Alternator failure - checklist discussion

[Andy]

Any CubCrafters aircraft with a Garmin G3X Touch system and electronic ignition depends on the alternator to maintain full system capability.

In the years since I put a deposit on my FX-3 I have studied the architecture of the the FX-3 electrical and avionics systems and thought a lot about how I would manage an alternator failure. I eventually realized that I would not remember all the things I had thought about when faced with a real in flight failure so I decided to use the Garmin checklist editor to create an alternator failure checklist.

My first draft checklist is based on the assumption that the standard emergency ignition battery is unsuitable for intended function and I would only select it as a last resort. My philosophy is that non essential main battery loads should be shed and the ignition system should run on the main battery until it is exhausted.

An IBBS with a battery in good condition will power the G3X system at least 4 times longer than the ignition battery will keep the engine running. I plan to revert to IBBS power immediately on alternator loss to save battery capacity for ignition.

The draft checklist is specific to my unique avionics configuration but I'd like to hear how other owners have planned to deal with alternator failure and hope we can all learn from a discussion.

[cavok84]

Nice job with the checklist!

While I've only had my FX3 for a year and ahalf, as an airline pilot, I am very familiar with checklists (i.e.,the strengths and weaknesses), immediate action items(emergency "flows"), and the potential pitfalls of checklist use when operating under the stress of a potential emergency situation. Checklists are great for stepping you through complex procedural items but lousy for fully connecting you to the operation.

It also depends on how you intend to use the checklist; is it a check of what you've already done or a Do-List you accomplish step by step? This is an important aspect of developing a good checklist (i.e., imagine the scenario, do you see yourself reading a step, then doing that step, then moving on? Or are you going through items and ticking the steps as confirmation that you completed them?)
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In my experience, when operating under the pressure of a time-critical situation, the simpler a procedure, the better. When racing against the clock, it isn't uncommon for experienced pilots to get sucked into and overly bogged down in a checklist, because they feel that time pressure, and miss the forest for the trees (e.g., maintaining aircraft control and directing it along the intended path).

In this situation, you are still flying, but if you linger too long, it could turn into an engine failure scenario. What we really need to do is to figure out if we can fix the issue, and if not, where are we going to land, and how to extend our flying margin.
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I am far from a CC expert, and my entire post may be BS for one reason or another, but I'll share my thoughts on your procedure, as well as how I have thought about this situation in the past.

To the best of my knowledge CubCrafters has not provided an alternator failure checklist "template".

Amplified emergency procedures for Alternator Failure per the CC AFM
Alt1.jpg


Considering the possible configuration and equipment packages available, as well as the experimental classification, theCCX2000 AFM offers very general guidance with respect to emergency procedures.

An IBBS with a battery in good condition will power the G3X system at least 4 times longer than the ignition battery will keep the engine running. I plan to revert to IBBS power immediately on alternator loss to save battery capacity for ignition.

*My manual states that the IBBS should run the G3X for one hour, not two hours as you have listed in your checklist. And the backup ignition battery should provide up to 30 minutes for engine power.

the assumption that the standard emergency ignition battery is unsuitable for intended function and I would only select it as a last resort.

Can you elaborate on this? If the alternator fails at a point that demands we take action to conserve every last second of ignition power (not within the pattern or five miles from an airport), presumably, we are at cruise or at least have a decent amount of altitude and speed. In which case, I'd prefer to save main battery power for arrival and landing.

My philosophy is that non essential main battery loads should be shed and the ignition system should run on the main battery until it is exhausted.

Again, I came to a different conclusion when I thought of this back when buying the plane. While I agree that all non-essential loads should be shed, I would rather have some main battery power when entering the most critical phase of flight.
The main battery will power both ignition systems, allow for avionics use (should you have plenty to spare) in the approach area (if in high traffic density airspace), power a last-minute landing light should you be coming in at night, and can serve as a reserve to a nearly depleted but in-use emergency ignition battery (I.E., If landing is assured, turn the MASTER back ON and if the BACK UP dies, your left ignition is automatically running. If on short final, turn OFF the EMER BACKUP and now both ignition are powered).

