Selecting tnS >er engine for homebuilt^

RON ALEXANDER

W

e are now at the point in our series on aircraft building where we need to select the engine. Obviously, this is one of the most important decisions any builder makes. What kind of engine should you put on your airplane? What are the horsepower requirements? Where do you get an engine? How do you know if it is a good engine? What kind of maintenance can you do on the engine? Before answering these questions, let's briefly discuss the history of aircraft engines. From the Wright brothers' first flight, aircraft engines have been designed with one primary ob-

jective—reliability. Pilots don't relish the thought of losing power on their aircraft's engine, and today's aircraft engines are very reliable. If properly serviced and maintained, they operate thousands of hours with few major engine problems. As engine designs have changed throughout the years their horsepower and reliability have increased. The Wrights' first engine weighed 150 pounds and developed less than 15 hp. Compared to engines today, early aircraft engines were not that reliable, and engine failures were relatively common. Over the years a number of manufacturers such as the Wright Aero-

nautical Corporation, whose powerplants are still in use today on many antique aircraft, started mass producing engines. Other companies that set the pace for aircraft engine development include Liberty, Kinner, Jacobs, Pratt and Whitney, Continental, Franklin, and Lycoming. A few are still in business today, and their engines are examples of improvements made through the years. One of the most popular in use on homebuilts today is the Lycoming O-360, which weighs approximately 290 pounds, develops 180 hp, and operates 2,000 hours between overhauls. Your airplane's engine will often Sport Aviation

47

comprise a third of the project's total cost. Most builders have been so busy constructing the airframe that the engine may be an afterthought, but planning is of the utmost importance. Decide what engine you want to use early in the project, and then start searching for it. Advice abounds as to what engine to put on your airplane, and this abundance often leads to confusion. The advice you should pay closest attention to is that of the designer or kit manufacturer. The engine or engines they recommend have usually been tested and proven on the design. Like all other phases of building, don't experiment without their approval. Designers select an engine for their airplanes with several factors in mind, horsepower requirements being one of the major considerations. Builders, on the other hand, want to place the maximum horsepower on their airplane, thinking it will make the airplane faster. More speed may not be the actual result. The airplane may climb faster, but the overall 48

JULY 2000

speed often isn't increased. What often happens, however, is that the bigger engine's torque and thrust loads may exceed the structure's design limits, reducing safety. Weight and balance is another thing a bigger engine may compromise if you don't use the recommended engine. A heavier engine will upset the structure's weight and balance limits, and the builder may have to extend or shorten the engine mount to compensate for the weight difference. Fuel usage is yet another consideration. More power burns more fuel more quickly, and that reduces the airplanes range and endurance. Adding additional fuel tanks returns builders to the weight and balance problem again. Engine installations requiring modifications will present problems. Designers usually provide instructions that make engine installation a relatively simple task. Builders who use a different engine are on their own when it comes to installation problems. In short, your custombuilt airplane is designed to be oper-

ated with a certain engine or group of engines—select one of them and don't experiment. Do not compromise the safety of the aircraft. Builders can choose from three types of engines: a type-certificated engine, an automotive conversion, or a noncertificated engine. Our discussion will focus primarily on certificated engines, but understand that as a homebuilder there's no regulatory restriction on the powerplant you use. Production airplanes, however, must use certificated engines. A type-certificated engine complies with Federal Aviation Regulation Part 23, "Airworthiness Standards: Normal, Utility, Acrobatic, and Commuter Category Airplanes," and FAR Part 33, "Airworthiness Standards: Aircraft Engines." These FARs give the design requirements and standards engines on production airplanes must meet. Continental and Lycoming engines comply with Part 33 and are type-certificated engines, and so are certain Rotax engines. Through their years of operation most certificated

engine designs have been proven reliable and safe. Parts are readily available, and FAA-certificated airframe and powerplant (A&P) mechanics are familiar with and can fix these engines. When it comes time to test fly your airplane, FAA Advisory Circular 20-27D, "Certification and Operation of Amateur-Built Aircraft," discusses certificated engines when addressing the number of test flying hours required. It says, "Amateurbuilt airplanes and rotorcraft will initially be limited to operation within an assigned flight test area for at least 25 hours when a type certificated (FAA approved) engine/propeller combination is installed, or 40 hours when a noncertificated (i.e.

