Lost all electrical

[GuppyWN]

757EFB98-CB69-4736-B943-1B928DAE6471.jpgGuys,

I didn't build my airplane and electrical is voodoo to me. Was flying today lost all electrical. Everything. First indication was turn coordinator half-flagged. A couple minutes later everything quit but the engine. Made a b-line for the airport. Short final everything came back up. After parking I fired it up again. 10 volts. Tried resetting the main and "alternator" circuit breaker. No change.

First thought was the stator but someone else suggested the voltage regulator. Not knowing any more than I do I'd think I could start the engine and check the in and out on the regulator and have a pretty good idea.

I know this is a VERY general question but - ideas? And just to verify, if this were to happen again and the battery was depleted the 912ULS engine will quit, correct?

[jrevens]

... And just to verify, if this were to happen again and the battery was depleted the 912ULS engine will quit, correct?

No, unless you have eliminated the original ignition system and are using something else that runs off the battery. The 912 engine produces its own dedicated power for ignition. Original builder or not, you should learn everything you can about your airplane and it’s systems.

[109JB]

The item I see under the battery is the starter relay.

[Dave S]

Guppy,

I'd fully support John's comment "Original builder or not, you should learn everything you can about your airplane and it’s systems."

Hopefully the original builder created and provided an equipment list which should tell you what kind of battery you have and how it should be handled/charged/diagnosed as well as kept the build manual with the aircraft for reference concerning how the system is assembled. These items are key to learning and understanding the systems.

There are standard lead acid, AGM and lithium batteries used by various builders. The lithium ones in particular have some unique handling/charging procedures. I am NOT suggesting the battery is the problem; however, the operating system voltage should be 14 volts. 10 volts @ operating conditions suggests the battery has lost much of its charge and is not getting recharged for some reason.

What you have provided indicates the charging system is not doing its job; but, I don't want to venture any specific guesses about what the problem might be because that could potentially mislead you.

Careful and purposeful diagnosis will get you there.

[jiott]

Several years ago I had pretty much the same thing happen. I saw the battery voltage going down and not recharging; fortunately I noticed it in time and was able to make it back home before everything shut down (the engine would have continued to run). It turned out to be a failed voltage regulator; replaced it and all was fine.

[n85ae]

With your battery down to 10 volts, it sounds like your fault is in the charging system and things started dropping off as
the battery ran out.

Charge your battery up, start the engine and see what your voltage is with the engine running. It should be 14+ if the
alternator is working.

next step would be to figure out the wiring of your alternator/regulator, most likely it will be exactly as per the manufacturers
schematic, so it will probably be simple.

Voltage regulator seems a logical guess.

I'm not a Rotax owner, but this seems a reasonable guide:

Testing Rotax 912/914 Generator and Voltage Regulator/Rectifier (pointsforpilots.blogspot.com)


I have read some notes about Lithium batteries, and that the surge current for charging after
an engine start is suspected of causing some alternator failures with Continental engines. Not sure that
this is at all related, but I'd be a bit suspicious about problems if this is what's installed.


Jeff

[Eric Page]

Without being there with a multimeter it's hard to diagnose anything, but the first things I would check are to ensure you have a clean, tight ground from the engine/alternator to the firewall ground point, and that all other connections on the alternator and regulator are clean and tight as well.

If you don't have it, consider installing an active notification of low voltage, with a set-point just below the normal operating bus voltage, but above battery voltage. This can be an alarm in your EFIS or a simple "idiot light." Either way, it will tell you immediately when the charging system isn't working and you're operating on battery only.

---

Your photo also shows an unrelated problem: the builder secured hoses and wires directly to the engine mount tubes using nylon zip ties. Believe it or not, over time engine vibration can cause those ties to chafe into the tubes, causing damage. The rubber hose hanging from a tube at bottom right in the image is especially problematic due to its weight and its connection to the engine, which moves relative to the mount. I would replace any nylon ties on a steel tube with Adel clamps or at least a non-chafing zip tie like GripLockTies.

757EFB98-CB69-4736-B943-1B928DAE6471.jpg

[jiott]

[QUOTE=Eric Page;98368]
I would replace any nylon ties on a steel tube with Adel clamps or at least a non-chafing zip tie like GripLockTies.[QUOTE]

Or use silicone tape around the steel tubes, under the nylon zip ties.

[Delta Whisky]

Jeff - thanks for posting the regulator test link. It is now bookmarked (for the day I hope I don't need it.) I was surprised to see the author say the open circuit voltage (alternator) at high rpms is 30 - 40 Vac. Other sources have written that it approaches 100 Vac. I'm wondering if Rotax made changes of that magnitude between dates of articles. (Or, I just read something wrong.)

[GuppyWN]

Learned a bunch so far guys. I'll report back. Appreciate it!