Flight Training - January 2012 - 28

WHAT’S IN A NAME?
Aircraft engine designations can be confusing. Lycoming and Continental, the two biggest manufacturers, have a consistent nomenclature. That can be good in that it’s easy to identify similar characteristics, but bad in that a Lycoming O-320 and Continental O-320 are completely different powerplants. Each engine has a series of letters, then a number, and sometimes another letter or series of letters and numbers at the end. The letters designate a characteristic, as shown below, while the number denotes the engine series—often based on its displacement, which is the volume of an engine’s cylinders and an indicator of the engine’s size and power. The final letter or series further distinguishes the engine, almost like a trim package within a singular car model.

O–Opposed, as in horizontally opposed cylinders

I–Injected, or fuel-injected instead of carbureted

T–Turbocharged A–Inverted
mount

AE–Aerobatic, presumably inverted fuel and oil systems

H–Horizontal mount, usually for helicopters

L–Counterrotating, or left operation for twin-engine applications

F–FADEC equipped

TS–Twin
turbocharged

For example, an AEIO-360 is an aerobatic engine that is fuel-injected and horizontally opposed. There are some variations among the letters, more common with rare or unpopular models.

intake. One of the valves opens to allow air and some fuel into the cylinder, while the piston moves down the cylinder. Act two is compression. Here, the cylinder moves up and compresses the fuel/air mixture. Then the mixture is burned off in act three, the power act; that controlled explosion pushes the piston back down the cylinder and another valve opens to vent the residue of the burn (exhaust) out of the engine. Each cylinder is able to move into position at the right time because they are all connected via a crankshaft. As one piston produces power, it is forced down, and another is forced up. Because the cylinders are such an important part of the engine’s health, making sure they are working in top order is critical. Unfortunately, there is little a pilot can do to diagnose problems. Instead, we can only make sure we are operating within the correct parameters. In general, heat is a good thing for an engine, but too much heat is a bad thing. That’s why the oil temperature, cylin-

der head temperature, and exhaust gas temperature gauges are critical elements in the pilot’s arsenal. The airplane and engine handbook for your aircraft will be explicit about those temperature limitations. Sometimes controlling heat can be difficult. Since the engine is usually hottest on takeoff (high power, low amount of air coming in), lowering the nose to bring more air in can help, as can reducing power when possible. Otherwise, controlling heat is done through the mixture. Fuel is a cooling agent, which is why most of what we do in terms of controlling temperatures is achieved through leaning the mixture. In the performance section of your pilot’s operating handbook, you’ll likely see range calculations for both best power and best economy. The pilot attains these performance figures by hitting target exhaust gas temperatures. When you lean the mixture, the engine starts to hesitate, and then the mixture is enriched

slightly, that is more or less the highest, or peak, exhaust gas temperature. Modern digital engine instrumentation will show this peak to the degree, but in older airplanes we have to improvise or use the rudimentary EGT gauge that may be available. This peak EGT setting is for best economy, meaning you’re using the least amount of fuel possible for that given power setting. Increase the mixture until the gauge reads 50 degrees cooler (or rich) of peak EGT, and you get best power. Here you’ll be burning more fuel but also going faster. There’s a debate about whether it’s safe to operate an aircraft engine at 50 degrees rich peak of EGT. Some people say that’s actually the worst possible temperature at which to operate. Your instructor or flight school’s mechanic should be able to advise the best setting on the rental airplanes. But once you buy an airplane, talk to your mechanic at length to determine your own comfort level. On some aircraft

ON MODERN ENGINES, operating parameters, such as oil temperature (left) and oil pressure (right), are sent to the panel instrumentation with electronic probes. Older airplanes will have a direct hose that sends fuel or oil to the back of the instrument.

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Flight Training - January 2012

Table of Contents for the Digital Edition of Flight Training - January 2012