AlanA Posted October 31, 2014 Report Share Posted October 31, 2014 I had an interesting commute home yesterday. First my autopilot stopped working. I tried to troubleshoot and and eventually just pulled the circuit breaker. But when my Garmin 430 died I realized I had a bigger problem. Pulled out the emergency check-list and again tried to trouble shoot without success. Reduced electrical load as much as I could. I was in the middle of Nevada without many choices so decided to keep going to my final destination. No radios were working when I got there. No strobe or landing lights. Thankfully this was all in the daylight. Had to use the emergency clutch to lower the landing gear. Landed without problem. Interesting though as I taxied to the ramp my electrical came back. The mechanic looked at it today and found a loose alternator belt. He tightened it and all ok now. He said the plane had been flown 141 hours since last annual and so he was not surprised that it was loose. So I mention my experience for three reasons: 1) Just to let others know that the plane flys just fine with a dead battery, 2) That finger checking the belt on pre-flight won't catch this, and 3) I wanted to ask the question if removing the cowl and checking and tightening the belt is a maintenance item that others of you do on a routine basis? Epilogue: I bought a new handheld radio today (My old one doesn't charge anymore). If this would have happened at night how would I have turned on the airport lights? And of course no radio communications for position reports or weather. Quote Link to comment Share on other sites More sharing options...
philiplane Posted October 31, 2014 Report Share Posted October 31, 2014 Finger checking the belt should result in 3/8" deflection, and no more than 1/2". If it loosens in flight, you may have a cracked alternator ear, or the alternator boss mount to the case is loose. If you simply tighten the belt without checking these items, it will get worse. And if the belt was really slipping that long in flight, it should have been replaced, not tightened. Slipping for just a few minutes reduces the v-belt cross section making it prone to roll over on the pulley and then shred. So again, if you finger checked it before flight and it deflected less than 1/2", you really out to investigate it further. It's extremely unusual for a belt to suddenly loosen on its' own. 2 Quote Link to comment Share on other sites More sharing options...
kmyfm20s Posted October 31, 2014 Report Share Posted October 31, 2014 I glad everything turned out OK and you kept your cool! Did you do a 100 hr inspection? They are often over looked. Quote Link to comment Share on other sites More sharing options...
N601RX Posted October 31, 2014 Report Share Posted October 31, 2014 Lycoming has a good method of setting the belt tension with a torque wrench. I don't have the numbers in front of me, but essentially you put a torque wrench on the nut that holds the alternator pulley on and then adjust the tightness until the pulley slips on the belt at a predetermined torque. Its hard to imagine that the belt was slipping so badly that it would not keep the battery charged and not burn the belt completely up. In addition to what was mentioned above, bad bearings in the alternator can also loosen up the belt. SI 1129B.pdf 1 Quote Link to comment Share on other sites More sharing options...
Mooneymite Posted October 31, 2014 Report Share Posted October 31, 2014 Keep us posted. Let us know after a few flights if everything is still good. I'm interested to know if the entire problem was a slipping (but undamaged belt), or if other issues are involved. I'd be somewhat suspicious. Quote Link to comment Share on other sites More sharing options...
N201MKTurbo Posted October 31, 2014 Report Share Posted October 31, 2014 That just sounds a little fishy. I've had broken alternator mounts before with the alternator just laying on the belt with no pressure. It still worked. Quote Link to comment Share on other sites More sharing options...
DAVIDWH Posted October 31, 2014 Report Share Posted October 31, 2014 Glad to be aware we can still fly on battery. My recent experience is a bit different. Last week on a commute in solid IFR all my electrical gauges went to zero and the engine just stopped cold. All methods to restart engine failed. So, called tow truck and F-150 was towed to local mechanic shop. Mechanic rapidly diagnosed a failing alternator as the culprit. When I asked, why the engine stopped and all electrical went to zero with a fairly new battery, his answer was, in the old days the engine would not have stopped, but with today's new computers, the engine just stops with a failed alternator. Hopefully TCM and Lycoming will stay at arms length from computerized engine management. Quote Link to comment Share on other sites More sharing options...
