Essential Bus

[Danzer1]

Hank,

Good info for all. Can you post a link to the solar panels you used?

Greg

[Av8r_Sed]

Any idea on why the cap blew up? What was its voltage rating, value, type and how old was it? I've got an aluminum electrolytic in mine and I'm not fond of in-flight surprise explosions.

[Dave S]

I have come to the conclusion that if a person shares a cockpit with an electrolytic capacitor for enough hours/years, the opportunity of experiencing this kind of excitement increases.

I have had friends with normally certificated aircraft as well as experimentals have one go - always the same - a real good pop, smoke, stink etc that indicates it is well to land soon. Fortunately none of the incidents resulted in fire although the effects were certainly indicative of fire.

In my meager understanding of electrolytic capacitors, I hear a few things can cause one to pop including 1) reversed polarity (including a diode failure or short in the case of an alternator used in a DC charging system - which I understand can expose the cap to alternating current) 2) Overheating - which may be an effect of some other problem, 3) Physically decayed or corroded internally - that can happen with the liquid in the mat over time in a cap; and, 4) overloading (which likely results in overheating or internal shorting if the voltage is too high). Don't know the validity of the source; but, there was some scuttlebut about capacitors out of certain companies in Taiwan in the late 1990's and early 2000's with excessive failure rates.

Engineering options into an aircraft electrical system is certainly a route that can get a person out of the back country if something like this happens. I thought about that since most of the problems I experienced with normally certificated aircraft (or at least the ones I could afford to rent) involved charging system/electrical failures and I kept thinking nobody is going to flip start a rotax in the outback.

We took a slightly different route and used two complete and separate electrical systems - using the on board Rotax charging system for one and the optional auxillary alternator for the other - two busses, two alternators, two batteries (So I could be criticized for making the aircraft excessively heavy) two masters and a cross tie plus alternator breakers that can be pulled to disconnect if that becomes necessary - Normal operation - one system feeds the low draw equipment and the other system feeds the high draw equipment (the high draw equipment was the reason I wanted the aux alternator in the first place). A person can start and run the engine off either side or, use the cross tie to run both busses off either system with the other alternator & battery disconnected. The only real limit is no night flying if the low output rotax alternator is all that is left because it won't keep the radios and the lights going at the same time. (I know....there are LEDs available now, but that wasn't in equation when the plane was built.)

Sincerely,

Dave S
KF 7 Trigear
912ULS Warp Drive

[henrysamson]

The only real limit is no night flying if the low output rotax alternator is all that is left because it won't keep the radios and the lights going at the same time. (I know....there are LEDs available now, but that wasn't in equation when the plane was built.)

Sincerely,

Dave S
KF 7 Trigear
912ULS Warp Drive

I was looking at the same issue when I was building my airplane. I bought the lighting with the kit in '97. In the final months of construction I just replaced all of the bulbs with LEDS. Aircraft Spruce has the LED replacements for my Whelen wingtip nav and strobe light combo. I did not have to do anything but unplug the old bulbs and insert the LEDS. The only non LED lighting are the post lights on the panel but the current use is minimal and I wanted to be able to keep my low tech dimmer so they are original Now night flying is no issue as far as power is concerned. Actually, I keep all of the exterior lights on night and day for visibility.

[henrysamson]

Hank,

Good info for all. Can you post a link to the solar panels you used?

Greg

http://www.aircraftspruce.com/catalo...clickkey=13768

The larger one. I have it mounted in a manner that makes it very easy to remove. There is extra cable at the panel so I can, if needed remove the turtle deck, remove the panel and place it a few feet away, outside the aircraft and pointed directly at the sun. Never have had to use this feature although if I was really stuck in a remote location with a dead battery I would. It is covered by the Kitfox Aircraft cover which I usually put on the aircraft when parked overnight on an airport ramp. Which is too bad but I like to have the plane covered.

The output from the solar regulator is connected to the battery through a 15 amp line fuse using a molex plug. I can disconnect the solar regulator and have adapted a battery charger so I can plug it in at the same location. Makes it easy to give the battery a couple of hours of charge if I have not flown it for a while. I don't have to remove the cowlings and the battery box cover. The fuse is to avoid problems if there is a short.

I can also plug the solar panel directly into a usb adapter that allows me to charge my tablet computer or phone In the desert, after flying I often plug my tablet in to let it charge for the afternoon.

Any idea on why the cap blew up? What was its voltage rating, value, type and how old was it? I've got an aluminum electrolytic in mine and I'm not fond of in-flight surprise explosions.

The capacitor was provided with my firewall forward from Skystar back in '03 and flying since A/C completion in May '13. I still have it and will take a look next time I am at the airport and give the specifics and take a picture. The new one is the one sold by ACS and is much larger. I think that perhaps the extreme heat in the desert had something to do with it. It is pretty brutal. I also flew trough a lot of rain on the way there and perhaps some moisture made its way in although I had no other problems. Everything was working fine until it blew. I have an over voltage "crowbar" that would take the alternator offline on the DC side if the voltages go over about 16.3 volts.

Another pilot at the burn is an A&P and an authorized Rotax mechanic. He said that some of the newer light sport aircraft that he works on have dispensed with the capacitor completely. Perhaps the regulator/rectifier is not as sensitive as the earlier ones were reported to be. Also, I did use my radio, intercom and music after the regulator came back online and without the capacitor and there was no audio noise which is one of the reasons for having the capacitor in the first place. Along with protecting the regulator/rectifier.