From the Experts:

Engine Operation and Maintenance Sun ’n Fun provided the opportune venue to solicit tips and tricks for the engines commonly used in Experimentals. BY RICK LINDSTROM

ne of the best things about any aviation convention is the phenomenal amount of aeronautical knowledge concentrated within a relatively small area; and the recent 2004 Sun ’n Fun extravaganza was no exception. It seemed like the perfect opportunity to ask the experts to share their opinions on aircraft engine operation with an eye toward longevity and safety—I wasn’t disappointed. With just a little time invested in meandering around the aircraft display area and in the exhibit halls, I gathered some pearls of wisdom well beyond the conventional engine operating techniques of most pilots. So, if you’ve ever wondered if there’s anything you should be doing beyond warming up the oil before takeoff and leaning above 4000 feet, here are a few gems that just might save some maintenance money in the long run while keeping that engine faithfully producing thrust when you need it the most (while airborne, that is).

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Gary Hunter, crew chief for Bruce Bohannon’s Flyin’ Tiger, says that understanding where a specific engine/propeller combination is most efficient without exceeding design or temperature limits is crucial.

Toeing the Redline I chatted with Bruce Bohannon’s crew chief, Gary Hunter, as Bohannon was otherwise engaged in setting a new world record for time-to-climb in the Exxon Flyin’ Tiger—a highly modified RV-4. “There is no redline when setting records,” Hunter said. He explained that many geared piston air-

craft engines routinely run well beyond the typical 2700-rpm redlines found on most engines that have the prop directly attached to the crankshaft flange. The redline only applies to that model of engine attached to a specific prop, so pilots should understand that redlines are not absolute values. They can be higher or lower than depicted on the tachometer, depending on the selected propeller. For experimenters, homebuilders and record-setters who routinely mix and match propeller and engine combinations, understanding where a specific combination is most efficient without exceeding design or temperature limits is crucial. A good engine monitor is an essential for this, according to Hunter—a must have. Keeping cylinder head temperatures (CHTs), exhaust gas temperatures (EGTs) and oil temperature within design limits during prolonged flights is much more important to an engine’s longevity than keeping the turns under redline while other W W W . K I T P L A N E S . C O M

parameters wander off the chart. Another important factor in an engine’s long-term health is ensuring that the oil gets hot enough to dissipate any accumulated internal moisture that’s crept in from sitting idle. Most engine vernatherm valves are set to open at 180°, rerouting the oil to an outboard oil cooler, which helps to maintain the oil temperature very close to that setting. But Hunter strongly feels that oil temperatures should run closer to 200°, where moisture is sure to be exorcised from the oil and crankcase. While pushing airplane and engine performance well beyond normal limits in setting new aviation records, oil temperatures of 240° to 260° are often seen—without major damage as a result. Of course, temperatures like these are only for short durations of extreme operation, not typical of normal cruise operations. Hunter also mentioned that a good way to accelerate engine wear is to subject it to full power operations before the oil has had a chance to warm up a bit. Many pilots will check their CHTs, see them coming up nicely and start the takeoff roll without consulting the oil temperature gauge as well. It takes a while for that cold, thick oil to start to flow nicely around the engine. High-power operations with cold oil may not immediately show any adverse effects, but will definitely add up with every cycle. Hunter’s wealth of experience from preparing record-setting pistonpowered airplanes can be used just as effectively in preparing for your personal burger run. His advice boils down to this: Make sure the oil is hot enough to dissipate internal moisture, warm enough before the takeoff roll and use a good engine monitor to keep an eye on your engine’s health. Understand where your airplane’s particular redline came from and what it means in real-world operations, and don’t let it frighten you.

