Electronic ignition promises enhanced fuel economy, less maintenance, and safer operation when compared to traditional magneto ignition. Steve Ells takes the plunge and upgrades his 1960 Comanche with an Electroair electronic ignition system (EIS).
This past winter, as my traveling season slowed down into my “work on the airplane” months, I started listing airplane maintenance tasks only to realize that my 1960 Piper PA-24-180 Comanche 180, Eight-Five-Papa, is finally up to snuff.
I flew Papa from my home on the California coast to AirVenture in Oshkosh a couple of years ago and he never missed a beat. I am confident that, given enough Avgas, Papa is safe to fly anywhere.
I’ve been refurbishing Papa since 2004. I bought the airplane from a friend who was selling it for a friend. They were having a hard time finding a buyer because the aircraft’s maintenance logs only went back a few years. Missing maintenance logbooks can easily take 15 to 20 percent off the value of a good airplane.
The original logs turned up about 10 years after I bought Papa—a shop owner from a couple of stops back contacted me saying he had found them as he was cleaning out his hangar. He was willing to send them to me for cash. I considered them to very valuable, and after some easy negotiations, I sent him a couple of Benjamin. I now have complete records.
In addition to tracking down the logs, I’ve done quite a bit of work on Papa over the past decade. I reconfigured the instrument panel, rebuilt the engine, overhauled the prop and prop governor, sent the landing gear motor and transmission to Matt Kurke (the Comanche gear expert) for overhaul, completed the critical 1,000-hour landing gear AD (77-13-01) and installed shoulder harnesses.
I was finally caught up on deferred maintenance. It was time for an upgrade!
I had been wanting to install an Electroair electronic ignition system (EIS) for a long time. I’ve written about the advantages of the system and after speaking to longtime users, I’ve come to believe that the system does deliver an increase in fuel economy and smoother engine operations while also reducing ignition system maintenance chores.
Over the winter, I ordered and installed the Electroair EIS-41000 system on my four-cylinder 180 hp Lycoming O-360-A1A.
Why did I choose the Electroair system? First, I want Papa to operate as well as possible. I believe that the Electroair system provides measurable operational advantages including an increase in safety, performance and economy over my dual-magneto system.
Secondly, I have come to know Mike Kobylik and Peter Burgher at Electroair over the past decade. After watching Electroair grow and stand up for its customers, I have confidence in the company.
Just last year at AirVenture, Electroair introduced an electronic ignition system that is designed to replace the Bendix D-2000 and D-3000 dual magneto, something no other company offers. Electroair is not a “here today, gone tomorrow” company.
Finally, Electroair is the only aftermarket bolt-on electronic ignition system that is FAA-approved for installation in my certified airplane.
The Electroair system is approved for installation on almost all piston-powered certified and experimental airplanes. Buyers can elect to replace either the left or right magneto with either a magneto timing housing (MTH) on four-cylinder engines, or a crankshaft trigger wheel on six-cylinder engines. According to Kobylik, replacing a single magneto yields approximately 80 percent of the benefits of a fully-electronic ignition system.
Electroair does not provide the option of replacing both magnetos due to the cost and time needed to create the wide range of backup battery solutions to fit the many airframe configurations in the General Aviation fleet. Electroair believes that a combination electronic/magneto system is the best cost/benefit option.
Left or right?
I decided to replace the right (non-impulse-coupled) magneto with the Electroair system and kept the left impulse-coupled magneto. It could be argued that I should have replaced the left magneto, since impulse coupling failures can wreak serious havoc within an engine.
While there is always the remote possibility of a serious impulse coupling problem, there hasn’t been a new coupling-related AD for nearly 30 years. Additionally, I lessen the odds of failure by always complying with 500-hour magneto inspections. I send my magnetos to Clifton “Cliff” Orcutt at Aircraft Magneto Service (in Missoula, Mont.) I’ve known Cliff for over four decades and I’m confident in his shop since Cliff and his son Don don’t do anything but magnetos.
Ease of starting also factored into my decision to keep the impulse-coupled magneto. The impulse coupling on the left magneto retards the spark timing at starter-driven rotational speeds to make starting easier. Once the engine starts, the impulse coupling is no longer a factor and the timing reverts to the normal advance. If I had replaced the impulse-coupled left magneto, I would lose the ability to easily start the engine in the case of an electrical system issue.
