QUOTE=PapillonAir: George et. al.
When I said "second hand" I meant that I had heard it directly from the guy that had the problem, so now that I am passing it along it is now second hand info.
Thanks for getting back with more detail
recent flight, cruising along with everything normal, he decided to secure the alt. switch to see what sort of batt. capacity he would have available should he lose the alt. output (which I think is one of the reasons to have control of the alt. output, in addition to trouble shooting or securing a mis-behaving unit).
Absolutely, but only IF the alternator was misbehaving. Normal operation no. There is NO reason in my opinion the TEST the battery by turning the alternator off. There are load test you can do with them to determine their capacity. THIS IS IMPORTANT. A GOOD BATTERY IS SO VERY IMPORTNAT to a healthy electrical system. IT is not only for starting the engine and reserve power, it is the buffer or filter between the alternator and the BUSS.
He stated (in front of our chapter meeting) that as he re-activated the alt. he almost immediately got smoke in the cockpit, along with the little trim indicator meter literally blowing up and shooting out sparks and smoke!, all his "Vans" panel instruments were totally dead. He re-secured the alt. and got the thing on the ground asap.
LED's will blow easily with too much voltage, no kidding with a little bang and smoke. Van's gauges (I hate to be negative) are let's say built in the most cost effective way w/ no internal pwr filtering.
He found all his Vans engine instruments were melted / smoked with bad smells, and all other instruments / avionics having trouble or inop. Some good news from the avionics companies that were able to repair a lot of the damage, so he closed with the statement that he now will be going with the externally regulated type alt.
Yes the expensive stuff should have protection but don't always count on it. Old avionics allow outside supply power go direct to a "main board", unlike newer stuff. However some low cost stuff like the ICOM com radio (which I have and like) does not have internal protection, but it only cost $700.
I have come to the conclusion from hearing this incident and two other stories (which where minor but similar in that the pilot turned the Alt on/off under load), the common thread is switching the alternator while running. So if you don't do this you will have no problem? (rhetorical question).
At this point in the meeting, a close friend of his stood up to expand on his understanding of the problem, I think this guy is an electrical engineer - or at least gives that impression. He indicated that from the damage he saw, that the alt. output had easily exceeded 2-300volts, which is why so much damage had been done, in that the fuses in the aircraft will only protect from over-current situations and not over-voltage.
TRUE, 200 volts would be the high end for a little ND alternator, but alternators can burn out before reaching the absolute max. Regardless this was a true OV case without doubt. The theoretical max voltage is based on diode/wiring rating of alternator. Also the battery will absorb the over voltage and moderate it somewhat. A high/lo voltage warning light is critical an aircraft. Even with a B&C crow bar, there's a time delay to "Pop" the CB, plus the reaction of the relay magnetic field to collapse and open the relay.
It would be nice to pull the regulator and see what has failed. Does he still have it? I would like to evaluate it and would pay shipping. They are sealed units but they can be pried apart. Actually having the whole alternator to analyze would be best. Any chance of getting hold of the damaged alternator Dale? Again I would pay shipping and return it when done.
He indicated that in most situations that the internal systems work just fine, but the one type, can at times, if certain internal problems exist, go in to a run-away situation should the control lead be de-energized / re-energized - which is what the owner inadvertently introduced in this situation.
Now, in my own experience, when I purchased my alt. kit from Van about 4 years ago, all that they had was the non-internally regulated types and you were on your own to get something for regulation. I was aware of the BC unit, so I purchased that one as opposed to "experimenting" in trying to use some sort of automotive unit, which may have all sorts of specialty neuances.
The system worked great for me, except for at about 5 hours on the plane, my alt. bearings began to sing / and being ultra cautious at this point of any strange noised emanating from under my cowling... I chose to remove the alt. for inspection. I took in to a local auto alt. shop for testing and sure enough they found that my "brand new - rebuilt" alt. from Vans had bad bearings in addition to them finding the brushes almost worn out too... $55 later, had both replaced...
The expert seems to have insight, but I wonder specifically what internal problem? I do know the single fault point in the ND alternator is (in theory) the drive transistor to the FIELD. The ND alternator has a "A type alternator. One side is connected to positive (all the time) and the ground side is controlled thru a transistor controlled by the VR. In theory the field transistor fails causing a dead short to ground, bypassing VR control. With full voltage in the field and high RPM you the output goes very HIGH, which in turns excites the field more, thus runaway up to the physical limitation of the windings/components. The chance is better your prop will depart the engine. Also transistors fail open as well, which is a non event. The mean time between failure (MTBF) of transistors is millions of hours, and it's very over rated for the duty it sees in the alternator. Does cycling the alternator power instantaneously fry's the field transistor shorted out? I guess it's possible, but not sure exactly how or why, unless a post mortem is done. (My offer stands to examine it).
Van has sold the early 80's Honda/ND 35 amp alternator as long as I can remember, I think the one you have Dale and the 55/60 amp ND with I-VR. The 35-amp unit is designed for external regulation and a single cooling fan on the front, that for some reason Van takes off (cowl clearance?). Over the years Van has had (does have?) ?quality? issues with both alternators. I know some alternators that arrived DOA. You can buy them cheaper at an auto part store than what Van's sells them for. Based on track record my be other sources can do better. The problem is 35-amp is not enough for some builders who need more power with all the electronics used today.
Not all rebuilds are the same. There are 100's of local and several large rebuild companies that dominate the market nationally and worldwide. There are even more makers of aftermarket parts. It's possible sub-par repair parts are made not meeting OEM standards. While some aftermarket parts are fine, as good or better than OEM specs.
I AM VERY suspicious of the brand of alternator Van sells, the re-builder and the (aftermarket) parts inside. It seems Van my have gone with Low bidder. All the problems I am aware of came from Van's. As you say Dale, it?s not the first time I?ve heard parts are worn and apparently not replaced in the overhauled units! Original new ND alternators are obviously superior to rebuilds (no kidding). The 55/60 amp ND Van sells is not sold NEW all genuine ND anymore because they are not in production (89-95 Suzuki). However the industrial applications in current production can be found NEW. These NEW all ND alternators are mostly in the 45-amp size. I have a new genuine ND. It is like the Niagara unit. I am day/night VFR so I can get by with 45 amps. I could remove the I-VR and convert it to an external VR but I saw no reason to do it for my application. Since many need weight on the nose of there RV there is no reason to not use a 80/90 amp unit. Most come with serpentine belt pulleys, but easy to change to V-belt. They should fit and weigh a pound or so more. It's easier to find NEW in late model car units. Late model cars use alternators with more than 60 amps, that I know of.
My intentions were to just point out that problems can develop, and my experiences with the BC ovp have been fine... of course I had no option when I purchased my alt.
I guess the bottom line is here... if you have an internally regulated alt. you had better not be shutting the thing off in flight with the old circuit design of having a separate alt. switch ie. the Cessna split master switches.
Excellent point. I personally don't think there is a good reason to cycle the ALT. I use a DPDT (double poll double throw) switch that always turns the master BATT on and ALT (IGN wire) ON and OFF at the same time (always). Even a split Cessna unit allows inadvertent shut down of the alternator. IF you want to disable the the ALT while the BATT is still on you pull the ALT circuit breaker (CB), which you should have in series with the switch. I also have a CB on the B-lead. So in-case of Oh-**** you pull the B-lead CB. That is my main way to isolate the alternator, not the ALT switch, with an internally regulated alternator.
Dale,
Should you have further questions, and as to not bore the viewers to death you can contact me directly at drwittman_at_comcast.net
Thanks Dale, that explains quite a bit.
Thak sounds like an Ouch
Linear Mode
