Question How to get a red CAS alert for an alternator failure on the Garmin G3X?

[Neal]

A new thread to discuss a specific topic from this thread from an engine failure situation that occurred due to an alternator going offline due to a wire terminal failure. This thread is to determine how to configure the Garmin G3X using the advanced gauge display functionality and logic controls to show a red CAS alert when the alternator amps go below zero with the engine running.

Thank you to @Cactus Charlie for helping to figure this out.

I think the new G3X conditional scale color bands and alerting would make it quite easy to issue a RED CAS alert with Aural warning if battery amps went negative in flight while the engine was running.

See "advanced gauge" in the current G3X installation manual. It takes a bit of experimenting to understand the concepts but it opens up all sorts of possibilities for customizing the displays and alerting.

 

[Cactus Charlie]

Ok, the first step in any new design is to define the requirements.

We want to be alerted immediately to alternator failure but we don't want nuisance alternator fail alerts.

Most FX or EX with a Garmin suite will have standard CubCrafters instrumentation which means battery current is available but alternator current is not. So we use battery discharge as a proxy for alternator failure.

We are assuming that the existing amber BATT AMPS is not sufficient warning of alternator failure - Is that a valid assumption?

Battery will show discharge as soon as master is on and until engine start provides alternator output. Is engine running the only condition required for alternator fail alerting? If so, what rpm should we use?

Do we want alternator fail alerting on ground or only in flight? Can we assume that a pilot scans all the instruments before takeoff and would see amber BATT AMPS?

Garmin does not allow user defined alert text so any alert based on BATT AMPS will be "BATT AMPS". We define the color and the current (and other conditions for advanced gauges) at which it is displayed.

The simplest implementation would seem to be:

If engine rpm greater than idle (say 600 rpm?) and BATT AMPS less than existing BATT AMPS amber threshold then display BATT AMPS RED with aural "Current" alert.

It's easy enough to make the alert only display in flight based on airspeed and time but that may be an unnecessary complication.

Comments or suggestions?

 

[Neal]

We want to be alerted immediately to alternator failure but we don't want nuisance alternator fail alerts.

Correct

We are assuming that the existing amber BATT AMPS is not sufficient warning of alternator failure - Is that a valid assumption?

Correct

Battery will show discharge as soon as master is on and until engine start provides alternator output. Is engine running the only condition required for alternator fail alerting? If so, what rpm should we use?

600 RPM should work as it indicates engine started. I was thinking if we wanted higher like 1000 which is when loads are probably going to be brought online such as AV, etc. This may need adjusting.

Do we want alternator fail alerting on ground or only in flight? Can we assume that a pilot scans all the instruments before takeoff and would see amber BATT AMPS?

I want to know as soon as amps go negative so ground for me. I had a field breaker pop and I saw the negative amps. I'd rather not takeoff with a failure I didn't recognize.

My only concern in the config is that any loads added don't trigger an alert. My plane has two higher powered landing lights I upgraded to which draw 3.8 amps each (max) so if not in wig-wag and both are on it can be a higher load. Combine that with my pair of the same lights but taxi light versions I can get near 0 amps with the alternator running normally with iPhone connected (USB loads) and all four lights on in a worst case condition. So consideration for < 0 vs < -1 amps should be considered as to when we alert for a higher load scenario without failures.

 

[Cactus Charlie]

So consideration for < 0 vs < -1 amps should be considered as to when we alert for a higher load scenario without failures

The current readouts have some error so have to account for the worse case loading condition and any tolerance in the measurement. Give me a number and you can change it later if needed.

If you have logs showing battery current going negative with engine running at low rpm please email me.

I think I have enough to establish the structure. Fine tuning thresholds should be easy enough.

The basic concept is to establish an "invisible range" on the rpm readout. We'll assume that range is 600 - 3000 rpm. When rpm is in that range a logic signal will be set. There is no change to the presentation of the rpm scale. The change is invisible.

The BATT AMPS scale will be revised to have an addition set of color bands that are active only when that logic signal is active. The color band changes will include a "red +alert" range from zero to -30(?).

Maybe you can do it quicker than I can.

 

[Neal]

Let's use a negative 3 amps as the alert point. The gist for now is more how to do it, each aircraft owner can modify it. This is just a learning exercise to get us started and understand the advanced gauge and logic functionality.