Since I chose to retain the magneto with the impulse coupling, I will always be able to get my engine started by hand-propping even if the battery voltage is too low to fire the EIS system.
Long ago, I learned that redundancy is at the heart of airworthiness. It seems to me that the only drawback of an Electroair EIS is that it needs battery power to operate and continue to fire. The system requires at least eight volts when installed in a 12-volt airplane, or 16 volts in a 24-volt installation.
My thinking is that in the remote chance that I lose my alternator in flight or some other electrical system failure occurs that causes the electrical system voltage to drop below the Electroair system trigger voltage, the remaining standard magneto will deliver ignition for continued reduced-power flight.
As I mentioned earlier, in the case that I’m already on the ground and need to get started, by leaving the impulse-coupled left magneto in place and hand-propping the engine, I have given myself options.
Once the engine is started, there should be enough voltage in the battery to excite the alternator to get it back online. If the electrical problem is limited to a low charge on the battery, after the alternator has provided bus system power for a few minutes, the electrical system voltage will be high enough to fire the EIS. If this sounds like a doomsday scenario—hand propping, taking off behind an ignition system that is dependent on electric power when the battery is not fully charged, depending on an alternator to maintain voltage during the full-power takeoff—it is. My thinking is based on the years I spent in Alaska where “How can I make this work?” is a way of life.
If the alternator comes online, if there isn’t a major fault in the electrical system that has completely drained the battery, and if I can get the EIS system working long enough for a full-power takeoff, then I will most likely get Papa home on the working magneto if I can fly my route at 50 to 60 percent power which the engine will safely produce with one ignition source. That is a bunch of ifs—but assuming they line up, it would be possible to get home in a pinch.
The Electroair system arrived in a large box that contained a controller, a magneto timing housing (MTH), a manifold air pressure (MAP) sensor, a coil pack, a wiring harness, four REM37BY spark plugs, and automotive style spark plug ignition harness leads that I would need to cut to length for my engine.
From my experience and my discussion with installation centers, it seems that it takes about one workday for an experienced shop to install an EIS on a simple airplane with a four-cylinder engine. Six-cylinder engines and more complex installations will take longer.
The installation instructions specified that the MAP sensor and the controller needed to be installed aft of the firewall and that the coil pack should be installed on the firewall or at another location forward of the firewall.
The lion’s share of the installation time revolved around planning. Where was I going to install the components? Would I need to cut a hole in the firewall to run the wiring? Where would I tap into the manifold pressure supply line to feed the manifold pressure sensor?
Since there’s not a great deal of space between the aft side of the firewall and the forward side of the instrument panel in my Comanche, I built a wooden controller box and a wooden MAP sensor box so I could mock up different choices as I explored mounting options.
When Kobylik told me he had seen the MAP sensor piggy-backed on top of the controller, I realized I could do this too as I had room above the controller. I removed the metal cover of the controller and mounted the MAP sensor on that cover.
Years ago, I had installed a steel glove box on the right side of my instrument panel. This proved to be the perfect location to mount the piggy-backed controller and MAP sensor. I installed both on the top of the glove box.
I did have to check with Electronics International to see if their CGR-30P engine monitor would accept the 12-volt square wave tachometer signal from the EIS controller. It would. I made the tach connection, and found that the two systems play well together.
Electroair’s instructions recommend installing the coil pack on the firewall. However, I looked for a different solution since the coil pack weighs nearly three pounds and I wasn’t sure the thin firewall on my Comanche could support it. Instead, I opted to use high temperature Adel-style clamps to secure the coil pack to the steel tubing on the engine mount between the firewall and the cylinder baffling.
I removed the right magneto to make space for the new EIS magneto timing housing. I had to remove the drive gear off the magneto before installing it on the shaft of the MTH. I tightened the nut to the torques specified in the Slick magneto manual. I slowly rotated the drive end of the MTH until a small locating pin dropped into position. It was now ready for installation.
I positioned the engine to top dead center (TDC) position on the number-one cylinder and installed the MTH on the now-vacant right magneto mounting pad. During one of my previous improvement projects, I had plugged an existing one-inch diameter hole in the firewall. The wiring harness plug to the MTH fit easily through this hole; I didn’t need to cut another.
