After changing out the oil seal on Valkyrie?s Standby Alternator mount on Thursday, I took her up for a quick test hop. All was good, except for an occasional flash of my Master Warning light. This is driven by the EIS directly, but it was so brief (one machine cycle?) that I couldn?t see what was causing in. About 20 minutes into the flight, I got a ?Volts Hi? message on the EFIS, and sure enough, the Main bus voltage was wandering from 12.5 up to 15.2. One of the many neat things about the GRT EFIS/EIS system is the number of voltage readouts I have ? one for each of the three inputs to the EFIS plus the EIS voltage. I watched things as I headed back to the airport (I wasn?t too concerned, since I have two batteries and the standby alternator to get me home if I had to shut off the Main?), and sure enough, I was seeing erratic volts on all the buses. The only thing stable was my diode-isolated Aux battery.
This morning I went up for a quick check to get a little more data, and the wandering got worse while I was still in the pattern. Basically, the Alternator went from normal to occasionally busting 15.5 volts in about an hour of operating time. I killed the main alternator and landed with the backup systems ? no need to risk toasting anything!
I am running with the standard Van?s 60 amp, internally regulated alternator, and had a total time of 386.3 hours on it. During the first hundred hours or so, I was using a procedure where I?d start the engine with the alternator field off, then switch it on. After reading some of George M?s voluminous posts on the topic, I decided that this was an archaic procedure left over from the primitive alternator/regulator days, and that it makes sense with an automotive unit to essentially leave it connected to the ?ignition? switch (in our case, the master). I still have the split master switch, so I can turn it off if required, as I did today. Could the early hundred hours of operation have damaged the VR electronics? Quite possibly. I know that the new unit will only be off for a malfunction!
Now the best part. It?s a Saturday ? I?m not going to get an aircraft alternator anywhere. But I called the local auto parts emporium and asked for a ?Lester 14684? alternator, and hit pay dirt on my third try. (They all had them listed ? the first two didn?t have them in stock). I decided to check my watch as I worked. Five minutes to remove the cowl, ten to remove the alternator. Twenty to make a minor mod to the alternator boss mount (rounded a corner where it interfered with a more robust alternator housing casting), then another Twenty to reinstall, tension the belt, and safety wire. Ten minutes to close up. Heck, I could have done it on a deserted ramp in the middle of nowhere using the tools I always carry in the plane ? nice! The test flight showed the voltage on all busses to be rock solid.
One ?gotcha? for those still building, There are two bolts that act as pivots for the alternator, holding it to the mount. I had installed both of them with ?heads forward?, which seemed to make sense at the time. Of course, I probably mounted that as soon as I had hung the engine, because today I found that I couldn?t get the forward one out ? it bumped in to the ring gear on the front of the engine ? I must have installed the prop AFTER the alternator?. By removing the whole alternator mount from the engine, I was able to get the unit off and back on without removing the prop, but if you are still assembling, you might want to put that bolt in from the rear?.
So ? 385 hours on an alternator. How do I feel about that? Frankly, I looked back at the history of the certified alternators I had over the years on my Grumman, and they weren?t much better than that. In fact, I had two fail much earlier. The cost of the new (rebuilt ? they are all rebuilt?) one today was $112. That?s not really too bad, and it?s nice knowing that I can pick one up at just about any National Aircraft Parts Association store across the country. I am aware of the history of these units ? there appear to be good and bad rebuild shops, and quality can be an issue ? and we?ll see how long this one lasts. With the redundancy built in to Valkyrie?s systems, an in-flight failure is easily tolerated. But if this one dies early, I?ll probably switch to one of the new Plane Power units to get a little bit better assurance of quality.
One other thing that this lead me to do was to look through the Tech Specs of my avionics to see what kind of voltages they can tolerate. I was pleased to see that all of the expensive boxes are happy up to 33 volts (which I expected, knowing today?s electronics). Not that I want to try it?..
Paul
This morning I went up for a quick check to get a little more data, and the wandering got worse while I was still in the pattern. Basically, the Alternator went from normal to occasionally busting 15.5 volts in about an hour of operating time. I killed the main alternator and landed with the backup systems ? no need to risk toasting anything!
I am running with the standard Van?s 60 amp, internally regulated alternator, and had a total time of 386.3 hours on it. During the first hundred hours or so, I was using a procedure where I?d start the engine with the alternator field off, then switch it on. After reading some of George M?s voluminous posts on the topic, I decided that this was an archaic procedure left over from the primitive alternator/regulator days, and that it makes sense with an automotive unit to essentially leave it connected to the ?ignition? switch (in our case, the master). I still have the split master switch, so I can turn it off if required, as I did today. Could the early hundred hours of operation have damaged the VR electronics? Quite possibly. I know that the new unit will only be off for a malfunction!
Now the best part. It?s a Saturday ? I?m not going to get an aircraft alternator anywhere. But I called the local auto parts emporium and asked for a ?Lester 14684? alternator, and hit pay dirt on my third try. (They all had them listed ? the first two didn?t have them in stock). I decided to check my watch as I worked. Five minutes to remove the cowl, ten to remove the alternator. Twenty to make a minor mod to the alternator boss mount (rounded a corner where it interfered with a more robust alternator housing casting), then another Twenty to reinstall, tension the belt, and safety wire. Ten minutes to close up. Heck, I could have done it on a deserted ramp in the middle of nowhere using the tools I always carry in the plane ? nice! The test flight showed the voltage on all busses to be rock solid.
One ?gotcha? for those still building, There are two bolts that act as pivots for the alternator, holding it to the mount. I had installed both of them with ?heads forward?, which seemed to make sense at the time. Of course, I probably mounted that as soon as I had hung the engine, because today I found that I couldn?t get the forward one out ? it bumped in to the ring gear on the front of the engine ? I must have installed the prop AFTER the alternator?. By removing the whole alternator mount from the engine, I was able to get the unit off and back on without removing the prop, but if you are still assembling, you might want to put that bolt in from the rear?.
So ? 385 hours on an alternator. How do I feel about that? Frankly, I looked back at the history of the certified alternators I had over the years on my Grumman, and they weren?t much better than that. In fact, I had two fail much earlier. The cost of the new (rebuilt ? they are all rebuilt?) one today was $112. That?s not really too bad, and it?s nice knowing that I can pick one up at just about any National Aircraft Parts Association store across the country. I am aware of the history of these units ? there appear to be good and bad rebuild shops, and quality can be an issue ? and we?ll see how long this one lasts. With the redundancy built in to Valkyrie?s systems, an in-flight failure is easily tolerated. But if this one dies early, I?ll probably switch to one of the new Plane Power units to get a little bit better assurance of quality.
One other thing that this lead me to do was to look through the Tech Specs of my avionics to see what kind of voltages they can tolerate. I was pleased to see that all of the expensive boxes are happy up to 33 volts (which I expected, knowing today?s electronics). Not that I want to try it?..
Paul
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