I'll start by saying, I really like what you've done; I've never used the garmin checklist editor. Very cool.
But for me, I'm not overly fond of pulling a bunch of breakers (I do think pulling the ALT CB is a good idea) when i could do the same thing with the master switch, especially when I'd be in a safe place to confirm the backUP battery was working just fine.
Even if your procedure extends ignition life by a minute, there is a good chance I didn't turn to the airport as soon as I could've or am wandering around while reading the checklist.

I also would be somewhat concerned that the checklist could elicit a kneejerk reaction to shutting off equipment when you may-in fact-be able to recover the alternator (if a transient issue).

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So, here is how I thought of this situation (keep in mind I'm just now writing it down- off the top of my head).
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Let's set the stage.
Cruising along on a cross-country flight, we see the signs of an alternator failure--no smoke, electric fumes, or fire. Maybe we hear or feel signs of a mechanical or belt failure, or maybe one of our strobes shorted the system. Either way, we need to troubleshoot, and to do that I'd get rid of the electrics I don't need.

Troubleshoot:

Is there a chance I can get the alternator back online? Did a breaker trip? Unless I had to, I probably don't want to reset the tripped breaker until I know why it tripped).

· Shed unnecessary equipment (autopilot servos, strobes, lights, avionics)

· EMERGENCY IGNITION ON (provides for a quick warm and fuzzy test of the backup battery (right ign) AND keeps your engine running when turning the master OFF.

· MASTER OFF--after a few seconds--MASTER ON

-----ALTERNATOR REMAINS FAILED

Accomplish Emergency procedure:

If you were in contact with ATC, consider a BRIEF radio call: must turn off electrical equipment, need a vector to nearest field OR vector for flattest lowest terrain/road/highway. Remember that each radio exchange is eating into engine life, but depending on the environment, it may be worth it. DO NOT get into a protracted conversation and only bother with this if the benefits likely outweigh the costs. Hack your watch or clock if you have one!

· Master OFF—(Avionics OFF) Using your IBBS and GDU GPS, use the nearest function and sound judgment determine your destination (nearest airport with respect to flight time, weather, nearby terrain, roads etc.)

· FLY—Point the plane in the right direction; consider gaining altitude if low in a cruise climb. Think about your approach, develop contingency plans.

· Monitor Backup Battery Voltage—Should have 30 min, but I'd plan on no more than 20.
----Engine roughness
OR
----Approaching airport/Landing

· MASTER ON—If entering a towered airport or busy field AND you have the spare brain cells, establish communication (AVIONICS ON), otherwise (AVIONICS remains OFF) Lights on if landing is assured.


I like this because I shed everything with the MASTER, freeing me to focus on getting the plane moving in the right direction. It also saves a better ignition source for the far more critical phase of flight that is approach and landing.

[Andy]

Thanks for the comments.

I used the checklist editor as a convenient way to record my thoughts and to have them available for review in the aircraft. I think I know the aircraft systems well enough to shed non essential loads without referencing it.

My IBBS useful time and my emergency ignition useful time are based on actual discharge tests. I have observed an IBBS in good condition power my G3X system for over 3 hours. 2 hours is quite conservative. My low confidence in the ignition backup battery is also based on test data. I plan to replace the ignition battery with a second IBBS.

I see no value in attempting an alternator reset but I do see value in shedding the field current. I should have said FIELD CB not ALT CB. I'll edit that.

I have no main battery discharge test data but I'm confident that a fully charged battery will keep the engine running for a least 2 hours after shedding non essential loads.

We seem to disagree about the use of the emergency ignition battery and that's good because it's a subject I'd like all EX and FX owners to think about. I run on the ignition battery for about 10 seconds at every run-up. I periodically plot the data and the loss of capacity with time is very obvious.

[Andy]

"· EMERGENCY IGNITION ON (provides for a quick warm and fuzzy test of the backup battery (right ign) AND keeps your engine running when turning the master OFF."

Master does not control the ignition, ignition is battery direct. Each ignition module is fed by a circuit breaker on the front of the seat pedestal. Unless those breakers are pulled the ignition modules always have power. However, the ignition modules draw no current if the ignition switch is off.

Selecting emergency ignition at this procedure step tells you nothing except the the LED is working as the engine power does not change when RIGHT is on emergency but LEFT is still powered and On. Remember that the emergency ignition test during run up requires the ignition switch to be on RIGHT only.

