AUR operated 2 DHC6 a/c some time ago - I think that it was late '80s or early 90s. They gave up on them after a few years & the reason stated was that the short flights & the sea air gave them operational problems. I am not a mechanic, so,I don't really understand what those problems were. But, the airline definitely had a problem with the a/c & the engines - enough to take them out of service.