Choosing the Right Engine

There are many who look for an aircraft engine on the open market. While there is nothing wrong with this approach to acquiring a needed power plant, it sometimes results in an unfortunate choice. Perhaps a little information on the possible pitfalls may help to reduce the number of bad choices.

Individuals working on home-built aircraft may be particularly susceptible to this type of error. At Lycoming, there have been many calls from people who grabbed an engine that seemed to be an exceptionally good deal—only to find that this “engine of their dreams” would not fit into the aircraft they are building.

Consider the circumstances which lead to these problems. The person looking for an engine is usually building an aircraft from his own plans or from a kit supplied by a kit manufacturer.

As the airframe begins to take shape, obtaining a suitable engine may be the reason for some concern and anxiety. When a Lycoming 0-320, 0-360 or another engine with appropriate horsepower rating is found, there is a temptation to buy now and ask questions later. This could be a serious mistake.

The article "Low-time Engine May Not Mean Quality and Value" explains that old engines with low time are frequently affected by internal rust and corrosion. Any engine that is not used frequently should be preserved. The condition of the engine is just one of the items to be considered when acquiring a power plant in the resale market.

Other mistakes often involve the engine model. There are some who believe that all Lycoming 0-320 engine models are alike and that all Lycoming O-360 engine models are also very similar. The Lycoming-certified aircraft engine list shows 58 O-320 models and 51 0-360 models. While these engines may be similar in many respects, it is the differences that are likely to cause installation problems. These differences should be well understood before an engine is purchased.

What are the differences that may cause installation problems? The engine mounts should be considered. Older engine models were built with conical mounts that make installation somewhat easier, but which do not dampen engine vibration as well. With very few exceptions, engines certified during the l970s and 1980s have dynafocal mounts.

Although the type of engine mount is not likely to be a serious problem, the shape of the sump, the location of the carburetor or an engine-mounted oil filter may result in airframe interference which makes installation of a particular engine model difficult or impossible. Some aircraft, for example, do not have enough space between the engine and the firewall for an engine-mounted oil filter. In the case of an engine with a single-unit dual magneto, there is nothing that can be done since the filter is a required part of the engine design. All Lycoming engines with two individual magnetos can be configured to operate without an oil filter. Should an oil filter and the space needed to remove it be the only problem in adapting this type of engine to an airframe, the filter and adapter can be removed and an oil pressure screen housing can be installed instead. Should this step be necessary, the recommended oil change interval is reduced to 25 hours. A second option would involve removing the filter from its standard location and mounting it remotely

Engine to firewall is not the only area where space may be limited. The sump is often tailored in size and shape to meet the requirements for a particular airframe. For that reason, the home-builder may find that some engine models will not fit the plane being built because of interference. As if this were not enough to be concerned about, the carburetor or fuel injector location must also be considered. These fuel-metering devices are frequently mounted under the engine in an updraft configuration, but there are also front- and rear-mounted configurations. Some engine models are equipped with horizontal carburetors. All of these variations in model, may have an effect on engine/airframe fit.

Another error in choice which occurs all too frequently is the purchase of an engine originally designed for a high-wing aircraft when the builder has a low-wing design under construction. The low wing needs a fuel pump, but the high wing usually delivers fuel to the carburetor by gravity. In most cases, a fuel pump cannot be added to the engine because the drive mechanism was not built in during engine manufacture, and the accessory housing was not machined to allow mounting of a fuel pump.

As a result of contacts with individuals who have made engine purchases for their aircraft, we know that the variations in engine configuration outlined in this article have resulted in problems. The purpose of bringing these issues to the attention of Flyer and Key Reprints readers is to help them avoid making the same mistakes others have made. If a particular engine model has been recommended by a kit manufacturer, it is best to search for that model. Although similar, other engine models may not meet your needs.

Choosing the right engine is often a difficult decision that ultimately could affect the success of the home-built aircraft. Finding a used engine is tricky and, as we have already covered, the builder has to consider a lot of factors such as size and configuration.

Lycoming recognizes that home-built aircraft builders are mechanically inclined and technically trained and are always striving for more options and new technologies. Therefore, Lycoming has recently launched several new product lines that offer builders the “Power of Choice.”

Lycoming works very hard with Experimental Aircraft Manufacturers to ensure that they have power plants for their customers. Lycoming currently offers fully assembled Certified and Non-Certified Engines through most if not all Experimental OEMs. Since these manufacturers designed the aircraft, they are well equipped to handle your powerplant questions and needs.

Lycoming has recently launched Thunderbolt Engines. This is where technology and passion meet. Only the most premium engines carry the Thunderbolt Engine Medallion. These engines will be custom-built to your specifications from horsepower to engine color and everything in between at Lycoming’s performance-proven facility in Williamsport, PA. It’s one-of-a-kind pairing of Lycoming reliability and cutting-edge technology for the kind of power and status only the most passionate ever attain. Please contact Thunderbolt Engines at 570-327-7115 to exercise your “Power of Choice.”

Lycoming has also launched an impressive lineup of engine kits that are available through an exclusive network of internationally recognized shops. These engines will be assembled from 100% Lycoming parts and tested before delivery. Through this exclusive network, Lycoming’s Kit Engine product line delivers the power plant solutions that experimental aircraft builders have been asking for.