[Andy]

Accomplish Emergency procedure:

If you were in contact with ATC, consider a BRIEF radio call: must turn off electrical equipment, need a vector to nearest field OR vector for flattest lowest terrain/road/highway. Remember that each radio exchange is eating into engine life, but depending on the environment, it may be worth it. DO NOT get into a protracted conversation and only bother with this if the benefits likely outweigh the costs. Hack your watch or clock if you have one!

· Master OFF—(Avionics OFF) Using your IBBS and GDU GPS, use the nearest function and sound judgment determine your destination (nearest airport with respect to flight time, weather, nearby terrain, roads etc.)

· FLY—Point the plane in the right direction; consider gaining altitude if low in a cruise climb. Think about your approach, develop contingency plans.

· Monitor Backup Battery Voltage—Should have 30 min, but I'd plan on no more than 20.
----Engine roughness
OR
----Approaching airport/Landing

· MASTER ON—If entering a towered airport or busy field AND you have the spare brain cells, establish communication (AVIONICS ON), otherwise (AVIONICS remains OFF) Lights on if landing is assured.


I like this because I shed everything with the MASTER, freeing me to focus on getting the plane moving in the right direction. It also saves a better ignition source for the far more critical phase of flight that is approach and landing.

I agree that MASTER OFF is the ultimate load shedding procedure. It's simple and easy to remember.

MASTER OFF automatically activates the IBBS as long as it was enabled. That's much simpler than forcing IBBS use when MAIN bus is above the IBBS activation threshold of approximately 11.5 V. However, it has the disadvantage that COM and transponder (ADS-B in and out), lights, strobes, are also lost. I'd prefer to spend a few minutes deciding what I can manage without, rather than rush to kill everything.

Monitor backup Battery voltage - this won't change as emergency ignition has not been selected on. If there was a procedure step that said Emergency Ignition On then right ignition is fed by the emergency battery and left continues to run on main battery.

[kshunz]

I agree that MASTER OFF is the ultimate load shedding procedure. It's simple and easy to remember.

MASTER OFF automatically activates the IBBS as long as it was enabled. That's much simpler than forcing IBBS use when MAIN bus is above the IBBS activation threshold of approximately 11.5 V. However, it has the disadvantage that COM and transponder (ADS-B in and out), lights, strobes, are also lost. I'd prefer to spend a few minutes deciding what I can manage without, rather than rush to kill everything.

Monitor backup Battery voltage - this won't change as emergency ignition has not been selected on. If there was a procedure step that said Emergency Ignition On then right ignition is fed by the emergency battery and left continues to run on main battery.

Andy, I'm confused by your last sentence. Is that possible, to simultaneously have the main battery feeding the left ignition and the backup battery feeding the right? I thought draw from the backup battery only happened with the right ignition selected and the ignition battery switch in EMERG position.

Copying you I think, I've been tracking voltage drop on the backup battery over the last 18 months. During runup, I select the right ignition, turn the ignition battery switch to EMERG, and wait 10 seconds. The voltage drop during those 10 seconds varies from 1.7V to 2.4V, but there doesn't seem to be any obvious trend.

ignition_voltage_drop.jpg

Perhaps it has to do with temperature?

I replaced the backup ignition battery at my recent annual inspection. But it turns out, that "new" battery was flat and wouldn't accept a charge. So I'm still running on the old battery while a new one is on order.

I test the IBBS battery annually. For the second year now, the voltage didn't change after 1 hour of use. (Apparently, that's the limit of my patience.)

With my 13-month-old backup ignition battery installed and a replacement coming, I'd love to devise a test to see how long it would keep the engine running. So far I haven't come up with anything that meets my risk/reward threshold.

[Andy]

Andy, I'm confused by your last sentence. Is that possible, to simultaneously have the main battery feeding the left ignition and the backup battery feeding the right? I thought draw from the backup battery only happened with the right ignition selected and the ignition battery switch in EMERG position.

The primary function of the emergency ignition switch is to change the power supply source of the right ignition module between BATTERY DIRECT and the emergency ignition battery. That power source change is not influenced in any way by the OFF/LEFT/RIGHT/BOTH ignition switch position. Also the emergency ignition switch has no influence on the power source for the left ignition module. Left is always powered by BATTERY DIRECT.

The emergency ignition switch has other functions and my schematic is annotated with several notes. The other functions include disconnection of Main Bus as the emergency battery charging source, the routing of alerting discretes to the G3X system, and powering the amber LED.

