As the pilot of the Brasilia was applying take-off power, a nickel leading edge erosion strip separated from one of the left propeller blades. The strip then bounced off the tarmac under the aircraft and struck the right propeller blades. The engines were shut down and all passengers disembarked safely.
The propeller blades had completed a total of 17,161 hours in service. The last repair work including the fitment of the nickel sheath protective strips took place approximately 2,100 hours prior to the incident.
The erosion strip was recovered and was forwarded for specialist metallurgical examination. This examination confirmed that the erosion strip had separated due to loss of adhesion at the adhesive to sheath interface.
The propeller blade and the failed portions of the nickel sheath were returned to the manufacturer for detailed examination including investigation of the procedures used to perform the nickel sheath replacement. It was found that the sheath had been bonded using an approved adhesive AF111. Inspection of the nickel sheath showed that the surface had been prepared correctly prior to the adhesive being applied. Examination of the blade and nickel sheath showed the cause of the separation to be cracking of the sheath-to-blade bond joint. Spectrum analysis of the adhesive showed the presence of silicone.
The investigation determined that this contamination was introduced during the bonding process. Review of the process showed that an adhesive tape containing silicone had been used, and this is considered to be the most likely cause of the introduction of silicone.
The propeller manufacturer has reviewed its procedures associated with this process. Improvements have been identified and are being incorporated into the manufacturer's Component Maintenance Manuals.