Hot Stuff: Unison’s LASAR Ignition System (Part One)

Unison's LASAR is the first microprocessor-based, FAA-certified engine control system available for widespread application in general aviation aircraft. But how does it work? How involved is the installation? Does it require changing the way you fly your Lycoming engine? AVweb's Dave Higdon just installed a LASAR in his Piper Comanche and answers those questions and more in this first of a two-part series.


I‘m really glad that using the latest version of Unison Industries’ Limited Authority Spark Advance Regulator (LASAR) is far easier than installing it. Through no fault of the Unison’s LASAR hardware itself, a team comprised of one aircraft owner, one experienced IA, and one factory field representative from Unison managed to take six or seven hours of work and spread it out across 48. Our team worked from early afternoon Monday to early afternoon Wednesday before we were able to fly a few turns around the pattern at Dead Cow International Airport (71K) in my newly LASAR-equipped Comanche 180. In between opening the first box of the LASAR system hardware to that first no-squawks start, Murphy ruled, assuring that whatever could go wrong, did – or at least went somewhat awry.

But that’s the bad news. The good news is that, after working through a number of foibles and clearing a couple of unavoidable obstacles, we achieved a very clean installation of a cutting-edge ignition system, one that matches what today’s pilots and aircraft owners demand at every turn: modern powerplant systems to match the modern avionics they’re installing in their older airplanes. Even before that first circuit around 71K, we noticed differences in how easily and smoothly the Lycoming O-360 started. Now, Air Comanche starts quicker and easier than most small-bore Lycomings. The engine felt immediately smoother, without struggling a few seconds to clear its throat before settling down to a smooth idle after starting. At that moment, the thought of hundreds of equally-easy starts in the future erased any doubts built up during the prior 48 hours. But before going any further, let’s discuss what the LASAR system is and what it does.

Of Brains and Maps

The Basics…

As far was what the left-seat occupant sees, Unison’s LASAR system simply replaces the old mechanical magnetos with newer ones designed for the LASAR, plus some black boxes and a bit of wiring.. From the panel, all the pilot sees is an annunciator light that informs of a successful self-test cycle or a controller-box failure. What you get in place of inefficient, fixed-timing magnetos is a system that matches the modern Capacitive Discharge Ignition, or CDI, that began replacing breaker-point ignition (coils, distributors and points) in automotive engines a quarter century ago. LASAR delivers a hotter spark, uses both mags during engine start and provides an engine with seamlessly-variable spark timing precisely matched to the power setting.

The complete Unison LASAR system components for a Lycoming O-180, sans sparkplugs.

LASAR also incorporates its own spark-boosting hardware comparable to the circuitry in Unison’s SlickStart spark-booster system. That integral circuitry sends roughly double the voltage that mechanical mags generate to the spark plugs, resulting in a hotter, cleaner spark across the electrodes. In turn, this hotter spark helps burn away carbon and lead deposits, and overcomes flooding and worn or mis-gapped plugs. Many piston engines start on only the left magneto, with timing retarded by either an impulse coupling or a so-called shower-of-sparks circuit working through the left mag. But with LASAR’s electronic “brain” controlling both magnetos’ timing, the system retards the timing of both mags and fires them during an engine start.

LASAR does not use a flat percent-of-power line, but a binary “map” that retards or advances the ignition timing based on the different RPM and manifold pressure combinations for the same power level. As a result, the engine gets the best spark timing for any given power level, regardless of whether you use the highest RPM and lowest manifold pressure or flip the combination to the highest manifold pressure and lowest RPM. The map, which is stored in the electronic brain or controller box of a LASAR system, helps the brain decide whether to fire the plugs earlier or later depending on the combination of engine speed and manifold pressure selected. The controller box gets its speed and crank-angle readings from sensors in the magnetos. A manifold pressure line from the engine plugs straight into the controller box, as does a bayonet-style cylinder-head temperature probe.

