That's why I really like practicing IFR with MS Flight Sim. I set the
instruments to fail randomly. The first few times the AI failed, I did tend
to follow the dead AI as it keeled over. I think it really improves your
scan. It just isn't the same when the CFII slaps a plastic disc over it and
says "You've just lost your AI." A good portion of the lesson was lost
already at that point.

" That is the main flaw with partial panel practice. You know the gyro
has failed. In a real failure, you may well not notice the failure until
it is too late.