This is one of the most important decisions any builder makes. modified type certificated or automobile) engine/propeller combination is installed." Opinions about converting auto engines for aviation fall on two sides of the fence, and I don't intend to address those issues here. If the designer of your aircraft recommends an automotive conversion, then the designer should have investigated the problems associated with using that type of engine and feel confident in recommending it. Other than the kit manufacturer's recommendations, you have to address several other factors before selecting your engine. For example, what type of engine mount will you use? There are different types—conical, dynafocal, and bed mounts—

Attention Pilots...

...Get DUATS* Freer Receive FREE color weather graphics for offline viewing when connecting through Cirrus For DynCorp DUATS Windows software. Features include: • Version 3X now available

• Satellite Infrared • Internet Access via Cirrus

• Satellite Visual

Developed exclusively by Mentor, a Jeppesen Company, Cirrus gives pilots easy access to free up-to-date color weather graphics and graphics-based flight planning.

To receive your free copy of Cirrus on CD-Rom, electronically, or by e-mail, contact [email protected]. To download Cirrus DUATS from the World

DynCorp

Wide Web, visit us at http://www.duats.com. For DUATS help, contact the Technical Support and Order Line at

DynCorp Information Systems 15000 Conference Center Drive Chantilly. VA Z0151-3803

(703) 818-4000 www.dyncorp.com

1-800-345-3828, or by e-mail at [email protected]. For DUATS access, call 1-800-767-9989, Internet Telenet at duats.gtefsd.com, or Internet Web

site at www.duats.com.

"DynCorp DUATS was previously known as GTE DUATS

at iust $23,500.

Imagine building and flying your own plane, able to make 1240 NM cross country trips, carrying four adults with luggage in comfort - at speeds over 200 mph! Choose from seven models, with a wide range of available options. Sleek, fast, stable and efficient...the perfect description for Velocity sport aircraft.

^ip

^BHBPBmBBwdlBBBB^r

^^fj^^^^^r

^^^ ^^^^f

velocityaircraft.com

30 min Video & Info Pak $29.50 US & Canada $39.50 International (Visa/MOCheck/US$ Money Order)

200 W Airport Drive, Sebastian FL 32958 • (561) 589-1860 For more information, visit SPORT AVIATION on the Web at www.eaa.org

Sport Aviation

49

and the engine you buy will work with just one of them. Most people prefer a dynafocal mount because its large rubber discs better dampen engine vibrations. If you order or build a dynafocal mount, this limits your choice of engines. What propeller you plan to use is your second major consideration when selecting an engine. If you plan to install a constant-speed prop, for example, your engine must have a hollow crankshaft and a provision for a propeller governor.

Engine Availability

Once you've decided what engine to put in your airplane, you'll probably ask what certificated engines are on the market, where do you find them, and how do you know which one to purchase? Factory New Engine: If your budget allows, this is the way to go. The cost will be high compared to a used engine, but the reliability should also be highest. The engine

Foils Jones installed a Subaru auto engine in his Murphy Renegade. Auto engine conversions have their detractors, but many enthusiasts advocate their benefits.

logbook will show no time on the engine, and every part will be new. And the engine is test run prior to shipment. Several kit manufacturers offer discounted prices for new engines. They have an OEM sales agreement with the engine manufacturer that allows them to buy new engines at a

reduced price, which means they can pass that discount to you. This usually represents a major savings for the builder. Factory Remanufactured Engine: This type of engine has been completely rebuilt by the factory to meet original type specifications and is sometimes called a "zero-time" engine. The factory has taken a used engine core and completely rebuilt it using new parts as required. This engine should be as reliable as a new engine, and its logbook will show zero time. The cost of a remanufactured engine is usually less than a new engine. Remanufactured Engine: A remanufactured engine has been restored to new specifications by a facility other than the factory. Overhauling an engine to new limits means the facility has checked the wear on all parts and replaces those outside the limits of a new part. If done by a reputable company, this engine should be as good as a fac-