Oil for Planes and Pilots Although Castrol has been producing single-grade aviation oils since 1994, it just introduced the product to PHOTOS: RICK LINDSTROM

In 2003, Castrol introduced its single-grade aviation oil to the U.S. market, though the company has been producing the product since 1994. Jim Olaffson shows off Castrol’s unique 1-liter bottle.

the U.S. market in 2003, which explained the appearance of a new green and white tent out on the Lakeland flight line this year. So I moseyed on in, expecting to hear some conventional lubrication wisdom from an oil sales guy. But Castrol’s Jim Olaffson has an impressive personal background in military and civil aviation maintenance, complete with engineering degrees, so I paid a bit closer attention to what he had to say. Olaffson likes using single-grade oils in piston aircraft engines, changed seasonally as ambient temperatures dictate which viscosity should be used. He points out that certain multi-grade oils are loaded with additives and other compounds, leaving less volume for the oil itself to provide the necessary lubrication. Like Hunter, Olaffson says it’s absolutely crucial to get the oil temperature to a minimum temperature of 140°C to cook the moisture out of the engine; any engine that sits without operation for longer than two months should be put into long-term storage to avoid damage from internal corrosion. If you see gray/white sludge come out of the crankcase when starting an oil change, you can bet that the oil isn’t getting hot enough to get rid of the water. According to Olaffson, Castrol takes its aviation oil production and

bottling seriously, dedicating a production line to aviation oil only instead of the more conventional method of running all sorts of lubrication products through the same refinery pipelines. And he’s especially proud of the 1-liter bottle that the oil comes in, which looks like no other oil container I’d seen before. It has a view band that is transparent enough to see clean oil level, a spout that actually fits during oil transfer to the engine and a molded eye so the bottle can be bungeed firmly in place during oil replenishment. It’s obvious that serious thought has been given to the realities and headaches of aircraft oil changes—and that someone has finally looked at the problem from the user’s perspective.

Spark Plugs and Mags Since Unison manufactures Autolite aviation spark plugs and Slick magnetos, I figured the company’s booth was a good place to get some advice on keeping the sparks flying. Jim Logie is a walking encyclopedia of good, usable maintenance tips, and he quickly hit the high points of magneto and spark plug longevity. In most engines, spark plugs will provide anywhere between 400 and 600 hours of service, assuming that they’re cleaned, gapped and rotated every 100 hours. They should be discarded when the center electrode is worn away beyond 50%, easily determined with a small, inexpensive spark plug tool that costs a few dollars. The gap should be maintained between 161⁄ 00021 ⁄1000, and the rotation pattern should end up with top and bottom plugs being reversed, as well as short-lead to long-lead lengths being swapped. It’s important not to overblast the plugs with grit while cleaning them, taking off more plug material than necessary while removing carbon deposits. A handheld vibrator tool is handy for reaching and dislodging those deepseated lead deposits, but any small tool can be used in a pinch, including a stiff piece of safety wire. A wire brush and an air hose make quick work of ensuring that the plugs are clean and the threads are free of grit before they go back into the engine. Anti-seize compound should only be used on the top few K I T P L A N E S

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familiar with your particular Slick magneto is to fire up your computer, go online and visit the Unison website at www.unisonindustries.com.

Power from Knowledge

Unison Industries, manufacturer of Autolite aviation spark plugs and Slick magnetos, recommends that pressurized magnetos be removed and inspected every 250 hours; unpressurized mags every 500 hours.

Maintenance Tips CONTINUED

threads of the plug to prevent the combustion process from carbonizing the anti-seize compound, negating the whole intent by making the plug even more difficult to remove. Of course, new copper washers should be used whenever the plugs are removed and reinstalled, and care should be taken not to overtorque and crack the aluminum B nuts that attach the leads to the plugs. Just snug is enough. The best way to avoid excessive carbon and lead deposits is to not make them in the first place; lean your engine in flight and on the ground when and where it’s appropriate. The best way to precisely lean for the cleanest combustion and best efficiency is to use a good engine monitor to ensure that the mixture is ideal for whatever flight regime you’re in at the time. Both your engine and your wallet will thank you. Magnetos are the heart of the aircraft ignition system, and the technology has been proven reliable for well over a century. Most pilots prefer to leave periodic maintenance and inspection to a savvy A&P or good magneto shop, but if you like delving into things yourself, they’re not so complicated that homebuilders can’t achieve good results. Magnetos are relatively simple devices with inexpensive and widely 22 K I T P L A N E S

