By Paul Bertorelli

In the panel of every state-of-the-art GA airplane, you’ll find an eloquent answer to the question, “what if...?” It’s in the form of three steam gauges somewhere in the panel, an iron gyro, an airspeed indicator and altimeter fed by a conventional pitot/static system. By implication, the industry or the FAA must therefore think PFDs aren’t reliable enough to do the job without backup. Carrying the thread forward, one might conclude PFDs just aren’t that reliable to begin with. …