Engine Terms

TTSN—Total Time Since New (the

FAA Advisory Circular 43-11 addresses engine overhaul terminology and standards, and it's a good AC to have. Addressing certificated engines only, here are the definitions of a few terms you'll encounter

since it was new).

when searching for an engine. Manufacturers identify their engines using a standard "code." Using a Continental IQ-240 as an example, the prefix letters indicate the engine configuration and the number gives the engine's displacement in cubic inches. An IO-240 is a fuel-injected (I) engine with opposed cylinders (O) that displaces 240 cubic inches. Often you'll see numbers and letters that follow the displacement, and these identify variations of the basic engine. When reading ads listing engines for sale, you'll encounter a number of other abbreviations. Here are the most common: SMOtf—Since Major Overhaul (the amount of time on the engine since its last overhaul, i.e. 500 hours SMOH). 50

JULY 2000

time on the engine

SFREM—Since Factory REMmanufacture (the time since the original manufacturer remanufactured the engine, returning it to a like-new condition). STOH—Since Top Overhaul (the time since the cylinders were overhauled). TBO—Time Between Overhauls (the manufacturer-

recommended overhaul intervals. In other words, 2000 TBO means the manufacturer recommends that the engine be overhauled every 2,000 hours of operation.) TT—Total Time OEM—Original Equipment Manufacturer

Yellow Tagged—the part or engine is airworthy and ready to run. Red Tagged—the part or engine is not airworthy. Core or Run-Out—the engine is past its TBO and needs to be overhauled. FWF—HreWall Forward

tory remanufactured engine. You should also realize a cost savings. The main difference is in the logbook. It will show the total time accumulated on the engine. Overhauled Engine: This encompasses a wide range of engines. The reliability of an overhauled engine depends on who did the work. Legally, any A&P mechanic can overhaul an engine, and who did the overhaul should be one of your first questions. You may sometimes hear this called "majoring an engine," meaning a major overhaul. Advisory Circular 43-11 says: "The selection of an overhaul facility by the average aircraft owner is usually determined by the cost quoted by the engine overhauler. Engine overhauls can be accomplished to a variety of standards. They can also be accomplished by many different facilities, ranging from engine manufacturers, large repair stations, or individual powerplant mechanics. The selection of an overhaul facility can and does, in most cases, determine the standards that are used during overhaul." When considering an overhauled engine, find out who did the work. Was it an experienced engine rebuilder or a known engine overhaul facility? Check out the rebuilder's reputation and think about visiting the shop. Continental and Lycoming sell overhauled engines, and they use more new parts than some field overhaulers. Most major overhaul companies advertise in Trade-APlane, and they often are a good source for where you can save money by purchasing a newly overhauled engine. Engines are overhauled to service limits, which means the parts are checked for wear and replaced only if they do not meet them. For example, if the crankshaft shows wear but is within the tolerance set by the manufacturer, it will remain in service. The logbook will show the engine as being overhauled along with the total time that has accrued on the engine. Ads for such engines

AIRCRAFT BUILDERS' WORKSHOP Shawnee, Oklahoma August 26th -27th • • • • • • •

Basic Sheet Metal Fabric Covering Composite Construction Intro To Aircraft Building Electrical Systems, Wiring and Avionics Gas Welding What's Involved in Kit Building

EAA MEMBERS $199~ $279

NON-MEMBERS $219~ $299

AIRCRAFT BUILDERS' CONFERENCE Oshkosh, Wisconsin • September 9th • Intro To Aircraft Building • Sheet Metal Basics • Electrical Systems EAA MEMBERS $89

• Fabric Covering • Engine Installation • Composite Construction

NON-MEMBERS $99

AIRCRAFT OWNER MAINTENANCE Oshkosh, Wisconsin • September 10th A one day hands-on, course detailing the 28 maintenance items a pilot/owner can perform on their airplane without the presence for an A&P mechanic. Save money! Know your plane! EAA MEMBERS $129

NON-MEMBERS $149

WORKSHOPS "Under EAA's leadership these workshops are better than ever," Ron Alexander— workshop developer.

800-967-5746 www.sportair.com

Call or log-on for our complete workshop calendar

"U