AOPA's Catch-A-Cardinal Sweepstakes

Upgrades to your Cardinal's electrical system

An airframe lasts a long time, if it's maintained with care. But besides the spar, ribs, and skins, a lot of moving pieces and critical connections go into even the lightest of light airplanes. Aircraft systems age along with the metal and composite structures enclosing them. And when it comes time to refurbish or restore your airplane, you must do so with an eye to vital areas such as the fuel system, the pitot-static system, the environmental system, and (if you're so equipped) the electrical system.

The same holds true for your 1977 Cessna 177B Cardinal that we're waist deep into refurbishing for AOPA's 2007 Catch-A-Cardinal Sweepstakes. As our team in Griffin, Georgia, delved into the airplane, each system underwent a thorough inspection, led by our chief inspector Danny Rexroad. Most areas held up well under the microscope, especially when viewed through the lens of the airplane's three decades of service.

Tools from the trenches
When to wire? Three clues

1. You're installing new equipment.

Any upgrade in the radio stack typically means a new wiring harness for that component. This isn't window dressing — it actually saves money in most cases, because the cost of the new wire is cheaper than the labor cost to trace and reuse the old wire.

2. You find evidence of aging or degradation of the wiring.

Wiring is installed with an eye toward eliminating any chafing points — but maintenance in other areas, and environmental effects, such as vibration, can cause wires to migrate and rub in places. Also, if corrosion sets into a wire, it can rapidly run the length of that wire, although this situation is rare.

3. You're embarking on a detailed restoration.

Modern aircraft electrical systems come with copper-core wire rather than aluminum-core wire. Copper-core wire conducts better, so a thorough refurbishment of the system might change out the wiring for this reason, in addition to those listed above. — JKB

But some components have been replaced in production aircraft over the years with better materials and solutions. For example, the Cardinal's ventilation system uses two- and three-inch-diameter tubing to route air from the fresh air scoops to the cabin vents, and this gets brittle over the years. Plus, the black cat tubing, made from fiberglass-coated neoprene rubber, has been replaced in new-generation aircraft with orange scat tubing (the S stands for silicone), which stands up better to the moisture of condensation inherent to such systems. When we put your airplane back together, new scat tubing will handle the job, and help minimize the possibility of corrosion near the main spar.

Once the efficient team from Air Wrench pulled the Cardinal's floorboards and instrument panel, on-site project manager Dan Gryder, of The AvNet, saw a big place for improvement — the electrical system's hundreds of feet of wiring, piles of connectors, and rows of well-used switches and circuit breakers. In conjunction with our avionics installation folks at Sarasota Avionics International, he'd address the components clearly ready for retirement after years of dedicated service. In fact, we promptly decided that we would take the opportunity to replace the airplane's entire wiring scheme.

With our level of restoration, what good would a new panel be without new wires to faithfully deliver the juice?

Gryder's talent for strategizing the overhaul of aircraft electrical systems and developing innovative panel layouts took shape during the restoration of a Cessna 210 that he undertook 12 years ago, and hit full stride as he envisioned the best possible changes and updates for our sweepstakes airplane. And these are concepts that you can put into play should you ever want or need to refurbish the central nervous system of your airplane, and take it into the future with the latest safety advances.

The essential bus

If you just hop into the newest Cessna off the line — or Cirrus, Diamond, or Mooney, or virtually any new IFR-certified airplane — you may not notice the electrical system improvements underlying all the flashy avionics. One of the most important has to be the inclusion of an essential bus, which is a separate bus within the electrical system that ties together a handful of the most critical devices and powers them through a second source — or in our case, a second set of wires that bypasses the battery relay, in the event that relay opens or a complete short to ground of the main DC bus results in high current flow.