Thanks!

 

[Cactus Charlie]

I remembered this morning that "BATT AMPS" is not standard. I renamed AMPS to BATT AMPS to distinguish from ALT AMPS.

I looked back through some early screen shots and I don't see any alerting for battery current before engine start. In my current FX-3 configuration I do have battery and alternator current alerting before engine start. Both would remain displayed after engine start if the alternator was not working.

If my interpretation of my early screen shots is correct the only alerting for alternator failure in a standard FX-3 would be VOLTS 1 (red) but that won't be seen until the battery has discharged.

Here are my alerts before engine start. All go away after engine start if systems are normal. I could suppress most of these before engine start using the new advanced gauge logic but that was not available at the time I created these alerts.

 

[Neal]

I downloaded the latest G3X Installation manual to be sure I had the latest and extracted the two sections regarding Advanced Gauge Configuration and the samples in the Appendix. I attached the two PDF excerpts to the original post of this thread.

@Cactus Charlie and I are testing offline at the moment to create a config for my plane which I'll be testing shortly. Looks like an amazing capability, really cool!

It seems though the first simple solution is go to SHUNT 1 and set an alert on a lower threshold AMP setting. Currently it seems CubCrafters doesn't alert on negative amps until -10A. The config @Cactus Charlie is working on will check RPM to ensure engine is running and alert when AMPS go below -3.

 

[Cactus Charlie]

It seems though the first simple solution is go to SHUNT 1 and set an alert on a lower threshold AMP setting. Currently it seems CubCrafters doesn't alert on negative amps until -10A.

The standard configuration is hopelessly inadequate for alerting of alternator failure. Early in my FX-3 ownership I changed my Amps scale to "yellow + alert" when battery current is negative.

With conditional alerting it would be easy to have a yellow CAS alert before engine start and a red alert after engine start if alternator fails.

Red CAS alerts should give an aural warning so there is some advantage to going to the conditional alert solution.

 

[Neal]

I really hope as well that people will add AMPS to their EIS side bar. It's such a critical item to monitor in this plane with electronic ignition. Discussed in this thread.

 

[Cactus Charlie]

I really hope as well that people will add AMPS to their EIS side bar. It's such a critical item to monitor in this plane with electronic ignition.

I see no need to monitor a parameter that will be constant for most of the flight. I do think it critical to have adequate alerting for abnormal conditions. I do not have any voltages or currents on the sidebar.

 

[Cactus Charlie]

Some info the alerting configuration I tested for Neal.

He emailed me his current config file. I loaded it on my aircraft and made the changes outlined earlier in this thread. I then ran the engine and pulled the alternator field circuit breaker. AMPS red was added to the existing alerts.

The MFD electrical pane showed AMPS red but MAIN bus voltage well outside the alerting range:

Alerting for alternator failure happened a few seconds after the field CB was pulled. It would have taken several, perhaps many, minutes for the battery voltage to decay to alert level and the standard AMPS scale would never have alerted because current is far less than standard alerting threshold.

I did not have the headset on and did not verify that an aural alert was given.

(The other alerts may need explanation - FUEL PRESS was way higher with this config file than normal for my aircraft. Either Neal's aircraft uses a different fuel pressure sensor or there is a big difference in sensor calibration. TRAFFIC FAIL is because I did not power AVIONICS bus for this test. SET BARO cause is unknown. This alert is never present on my aircraft.)

 

[Neal]

I look forward to testing it mid-week. I know you said you don't put this info in the sidebar, I do and I keep my crosscheck on it. CubCrafters relies on VOLTS 1 in the side bar (starter battery) and I personally want to know as soon as possible my AMPS go negative. @Cactus Charlie used -3 AMPS for the alert per my request. I noticed from his screenshots CubCrafters doesn't have it configured to alert until -10 and quite frankly I'm not sure how far negative it will realistically go before it's too late and when the alert would trigger. This is a bad setup in my opinion so aircraft owners should be aware and consider at least putting in an earlier alert level.

@Cactus Charlie will share more once the testing is complete. Staying informed and alerted is extremely important to me especially with my lack of trust in the installed ignition backup battery which is probably a $10 battery that we pay $27 for (unless you buy from CubCrafters for $90).