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available component parts, so there’s really nothing to fear inside. Logie recommends that pressurized magnetos be removed and inspected every 250 hours, and unpressurized mags get a good once-over every 500 hours. A good rule of thumb in knowing when a mag should be opened up for service is after the third adjustment needed to bring the ignition timing back to specification. As the points wear in the magneto, the ignition timing will drift correspondingly a few degrees, and after three adjustments, it’s a good bet that the points will need to be serviced soon to keep the sparks coming down the wires reliably, without sudden interruption. Most magnetos have only four screws holding them together, and it takes very little effort to open one up, inspect the points for uneven wear and pitting, look for carbon tracking and contact wear on the distributor block, and check for any other signs of abnormalities. It’s also the ideal time to pull out your multimeter and check the coils for proper resistance and ensure there are no signs of insulation damage, arcing or other electrical abnormalities. The bible on Slick magneto servicing, according to Logie, is the Unison L-1363 Maintenance and Overhaul Manual, which contains everything you’d ever want to know about servicing the entire Unison/Slick magneto lineup. The easiest way to become

In an unending quest to get the highest level of performance and efficiency from injected big bore Lycomings and Continentals, George Braly, Tim Roehl, Mack Smith and the rest of the gang from Ada, Oklahoma, continually raise the knowledge bar when considering piston engine operations. Through the development of GAMIjectors and the following research in engine cooling and precision ignition systems, Braly and company aren’t afraid to challenge conventional wisdom and old wives’ tales when taking the scientific approach to piston aircraft engine design and operation. Their leading edge engine test cell has provided sometimes surprising results, with the predictable controversy always close behind. So the GAMI booth is usually surrounded by a crowd of pilots who, sometimes passionately, can be found desperately clinging to dated theories and outmoded thinking while debating the “right” way to operate your engine with the GAMI guys. So a quick visit was imperative to hear what discovery the latest round of testing and research had unearthed. I wasn’t disappointed. Braly has recently discovered that the stock fuel flow and mixture setup of the big bore engines he specializes in is frequently not quite rich enough during fullpower takeoffs, where the cylinder pressures and temperatures are highest. This too-lean condition frequently leads to premature cylinder barrel wear and valve failure, right when you need to have the highest level of confidence in your engine’s continued, immediate operation. Depending on the engine model and injector setup, it may be as simple as turning an adjustment screw to correct. But you’ll never know if you don’t have the precise data available from a good engine monitor and know how to interpret the raw data. Generally speakW W W . K I T P L A N E S . C O M

ing, EGTs should stay under the low 1300s during takeoff and climbout, even at maximum power settings. Braly has become convinced that the engine monitor just might be one of the most important developments in

aviation safety for piston-powered aircraft, and a lean of peak magneto check in flight will yield enough information about an engine’s health to virtually eliminate unpleasant surprises at the worst possible time—takeoff.

But to take advantage of this cheap insurance, you not only need to obtain the data, but also need to know how to correctly infer what it likely means. To this end, the guys from Ada have joined forces with Walt Atkinson and John Deakin, both sages of intelligent big-engine operation, to produce the Advanced Pilot Seminars. [See “Advanced Pilot Seminars” in the April 2004 issue for a report.] According to Braly, the most crucial element of proper engine operation and maintenance is a knowledgeable pilot who can understand what’s being shown on a good engine monitor. His advice is relatively simple: Get a good monitor, learn how to use it and that alone will quickly pay for itself, no matter what type of engine you fly behind.

Achievable Endurance

George Braly of GAMI described how even at a full rich setting, many engines operate under a too-lean condition on full-power takeoff, which frequently leads to premature cylinder barrel wear and valve failure.

Eric Tucker is a technical director for Rotax, and our conversation centered around the 80- and 100-hp fourstroke engines that seem to be ending up in the nose of more Experimentals. Although these engines resemble a typ-

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Maintenance Tips CONTINUED

ical small, flat, horizontally opposed aviation engine at first, Tucker stressed that they really have more in common with a modern motorcycle engine. This fact alone completely changes the maintenance picture from a periodic service standpoint. A good semi-synthetic oil is recommended, along the same temperature guidelines you’d use for a car or motorcycle; 20/50 multigrade is recommended for hot climate operations, dropping to 10/30 for cold. Since the engines have hydraulic lifters and propeller speed reduction units (PRSUs) that share the common oil supply, it’s also important that the oil contain a gear additive designed for the stresses found in gearboxes. Further, Tucker warned not to use a friction modifier in an attempt to reduce internal frictions, as the Rotax series does have an overload clutch that is designed to slip at a certain point with conventional lubricating oils. Friction modifiers can cause the clutch to slip much earlier than planned, meaning less power is available at the propeller. Even though multigrade oils are recommended, Tucker recommends using preheat as you would with a

