GRT Avionics

My engine has one electronic ignition and one magneto. They are wired to the EIS RPM/N1 and RPM/N2 inputs, respectively. I have verified that both N1 and N2 data are recorded in the EIS data stream. Usually, the two data fields have the same number, but during start or other changes in RPM, the two fields will show different values.

During engine runup, turning off the electronic ignition makes the tach display dial on the ENGINE page go to zero. This is a minor annoyance, as I am unable to quantitatively assess the RPM drop due to operation on a single magneto. My recollection was that the display is supposed to use RPM/N2 if RPM/N1 drops out, and vice-versa.

Recently, I had a failure in my electronic ignition during flight. For the remainder of the flight, I had no tachometer, and tach time stopped advancing.

Is there some setting that I have wrong? I think it is important to display RPM data from whichever source is active.

Thanks,
Byron

The standard tach inputs for a piston engine EIS and "RPM" display work this way since around EIS software version 75 (2009). If your EIS has software to show two independent tach readings such as on a turboprop/turbine then it will work differently. If you are showing "N1" or "N2" then those can stay separate because N1 and N2 are normally for monitoring different parts of the engine. The timers stopping with tach1 are a known software issue in all versions of the EIS.