All you need to keep the blue side up is an AI
. Why not use the compass? Lead it and lag it and all that fun stuff. If they stick a backup turn coordinator and DG
in there, they may as well ditch the PFD and go back to the classic sixpack. If you're in radar and radio contact so much the better. ATC
can tell you when to start and stop your turn.
The backup AI
is electric and independently powered, just as reliable as a turn coordinator. Of course it has the potential to tumble, but if you manage to do that, you probably wouldn't recover with a turn coordinator either.
Really it's just a paradigm shift. The old partial panel was airspeed, altimeter, VS
, and TC
. The new partial panel is airspeed, altimeter and AI
. Different, but not worse. Instead of turning at standard rate, you'll turn at a set bank angle and speed to give you an appropriate rate of turn (figure this out before you have to do it for real).