Factual Information
On 10 May 2013, a CASA 212-200 aircraft, registration PK-TLG, operated by PT. Nusantara Buana Air, was conducting scheduled passenger flight NBA 868 from Sultan Babullah Airport, Ternate, to Gebe Airport, North Maluku. The flight was the third of the day; the first two flights were normal. During climb, after passing 6,000 feet, the left propeller detached from the rear hub half. The pilots shut down the engine and subsequently landed at Sultan Babullah Airport. No injuries to persons were reported. The aircraft sustained damage from the propeller separation.
Analysis
The investigation by the Komite Nasional Keselamatan Transportasi (KNKT) found that the left propeller failure was caused by fatigue cracks. Examination of the failed part revealed fatigue cracks that initiated from the edges of fastening holes on the propeller hub. Two initiation points (A and B) were identified. Striations on point A had a spacing of approximately 500 μm, indicating crack growth. The fatigue cracks propagated over time, leading to eventual failure of the hub. The maintenance records indicated a misinterpretation of maintenance intervals, which may have affected inspection schedules.
Findings
The KNKT identified several findings, including that the propeller hub failed due to fatigue cracking initiated at fastening holes. The aircraft maintenance records showed inconsistencies in tracking propeller overhaul intervals. The operator's continuous airworthiness maintenance program (CAMP) had not been correctly applied in some instances.
Contributing Factors
The contributing factors identified in the report include the misinterpretation of the propeller maintenance interval by the operator, leading to the propeller not being overhauled within the required time limits, and the fatigue cracking that resulted in the detachment.
Safety Actions and Recommendations
Following the accident, PT. Nusantara Buana Air revised its maintenance procedures to ensure correct interpretation of overhaul intervals. The Directorate General of Civil Aviation issued recommendations to improve oversight of maintenance tracking.