After some discussion with Mike Kobylik and installation centers familiar with the Electroair, I also chose to replace the ancient magneto key switch with one of Electroair’s newest products—the FAA-approved 1300M switch panel.
This small panel has one toggle switch for the EIS and one for the magneto, and a push button to engage the starter. It can be mounted vertically or horizontally. ACS magneto key switches that were installed on a large number of Cessna single-engine airplanes are subject to recurrent ADs, and the installation of an Electroair 1300M replacement will terminate these switch ADs.
The 1300M switch panel eliminates the possibility of an ignition miss that does occur when a standard key switch is cycled during the pre-takeoff runup. Depending on when (in the engine rotational cycle) the switch is moved from ‘both,’ there often is a one- or two-rotation ignition miss of the EIS since the controller box must see a pulse from the MTH or trigger wheel to fire the coils. The standard magneto still fires the plugs so there’s no dead zone in engine operation; it’s just different than the mag check with two magnetos.
I found that the engine rpm drop during the pre-takeoff ignition system check is around 30 rpm when testing the EIS, and around 90 rpm when testing the magneto. This is a result of a long-duration hot spark. I’ll explain how that works (and the benefits it offers) next.
Long-duration hot sparks
The EIS system delivers a white-hot dose of spark energy, especially compared to the output of a well-maintained magneto. On average, a standard magneto delivers 12,000 volts over a five-degree rotation of the crankshaft when running, and around 6,000 to 8,000 volts during the starting cycle.
In comparison, the EIS system delivers around 70,000 volts across 20 degrees of crankshaft rotation at all rpms. A much hotter spark over a much longer period eliminates hot starting problems that are common on fuel injected engines, and makes cold weather starting much more reliable.
Each EIS-powered spark plug fires every time the piston comes up in the cylinder. One pair of the two paired coils in the coil pack fires at the same time. One is firing on the compression stroke while the other in the coil pair is firing on the exhaust stroke. This “wasted spark” system is different from a standard magneto which incorporates an internal distributor to deliver the high-energy spark only on the compression stroke.
Unlike a magneto, the EIS doesn’t deliver spark energy only on the compression stroke; each spark plug fires every time the piston comes up in the cylinder. One pair of the two paired coils in the coil pack fires at the same time; one is firing on the compression stroke while the other in the coil pair is firing on the exhaust stroke. This is termed a “wasted spark” system. It simplifies the EIS since it eliminates the need to time the ignition event to the compression stroke, and is common on electronic ignition systems.
Electroair suggests widening the spark plug electrode gap by a factor of nearly two—from .016 inch or .018 inch for the magneto-fired plugs to .036 inch for plugs fired by the EIS. A much hotter spark for a longer period over a wider gap produces a more complete fuel burn, and thus better fuel economy.
The other fuel economy enhancing component of the EIS is the manifold pressure sensor. Standard magnetos deliver energy at a fixed point in the crankshaft’s rotation. For instance, the left and right magnetos on my Lycoming engine are designed to fire at 25 degrees before top dead center (BTDC) on the compression stroke. That point is static—it doesn’t matter if the engine is turning 2,700 rpm during takeoff or idling at 600 rpm.
The spark timing also doesn’t change based on altitude and air pressure. It’s the same timing if the aircraft is at 0 feet msl or 10,000 feet msl.
The MAP sensor signals the EIS controller to adjust ignition timing based on atmospheric conditions to enhance fuel economy. The Electroair’s MAP sensor is connected to the controller by a three-wire harness. The controller automatically advances the timing of the spark event in a linear fashion from the fixed timing point of 25 degrees BTDC on my Lycoming to a maximum of 40 degrees (15 degrees advance) BTDC when the engine manifold pressure drops to 17 inches.
As airplanes ascend, the air becomes “thinner” which means the prop doesn’t have as much air to grip and the wing doesn’t generate as much lift. An EIS can’t change the physical properties of air, but it can advance the spark as manifold pressure decreases. An advanced spark moves the peak pressure generated by the less dense, weaker fuel/air mixture to a more advantageous point than if it were maintained at 25 degrees BTDC.