Marauder Posted October 31, 2014 Report Share Posted October 31, 2014 When I first bought my Mooney, the previous owner warned me that the landing gear breaker had popped occasionally when the gear was being extended. Sure enough, on my first solo night flight, the breaker popped. I reset it and the gear extended. I had the system checked out and nothing was found to be problematic. After the second time it happened, the mechanic started a more extensive albeit an expensive path of replacing hardware to eliminate the cause. After the alternator was pulled and tested, the only thing left in the electrical system was the belt itself. Sure enough, the belt was replaced and the problem went away. The hypothesis presented to me was that the belt was probably always slipping but my electrical load was never enough for me to notice it. Not sure I completely bought into it, but the belt replacement eliminated the problem. Quote Link to comment Share on other sites More sharing options...
N601RX Posted October 31, 2014 Report Share Posted October 31, 2014 When the alternator stops working and you remove remove all the excess load by pulling breakers to unnecessary equipment be sure to pull both the field and alternator breakers also. In the case of a broken or slipping belt all the voltage regulator knows is the alternator isn't producing enough voltage and it will ramp the current up to the upper limit of the regulator to try to get the alternator voltage back up. 1 Quote Link to comment Share on other sites More sharing options...
Bartman Posted November 6, 2014 Report Share Posted November 6, 2014 That just sounds a little fishy. I've had broken alternator mounts before with the alternator just laying on the belt with no pressure. It still worked. I don't buy it either and would not be surprised if it happened again. I don't know what the problem is, but I would not fly IFR and bet that the belt was the problem. If it was slipping that much in flight it would glaze e belt at the very least, and I would expect it to produce smoke. If it was the belt, it needs to be replaced in my opinion. I am not and AP or IA and did not stay at a holiday inn. Quote Link to comment Share on other sites More sharing options...
jetdriven Posted November 7, 2014 Report Share Posted November 7, 2014 When the alternator stops working and you remove remove all the excess load by pulling breakers to unnecessary equipment be sure to pull both the field and alternator breakers also. In the case of a broken or slipping belt all the voltage regulator knows is the alternator isn't producing enough voltage and it will ramp the current up to the upper limit of the regulator to try to get the alternator voltage back up. if you cant fly 30 minutes with battery then your battery isnt airworthy. In an electric airplane, bus voltage should be in your scan. The first symptom of alternator problems should be a drop from 14.1V to 12.9V, followed by 30 minutes to an hour or more of battery capacity. Not complete system failure and an attempt to use a handheld with a dead battery or no range to talk to center. Quote Link to comment Share on other sites More sharing options...
triple8s Posted November 7, 2014 Report Share Posted November 7, 2014 Not sure if you have one or not but I had an engine monitor that had a feature where you could set alarms one was an alarms that would let you know if buss voltage was below a user specified level. It would flash a red LED and could also beep. Was a UGB-16. Things like that sure make a person think about the mechanical gear. Quote Link to comment Share on other sites More sharing options...
flyboy0681 Posted November 7, 2014 Report Share Posted November 7, 2014 if you cant fly 30 minutes with battery then your battery isnt airworthy. In an electric airplane, bus voltage should be in your scan. The first symptom of alternator problems should be a drop from 14.1V to 12.9V, followed by 30 minutes to an hour or more of battery capacity. Not complete system failure and an attempt to use a handheld with a dead battery or no range to talk to center. Those flying with the Monroy ATD-300 will hear a cute, calming voice come over the headset stating "low voltage". Quote Link to comment Share on other sites More sharing options...
wishboneash Posted November 7, 2014 Report Share Posted November 7, 2014 Epilogue: I bought a new handheld radio today (My old one doesn't charge anymore). If this would have happened at night how would I have turned on the airport lights? And of course no radio communications for position reports or weather. I have a very old Icom A-22, still works but I have replaced the Ni-Cd batteries about 3 times in the 20(?) years I have had it. I got a AA battery holder which I now use for flights as backup. The Ni-Cd battery is useful on the ground to listen to ATC and I don't care if dies in 1/2 hr. Quote Link to comment Share on other sites More sharing options...
