What happened
On May 28, 2008, a Beechcraft 95-B5 and PT-DRI was performing a domestic flight from Recife (SBRF) to Maceió (SBMO) carrying one pilot and three passengers. Shortly after takeoff, once the landing gear had been retracted, the aircraft experienced a violent impact and intense vibration. The pilot immediately extended the landing gear and performed an emergency return to the runway, landing successfully.
The separation of a blade from the right engine propeller caused severe damage to the propeller hub, the engine mount, and the nose landing gear fairing. Despite the severe damage to the aircraft, all four occupants escaped without injury.
The investigation
CENIPA investigators examined the wreckage and the maintenance history of the aircraft. Technical analysis by the Aeronautical Institute of Aerospace (IAE) revealed that the propeller hub showed signs of cracks and oxidation. The investigation determined that the failure was caused by a fatigue mechanism originating in the threads of both the blade and its housing.
Investigators found that during the previous 1,500-hour overhaul, the propeller blades were not secured with the correct torque. Furthermore, the mandatory use of "Red Dye"—a specialized oil used to detect cracks during inspections—was omitted during the overhaul. Because this dye was missing, subsequent 100-hour inspections failed to detect the developing cracks in the hub.
Findings
- Improper maintenance torque: The blades of the right engine were secured with incorrect torque, initiating the fatigue process.
- Failure to use inspection dye: The omission of Red Dye during the overhaul prevented the detection of cracks during routine inspections.
- Inadequate maintenance supervision: The maintenance facility failed to properly supervise the overhaul process.
- Training deficiencies: There was evidence of inadequate training or difficulty in interpreting technical publications by the mechanics involved in the overhaul.
Safety action
CENIPA issued several safety recommendations, including:
- A recommendation for the maintenance facility to provide theoretical retraining for mechanics regarding technical publications and inspection procedures.
- A recommendation for ANAC to evaluate the implementation of standardized training programs for maintenance organizations and to increase oversight of maintenance workshops to ensure compliance with manufacturer specifications.