Good point.  The commercials and the military for many years used a Jet (brand name) backup gyro that is electric.  It is 2.25” in diameter and its utility was that it was supposed to deliver 15-20 minutes of useful data after loss of electric power as long as turns were gentle and g forces kept out of the picture.

I have one in my IVP and I’m not sure just how reliable those promises are.  It’s been overhauled several years ago and now it looks like it holds attitude for a little while after shutdown, but I plan to do more monitoring of it as time goes on to find out just how much information would be available in the event of ---------------------@#%@.

John

I’ve noticed that the term ‘spinning mass gyro’ is being used in this discussion, as opposed to ‘vacuum driven gyro’. Does that mean you all are comfortable with an electrically driven AI? That would make sense if the AI contains only contains a simple electric motor which consists of windings and permanent magnets. Those tend to be very tolerant of voltage spikes. But if the electric AI contains even a single electronic component (voltage regulator, integrated circuit, etc), wouldn’t that make it vulnerable to the same lightning strike that took out my fancy EFIS, charging system, isolating diode, and backup battery?

Thanks,

Answer is pretty simple.  What makes it work?  If loss of electricity will mean loss of the instrument then that’s the reason not to replace your spinning mass gyro with this.  There are a couple of other instruments on the market similar to this and they are very tempting but they have the same drawback.  The steam gauges are there for only one reason -  save your ass if everything that can hit your avionics does so.

John Barrett