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).

 

[Cactus Charlie]

From the G3X Touch Pilot's Guide - "When enabled, the 'SET BARO' CAS message will be displayed on the PFD if the barometic altitude diverges from the field elevation, while the aircraft is on the ground."

I do not have this alert enabled but it seems it was enabled in the "guest" config file.

 

[Neal]

Yes. I get that message.

 

[Neal]

Just to reiterate, it's important to know your aircraft and your systems. Something drilled into us in the Air Force via classroom, it was not an option.

If you have VOLTS 1 (starter) battery voltage on the sidebar and not AMPS then by the time you get a failure indication you're already in a secondary failure. Your alternator failed and now your starter battery is alerting and now you need a plan and fast. I don't ever want to be in a condition where I have to rely on my backup ignition battery, personally! Being aware of any failures as soon as they occur is critical to me. Personal preference but as noted, this is why I actively monitor AMPS but with the new config it will help me with my awareness.

At delivery (CubCrafters aircraft) you are not aware of an alternator failure until you are at -10A for alerts. I'm not sure when that occurs, maybe it's instant when the alternator goes offline, I'd have to pull the FLD (field) breaker to see what happens.

Keep learning! Don't be ignorant of your aircraft systems, engine, avionics, flight controls, etc. I have a passion for learning so this aircraft ownership experience, especially with limited information provided to aircraft owners, has been quite the journey.

 

[Cactus Charlie]

At delivery (CubCrafters aircraft) you are not aware of an alternator failure until you are at -10A for alerts. I'm not sure when that occurs, maybe it's instant when the alternator goes offline, I'd have to pull the FLD (field) breaker to see what happens.

The battery discharge current will depend on system load and that will vary with aircraft configuration.

My aircraft with all avionics on, strobes on, and landing lights flashing, pulls less than 10 A. I would not expect to ever get battery AMPS Alerting in the "as delivered" alerting configuration.

If you test by pulling the Field CB you need to do it at typical cruise rpm as the ignition module current increases with rpm. Do it with and without the electric fuel pump on. (I would suggest not running the test in flight.)

The following plot is a typical flight for my FX-3. I derived system load by subtracting battery charge current from alternator output current. The variation of load for run-up, takeoff, and fuel pump on/off can be seen. Derived system load is the current that would have to be supplied by the battery if the alternator failed.

 

[Neal]

I got the new config installed but not yet tested, may be able to get the plane out of the temp hangar tomorrow. Was blocked tonight.

I changed the SHUNT 1 config so it will alert at -5 AMP instead of the factory set -10 AMP condition which is not a good config. My custom setup done by @Cactus Charlie will alert me at -3 AMPS with the engine running but everyone should consider the change below for your alert level of a failed alternator. Ignore the asterisked item, that's what @Cactus Charlie added.

FACTORY CONFIG:

NEW CONFIG:

 

[Cactus Charlie]

I cannot let this go without comment.

You need to know immediately if the alternator has stopped providing sufficient current to maintain all system loads. That point is reached when the battery current becomes negative.

Anyone who does not want their Carbon Cub wrecked because the alternator fails should configure a battery current alert that triggers at ZERO amps.

I did this over 4 years ago on my FX-3 and nothing in this thread has given me any reason to doubt or change that design decision.

(I created a red+alert configuration that tripped at -3 A for test because that is what I was requested to do, not because I thought it was a good design).

 

[Neal]

You certainly didn't give any feedback for discussion

It's dependent on the plane. My plane at max demand will go to zero amps which is landing lights on steady and taxi lights on. That's 4 x WAT G3's which can draw up to 3.8A each. Add in the avionics and I'm at zero amps at full load.

This is why I chose -3. Maybe I'll tweak it to -1. Maybe through discussion here people including self will learn that -5 for the alert is incorrect and it should be a lower threshold. In my case I'm expecting the custom config of -3 to alert me first. I expect at normal load for daytime flying on a glass panel, at least IFR config, -3 will trigger on alternator failure, if not even -5. This is assuming a fully charged EarthX which can draw over 20 amps when charging. But the calculation comes in as to what load am I pulling from the starter battery without an alternator and that's what people need to ensure that value that will go negative will trigger an alert.

It wouldn't hurt to set a low negative value such as -1 and see if you're getting false alerts. You probably won't. If you find you are getting alerts then adjust as needed. In the end, know how to make this change in your G3X configuration area.

The WAT Parmetheus Plus in your FX-3 and most other CubCrafters aircraft until recent are insufficient for lighting IMHO. I upgraded mine. Huge difference but needs more power. I digress.

 

[Cactus Charlie]

You make something very simple seem complicated. It really isn't.

