Aztec Driver
Line Up and Wait
Not wanting to thread drift the other thread, I thought I would ask my question here.
Over the past several days I have learned a great deal more about my ignition system than the normal rote memorization and rudimentary analysis of reading comprehension of the POH. Since the Aerostar I fly had a left mag failure on the left engine, and the A&P came out, I have learned a bit through the process of repairing it.
He did one test that I did not believe would work, until I looked at all of the mechanics involved with the system. He grounded all of the spark plug leads except for #1 from the left mag, and disconnected the starter. We then turned on the master and ignition to start and he says we should get a spark at the lead. I was skeptical, because I was under the impression that the mag certainly had to be turning to produce any spark. In looking at the circuitry, though, with the starter/vibrator, the voltage at the primary actually pulses, causing a pulsed DC voltage enough to cause spark when at TDC. We never did get a spark, but we had voltage at the mag from the starter/vibrator circuit.
We changed the left mag, but we still had no spark at the lead, but we decided to try it anyway. It started right up and all checks were good.
One thing that puzzles me, though, is we had the starter/vibrators replaced with new solid state units and are unsure if they produce a pulsed DC voltage, which would allow a spark to generate without turning the mag, or if it only adds a small voltage to the primary to induce a hotter spark during the start sequence. Voltage checks at the p lead seem to indicate the latter.
Does anyone have any knowledge of the new solid state units and how they work as compared to the starter/vibrators?
Over the past several days I have learned a great deal more about my ignition system than the normal rote memorization and rudimentary analysis of reading comprehension of the POH. Since the Aerostar I fly had a left mag failure on the left engine, and the A&P came out, I have learned a bit through the process of repairing it.
He did one test that I did not believe would work, until I looked at all of the mechanics involved with the system. He grounded all of the spark plug leads except for #1 from the left mag, and disconnected the starter. We then turned on the master and ignition to start and he says we should get a spark at the lead. I was skeptical, because I was under the impression that the mag certainly had to be turning to produce any spark. In looking at the circuitry, though, with the starter/vibrator, the voltage at the primary actually pulses, causing a pulsed DC voltage enough to cause spark when at TDC. We never did get a spark, but we had voltage at the mag from the starter/vibrator circuit.
We changed the left mag, but we still had no spark at the lead, but we decided to try it anyway. It started right up and all checks were good.
One thing that puzzles me, though, is we had the starter/vibrators replaced with new solid state units and are unsure if they produce a pulsed DC voltage, which would allow a spark to generate without turning the mag, or if it only adds a small voltage to the primary to induce a hotter spark during the start sequence. Voltage checks at the p lead seem to indicate the latter.
Does anyone have any knowledge of the new solid state units and how they work as compared to the starter/vibrators?
