Bell has been made aware of cases where corrosion has been found on the freewheel assembly housing surface to the engine gearbox interface. Following investigation, it was discovered that the surface paint masking of the interface of freewheel housing 406-040-500-107 is best adapted to fit on the model 206L4 and 407. This freewheel housing when fitted to the Arrius2R engine, as installed on the model 505, is not of the same imprint which allows for unpainted surfaces to be exposed to the environment. This bulletin introduces an immediate fix to apply sealant to these exposed surfaces to mitigate any potential for corrosion propagation. Applicability of this bulletin to any spare part shall be determined prior to its installation on an affected helicopter.

Document is at https://www.bellcustomer.com/Bulletins/Download?filename=TB_505-18-14.pdf