BY DALE SMITH EC T
here have been a lot of discussions recently about pilots becoming over dependent on automated
systems. While there is still much to be said about the reliance on digital displays and autopilots, when you’re talking about piston engine aircraft, there is one emerging automated system that will have nothing but positive impact on both reducing the pilot’s workload and improving overall aircraft operations. The cure all for cockpit automation for which I speak is Full Authority Digital Engine Control (FADEC). Having experienced the technology first-hand, I can tell you that, from an engine management perspective, it is truly a game changer. But before we get too deep into what benefits the technology brings to the cockpit, let’s define what FADEC is: The official book definition is found in FAA Advisory Circular 33.28 (www.
faa.gov). The advisory says that FADEC is an engine control system by which the primary functions are provided using digital electronics and the Engine Electronic Control (EEC) unit has full range authority over the engine’s entire range of operations. “For a FADEC system (on a piston engine) you essentially have two sets of redundant computers with discrete redundant power supplies that make all the decisions about engine management based on what the pilot input is,” explained Keith Chatten, senior program manager, Continental Motors. “It is basically monitoring the air density in the manifold, cylinder head temperatures, exhaust gas temperatures, fuel pressure, engine speed – and making the appropriate adjustments to fuel flow and spark timing multiple times on every engine cycle.”
“When you think about what every engine cycle means, at a typical cruise speed a FADEC system is adjusting the conditions about every four-one thousandths of a second,” he said. “On a six-cylinder engine we have 24 individual sensors monitoring the engine 250 times a second. The sensors are giving information on individual cylinders, fuel injectors and spark coils on a discrete basis – every cylinder gets a command for exactly what that cylinder needs.”
One common misconception is that EEC is the same as FADEC. Not so. An EEC has limited authority to the engine control. “What that really means to you and I is that EECs usually have some sort of mechanical backup and not dual computer redundancy,” Chatten said. “Early on many companies were perusing EEC systems. They had one electronic ignition system and one magneto system still on the engine. It’s a way to get better engine performance, but not the best overall performance.”
FADEC Benefits
While an obvious benefit to a FADEC system, whether installed on a piston or turbine engine, is improved engine performance and efficiency, it’s not the only one pilots and operators enjoy. “Reducing pilot workload is also a major benefit,” explained Guido Defever, VP research, development and engineering for Lycoming Engines. “It’s especially helpful in bad weather and high traffic situations. The pilot can focus on flying the airplane instead of continually having to manage the fuel control and manifold pressure.” “You have a team of engineers who have created software to actually make all of your engine management decisions based on actual conditions instead of the pilot trying to decide where to put the fuel, mixture and propeller knobs,” Chatten added. “Along with proper engine management, you can also get real-time engine diagnostics. For example, if your fuel pressure is going down because of a clogged filter or injector the system will tell you with a warning. The systems will also actively enrichen a given cylinder if it starts to over temp. It can react a lot faster than a pilot.”
The active diagnostics will also benefit technicians. “The troubleshooting aspect will have new tool for the system,” Defever said. “Similar diagnostics tools and steps to what an automobile technician uses. You will have an active diagnostics unit. You just plug-in a laptop with the appropriate software and the diagnostics will download all the fault codes.”
Aviation Maintenance |
avm-mag.com | December 2011/January 2012 53
GENERAL AVAITION
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