New alternator kit from Vans with OV

[rwtrwtau]

I have a B&C SD-8, standby alternator to install on the vacumm pad. I want to be able to turn the main alternator on and off in flight to check the SD-8 is operational. Does anyone know if this is possible?

I asked Vans and they told me all of their alternators could be switched off in flight. I seem to recall hearing on the aeroelectric list that this was not the case.

Another option is to adjust the regulator on the SD-8 such that it puts out 0.5V more than the main alternator. That way I would not need to turn the main alternator off once energised. Does anyone know if this would work?

Thanks
Richard

(Desperately trying to avoid spending $'s on B&C externally regulated alternator)

[gmcjetpilot]

Originally Posted by rwtrwtau

I have a B&C SD-8, standby alternator to install on the vacumm pad. I want to be able to turn the main alternator on and off in flight to check the SD-8 is operational. Does anyone know if this is possible?

I asked Vans and they told me all of their alternators could be switched off in flight. I seem to recall hearing on the aeroelectric list that this was not the case.

Another option is to adjust the regulator on the SD-8 such that it puts out 0.5V more than the main alternator. That way I would not need to turn the main alternator off once energised. Does anyone know if this would work?

Thanks
Richard

(Desperately trying to avoid spending $'s on B&C externally regulated alternator)

Let me say that (I think) this info comes from me. If you have a stock ND (nippondendso) alternator with an internal voltage regulator, I would Highly recommend you don't do it (cycle main alternator) in flight, or at all, ever. Yes the IGN wire may turn the alternator ON and OFF, as Van says while the engine is running, but it appears that grief can happen and has happened to those who tried this.

Why? No definitive reason, but it seems that when you do thus, ESPECIALLY, at high RPMs and with electrical load the alternator does not like it and can do weird things. Weird things? Yes fail or it becomes unstable and the voltage becomes erratic. How do I know this? I have made it a little mini mission to get the truth. I was reading about all these hysterical sensational stories of bad things with I-VR's a few years ago. Some where suspect at best and sounded like a sales pitch for another brand. After much research I found most stories where just that, stories, urban legend, either exaggerated, about another alternator altogether or just fiction.

HOWEVER that does not mean all is perfect. There have been many cases of low grade over voltage conditions. (Low grade, under 18 volts). Now the PUNCH LINE. Many of the problems seem tied to the pilot flicking the alternator ON and OFF while it is running under load. One guy always started the engine with the alternator off, than would flick the alternator on after start, and he would shut the alternator off before shut down. WHY? It does nothing and the alternator needs little power or HP to turn during start, because they don't come "on line" until the RPM comes up. After a while the alternator stopped responding to the IGN (ALT) switch and had unstable voltage. Another case the guy did what you say you are thinking of. Cycle the alternator in flight under load. When the pilot did this, to an alternator that was fine just before, the alternator voltage became unstable.

Keep in mind these alternators are made originally for cars. How do they work in cars? They are energized before starting the engine and are turned off when you turn the engine off (and much of the electrical load). Remember that I-VR alternators, the ND's in particular are internally powered. The "IGN" wire is only a signal to tell the alternator to rest when the car engine is not running, to save the battery. It can turn the regulator on and off under load apparently, but that is not the function it was meant for. The regulator gets its power from the B-lead (battery lead) not the IGN lead.


Long and short, there are better ways to see if the AUX alternator works. One method would be a dedicate maintenance run up. Do not turn alternator "IGN" power on and start engine. As Van said it should control the alternator. Turn AUX alternator on and apply electrical load (landing lights). Not Volts/Amps as appropriate. Shut engine down (with out powering the main alternator).

The other method is before shutting down the engine after a flight, turn all electrical power off, go to low idle and turn the main alternator off. I know I said don't turn the alternator ON/OFF while the engine is running at full speed, but I think the least risk would be to do it at idle with min electrical load. Once the main alternator is off, turn AUX on, Rev the engine, apply load and observe instruments. After test shut engine down. Do not turn alternator on.

As far as risk, the worst thing you can do is have the engine at relatively high RPM, with electrical load and turn it ON. There is more than one case where a normally operating alternators was cycled in flight, followed by immediate problems. I have no hard evidence, just that I can point to the application the alternator was designed for does not subject it to this kind of LOAD DUMP/SURGE. I could 100% wrong, but after following the few problems, in every case but one, the pilot did some variation of cycling the alternator under load; I am convince there is a correlation.

The IGN lead is not intended to "switch" large amps. It is just a go to sleep or wake up signal while the alternator is about to start turning or stop turning. Be nice to your alternator.

George

PS. I don't know if running the main and the AUX in parallel is a good idea. I think the idea of not turning the main alternator on, to do a dedicated AUX Alt ground test is best and eliminates of any worry. How often do you need to test the AUX anyway. Once a month, a year?

[RudiGreyling]

Just to open this thread again...has anyone fitted a new Vans Altenator to an XP360 without any problems. I remember seeing some picture of slight belt miss allignment somewhere, but cant remember if it was the new or old type of altenators.

Any info appreciated.

Kind Regards
Rudi

[Gary Bricker]

The main difference is the quality. We had a couple of the RB in my area that would not work out of the box. One builder took it to a alt shop and he said it looked like a wrecking yard unit.

[Jekyll]

Originally Posted by rwtrwtau

I have a B&C SD-8, standby alternator to install on the vacumm pad. I want to be able to turn the main alternator on and off in flight to check the SD-8 is operational. Does anyone know if this is possible?

I asked Vans and they told me all of their alternators could be switched off in flight. I seem to recall hearing on the aeroelectric list that this was not the case.

Richard

(Desperately trying to avoid spending $'s on B&C externally regulated alternator)

Richard:

I've got the same set up and had the same question. I conferred with both Bob Nuchols and the designer/manufacturer of the Plane Power alternators to discuss the point about shutting off the main alternator to test the SD-8. Both said not a problem. You will be doing this at a low power level (engine and amp draw) so it won't pose any problems.

I dumped my plan to buy a B&C alternator and LR-3C-14 regulator and went with the Plane Power 60 Amp alternator. I redrew my schematics and saved enough money to upolster my seats with the difference.

Jekyll

[Sprig]

Hail RAF Warrior Richard,

Originally Posted by rwtrwtau

...I want to be able to turn the main alternator on and off in flight to check the SD-8 is operational. ...

I'm not real knowledgeable on multi-sourced power systems.

However, having said the above, I'd rather LEAVE both systems ONLINE and functioning, then INTENTIONALLY shutting one OFF in-flight.

In MY opinion, the best solution is to use an ESV to monitor both outputs. If the SD-8 IS operational as backup, and you "shut down" the main system. You may also be inclined to further troubleshoot the SD-8 and "shut it down" too!

Shutting down a system, to test the backup system, seems a poor choice to me.

I'd like to KNOW if the backup was working (and the primary too!) before the primary fails.

Maybe I'm only half as smart, and twice as crazy as I think I am.

[Jekyll]

Richard and Sprig:

Sprig, I agree, don't be turning that charm off in flight, save it for when you're on the ground.

Shut down the main alternator on run-up to test the SD-8 before flight. Or, start you engine using the e-buss to check your SD-8. Lastly, an alterrnate method is to shut down the main after flight during your shut down sequence to test the SD-8.

Here's a tid-bit I just read from Bob Nucholls, I'll paraphrase:

"the chance of both your main alternator and your backup going bad on the same tank of gas is astronomical"

Further, the SD-8, being a permanent magenet, should have VERY high reliability.

Jekyll