[hblanks]

It'd be hard to understand without feeling it for yourself, but in actual instrument conditions (IMC), it's easy for your sense of balance to mislead you into thinking you're level, when in fact you're turning.

There's some physiology to explain this, but one key point is that once you're in a coordinated turn, even a descending one, your weight is still going straight down the vertical axis of the seat. So, you'll think you're doing fine, and possibly even pull the turn tighter (the graveyard spiral), and fixate on things other than the attitude indicator and your plummeting altitude.