Alternator cooling

[Nev]

Should I be putting a blast tube on the alternator? Is this a thing ?
I’m running tubes to the battery and both PMAGs.

[Nev]

In addition, what else should I be cooling?
I have an EarthX battery contained in a heat shroud. Should this normally receive blast air to the top as well ?
I’ve also seen mention of cooling for fuel pumps. Can someone tell me, is this for electric fuel pumps or engine driven ?

Thanks.

[svyolo]

It has been a while since I read anything on alternators, but I think the folks running blast tubes are using internally regulated alternators. FWIW I am also using a blast tube to my high mounted EarthX. 1/2 inch tube, just enough air to keep hot air out of the box. My dual EFI fuel pumps are low on the firewall, just above the exhaust. They are in a box, also with a blast tube.

[m.mooney]

I have an earthx on the engine side of the firewall and it was throwing a red overheat light at me during climb during hot summer temps. Installed a blast tube and it’s been happy ever since. My box is not the earthx insulated box, for reference.

[Nev]

I have an earthx on the engine side of the firewall and it was throwing a red overheat light at me during climb during hot summer temps. Installed a blast tube and it’s been happy ever since. My box is not the earthx insulated box, for reference.

Out of interest, how do you have the warning light set up ? Mine is currently wired to a spare input on the Dynon. The issue is that it won’t show the different flashing sequences, rather either an ON or OFF, which really tells me very little other than “hmmm, I have a battery problem but I’ve no idea what it is”.

[m.mooney]

Mine is just the earthx remote light installed in the panel. Sorry I can’t help with the dynon.

[Bcone1381]

Regarding Fuel Pump cooling From Post #2. Many engine driven fuel pumps are not cooled but it can be cooled air supplied from the upper plenum to a shroud. https://shop.vansaircraft.com/cgi-bi...product=shroud

Heat seems to be the enemy of running Mogas in a FI engine. The folks at Airflow Performance tell me if we Keep mass of the fuel system out of the fire wall fwd area the chances are much improved to run Mogas. (bendix mechanical FI) If you wont run Mogas, I would not worry about the shroud.

[PaulSA]

Nev. I think there is a way you can set up the Dynon warning so that it doesn't latch in; ie, when the warning ceases, the "light" goes out. That way it should flash. I'd also configure it so it doesn't give an aural warning otherwise it could get extremely annoying.

The only time you really have to worry is if the charge voltage is over 15.2v. That means all the safeguards (regulator, overvolt protection and BMS) have failed and you now risk blowing up the battery. That's a "memory item" - ALT FIELD to OFF. Everything else, you can continue and troubleshoot on the ground. Unless you have the battery on the firewall, you are unlikely to get an overheat - use a blast tube and you shouldn't have issues.

On my -10, the "Warnings" I have had have all been cell-balancing issues. It normally sorts itself out. Otherwise, I live with it till I next get the baggage bulkhead off and put the charger on which fixes it. The charge voltage is the critical thing.....

[Battson]

I installed blast air onto my alternator after I had the over-temp protection system operate one summer's afternoon during a long cruise climb.

So yes, I think so, but beware installing too much or unnecessary blast air - remember that every extra tube slows the aircraft down.

[svyolo]

My EFIS has an input for OAT. My EIS has another input for OAT. It also has an input for carb temp. I will use one of those to verify the temps that my battery and fuel pumps are seeing.

[BravoGolf]

I had high temperature issues with an Earthx battery on my RV-7. On a hot day it would start flashing pretty quickly. After trying different size blast tubes I ended up with a 1” tube directed at the battery. The battery box is wrapped with a head shield material to reflect heat. Since those modifications the EathX battery warning light has not come on. I also put the Dynon carb heat probe next to and above the battery. I’m sure I get some temperature influences due to the blast tube, but the temp around the battery seems to run around 95-100. On long taxis it can climb to 130.

