that an aluminum pipeline connecting the governor to the crankshaft front bearing had been perforated. This perforation was caused by friction from a bolt from a secondary alternator support.
Further analysis revealed that the primary alternator support had previously broken, but the alternator continued to function because its weight kept the belt tensioned. The investigation also found significant discrepancies in aircraft record-keeping; the owner had failed to record flight hours in the airframe and engine logs for several years. Additionally, while a 100-hour inspection had been performed in June 1999, not all airworthiness directives and maintenance guidelines had been implemented. The investigation also noted that the aircraft was likely operating near or above its maximum weight due to full fuel tanks and heavy luggage.
Findings
- Inadequate maintenance supervision and failure to follow all inspection guidelines led to the undetected breakage of the alternator support.
- Deficient maintenance control by the owner, evidenced by outdated and incomplete aircraft logbooks.
- Lack of pilot experience with the specific aircraft type, as the pilot had primarily flown much simpler, fixed-gear aircraft (Aeroboero AB-115), which may have contributed to improper emergency procedures and the failure to extend the landing gear.
- Improper flight planning regarding weight and balance, as the aircraft was likely overweight due to full fuel tanks and passenger luggage.
- Mechanical failure of the alternator support caused a bolt to vibrate against and eventually puncture the engine's oil pipeline.