If LASAR has a weak link, it’s in its power source. The LASAR system needs at least seven volts to work, meaning that a dead battery prevents you from starting the engine, even by hand-propping it. To fix this shortcoming, Unison developed the LASAR Bush Kit, which adds an impulse coupling to the left mag. With the Bush Kit, a LASAR-equipped engine can be started with a dead battery, a failed controller box, or both.

…Why It Does What It Does…

The earlier the plugs fire, the more you can lean the engine to reach peak; the more you can lean, the less fuel you consume. Incomplete combustion wastes expensive fuel and prevents the engine from producing the maximum possible power from each explosion in each cylinder. Providing the optimum spark timing for every possible combination of power levels improves an engine’s efficiency by burning its fuel for maximum power. That perfect zone exists only at one combination of manifold pressure and RPM in an engine with fixed-timing ignition. The fixed timing compromise matches only one power setting across the infinite combinations available to the pilot. All other settings mismatch the spark timing to some degree and fail to fully consume even the best-metered fuel mixture. With settings available from zero to 42 degrees before Top Dead Center, however, the LASAR matches the spark advance to make possible the most “fire in the hole” from the smallest possible amount of fuel.

…And LASAR’s Lineage

Other, experimental electronic ignition systems preceded Unison’s to the market. The LASAR system, however, is the first to win FAA approval for type-certificated airplanes. Most of the earlier experimental systems required some type of alternative ignition source – retaining a single, mechanical magneto, typically – or, at the least, an alternative power source for the electronic systems. Unison covered that redundancy problem completely in the LASAR system. Upon failure of the controller, or any of the magneto hardware that talks to the controller box, the system instantly and without pilot intervention reverts to the old, reliable, proven mechanical function of the Slicks magnetos that are part of the system. In effect, it’s like having four ignition systems: two independent electronic systems and two redundant mechanical systems.

Unison’s certification work earned it FAA approval for virtually every Lycoming engine flying, along with STCs for installation in most Lycoming-powered airframes. In a bit of good news for Continental drivers, the word to me is that Unison has secured access to Mobile-built engines and has started the extensive test-cell work needed to make LASAR available for the TCM line sometime next year. Meanwhile Lycoming drivers are making the switch.

On-The-Job Training

Lessons Learned…

The old starting vibrator removed from Dave Higdon’s Comanche during the conversion to the LASAR system.

Obviously, anyone contemplating installing the LASAR system on their airplane wants to know how that changeover will go and whether the work is worth it. For me, working on and learning about my airplane is an enjoyable, worthwhile activity: This upgrade, like any other, should be fun. Which brings me back to illuminate why Murphy and his law paid us a visit and explain why our experiences are worst-case.

Lesson One: Murphy can show at his own whim, despite your best efforts. And particularly without good preparation. Give in and Murphy can nearly take over a job and make you question your decision, or even your reason for living. Ignore the question; it’s a trick question. Ignore Murphy, too; at some point the tricks run out.

Lesson Two: If you decide your plane deserves this system, work with a good professional and the factory in advance. Remember: You decided on its worth to your flying; don’t be swayed by opinions or predictions as unpredictable as what might go wrong. You’ll see what I mean below.

Lesson Three: Just remember one big thing up front: A decision to install the LASAR system should be based mainly on an honest assessment of how it performs, not how easy it is to install in your airplane the one and only time you’ll need to do it.

…The Cost-Benefit Analysis…

If Unison’s claims bear fruit in better performance, lower fuel consumption, a stronger climb (thanks to greater power at altitude), cleaner plugs and less maintenance, then the $2,600 retail price represents more of an investment than an expenditure. At some point, that investment will pay off and begin to return dividends. At least, that’s my justification for wanting a LASAR system on our Comanche. At our utilization level, any significant reduction in fuel cost translates into shorter, less-expensive visits to the gas pump. Reduced maintenance requirements, longer plug life, and easier starting are also attractive inducements. The bottom line overall savings serve to well-ice the cake.

But for the moment, these are strictly open questions that I’ll deal with in much greater detail in Part Two of this product review of Unison’s LASAR: A few more hours of structured flights and we’ll have what we need to weigh the performance evidence.

