Magneto Power
The micro processor has revolutionized general aviation, while aircraft magnetos have changed very little in the last century. Engine magnetos are critical components to the functioning of an aircraft during flight. We have all experienced the impact of a failed magneto during the preflight run up check. Testing the left and right magneto by turning it off will show an RPM drop.
A traditional aircraft magneto (TAM) is an engine driven electrical generator that uses permanent magnets and coils to produce high voltage to fire the aircraft spark plugs. TAMs are used in piston engines and known for their simplicity and reliability. Often installed in pairs, or as a dual magneto, a TAM requires no external electrical source to operate. In the event of an electrical failure, an aircraft engine will continue to run. Two of the most common are the Slick Magneto by Champion Aerospace and the Bendix Magneto by Teledyne.
Magnetos are mechanical devices containing components which are adjustable and wear over time requiring overhaul at 500 hours. I was on a flight over Lake Erie when the left magneto powering the IO540 in the Commander decided that its timing was going to change, resulting in a rough running engine. I put the Commander down at the Burke LakeFront airport (KBKL) where a local mechanic cleaned the plugs, adjusted the timing on the magneto and sent me on my way.
There are a number of aviation companies revolutionizing the engine industry. SureFly (www.surefly.aero) and Electroair (www.electroair.net) have developed a solid state magneto (SSM) and electronic ignition system for certified and experimental aircraft. Electroair’s system has more components and requires more labour to install than the SureFly. SureFly’s SSM has a 2,000 hours time before overhaul limit versus the traditional 500 hours. Unlike traditional magnetos, an SSM has no moving parts. As such, the SSM is replaced with new and not overhauled.
New mechanical magnetos are specific to an engine and range in price from $1,200 to $7,500 (CND plus installation costs), the average is $1,850, while an average overhauled magneto is $1,000. The SureFly SSM is $1,550 (USD) for a 6 cylinder engine. Electroair’s EIS-61000 electronic ignition kit is STC'd for Continental and Lycoming engines and costs $4,795 or $5,500 (USD depending upon engine model). The cost per flight hour, based upon average costs, is $4.65 for a new TAM, $2.95 for an overhauled TAM and $1.10 for SSM.
SSM’s value proposition focuses on cost, reliability and engine performance. The installation process for SureFly is roughly 1 hour with a few new connections, being manifold pressure and battery. FAA rules require that a critical component have independent power sources. A traditional magneto does not require a power connection. However, as SSM requires a power connection it falls in scope to the regulator’s requirements. Three types of aircraft configurations may have different regulatory compliance connotations. Type A, say a Cessna 172, with a single SSM and a traditional magneto may conform with no additional components. Type B, a Cirrus SR20/22, with two batteries and independent electrical buses, may have dual SSMs. Type C, an aircraft without independent electrical systems, which desires dual SSMs, may require a battery backup source for the second SSM. These requirements may change as the regulators work through the certification process. SureFly is developing a battery backup electrical bus module which will provide 1.5 hours of electricity, to meet regulatory compliance. SureFly’s SSD for uncertified aircraft is shipping now, with an STC’d certification expected in Q1 of 2018. ElectroaIr’s technology was developed in 1992 and has over 2,500 units shipped.
Reliability of SSM is enhanced through the nature of solid state technology. With no moving parts, wear and tear is eliminated. With the time before overhaul quadrupled, maintenance induced risk during flight is reduced by four times. With dual SSDs installed, that risk could be reduced eight fold.
Engine performance is enhanced through the variable timing which SSD delivers. The SureFly SSD monitors manifold pressure in real time. In a non turbo charged aircraft, as the aircraft climbs, manifold pressure will reduce. As the MP reduces, the algorithms in the SSD advances the timing, improving the power performance of the engine. Engine startup is enhanced as SSD delivers three times the spark energy than a traditional magneto. SSD is a bandaid for hot starts and not a solution, which requires technology to manage fuel to air ratios. IStartAir’s (www.iStartAir.com) technology eliminates a three handed hot start procedure (full throttle, mixture ICO and starter engage) which an average fuel injected engine requires.
SSD will reduce fuel consumption during cruise flight by roughly 10%. With variable magneto timing, a wider fuel-air range is provided, which allows more aggressive leaning. The Commander in cruise consumes 14 gph, at an average price of $2.00 per litre, that delivers an operating savings of $10.60 per hour.
Aircraft innovation has been hampered by the regulatory certification process, costs and contingent liability. The avionics industry has set the stage to implement meaningful change which has impacted everyday flying. Engine technologies are next on the horizon to deliver technological change.