If the battery current is negative the alternator is not supporting the current system load and the battery is discharging. I want to know that immediately. No alerting threshold except ZERO gives me that information!

 

[Neal]

It’s fine. It’s how I iterate a problem to come up with a solution. If we didn’t have these discussions I would have never been aware of the current alert setting of -10 amps which obviously needs adjusting.

 

[Cactus Charlie]

You make something very simple seem complicated. It really isn't.

Well, having given everyone the chance to contest that statement, I'll tell you why it is actually a bit more complex.

In an FX-3 or EX-3 the ignition modules are powered directly from the battery and are powered regardless of the state of the Master contactor. They only draw a few micro amps when the ignition switch is Off.

When the alternator is working and charging the battery, the shunt current (AMPS display) is the sum of the battery charging current and the current drawn by the two ignition modules. Any system load (lights, strobes, avionics, etc) is powered directly from the alternator and this current does not pass through the shunt.

When the alternator fails, if MASTER remains On, the shunt current (AMPS display) is the system load (lights, strobes, avionics, etc) but does not include the ignition module current. The actual battery discharge current is now AMPS readout plus about 2.4 A for the ignition modules.

This does not change my position that zero amps is the correct threshold for AMPS alerting. However, it may provide some insight on how to interpret the AMPS reading, particularly when load shedding after alternator failure.

 

[Neal]

I don't see how alerting at zero amps can hurt for people to set as a starting point and learn from there. If you're getting alerts and you think you shouldn't then dig into why you're getting an alert. I may set my "engine running alert" to 0 and my default alert to -1 and see how that works. Knowing I'm exploring with alerting I'm not going to pull the BRS if I get an alert

In my case I need to test at full load as mentioned which is all 4 WAT lights on. I only tested this briefly to make sure I wouldn't go dark at night if I opted for all lights. I only anticipate using this configuration in a high traffic environment for anti-collision purposes.

 

[Cactus Charlie]

If all light on causes AMPS less than zero it is no reason to change the alert threshold from zero. It is correctly warning you that the battery is discharging, a condition that will eventually cause the engine to stop.

Don't want to discourage you from experimenting though and you need to decide what works for you.

 

[Neal]

Thanks. Good points. I'm just trying to learn and understand the ramifications so I don't get an alert unnecessary. This is the reason for this discussion and why I like this forum so I can learn and others watching this can learn too. Obviously the -10A alert should be a red flag to people to change, in fact CubCrafters should publish a bulletin to make owners aware after what I (we) have learned here.

Now I'm wondering if the advanced gauge setup is even needed if I'm going to set an alert at 0 amps? It may be moot now.

 

[Cactus Charlie]

Now I'm wondering if the advanced gauge setup is even needed if I'm going to set an alert at 0 amps? It may be moot now.

I have had yellow AMPS alerting at ZERO amps for over 4 years and it has never tripped in flight. I have not configured a conditional AMPS red alert but I do have Alternator current monitoring and alerting on my FX-3. Any red alert that I added would be on alternator current not shunt current.

I don't know what alerting convention was used in the A-10 but, for the transport aircraft I worked on, RED with master warning means immediate crew action required.

FX-3 alternator failure requires master warning but a brief battery discharge does not. You can't implement that with shunt current only, you also need alternator current monitoring.

 

[Neal]

Good point. Yeah, we had an entire panel of rows of lights that triggered the master caution. I think anything out of limits triggered, there was not warning stage. I think the yellow vs red concept is a good point. 0 for a yellow alert, use the conditional at -2 or -3 for a red alert so it is a progressive warning system.

 

[Cactus Charlie]

"If warning, caution, or advisory lights are installed in the cockpit, they must, unless otherwise approved by the Administrator, be--
(a) Red, for warning lights (lights indicating a hazard which may require immediate corrective action);
(b) Amber, for caution lights (lights indicating the possible need for future corrective action);
(c) Green for safe operation lights; and
(d) Any other color, including white, for lights not described in paragraphs (a) through (c) of this section, provided the color differs sufficiently from the colors prescribed in paragraphs (a) through(c) of this section to avoid possible confusion."

ref - https://www.faa.gov/regulations_pol...ttees/documents/media/TAEas-wcal-04232002.pdf

 

[Neal]

Here is my latest revision which I flew last night. I did not mess with any breakers or test things, it's been a while since I flew and I was racing sunset. I made a revision prior to flight, didn't like it, revised after flight to come up with this. I welcome any and all feedback.

The * item is the conditional alert that only triggers with the RPM > 600, i.e. engine running alert.

I wish they allowed decimal amps.