The reason that emergency ignition is tested with "mag" switch on RIGHT ONLY is that the engine runs at the same RPM with one ignition system operating as it does with both ignition systems operating. If the emergency ignition system was inoperative there would be no change in RPM if mag switch was BOTH. The engine will stop firing if only the RIGHT system is in use and emergency power had failed.

[Andy]

Refer to schematics -105 CC11-160 IGNITION SYSTEM and -107 CC11-160 IGNITION BACKUP BATTERY SYSTEM

My comment on the emergency ignition switch reads -

"Switch is shown in Emergency Off position. In this position points 1/2 are connected and right ignition has normal power from IGN R circuit breaker. Emergency battery is charged from MAIN BUS through switch jumper 5/3.

When switch is selected to Emergency On:
Main Bus is isolated; Right ignition point 2 is fed from Emergency battery via switch contacts 2/3; Warning LED is power by emergency battery through switch jumper 3/5 and switch contacts 5/6. Return path for LED and right ignition battery is via battery cable shield and point 7 (sheet 4 D4). This appears to connect to GEA 24 ground on P242 pin 6. "

[hawgdrvr]

I'm not confident in how long the ignition backup battery can power the ignition. I flew yesterday and did a more lengthy test (watch) of the battery drop during run up checks. It is a significant drop, I waited and wondered at what point is it going to stabilize down to. I think it was near 12, maybe 12.2, but it sure seems like a hefty load on that small battery. Anyone really tested how long we can rely on that battery for?

The other question I have on this topic is what are the real loads and what is the alternator really supplying? It seems for most of us or from what we see it's starter battery charging. But something is different in what we see in ALT loads vs other aircraft such as a friend with a RV-14. He see's a steady load of around 16A if I recall where we see typically around 2'ish once the starter battery is charged so we are not really seeing what current the ALT is supplying on a steady state purpose. This guy is a former FX-3 owner so this was eye opening to him and he asked other RV owners and they said it's normal what he is seeing. So that begs to question what are we reading and what is the real continuous demand on our alternators so if we were to lose that we can better know the impact.

[Andy]

Copying you I think, I've been tracking voltage drop on the backup battery over the last 18 months. During runup, I select the right ignition, turn the ignition battery switch to EMERG, and wait 10 seconds. The voltage drop during those 10 seconds varies from 1.7V to 2.4V, but there doesn't seem to be any obvious trend.

Perhaps it has to do with temperature?

I replaced the backup ignition battery at my recent annual inspection. But it turns out, that "new" battery was flat and wouldn't accept a charge. So I'm still running on the old battery while a new one is on order.

I test the IBBS battery annually. For the second year now, the voltage didn't change after 1 hour of use. (Apparently, that's the limit of my patience.)

With my 13-month-old backup ignition battery installed and a replacement coming, I'd love to devise a test to see how long it would keep the engine running. So far I haven't come up with anything that meets my risk/reward threshold.

The emergency ignition battery type is rated for 5 year life in standby use. I think it is used in alarm and emergency lighting systems. That environment most likely has zero vibration, controlled temperature, and a well regulated float charging source.

The environment in the CubCrafters application is the opposite side of all these desirable conditions.

Your battery test data is interesting. It does not show the rate of voltage decay but the end point voltage should still give good condition trend information. I don't know why you don't see the same trend as I do. I have similar data for, I think, 3 different batteries and they all look similar although some last longer than others.

I ran one in-flight discharge test a few years ago. I left the ignition switch on Both and selected emergency battery for right system. I considered this to be very low risk as the left system was powered by a fully charged main battery with a functioning alternator. I could have terminated the test at any time putting the right system back on normal power.

The reason I never did this test again had nothing to do with risk. I have emergency ignition battery current monitoring on my FX-3. I found that the charge current after 30 minutes use greatly exceeded the max allowed for the battery type. I considered the charge current to be potentially damaging to the battery. I did develop and test a simple charge current limiter but I never fitted it. I decided that the 10 second test gave good condition data and the charge current after that test is not damaging.

To produce the trend plots I cut the battery voltage data from the log file and import it into a separate spreadsheet. That spreadsheet has multiple columns of Volts 2 data and they are aligned vertically so the first voltage drop is at the same row in each column.

It would be interesting to see your data in the same format. PM if you want the spreadsheet.