After years of hemming and hawing, the piston aircraft engine industry could be finally coming to its senses by embracing electronic ignition. Electroair has been selling electronic ignitions for a couple of years, and now SureFly—a company stemming from Sky-Tek (starters) and Plane-Power (alternators)—is nearing FAA certification of an electronic replacement it calls the SIM, for SureFly Ignition Module.
I recently visited with Granbury, Texas-based SureFly for a close look at the product. Here’s a report.
You know, we fly some pretty darned interesting machines. They are made as lightweight, strong and redundant as possible considering the materials needed. If the electrical system fails, the engine will keep running thanks to technology developed for cars in the late 1800s.
The spark plugs do their job because of the magnetos. Think of magnetos as small generators that create electricity independent of the electrical system by spinning a magnet in an electric field. Andre Boudeville developed the first low-voltage mag, but the high-voltage (or tension) magnetos were developed in 1889 by Fredrick Richard Simms and Robert Bosch, with the addition of a coil. These created a high-voltage spark that was needed for ignition systems in automobiles. Some used a secondary coil to increase the voltage and some presented the charge directly to the spark plug.
For aircraft engines, magnetos were a godsend because they were independent of the electrical system, fairly compact and relatively lightweight. Aircraft engines were designed with two spark plugs per cylinder and two mags simply as a means for keeping the engine running should one of each fail.
I once lost an alternator in a Grumman Tiger after taking off in New Mexico. Rather than being stranded, I simply turned off the electrical system and flew the airplane (in Piper Cub fashion) back to home base. A rebel, perhaps, but I might not have tried this with just one magneto on the engine.
Electronic ignition retrofits for aircraft engines have been around since the early 1980s. Klaus Savier sold the Light Speed system starting around 1986, and these have worked on plenty of experimental aircraft engines—relatively problem free—for three decades. But since things in the certified world seem to drag on, electronic ignitions haven’t gained traction. Change could be in the air.
There are two challenges in bringing electronic ignitions to market and in a way, they’re both related. One is a price-sensitive market and the other is dealing with the rigors of FAA certification. The certification effort is incredibly costly and ultimately passed down to the consumer. Moreover, it would seem that the FAA hasn’t been exactly welcoming of electronic ignition technology.
Developers (including SureFly) recognized this and have pursued STCs that require the retention of the right-hand direct-drive mag (or typically the one without the impulse coupling), while replacing the left mag with the electronic unit. Retaining one mechanical mag retains some system independence from electrical requirements—significantly easing certification efforts.
Michigan-based Electroair has led the field with certified kits for both Lycoming and Continental engines. It obtained its first AML-STC in 2011 and the list is growing. We covered the Electroair ignition in the October 2014 issue of Aviation Consumer.
SureFly was started by the brainchildren of Sky-Tek and Plane-Power. After selling those companies, the crew began thinking about electronic ignitions. Jason Hutchinson, SureFly’s general manager, told me the SIM electronic ignition (which is expected to be certified in the coming months) was designed in only 30 days. The idea was to keep it simple, dependable and inexpensive. Essentially, the SIM is designed to directly replace and do what a traditional magneto does—no more. SureFly built several prototypes and installed them on the Lycoming engine in Hutchinson’s RV-6 and on the engine of an experimental Bellanca Viking.
Like Electroair’s system, the SureFly electronic magneto is completely solid state. Rather than using spinning magnets and a bunch of anachronistic parts, the concept is to electronically convert battery power into a high-voltage signal and pulse it to the right cylinder at the right time. Like the Electroair system, the SureFly ignition uses standard wiring harnesses for a given engine.
The beauty of the SureFly system is its simplicity. One unit is basically the same size and weight as a Slick mag and a couple of pounds lighter than a Bendix. There are no moving parts, it’s fully electronic and it requires no software updates.
The electronic mag can be adjusted to any engine’s base timing advance (specified on the engine data plate) by a little switching module that is accessible through a large port on the case. There is more spark energy throughout the RPM range and the dwell is adjusted automatically. Each spark plug has its own dedicated coil, virtually eliminating coil failures.
There is no impulse coupling, as the unit controls timing by manifold pressure and RPM. Below 400 RPM, the timing is set to TDC, with a longer dwell and increased voltage, ensuring cold or even fouled spark plug starts.
The SureFly SIM is quite simple to install. According to SureFly, it should take an experienced tech roughly an hour to install the first one, not counting disassembly. There are no extraneous boxes or wiring harnesses to retrofit on the engine.
A power wire, ignition switch P-lead and manifold pressure connection are required for the installation. The engine’s RPM signal is picked up within the module from the crank gear. Designed to last throughout the TBO of the engine for which it’s installed on, there should be no downtime for regular inspections, no messing with the timing or risking the possibility of failures due to these inspections/adjustments.
As for instructions for continued airworthiness, SureFly’s SIM installation manual advises, in part, that during the annual or 100-hour inspection one should simply check the installation for engine oil leaks.
During installation, power is applied to the timing lug and before tightening the base clamps, the unit is moved slightly left and right to ensure that the LED indicator is off. The power lead is then moved to the power post and the engine is ready for ground running.
SureFly is expecting to have FAA certification for its SIM before this coming summer. The SIM for four-cylinder engines will have a list price of $1250 and the six-cylinder SIM will cost $1550. Dealer discounting is possible. With disassembly, reassembly, paperwork and testing, typical labor costs should be well under $500—which is a real savings. The other savings, compared to traditional magnetos, is not having to pay for teardown and inspection.
But understand that the SIM doesn’t have unlimited life. Overhaul pricing hasn’t been determined, but there are simply two bearings and one drive shaft in the four-cylinder version and two additional bearings for the six-cylinder version. That could keep overhaul costs low.
Once the SureFly SIM is certified, buyers will have to choose between it and the Electroair ignition. The Electroair has a starting street price of around $1600 for four-cylinder engines and as high as $2500 for some six-cylinder engines. List pricing is considerably higher. The Electroair system is designed to last until the TBO of the engine.
If performance gains are the motivating factor, buyers will likely be drawn to the Electroair system because it has variable timing, which offers more power and better fuel efficiency. Electroair began development of its six-cylinder model in 2012, and has since received certification of the EIS-61000 system for large-bore Continental engines.
The SureFly SIM was not designed for performance enhancements, although some fuel efficiency is expected. The whole idea was to offer a dependable, low maintenance, stone simple electronic ignition that can be sold for a reasonable price. Remember, too, that SureFly’s SIM will be certified for basically all four- and six-cylinder engines immediately, due to the ability to adapt a common module to every four- or six-cylinder engine.
As it goes in all fields of endeavor, the last guy to bring something to the table has all of the first guys to learn from. In my estimation, the SureFly crew is a sharp bunch, they are all pilots and aircraft owners and they are all thinkers. They’ve had a proven track record of success from the get go, including their unabashed modification of automotive starters for aircraft application. After all, if it works, why redesign the wheel trying to change it?
For simplicity and for saving space in the engine bay, plus saving weight and reducing installation cost and complexity, the SureFly SIM could be the best choice for an electronic ignition retrofit. On the other hand, it isn’t FAA certified yet, which—for now—gives Electroair a sizable advantage.
When he’s not drumming in his band Revolushn, contributor Jim Cavanagh flies and wrenches several of his own aircraft.