For a circling approach the DHC8 can be flown using CAT A speeds (we use circling speed of max 109 knots for precision circling, and the minimums are determined "-100 minimums" because they are aircraft specific). It really doesn't matter which aircraft you fly; it's the speeds you use that matter. On a CAT B approach you must stay below the maximum of 135KIAS when reaching minimums. Note that the Categories with reference to 1.3 Vs are different from the categories concerning the approach itself. If an apporoach is labelled 'CAT B only'; any aircraft can fly it, provided they'll remain at or below 135KIAS (or, say, 130KIAS for the MAPt).