Beyond Basics: Doing It

The folks at Unison’s spark-product division in Rockford, Ill., designed the system with a modest, unassuming appearance. They also made it modular, with the controller box resembling your basic paperback-sized black box with two computer connections and a pneumatic connection along one side. A sturdy-looking Y-shaped black wiring harness connects the control box to the LASAR magnetos.

The Mags…

The old Slick magneto removed from Dave Higdon’s Comanche is on the right. The new Slick mag, with the LASAR pigtail, is on the left.

Which brings us to the mags, themselves. One difference distinguishes what otherwise resemble ordinary-looking Slick mags: A unique, six-inch-long black pigtail, which provides the only external indication that the LASAR magnetos contain something different from the standard Slick. That pigtail connects the mag to the Y-harness that plugs into the controller unit. In fact, Unison’s engineers fit the hardware necessary to both conventional-magneto and LASAR-ignition functions into the same space as conventional Slick mags. So, installing a pair of LASAR mags involves nothing different from standard-magneto installation. Install the drive gear, fit the gasket to a clean accessory case flange, and snug it down with the new lugs provided. At this point, you can time the mags to the engine, before anything else gets installed or hooked up.

Properly timing the two mags requires a special “buzz box” from Unison that you or your shop can purchase. The magnetos’ pigtails plug into the timing box instead of hooking up to the hot lead. Once the self-powered timing box is hooked up, you first dial the mags in with the engine at Top Dead Center for the appropriate cylinder. In other words, this is done at Zero Advance. Then you check them for proper setting at 25 degrees of advance, necessary for proper mags function in their mechanical, back-up mode. Setting the mags involves nothing more complicated than setting mechanical mags with a traditional buzz box. That’s all there is too it.

…And Mounting The Black Box

The area aft of the engine and its accessory case and ahead of the firewall of Dave Higdon’s Comanche before the conversion to the LASAR system. Note the engine mount tubes.

As for the controller box itself, you have simply to find a space large enough to bolt it down and wire it up. My AI, The Leprechaun, and the very patient Unison field rep, John Newman, noodled out a location that takes advantage of the Comanche 180’s very long, very strong engine-mount tubes after finding every candidate firewall spot slightly smaller than needed. In this case, two existing tabs on the engine mount anchor the front of the mounting plate required for the controller. To mount the aft end of that plate, The Leprechaun used two Adele clamps around the mount tubes. In turn, the LASAR system control unit mounts to the plate.

The combination proved very strong, very stable, easy to reach and see, and convenient for routing the harness to the mags and pulling through the firewall the four wires that give power LASAR to the system and the malfunction annunciator light. Mounting the light took less time than deciding on a location. Installing a new 10 amp breaker in the breaker panel took no more time than the annunciator light. Actual total time for installing and wiring the mags, mounting and wiring the control box, the breaker and annunciator light totaled around six hours – with another 90 minutes devoted to troubleshooting some wiring mistakes (discussed below).

Meet Mr. Murphy

And His Partner, OPS…

That should have been the end of it, with first run the next step before noon Tuesday. But these efforts only concluded the portion of the project that went quickly and easily and began, shall we say, the less-productive moments of this project. For example, before we got an hour into it, Murphy struck, inflicting us with a nominal case of OPS: Old Plane Syndrome. OPS is an affliction symptomized primarily by spells of unexpected things breaking, failing or wearing out simply because they’re old and because they can. So, other work either stalls or gets sidetracked until the now-required replacement or fix is accomplished.

At its worst, OPS problems arise in the course of working on something otherwise simple and even unrelated. At its best, it happens to something you’re already working on and only adds time to the project. We endured a little of both extremes. And we suffered with Murphy.

…Day One…

The system controller was mounted to a plate bolted to the engine mounting tubes just forward of the firewall.

