Bill Boyd
Well Known Member
15 hours into phase one with a full Advanced Panel setup and dual alternators, Dynon shunt monitoring their combined output current...
Last week my Red Cube suddenly stopped registering in the middle of the day's flight tests. Visual inspection of the wiring at the cube shows no apparent damage - ok, I was thinking of moving it out of the tunnel anyway; replacing the Cube with a new one is my opportunity to relocate it. Meanwhile the plane runs fine without fuel flow monitoring so the test program soldiers on while I decide how to address the flow transducer failure...
Today in flight I get an aural warning "Check amperage!" The displayed amperage is typically about 25-30 with lights and full avionics load, but now I'm seeing single digits, dithering. Bus voltage rock steady at 14.2 under load. Now the alternator output is back to reading 25A... Now it's minus 9A... Back to positives... Down to zero, then negative... All the while the voltage is steady at 14.2V. I ignore the warnings and complete my test cards, land with the alternator output showing the nominal 25 amps or so.
Now I'm thinking back over the day's events - earlier I had an EGT probe (that I just replaced) read "---" for a few minutes, then revert to indicating normally ever since. Strange. Multiple electrical instrumentation anomalies that all have the EMS-220 in common. Tomorrow I'm going to do my RV yoga and crawl up in there to remove, inspect and re-seat the D-sub plugs on the EMS-220. Anyone else with Dynon/Advanced gear faced anomalies like this? My understanding of the basic electrical architecture is that it's not possible for the battery to push current into the alternator outputs (negative amperage reading), so the negative values I'm seeing would only be possible if the EMS/EFIS is somehow intermittently losing its reference to the amperage shunt offset/calibration values stored in the software. There's no way the battery could maintain 14.2V if the alternators were both dropping offline every few seconds, so I know they're not actually doing that.
Very curious what manner of wonkiness inside the EMS-220 could give readouts like this, and if it's somehow related to the sudden loss of my red cube readout the week prior. Input from any electron-herding guru's welcome!
Last week my Red Cube suddenly stopped registering in the middle of the day's flight tests. Visual inspection of the wiring at the cube shows no apparent damage - ok, I was thinking of moving it out of the tunnel anyway; replacing the Cube with a new one is my opportunity to relocate it. Meanwhile the plane runs fine without fuel flow monitoring so the test program soldiers on while I decide how to address the flow transducer failure...
Today in flight I get an aural warning "Check amperage!" The displayed amperage is typically about 25-30 with lights and full avionics load, but now I'm seeing single digits, dithering. Bus voltage rock steady at 14.2 under load. Now the alternator output is back to reading 25A... Now it's minus 9A... Back to positives... Down to zero, then negative... All the while the voltage is steady at 14.2V. I ignore the warnings and complete my test cards, land with the alternator output showing the nominal 25 amps or so.
Now I'm thinking back over the day's events - earlier I had an EGT probe (that I just replaced) read "---" for a few minutes, then revert to indicating normally ever since. Strange. Multiple electrical instrumentation anomalies that all have the EMS-220 in common. Tomorrow I'm going to do my RV yoga and crawl up in there to remove, inspect and re-seat the D-sub plugs on the EMS-220. Anyone else with Dynon/Advanced gear faced anomalies like this? My understanding of the basic electrical architecture is that it's not possible for the battery to push current into the alternator outputs (negative amperage reading), so the negative values I'm seeing would only be possible if the EMS/EFIS is somehow intermittently losing its reference to the amperage shunt offset/calibration values stored in the software. There's no way the battery could maintain 14.2V if the alternators were both dropping offline every few seconds, so I know they're not actually doing that.
Very curious what manner of wonkiness inside the EMS-220 could give readouts like this, and if it's somehow related to the sudden loss of my red cube readout the week prior. Input from any electron-herding guru's welcome!
Last edited: