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Rob's REBVAIR Project
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Date:  7-21-2015
Number of Hours:  4.00
Manual Reference:  
Brief Description:  ignition wiring part 2

Here are the dual (redundant) coils and their wiring. As described in part 1, the red and white wires carry the 12 v to and from the A and B coil. In the cockpit, one can switch between either circuit. Each coil has a high-voltage output that feeds into a solid-state diode array (round black device shown attached to the firewall under the box where the high voltage wires feed into, made by moroso) which allows only one of the two circuits to pass the high-voltage spike to the distributor. So the redundancy in this ignition system is really only the availability of two coils on separate circuits. From the diode array onwards, it's all single-point-of-failure (SPOF). If you're reading this disapprovingly, don't kid yourself: every airplane has SPOFs. It's really a question of reliability of the parts in that SPOF.

Think you're safer in a "certified" single engine aircraft? Consider this: While performing the annual inspection on our club's1979 Piper Dakota with an O-540 lycoming, the mechanic noticed that the magneto case had cracked, and was hanging on by one screw. When I remarked something like "well if that had failed, at least we'd still derive some power from the other magneto" the mechanic corrected that on this engine, both magnetos were housed in the same case, and that case failures were not uncommon on this powerplant. While the design was dropped by Lycoming only a few years later, there are plenty of'certified'aircraft still flying with this arrangement. So much for dual magneto/ spark plug redundancy.

In my case, these same installation methods have proven to work in hundreds of other corvair installations. The parts are race-quality, and secured at appropriate points so they won't work-themselves loose. At preflight, the connections can be visually and physically inspected for integrity. At run-up, and in flight, it is a simple matter to switch between circuits to check whether both are operational. Housed in this vented box, the coils stay cool and insulated from the heat in the
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looking up under the box cover

looking up under the box cover

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