Murphy struck first. We found that one of the new LASAR mags shipped to the shop was incorrect for this installation; the new Autolite spark plugs and high-tension leads would work but didn’t match the large-barrel hardware already on our bird, hardware better suited to the higher cruising altitudes we favor. An overnight shipment countered Murphy, who typically would not afflict someone dealing strictly through an FBO or maintenance vendor who examined the airplane and ordered the correct hardware. The information supplied by me to the folks at Unison didn’t deliver the complete picture a retailer would see before ordering the hardware for an installing shop. These problems weren’t their fault; Murphy and I made them happen..

And it didn’t really hurt us much in the time department since we still faced the jobs of: removing the existing mags, the plugs and ignition harnesses; locating space in the panel for a new warning light; finding a spot to mount the control box; making the electrical connections, wire a breaker, install a new bayonet-style cylinder-head temperature probe and tap into the manifold-pressure gauge line. Even without all the proper parts on hand, we had plenty to do to keep progressing.

Thinking ourselves not too hurt, we felt a little slapped around when taunted by the inaccessibility of screws on clamps holding plug wires to induction runners. With access so cramped and convoluted, finding tools that fit and loosening the clamps to remove the old leads consumed nearly two hours. Installing the new ignition leads and tightening the clamps proved much quicker with the proper tools already at hand.

We’d be ready when all the correct hardware arrived Tuesday. By the close of Day One, we knew we needed a new circuit breaker to handle the power load. But we didn’t know Murphy planned to spend the night.

…Day Two…

The correct mag and proper plugs and matching harness all arrived Tuesday morning. A little early, of course, teasing us with the prospects of completing the installation that day. But, it wasn’t to be. Instead, Murphy tossed us another load of OPS. This time up, a rivet snapped in the ignition switch, freeing a critical connector from the body of the device. Shortly, I was off to the Ignition Switch Store for a replacement. Oddly, the switch that broke was only 10 years old – much younger than the rest of our 1961 airplane. Oh, well.

Working under the panel on the circuit breaker swap and annunciator light is Spencer Atha.

Similarly, the new 10-amp circuit breaker came in with a slightly larger barrel diameter then the old breaker coming out. The smaller shafts went away years ago, I’m told. My slightly disembodied voice asked whether using a small, round file might provide the simplest solution. The safest option, The Leprechaun countered, was a hole-cutting tool to open the hole cleanly, uniformly. Another delay. And then some breaks came our way.

For example, a firewall-access point we used two years ago to route some new engine-instrument wiring gave us an easy path for the four wires that connect behind the instrument panel. The wires connected easily enough and the breaker slid right in to the newly enlarged opening. But, undaunted, Murphy fought back. First, between a misinterpretation of one wiring diagram and another schematic that was simply wrong, the annunciator light wiring had to be reworked. Likewise, the ignition-switch wiring went wrong somewhere – even though one of our crew carefully moved each individual wire to the new switch’s posts from the old.

We learned of this misstep the first time we turned the new ignition key that came with the new switch. Some reexamination of the wiring got us to where the starter turned. The ignition, however, didn’t come on until I released the key to “Run” from the “Start” position.

This is where having a Unison tech rep nearby came in handy. Newman plugged in his notebook PC, connected by a custom cable to the controller box, allowing us to see which mag was hot at which switch setting during the second round of troubleshooting. But high-technology aside, it still took The Leprechaun and his colleague Spencer, working together with a multimeter, to sort out the wires and their correct switch connections. In another 45 minutes, everything clicked. From that point forward, every start has been easier, quicker, smoother.

…And The Morals Of This Story

Let’s face it. Upgrading airplanes – especially older ones – always takes time; OPS, Murphy, new decisions. They all add up to extra effort and longer projects. In retrospect, using a committee of workers probably added to the time needed by dint of our efforts to divvy up chores according the aptitude required. An apprentice A&P could probably remove and reinstall plugs and leads faster than me. Call me mechanically-inclined, just not particularly practiced or polished. So, by my observations, our team collectively spent between 15 and 16 hours to complete the installation – a period that included pulling old spark plugs and leads, opening new factory-fresh plugs, checking their gaps and installing them, and routing and tying off the new high-tension leads.

