I heard accounts too, that doesn't mean I believed them.
I read a account in Popular Mechanics before I was even in the USAF of a OH-13 coming back from a mission, with a arrow stuck in it.
The tailrotor gearbox isn't just thin sheetmetal, it was cast aluminum, IIRC, I just don't think a arrow wouldn't penetrate it, it might crack it.
I just don't see a VC or NVA expending the effort with a arrow when they had plenty of small arms, and light AA even.