Lycoming or Continental engine should ambient temperatures drop below freezing. He also recommends against using inferior aftermarket oil filters in an attempt to save a few dollars. These filters do not have the bypass pressure capability found in genuine Rotax filters, which open up at 13-19 psi—certain to enter into the long-term wear equation. Because the Bing carburetors have internal altitude compensation, setting the mixture manually is not a factor. But they do require periodic inspection and maintenance at 200 hours and should be resynchronized for maximum performance. It’s also a good idea to repack and shim the gearbox every 600 operating hours with the 80-hp engines, or 300-400 hours with the 100-hp engines, especially when running heavy propellers. If the gearbox clearances are neglected, it may result in hard starting symptoms due to the backlash in the drivetrain. Engine coolant temperatures should not exceed 225°F, and it’s a very good idea to use good fuel and change the spark plugs whenever wear approaches the limits of serviceability. According to Tucker, Rotax prides itself upon its proactive stance in the dissemination of service information. All maintenance information is easily

accessible online, where Rotax owners can register to receive periodic information specific to their engine model. After all, Tucker concluded, it’s in everyone’s best interest to ensure that all Rotax engines flying are maintained in the best possible condition.

The Turbine Way With more turbine-powered Experimentals showing up each year, I thought it would be a good idea to check in with Christian Koppe from the Turbine Solution Group. Standing proudly next to a Walter M601E, he talked about this engine finding its way into the nose of a Lancair IV, where the combination of the two results in 320-knot cruise speeds at 17,000 feet while burning 32 gallons of Jet-A per hour. With 750 shaft hp, turbine engines like the 601 are perfectly suited for the flight level crowd who need to get somewhere fast. And one of the biggest selling points is the comparative lack of maintenance needed when compared to a conventional piston engine. If a turbine operator is cognizant of the “big three”—temperature, torque values and speed—there’s really not much to be done beyond the 1500 hour inspect and repair as necessary (IRAN) cycle, other than a cursory inspection and oil change at 300 hours. There are some other considerations to weigh if you’re tempted to consider turbine power for your project, such as fuel system design and electrical considerations and accessories, but the relative lack of periodic required maintenance coupled with the worldwide availability of Jet A make the significant hard costs of going turbine seem very reasonable.

In It for Life

At the Rotax display, technical director Eric Tucker described how the company’s engines should be lubricated with an aviation-grade oil that contains a gear additive designed for the stresses found in gearboxes, since Rotaxes are used in conjunction with propeller speed reduction units. 24 K I T P L A N E S

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Whatever engine you live with, it pays to become as familiar with it as you can during your flights together. Some pilots I know treat their engines as mysterious entities, necessary for flight but not the kind of thing with which you’d want to socialize. This attitude might work for a while, but is not only expensive when all regular and remedial maintenance is directed to your local A&P, but can become unsafe when something is slightly amiss and the pilot really isn’t W W W . K I T P L A N E S . C O M

sure whether it’s a go or no-go item. Knowing how your engine is supposed to operate and being able to measure its performance and condition in flight not only keeps minor issues from becoming major ones, but does wonders in eliminating the “autorough” phenomenon when flying over hostile terrain or at night.

For those of us who have rightly earned the reputation of being…well…thrifty, getting the most from our engines between overhauls is strong motivation to stay actively involved with our engine’s health and doing as much as possible to avoid premature wear. And with just a little effort, patience and a good working

Contact Information EXXONMOBIL AVIATION LUBRICANTS

888/22TIGER www.exxonelite.com CASTROL

973/401-4350 www.airbp.com UNISON INDUSTRIES

904/739-4000 www.unisonindustries.com GENERAL AVIATION MODIFICATIONS INC. (GAMI)

888/FLY-GAMI www.gami.com ROTAX

242/356-5377 www.kodiakbs.com TURBINE SOLUTION GROUP

321/759-4817 [email protected]

Christian Koppe of the Turbine Solution Group stressed the importance of a turbine pilot remaining cognizant of the “big three”—temperature, torque values and speed.

knowledge of how your engine is supposed to work, it’s very possible to get that engine of yours happily committed to a long-term and happy flying relationship.

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