The standard atmospheric pressure lapse rate is one inch per 1,000 feet. I do most of my cross-country flying at between 6,500 and 8,500 feet msl. My wide open throttle (WOT) at 6,500 feet would be around 24 inches of manifold pressure; the point where the advance starts.
At 8,500 feet the advance would be four degrees for a spark timing of 29 degrees BTDC. When I need to climb to maintain clearance over terrain or choose to go higher than usual to take advantage of a tailwind, the automatic spark advance will continue to adjust to provide the spark advance needed to achieve optimum spark timing for my higher-altitude flying.
Standard magnetos require periodic maintenance. A 500-hour magneto service includes removal, cracking open the magneto housing and inspecting for wear, applying lubrication and installing new wear components. After reassembly, each unit must be tested to ensure it meets performance specifications. Both Slick and Continental Motors (formerly Bendix) recommend that these off-airplane magneto inspections be carried out every 500 hours.
Aircraft Magneto Service will do a 500-hour inspection on my Slick 4373 magneto for $365, or $765 if I need a new impulse coupling. That is the average parts and labor cost. The 500-hour inspection on a Continental (Bendix) four-cylinder magneto will average around $475, again including parts and labor.
Using the inspection rates cited above and factoring in the labor costs (from the Cessna flat rate manual) of an average time of two hours to remove, install and time the mag to the engine, it’s easy to spend at least $1,500 for maintenance of each magneto over a 2,000-hour TBO period.
Not so with the Electroair. One of the things I like best about the Electroair system is the almost complete lack of ongoing maintenance requirements. Oil leak inspections are required at every annual. The spark plug wires need to be replaced every 1,000 hours and at engine overhaul. In the event of a prop strike, the MTH must be exchanged for a replacement. That’s the entire list of items on the Instructions for Continued Airworthiness (ICA).
Adding up the benefits
According to Kobylik, an informal FAA study showed that safety was improved by two orders of magnitude when the Electroair system was used with a conventional magneto over a traditional dual magneto ignition system. I believe anything that improves safety is a good investment.
Most aircraft owners are also interested in the dollars-and-cents return. A certified EIS for a four-cylinder engine costs around $3,600 plus installation. The cost for a six-cylinder EIS is between $4,800 and $5,500 plus installation. Except for replacing the automotive-type ignition wires at 1,000 hours and checking for oil leaks at every annual, the ongoing maintenance costs are very small. My Comanche’s owner’s manual shows 75 percent power fuel burn at between 10 and 11.5 gph. Plugging in $5 a gallon Avgas and assuming that my 180 horsepower Lycoming will always consume 10 gph, I will burn approximately $5,000 of gas for every 100 hours I fly with standard magnetos. Installation of an EIS—which is advertised to provide a 10 to 15 percent reduction in fuel burn rates—will save me $500 every 100 hours. Over the 2,000-hour life of my engine, I’m way ahead by installing the EIS.
One of the things I noticed after I lit off the system for the first time was a more eager idle. I had to lean the idle mixture and back off the low rpm stop. Not only did the engine feel more eager at idle, it didn’t feel “lumpy” at 600 rpm. I believe the more vigorous ignition event contributed to the need to tweak the idle speed and mixture.
I was eager to see how the EIS performed so I did a full power climb up to 10,500 feet msl. Papa went right on up there with what seemed like a fresh eagerness and hasn’t missed a beat since. He starts right up which is rarely a problem with my carbureted engine but Kobylik says the long-duration hot spark eliminates heat-soaked fuel-injected engine starting headaches. I believe the EIS is a great upgrade to my Comanche. I haven’t yet flown enough to gather enough flight data to determine the economy gains from installing the EIS, but will in the future.
Any upgrade that promises improved safety, lessenes maintenance and lowers operating expenses is very tempting to aircraft owners. Based on my experience with the Electroair EIS so far, I’m glad I went for it.
Steve Ells has been an A&P/IA for 44 years and is a commercial pilot with instrument and multi-engine ratings. Ells also loves utility and bush-style airplanes and operations. He’s a former tech rep and editor for Cessna Pilots Association and served as associate editor for AOPA Pilot until 2008. Ells is the owner of Ells Aviation (EllsAviation.com) and lives in Templeton, Calif. with his wife Audrey. Send questions and comments to editor [AT] piperflyer [DOT] com.