For the Lu induced discussion on blades at night, see the following thread, bear with the banter, there is a lot of information in between:
Night Blade glow
For the original question: The Oz Army revealed significant dust erosion related issues when they first began operating the Black Hawk during a major exercise in 1989. The subsequent mods were later used by the US Army in G1. The mods included elastomeric pitch change links and blade erosion measures. Makes sense in such a dusty country as Oz.
(I wonder if these issues have been considered by the team that recently purchased the Tiger for the Aussies?)