Flying with alternator switched off causes total loss of engine power

[Waiex-guy]

There’s also the question of why were both batteries dead? Alternator off, so the first battery started the motor and ran the motor, until it didn’t. But what’s the point of having a backup battery if it isn’t charged. Or from the report, not selected either....

[MacCool]

Good cautionary tail. My new-to-me RV-9A has a (labeled) alternator switch, something I haven’t been used to in my decades of flying. Gotta remember to turn it on. It also has two switched batteries in parallel as well as two E-Mags. Their alternator function was checked at the condition inspection/pre-buy.

[MED]

Originally Posted by MacCool

Good cautionary tail. My new-to-me RV-9A has a (labeled) alternator switch, something I haven’t been used to in my decades of flying. Gotta remember to turn it on. It also has two switched batteries in parallel as well as two E-Mags. Their alternator function was checked at the condition inspection/pre-buy.

Check the pmag alternator function during every run-up. Run the engine up to 1800 rpm or so, then when you do your normal mag check, switch off the ship’s power to each pmag in turn, while the engine is running on that mag. (Hopefully, your installation includes these power interrupt switches. Otherwise, you would have to pull a breaker.). The pmags generate their own power when the engine is above about 800 rpm. If the internal generator has failed, you will know it when you switch off ship’s power. Fast and easy to check.

Edit: I just realized you wrote you had Emags. If that is true, they do not have an internal generator. Emags have not been manufactured for several years, but yours may be an old installation.

[Bicyclops]

Originally Posted by Waiex-guy

There’s also the question of why were both batteries dead? Alternator off, so the first battery started the motor and ran the motor, until it didn’t. But what’s the point of having a backup battery if it isn’t charged. Or from the report, not selected either....

The second battery probably was charged at first and ran down along with the other one with both switched on. A second battery is not a back up if it isn't held in reserve.

I have an electrically dependent engine and panel, two batteries, and two battery contactors. I have only one alternator and no alternator switch, just a pullable field breaker. The field is energized by either or both of the contactor switches. I normally close both contactors before engine start for faster spin and, once it starts, the alternator is running and charging both batteries. In the case of alternator failure, I would switch off one of the batteries to preserve it for later and run the other one down to about 10.5V (lead acid battery) before going to the reserve battery and getting on the ground at an airport of my choosing. I also have both batteries wired so that I can power my E-bus with either or both and not burn an amp on keeping the contactor closed. Yes, I do regularly check that the E-bus works with either switch and that either switch closes its respective contactor. Yes, I have good non-alternator load calcs.

Having a low voltage warning light is essential in an electrically dependent design. The pilot absolutely needs to have notice that the alternator is offline so that battery power can be managed. It is important that the battery(ies) be regularly capacity checked and that the pilot knows how long the system will operate with no alternator. That way an alternator failure is not an immediate emergency and never becomes one.

Ed Holyoke

[bobnoffs]

i have a viking 110 installed. it is operated on battery #1 or battery #2. it will also operate on only the alternator if both batteries go bad. batteries are earth x, each with its own warning light. my charging system has a warning light. each warning light has its own ''mini'' momentary switch to test each light before flight. i have a switch to turn on the alternator field and a 70 amp breaker on the b lead between the alternator and the bus. i also have an ovm on the b lead between the alternator and the breaker.

[Walt]

Originally Posted by vic syracuse

Another one of my pet peeves--- unlabeled switches!!!

Vic

I recently finished a CI on a "professionally built" RV14 with $$ glass, mag and a pmag. The pmag was never powered from external power from day 1, I figured out that a switch labeled 'com 2' was actually pmag pwr, however the owner never could figure out what the switch did so he just left it off.

[MacCool]

Originally Posted by MED

Edit: I just realized you wrote you had Emags. If that is true, they do not have an internal generator. Emags have not been manufactured for several years, but yours may be an old installation.

E-Mag is out of business?...I suspect they’d be surprised to hear that, and somebody should let Spruce know...

https://emagair.com/

https://www.aircraftspruce.com/catal...agIgnition.php

As to internal alternator...they say they have one, and my A/P tested for one and thought he found one.......but I’ve just come out of the dark certificated world into the light of the Experimental day. It would be easy to fool me.

[Toobuilder]

The "Emag" product, distinct from the "Pmag" product, has not been manufactured by Emagair (the company) in several years.

[MacCool]

Originally Posted by Toobuilder

The "Emag" product, distinct from the "Pmag" product, has not been manufactured by Emagair (the company) in several years.

Ah. I see...semantics. You’re saying that the current version of electronic ignition that E-Mag Air sells is the “P-Model”, which is self-powered. Yes. Now I get it. That’s what I have.

[MED]

Originally Posted by MacCool

E-Mag is out of business?...I suspect they’d be surprised to hear that, and somebody should let Spruce know...

https://emagair.com/

https://www.aircraftspruce.com/catal...agIgnition.php

As to internal alternator...they say they have one, and my A/P tested for one and thought he found one.......but I’ve just come out of the dark certificated world into the light of the Experimental day. It would be easy to fool me.

Emag, the company is alive and well. They now produce an electronic mag called a Pmag, which has an internal generator. They no longer produce an Emag, which did not have an internal generator. So, my previous description of how to test a Pmag during every pre-flight run-up apparently does apply to your electronic mags. Sorry if I created any confusion.