Originally Posted by
shdw
This isn't actually the case, though it seems intuitively so. As long as the descent rate is constant, this formula holds true.
While flying straight and level, lift must equal weight. When banked our total lift must increase to keep vertical lift equal to weight, just like when straight and level. But wait, doesn't lift also equal weight in a steady climb or descent?
descent rates in Ag turns, base to final turns, intial engine out glider turns, lazy 8s, wing overs, etc... don't have to be constant and the rule here doesn't apply.