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Back in December, Kirk Fryar, co-owner of Sarasota Avionics, and Dave Clarke, avionics manager, flew up at our invitation to Griffin, Georgia, where most of the work would be accomplished, to see the airplane firsthand. This initial meeting gave us a time when we could sit down with these electrical and avionics experts and strategize the overall goals for the sweepstakes airplane's electrical system and instrument panel overhaul.

A raised burly Sarasota eyebrow appeared more than once across the table during these negotiations, as some of what we asked for simply isn't done in light GA aircraft — outside of a masterful restoration of a classic airplane. Gryder had his wish list ready regarding some of the best upgrades to make to the airplane a truly unique creation. An essential bus was at the top of his list — and mine, after recent experience flying new piston singles with this no-brainer safety item (which places several critical safety-of-flight electrical components on a separate bus wired directly to a power source). But so was the removal of every single inch of original wire, upgrading the gauge of most of the wire, and wire stamping each wire at 6-inch intervals, as well as the more routine sweepstakes project goals of optimizing the panel layout and installing all-new avionics, and building a custom all-metal panel (you'll learn more about the panel itself in one of the next updates).

The reaction from Fryar and Clarke spoke volumes to us: "Yes, we can." And so we did.

More electric overhaul
If you fly an airplane from the now-classic years in the 1960s and 1970s, you take for granted, perhaps, the fact that your airplane has a generally reliable electrical system.

With systems elegant in their simplicity, most light general aviation singles from this era feature a 14-volt or 28-volt DC (direct current) electrical system powered through a storage battery. An alternator or generator feeds the battery, and the battery feeds the main DC bus. The system is set up this way because an alternator puts out alternating current (AC) and the main bus can't take AC, or, if the airplane has a generator, it puts out DC but the output varies as the rpm changes. The Cessna Cardinal that we're refurbishing has a 14-volt electrical system utilizing a 60-ampere alternator and a new 12-volt, 33-ampere-hour Teledyne Gill battery.

Though the layout changes with aircraft manufacturer, most aircraft of our Cardinal's vintage have the electrical system split into two busses, a main or primary bus, and an electronics, radio, or avionics bus. The busses are like power strips into which each component is plugged; devices plugged into different busses are isolated from each other, but are somewhat tied to the other devices with which they share the bus — a circuit breaker (or fuse, generally in older airplanes) between the device and the bus typically prevents a component from harming its neighbors if it malfunctions.

Earlier aircraft may have a single bus; at some point in the mid to late sixties, most GA manufacturers began further protecting delicate avionics with solid-state components from voltage spikes by placing them on a separate bus. A circuit-breaker type switch (you know it as an avionics master) added to this package by allowing the pilot to turn off all components on the avionics bus prior to turning the main aircraft master switch off or on. The first avionics or radio master switches as standard equipment came into play in the early 1970s. Another benefit of this switch is that it will open in the event of a short to ground of the bus, powering down the avionics bus and protecting the wiring from further damage.

Essential bus
We're taking the idea of separate busses to the next level: One of the most important upgrades we're making to the Cardinal is the inclusion of an essential bus. This is a separate bus within the electrical system that ties together a handful of the most critical devices and powers them by different means (perhaps a backup battery) — or in our case, a second set of wires that bypasses the battery relay and goes to the ship's main battery, in the event that relay opens or a complete short to ground of the main DC bus occurs because of high current flow. You find essential busses in many current-production singles, including Cessna, Cirrus Design, Mooney, Piper, and Diamond aircraft.

If your panel goes dark in the Catch-A-Cardinal, you can power the essential bus items directly from the battery by flipping the essential bus switch just to the right of the avionics master and horizontal situation indicator (HSI) power switches.

What's tied into the essential bus on your Cardinal? The number-two Garmin GNS 430W, the GTX 330 transponder, the Honeywell Bendix/King HSI, and the Castleberry Model 300-14EL electric backup attitude indicator.

In an electrical system emergency, the essential bus gives you the following tools. The 430 provides navigation and communication functions — a nearly full gamut of them, in fact, plus a moving map to boot. The bus connects the backup channel from the 430 to the pilot's headset jacks; it will not go through the audio panel. This mimics the "fail-safe" mode found on new Garmin G1000-equipped (integrated "glass" cockpit) aircraft — a failure of the audio panel in those airplanes also bypasses the audio panel's circuits and delivers com 1 to the pilot's headset jacks.

The HSI gives you both heading information and your number-one nav indicator. In the event aircraft electrical power is only coming through the essential bus, the nav portion of the indicator will be flagged — but the number-two indicator (the GI 106A just left of the radio stack) will still get information from the number-two 430, allowing you to use it to shoot an ILS, LPV, VOR, or GPS approach.

This was a choice made because the HSI is such a high-draw item, and, although the HSI isn't particularly failure-prone, we wanted to minimize our chances of losing both the heading information and the course information in the event of a main bus failure and an HSI failure. With the heading information from the HSI, and the electric backup attitude indicator powered up, you're assured of two familiar means of attitude and directional information to get you down out of the clouds.

From tips to tail
Another kind of safety equipment catches your eye when you see the Cardinal coming: Precise Flight donated its latest PulseLite landing light system, complete with supplemental type certificate for the Cardinal. The PulseLite system flashes the landing and taxi lights in unison to create an eye-catching display in the air that's hard for other pilots to miss. Because these lights are located adjacent to each other in the nose, our hard-working Sarasota Avionics team figured that we would pulse them together, rather than alternated, for the most dramatic effect. The system also can be set to respond to traffic alerts from the Garmin GDL 90 ADS-B (automatic dependent surveillance-broadcast) datalink system.

Adorning the wing tips and tail are brand-new strobes from Whelen Engineering, and an LED-lit rotating beacon. The LED (light-emitting diode) system features longer bulb life and greater visibility than stock systems. If you fly in congested areas, these are two great improvements to make to your airplane.

Not to be missed, if you look on the belly and the top of the Cardinal, you'll see a host of new, low-profile antennas, provided to the project by Comant, with the WAAS-compliant antennas supplied through Garmin. During removal of the old antennas, we found the GPS antenna had been improperly bolted to the airframe — with structural rivets drilled out to make way for the ones holding the antenna in place, a major no-no. Just another in the long list of examples why we chose the refurbishment course that we're following. It's a lot of work, as our shops and technicians will attest, but they payoff is the best product possible.

New antenna profiles and placement mean more work for our sheet metal magicians from Air Wrench. They're busy covering up the old holes with custom repair work. Once the shiny new paint from Advanced Aircraft Refinishers goes on, I challenge you to figure out where the ADF antenna used to be mounted, along with eight other repairs. Out with the old, and in with the new.

E-mail the author at julie.boatman@aopa.org.

Comant Industries, of Fullerton, California, in the antennas division, creates an entire line of navigation, communication, and datalink antennas for general aviation, including the VHF com, transponder, and marker beacon antennas for the Cardinal. Artex, of Aurora, Oregon, in the avionics and surveillance division, designs and manufactures next-generation ELTs, such as the ME406, a small-footprint ELT that transmits on both 121.5 and 406 MHz. Visit Comant's Web site or call 714/870-5133. Visit Artex or call 800/547-8901.