Aluminium + Carbon Fibre blade =?

[Ultralights]

well, dissimilar metal corrosion.

 

Discovered this during a pre flight inspection today, prop is 660 hrs old. prop and hub were inspected at 650 hrs, but no crack or corrosion was evident externally at that time, only light surface corrosion on the front face around the spinner.

 

 

 

 

 

so if you have a Aluminium hub and carbon fibre blades, inspect for dissimilar metal corrosion. als found corrosion in the bolt holes as well. Steel bolts and Aluminium are just as bad friends as carbon fibre and aluminium, especially if the gold Cadmium plating has been damaged in any way. throw in a bit of coastal flying, rain, and the stress of being a prop, and you get ^^ above.

 

 

[Ultralights]

Judging by the amount of "gold" tint, i would say they have only been alodine treated and not plated.

 

 

[Dieselten]

Interestingly, the inner surfaces appear to be bereft of an any "passivation" measures such as alodyning or anodising. My Bolly-prop hub appears to be alodyned externally and it is fading, but no signs of cracking. It currently has just 290 hours on it. Could be a good time for a disassemble, inspect, possibly some passivation internally, re-assemble, re-pitch and balance. These hubs are prone to water-ingress during washing etc due to their design.