The battery is in the standard RV-7 location, on the firewall right of center. I also have a smaller blast on the pMag, mag and alternator, but I don’t have any data or reference for the alternator tube.

[Nev]

PaulSA Thanks Paul, that’s really helpful (the EarthX Vol 8 ). I’ll do an unlatched warning, I know how to do that. Cheers.

[robcaldwell]

During my trip to Oshkosh, my main alternator (BC460-H) went offline. Once on the trip there during a fuel stop and while taxiing on a hot ramp. And once on the trip home after a long cruise climb. Fortunately, I have a back up alternator (BC410-H) mounted on the accessory case at the vacuum pump pad. The main alternator came back online after lowering the nose.

I am now considering where to install a blast tube for the front (main) alternator.

[zkelley2]

Jared, as far as the set voltage for the regulator, that's user adjustable. For the light, if you have an efis, there's not really a point. The EFIS should be picking that up.

[robcaldwell]

My battery is the Odyssey PC 680.

[jaredyates]

If you don't have a lithium battery then those numbers and behaviors are more alarming.

[Nev]

Rob, recently I had an electrical system fault indication in flight. We selected the electrical display on the EFIS and it showed the battery to be discharging at a fairly high rate. Fortunately I had another quick thinking Bearhawk pilot with me who grabbed my phone and videoed what we were seeing, and I sent the video to Dynon. The issue seemed to start when I was transmitting on the VHF.

Dynon replied that it was an indication issue caused either by having unshielded wires from the shunt, or having the VHF antenna cable running close to the shunt wiring. So in my case nothing was fundamentally wrong with the way the electrons were flowing, but the indication was showing a very high discharge. Probably very different to your case (particularly if the fuel flow transducer went offline), and I just mention it in case you do notice any similarities.

I gather that if your voltage indicated 12.9V for a period, then the battery wasn't being charged by either the main or backup alternator during that time, and was likely supporting the entire electrical load by itself (hence the high charging load when it came back online).

I have a cooling blast tube on my alternator running from the front intake with a lock wire through it that is attached to the alternator housing.

CF89CB4F-D8B4-4CA0-8C1D-FED052FB0DFA.jpg

[zkelley2]

Ya, mine did that to. Just re-route the VHF coax or just know it's an anomaly.

[rv8bldr]

Man, I'm loving the knowledge that is shared in these forums :-)

A big thank you to all you smart people who help us dumb people cope...

[Mark Dickens]

I was one of the early Dynon Skyview adopters having bought my equipment in the 2013-2014 time frame for the RV-8. After I finished my phase one testing and actually took it across the Memphis Class B, I noticed that when I keyed the mike, it all of a sudden would show my CHTs up over 500F (audio warnings and all) and then it would settle down after I let the mike key go. The frequency mattered and instead of being in the 122.XX range all the time, I was now below that or above it when talking to ATC. Apparently it was affected by all frequencies but some didn't cause the alarm to go off. Who thinks to study their CHTs when you key the mike?

Well, after contacting Dynon about it, they said, yeah we know about that and we'll fix it for free. And they did, but it was just the first of several issues like that where I had to dig out components of my Skyview system and ship them off to Dynon. The unfortunate thing is that they don't publish a list of "known issues", and I think they should. I'm sure that the equipment you're discussing is a lot newer than what I had, but still, it ought to be better at RFI filtering.

And yes, I'm using Skyview in my Bearhawk, even so...

[robcaldwell]

Nev "Rob, recently I had an electrical system fault indication in flight...."

Mark Dickens ... "I noticed when I keyed the mic...."

This is interesting... During my first flight and several others, my voltage indicator would shoot up when I would key the mic. I did not notice if this was frequency specific. I have since changed radios and have rerouted the coax cable to the antenna. I do not notice this indication quite as much, but to be honest, I really have not been looking. It really hasn't caught my eye. But will be on my list to look for when I fly again.

I am still on the path to install a blast tube that will be pointed at the back of the main alternator. (I need to terminate few other distractions before I can get to it.)