Tuesday, April 5, 2011
Caring For Your Aircraft
Part II: All About Engine Monitors
Insight's G3 (opposite) is a color engine monitor that fits in a standard instrument panel hole, and stores downloaded data on SD data cards. Dynon's EMS-10 (above) is an engine monitor for use in experimental and sport category aircraft. Electronics International's MVP-50P (right) is a large-screen engine monitor designed to replace conventional engine instruments.
As you moved up to larger airplanes with more powerful engines, additional instruments appeared, including manifold pressure (MAP) for airplanes with a constant-speed prop, and oil pressure and exhaust gas temperature (EGT) gauges. EGT was used for leaning, and was more accurate than just leaning until the engine ran rough and enriching to smooth it out, as was (and is) common in simple trainers.
But, how much information did those instruments provide about conditions in the engine? You had EGT and CHT for just one of the four or six cylinders in your engine. If you ran lean of peak, or rich of peak on just one cylinder, how do you know whether you're rich or lean of peak on the others? If your CHT shows a hot 400 degrees in climb, can you be sure the others are running hotter, approaching the point that aluminum begins to soften?
Graphical engine monitors address this problem. Instead of a single EGT and CHT, multiple probes are attached to the cylinder heads and exhaust manifold for each cylinder in the engine. The display shows those temperatures graphically, so that you can instantly see if any one value is higher or lower than others. Many of these instruments offer additional features, such as accurate fuel-flow monitoring, and options for other engine parameters, such as battery voltage, oil temperature, vibration, etc.
Avidyne's EX5000 is typical of glass panel MFDs that can display engine-monitor data.
Using an engine monitor begins during preflight: If it's equipped with a fuel-flow option, you'll need to make sure the amount of fuel set matches what's in the tanks. During run-up, watch the bar graph as you perform the magneto check. You should see a uniform rise of all EGTs (some monitors offer a normalize display mode that makes this obvious). If one cylinder doesn't rise, you may have a fouled plug.
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