What happened
On December 6, 2013, a Beechcraft B55, registration PR-VLB, was performing a cargo transport flight from Barra do Garças to Rondonópolis, Brazil. Shortly after takeoff from runway 25 at Barra do Garças Aerodrome, the pilot experienced a loss of traction and intense vibration in the left engine.
In response to the emergency, the pilot feathered the propeller and shut down the left engine. The crew, which included a pilot and a passenger, executed a single-engine approach using right-hand turns to keep the operational engine on the outside of the curves. The aircraft landed successfully at the departure airfield. Upon inspection on the ground, it was discovered that the tip of one of the left propeller blades had detached and was found approximately 43 meters from the runway centerline.
The investigation
CENIPA investigators initially considered whether the propeller had struck the ground during landing gear retraction. However, this was ruled out because the detached blade fragment showed no signs of impact with the asphalt.
Technical analysis of the Teledyne Continental IO-470-L(5) engine revealed significant metal shavings in the oil filter and crankcase, along with wear and overheating marks on the crankshaft end. This damage was determined to be a consequence of the engine imbalance caused by the propeller failure, rather than the cause of it.
Detailed failure analysis of the propeller assembly by the Department of Aerospace Science and Technology (DCTA) identified that the fracture surface exhibited classic fatigue characteristics. Electron microscopy confirmed that the fatigue process was initiated by a dent (plastic deformation) caused by the impact of particles on the propeller surface, which acted as a stress concentrator.