Earl Long (left, a.k.a. “The Leprechaun”) and Unison’s John Newman using the company’s special “buzz box” to set mag timing on Dave Higdon’s Comanche during the conversion to the LASAR system.

Remove from the picture the problem with the circuit breaker and the need to replace the ignition switch and reduce the humbling amount of time it took me to remove and replace the ignition leads. When you do that, the net amount of time actually involving the LASAR system hardware installation and hook-up took no more than half that time – between seven and eight hours, by my notes. And remember, we used several people on different areas of the installation: Imagine the advantages of a single, focused mechanic handling installation. So, it’s not hard to conceive that a skilled aviation maintenance technician will require much less time to install the system on an airplane that presents fewer complications. Ultimately, it’s easy to imagine a LASAR-experienced A&P getting the process down to the four hours Unison says it should take – after several turns at a particular aircraft type or one with easy access to the engine accessory case, firewall space and under-panel depths. And then, there’s the time involved in replacing items other pilots may opt to keep as-is. For example, many installation needs may not require the new plugs and new leads; they can justifiably forego that part of the job.

There’s no real trick to the installation, though, and if you fly Lycoming now and are coming up on time to rebuild or replace your magnetos, there’s really nothing in the installation itself to fear – except for Murphy and OPS, itself. In the end, however, the time it took us to install the LASAR in my Comanche is probably appropriate, especially considering the fact that The Leprechaun had never done one of these before. Similarly, the end result is an installation in which everything is easy to touch and check during pre-flight inspections. So far, after about 25 hours at the time this was written, there have been no problems with anything coming loose, nor any starting or operating problems.

The End Of The Beginning

But the fun part is still ahead: Airborne research that should answer the question – at least for me – of whether the LASAR can really make a difference and deliver on Unison’s efficiency and performance claims. As this was written, in the days immediately following the installation and with only some 25 hours of operating experience to draw on for comparing the pre-LASAR and post-LASAR performance of our Comanche, the upgrade already impresses me with ease of operation and its impact on starting performance. On the first point, the LASAR is operationally transparent; on the second, it’s hot stuff.

A close-up of Unison’s special “buzz box.”

Importantly, especially for club- or partner-operated airplanes, using the system requires no new procedures or special considerations. During the mag checks, however, the system-inoperative annunciator lights up and continues to glow for another 20 seconds after the mag checks are complete. And starting on the LASAR’s hotter spark – and with both mags sparking – lights up the combustibles in all cylinders with urgency and enthusiasm. The engine immediately settles into a smooth idle without any of the coughing or stumbling common when an engine with a conventional ignition wakes up itself.

But how well the LASAR works remains an unsettled question for me. As this Part One of AVweb‘s product review of Unison’s LASAR system goes together in final form, my time with it is at about the midpoint for reporting on its performance impact. About 25 hours of use have given me a chance to make some limited comparisons of fuel-consumption numbers against flows noted at various altitude and power settings with the old, traditional system, and a few things have become clear. Without going into any quantitative comparisons, these things are clear: Our Comanche seems happy with the change, as does our Comanche pilot and the keeper of our company books.

In Part Two, numbers to back up my preliminary impressions are coming from some solid flying hours, including flying some of that time monitoring the system on our notebook computer. Once my image of LASAR’s performance impact comes into final focus, I’ll pump them into Part Two so you can see the LASAR system’s impact on climb and cruise fuel consumption levels, differences at best-economy and best-power mixture settings, and a glimpse of the system at work during segments of these flights. With a little luck and my usual fall flying schedule, my research should be far enough along to give you some representative numbers in a few more weeks.

Based on my flying on LASAR ignition to date, you’ll want to check back in for Part Two and decide whether you might benefit from a LASAR system sparking your engine. Then we’ll talk more about how LASAR works, about some of its built-in functions, and look at screen shots of its digital brain at work.

Until then: Clear prop!

Editor’s Note:

To learn more about Unison’s LASAR ignition system, be sure to check the Unison web site.

Also, be sure to check out Part Two of this AVweb Product Review for additional details on Unison’s LASAR ignition system.