What happened
On January 22, 2012, an Airbus AS350 B2, registration PT-YLS, was performing a shuttle flight from Jacarepaguá Aerodrome to Angra dos Reis, Rio de Janeiro. While flying near Grumari Beach, the pilot heard an unusual noise from the rear of the aircraft, followed by a loss of engine power and the activation of the low RPM audible alert.
The pilot successfully executed an emergency autorotation procedure, landing the helicopter in the Grumari Ecological Reserve. Following the landing, the pilot utilized the engine shut-off valve to stop the engine. Shortly after, a fire ignited in the engine area. Nearby firefighters were able to extinguish the flames before they could cause further damage.
The investigation
CENIPA investigators examined the Turbomeca Arriel 1D1 engine and the aircraft's maintenance history. The investigation revealed that the engine's main oil filter and magnetic plugs were heavily contaminated with iron filings. Technical analysis of the engine's module 3 showed that the rear bearing had experienced overheating, causing the rollers to fuse to the inner race and the outer race to become misaligned.
Investigators also looked into environmental and human factors. It was noted that sunlight hitting the cockpit, combined with the pilot's use of sunglasses, may have hindered the visibility of the chip detector light, which could have provided an earlier warning of the metal particle contamination.
Findings
- The primary cause of the power loss was the failure of the rear bearing in module 3.
- The engine's maintenance records were up to date, and the component had not yet reached its extended 3,600-hour overhaul limit.
- The presence of metal filings in the lubrication system indicated significant internal wear prior to the failure.
- Environmental conditions, specifically high cockpit glare, may have prevented the pilot from noticing the chip detector warning light.
- The aircraft sustained substantial damage to the engine, tail cone, tail rotor drive shaft, and fairing, but the pilot was unhurt.