AlanA Posted November 16, 2014 Author Report Share Posted November 16, 2014 Some of you were right, the problem was more involved than previously thought. I had a repeat of my earlier event - only the battery didn't completely discharge this time. The mechanic checked it out again and determined it was a bad alternator. I'm getting that done now. Hopefully that takes care of the issue. Quote Link to comment Share on other sites More sharing options...
jetdriven Posted November 16, 2014 Report Share Posted November 16, 2014 A couple things to check before bolting that new 500$ alternator on. We recently had some alternator problems and I discovered a couple new things. The field wire comes from the cannon plug on the firewall to the alternator. Frequently these wires break right as they enter the crimp on the ring terminal at the alternator. Placing a WDG-2 or -1 adel clamp on the rear case of the alternator will shorten the free length of the field wire and may prevent it from breaking every 100hrs as I have found. Another thing, the field wire itself. The factory runs a shielded, jacketed wire from the cannon plug on the firewall to the alternator. What happened to ours, was the clear jacket breaks down. the shielding gets a little loose, then oil and grit gets under the shielding. Thirty years or more of heat causes the wire insulation to break down. Our field wire was cracked every half inch, and in many places, bare under that shielding. So what happens? The field wire shorts out and the alternator drops out. Then the field ungrounds and it works again. In our case I also feel it damaged the regulator. Now it has an alternator whine in the headset even after we changed the alternator. I figured it was AC ripple in the intercom from. Bad diode in the rectifier. I took it to FOUR places to get it checked. The first said it was a bad rectifier. He also messed up threads on the field terminal by arcing it with a screwdriver. The second place, highly regarded local starter/alternator shop, hooks it up to a 1950s generator tester where none of the gauges worked. Then then hooked up 12v to the field terminal and hooked up a voltmeter. Turns it on it said 15v and pronounced it good. When I asked if it checked for AC in the output as in a bad rectifier he said it wouldn't do 15v unless it was good. Autozone is so stupid they wouldn't attempt it. Seriously it's like the fry machine at McDonald's. Enter te part number it displays a flip chart shows how to hook it up. 1965 Chevelle alternator is externally regulated but he wouldn't put a jumper from the harness to the field. Oreilly auto parts did. I guess I'm saying be careful of someone declaring it good or bad. So you may want to check the condition of the terminal crimp, and sneak that shielding back down the wire to expose the inner wire and inspect that too. Quote Link to comment Share on other sites More sharing options...
N601RX Posted November 17, 2014 Report Share Posted November 17, 2014 Both the ring terminals in the pictures below are for the correct size for the alternator field terminal. The ring terminal on the right is a standard crimp that is sold at most any hardware or auto supply stop. It's actually the Amphenol brand. The one on the left is a heavy duty version available from Mcmaster. I've never had one of them break. Quote Link to comment Share on other sites More sharing options...
jetdriven Posted November 17, 2014 Report Share Posted November 17, 2014 I've never had the terminal break, but I've broken the field wire 2-3 times in 400 hours. The strands fatigue and break right where it goes into the terminal. Also my boss's arrow (same engine) did it too. I wonder why I still have whine in the headset with the new alternator. It just started. The pitch changes with rpm and the loudness of it with load. Did the field wire grounding out fry the regulator? Quote Link to comment Share on other sites More sharing options...
PaulB Posted November 17, 2014 Report Share Posted November 17, 2014 I've got that same whine. I figured it was normal. Guess not Quote Link to comment Share on other sites More sharing options...
BigTex Posted November 17, 2014 Report Share Posted November 17, 2014 It might be a wiring or filter issue but I had the alternator whine and resolved it by removing a ground loop found in my headphone jack. I had to add an isolation washer to the pilot's phone jack and it magically when away. You can try the following: Make sure none of the jacks are touching ground, including the music jack (if you have one). If they are, it could be causing a ground loop. Basically, remove intercom from the tray and get a continuity meter. Go to airframe ground and touch each nut on every jack and see if any are connected, if so, remove jack ground from airframe ground. Quote Link to comment Share on other sites More sharing options...
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