By Thomas P. Turner

It shouldn’t come as a surprise to learn that piston-powered airplanes have a number of limitations on their suitability for all-weather operations. Pilots—and Aviation Safety readers—have been known to argue vociferously about the relative safety and utility of various powerplant and system configurations. While consensus rarely results, few disagree on the need for some way to backup light-aircraft gyro instruments.

Especially in the case of IFR operation of older aircraft with gyros powered by air or vacuum pumps, we consider it essential that some sort of back up plan or equipment is carried. And even if you fly a newer aircraft with an all-electric system considered more reliable…