Tom Martin
Well Known Member
I have one Bendix mag and one Lightspeed EI on my rocket. The other day I did a mag check before take off and found that I had lost my electronic ignition.
A little trouble shooting pointed to a bad switch.
The switch that I chose, 750 hours ago was a Potter Broomfield breaker switch. This combines a breaker and a toggle switch in one unit and I used it in an attempt to lower my parts count. Documentation states that it can be used as a switch. I estimate that with starting, and mag checks over the years the switch probably had 2500 to 3000 cycles.
I replaced the unit with a separate breaker and toggle switch and all is well. In fact things are better then they were. Over the past year or two I have had some little glitches, minor things, that were not traceable. At higher rpms there was a bit of a vibration that went away at my normal 2200 cruise rpm.
Today that was all gone, and it runs smooth at all rpms. Keep in mind that it was just a tiny bit uneven, nothing that a passenger would note.
When I got home I took the old breaker switch apart to see what was going on.
Clearly it can be seen, at the pointer, that the little braided wire is broken
Now I flipped the switch to the closed, or ON, position and you can see that the broken braided wire actually makes contact with the other side of the broken wire. This explains a lot of my symptoms, the little glitches, etc. I have had two, one hour flights since changing this breaker switch to a new system and the plane is running better, no doubt about it. If the switch had not actually failed that one mag check then it is hard to say how much longer I might have flown with this faulty switch.
When testing the breaker switch before removal I would get continuity when it was closed but only partial voltage, around one volt, rather then the 12V in the system. This confirms the symptoms of intermittent contact.
Based on this type of failure I can not recommend breaker switches for use in our aircraft.
A little trouble shooting pointed to a bad switch.
The switch that I chose, 750 hours ago was a Potter Broomfield breaker switch. This combines a breaker and a toggle switch in one unit and I used it in an attempt to lower my parts count. Documentation states that it can be used as a switch. I estimate that with starting, and mag checks over the years the switch probably had 2500 to 3000 cycles.
I replaced the unit with a separate breaker and toggle switch and all is well. In fact things are better then they were. Over the past year or two I have had some little glitches, minor things, that were not traceable. At higher rpms there was a bit of a vibration that went away at my normal 2200 cruise rpm.
Today that was all gone, and it runs smooth at all rpms. Keep in mind that it was just a tiny bit uneven, nothing that a passenger would note.
When I got home I took the old breaker switch apart to see what was going on.
Clearly it can be seen, at the pointer, that the little braided wire is broken
![donnsj.jpg](/community/proxy.php?image=http%3A%2F%2Fi44.tinypic.com%2Fdonnsj.jpg&hash=ee9b2699adcb9bd673f1664e0404a7bd)
Now I flipped the switch to the closed, or ON, position and you can see that the broken braided wire actually makes contact with the other side of the broken wire. This explains a lot of my symptoms, the little glitches, etc. I have had two, one hour flights since changing this breaker switch to a new system and the plane is running better, no doubt about it. If the switch had not actually failed that one mag check then it is hard to say how much longer I might have flown with this faulty switch.
![iwsmfm.jpg](/community/proxy.php?image=http%3A%2F%2Fi40.tinypic.com%2Fiwsmfm.jpg&hash=79295be1359f4caa96eda2a5e331ec4b)
When testing the breaker switch before removal I would get continuity when it was closed but only partial voltage, around one volt, rather then the 12V in the system. This confirms the symptoms of intermittent contact.
Based on this type of failure I can not recommend breaker switches for use in our aircraft.
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