ScottHess
Member
I'm soliciting opinions as to how I managed to smoke my KX125, among other things today in my RV-4. My electrical system is really simple:
Yesterday I caught a slight whiff of smoke while on a short flight. I returned to the field and everything was fine with no signs of anything having caused it. Today, I took off and the smoke became obvious, about the same time all my electrical equipment signed off. I shut off the master and landed. On the runup prior to flight, ammeter was showing a charge, voltage was around 14v. The ammeter seemed to have a slight wiggle which may have been there, but no whine was heard. I recently installed new programmable fuel gauges (which are really nice btw) which have their own internal electroluminescent dials powered by a supplied inverter. They are powered by the dimmer circuits (2 Britta dimmers, separate, one for panel lights and one for an LED strip). Everything has been working fine, though the airplane has only about 50TT.
Upon landing and after shutdown, I flipped the master back on and everything seemed to work with the exception of my KX125 and dimmers (both). I opened the cover of the 125 and it looks like the fire went to two alarms, mostly on what appears to be the audio side of things. The internal fuse also blew, though the 10A supply fuse did not.
The field breaker never popped either. I did check the OV circuit before I installed it, and it did short at around 16V as I recall.
I've since checked the charging system which is still charging properly with proper voltage. Intercom still works, and still no alternator whine.
The master relay was not new when I installed it, neither was the Cessna master switch. I recall the master switch having been intermittent at first but I cleaned it and checked the resistance and it was fine, and has worked perfectly since. Of course I can't remember whether it was the battery or alternator side of the switch which had been flaky.
So here's the question, IF the master relay failed, or the master switch failed.. leaving the alternator to its own devices.. shouldn't the crowbar have tripped and taken the alternator off line? I clearly had some kind of event, and since the rest of the panel went out, it must have been because of a battery disconnect.
I'm really puzzled by this. In addition to the $$$ for the KX125, I'm going to replace the switch, master relay and alternator but I am not going to smoke another radio without finding the cause. The transponder, intercom, EFIS, etc. all seem fine. And the backlight does still work in the KX125.
Any and all opinions are appreciated!
Scott
- ND 35 Amp Alternator with Ford regulator
- Ammeter shunt is in between buss bar and master relay
- Alternator output also connected to main buss bar with a 40A fusible link.
- Most everything is fused off the main buss (radios fed from a secondary buss that is switched)
- Alternator field circuit fed from main buss with 5A breaker, crowbar OV in place
- Dynon D-6 always on, fed from main buss and separate CB
- Cessna type split master switch
Yesterday I caught a slight whiff of smoke while on a short flight. I returned to the field and everything was fine with no signs of anything having caused it. Today, I took off and the smoke became obvious, about the same time all my electrical equipment signed off. I shut off the master and landed. On the runup prior to flight, ammeter was showing a charge, voltage was around 14v. The ammeter seemed to have a slight wiggle which may have been there, but no whine was heard. I recently installed new programmable fuel gauges (which are really nice btw) which have their own internal electroluminescent dials powered by a supplied inverter. They are powered by the dimmer circuits (2 Britta dimmers, separate, one for panel lights and one for an LED strip). Everything has been working fine, though the airplane has only about 50TT.
Upon landing and after shutdown, I flipped the master back on and everything seemed to work with the exception of my KX125 and dimmers (both). I opened the cover of the 125 and it looks like the fire went to two alarms, mostly on what appears to be the audio side of things. The internal fuse also blew, though the 10A supply fuse did not.
The field breaker never popped either. I did check the OV circuit before I installed it, and it did short at around 16V as I recall.
I've since checked the charging system which is still charging properly with proper voltage. Intercom still works, and still no alternator whine.
The master relay was not new when I installed it, neither was the Cessna master switch. I recall the master switch having been intermittent at first but I cleaned it and checked the resistance and it was fine, and has worked perfectly since. Of course I can't remember whether it was the battery or alternator side of the switch which had been flaky.
So here's the question, IF the master relay failed, or the master switch failed.. leaving the alternator to its own devices.. shouldn't the crowbar have tripped and taken the alternator off line? I clearly had some kind of event, and since the rest of the panel went out, it must have been because of a battery disconnect.
I'm really puzzled by this. In addition to the $$$ for the KX125, I'm going to replace the switch, master relay and alternator but I am not going to smoke another radio without finding the cause. The transponder, intercom, EFIS, etc. all seem fine. And the backlight does still work in the KX125.
Any and all opinions are appreciated!
Scott