Hmm... Would be difficult to target small helicopters popping up for just a short period of time over hills to fire TOW missiles, according to you DIA document. I think the U.S repeated their mistake ( or did they ) when they overestimated yet another piece of Soviet equipment. It's good, but not THAT good people
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Picking out only one element of a multi level air defense system, can easily lead to over/underestimate its standalone capability.
(Strela-2/Igla, Strela-1/Strela-10, Shilka/Tunguska, KUB, KRUG/BUK) all of these were used to overlap each other.
Usually the Shilka operated in pairs (with Strela-1/10 pairs), two pair per tank/motorized regiment.
The OFZT flies at Mach3, while the TOW flies around Mach1...