Case in point? Everyone who's had an engine failure, raise your hand. OK, how about everyone who has had some piece of electrical equipment fail (whether it was the clock or the alternator or something in between)? I know the electrical gremlins carry the day. And depending on the way your system is wired, a single component failure could bring down the whole system. We have batteries to carry emergency loads, but, the way the Cardinal was previously built, if a complete short to ground occurs in the main bus, all the battery power in the world won't power your nav/coms. The Cardinal didn't come with a separate essential bus — no aircraft of its class built in the 1970s did, to my knowledge. We're upgrading this Cardinal.

In designing the essential bus, Gryder took into account the crucial tools that a pilot needs to get on the ground safely in instrument conditions and in air traffic control contact. So the bus on your Cardinal includes the number-two Garmin GNS 430 (with both nav and com capability, plus a moving map), the GTX 330 transponder (so you can get vectored onto an instrument approach — a great workload-reducing technique), the Honeywell Bendix/King KI 525 horizontal situation indicator (which includes both a directional gyro and your number-one nav indicator), and the Castleberry Model 300-14EL electric backup attitude indicator.

The HSI also has a separate switch, so it can be isolated if it's the culprit — the HSI is a relatively high-current-draw item. The other hungry component is the transponder (when it's being interrogated), and it can be turned off through the power switch on the unit, as can the 430 — which draws fairly little current unless you transmit.

So if you're flying our Cardinal and the panel goes dark, with the flip of a switch to energize the essential bus you're in business again. You can elect to do the same electrical system upgrade with your airplane; at this point, you'll have to go through a field approval process, as we are, to accomplish it.

Stamp it out

Another think-ahead item on the Catch-A-Cardinal aircraft involves the many bundles of wiring used to power all the cool stuff in the panel and throughout the airplane. Aircraft wires are required to be easily identified so that technicians can locate the correct wire for a component. Typically, on an aftermarket avionics installation in light aircraft, most shops label new wires in a couple of places along their length.

Who's behind us?
Classic Aircraft Maintenance's Danny Rexroad

When Danny Rexroad retired from his career as a mechanic, inspector, and quality assurance auditor for a major airline and 26 years in the Naval Air Reserve, it opened up his schedule so that he could concentrate on what he really enjoyed: taking care of GA airplanes. Of course, we're making great use of his talents as an inspector and parts manager on the Catch-A-Cardinal project.

Rexroad, based at the Newnan Coweta County Airport in Newnan, Georgia, is a single-engine Cessna specialist, who has on his client list a variety of airplanes for which he is responsible on an ongoing basis. "I really like the 206 on down," says Rexroad, who owns and flies a 1966 150F. Rexroad also has considerable experience overseeing the maintenance programs on a couple of very special Douglas DC-3s.

Call 678/372-6346 or e-mail [email protected].

With your airplane, we're taking the concept a step further and doing what manufacturers of production aircraft do now — we have used a wire-stamp device to permanently mark each wire at periodic intervals along its length. Sarasota Avionics has this capability, and it means that down the road, a technician can identify any wire on the airplane in seconds, at virtually any station on its length. The time savings and increased accuracy during maintenance that this makes possible will be a boon to our winner.

You'll be able to see the electrical system upgrades as we showcase the airplane at the Sun 'n Fun Fly-In in Lakeland, Florida, from April 17 through 23. The avionics gurus from Sarasota will be there to answer your questions, along with engineers from Cessna, and a host of other contributors to the project.

It all goes together

Those wires extend to the far reaches of the Cardinal, connecting other new safety systems from the nose to the tail.

From Precise Flight we were thrilled to receive 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 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.

CONTACT

Air Wrench
Castleberry Instruments & Avionics
Garmin International
Honeywell Bendix/King
Sarasota Avionics International
The AvNet
Whelen Engineering

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 (see " Featured Contributors: Cobham, plc: Comant and Artex," on page 114) and Garmin. With the airframe open for business, precise installation of the antennas was easy — and during removal of the old antennas, we found the GPS antenna had been improperly bolted to the airframe.

With all of the groundwork completed, the panel stands open for the installation of the flight instruments and avionics stack — and you'll like what we've chosen, because they are among the favorites you have reported to us at AOPA Pilot over the years.

E-mail the author at [email protected].