Waypoints

Here a gram, there a gram

November 1, 2006

Thomas B. Haines has served as editor in chief of AOPA Pilot for the past 12 years.

Those connecting rods may not look like much to you and me; they could well be mil-spec bubble-blowing wands. But to the technicians at Teledyne Continental Motors (TCM) they represent the latest in manufacturing techniques designed to provide smoother and longer-running engines for those of us who pay the maintenance bills. Balancing connecting rods to within 2 grams across the set represents just one of many ways that TCM has moved its manufacturing processes from early twentieth century to the twenty-first century. Two grams is, by the way, about the weight of a dime.

Although Continental is celebrating its 100th anniversary this year, it is not just looking back. Fifteen years ago it set out on a $40 million capital investment plan to modernize its facilities and operations. Today, it occupies 250,000 square feet of manufacturing space at its Mobile, Alabama, headquarters — down from the 1.1 million square feet it once occupied. Two computer-controlled machines now do the work that once took 15 machines. Preparing a core forging for final assembly once took as much as 11 weeks in fits and starts; it now takes about eight hours.

Overlooking the whirring manufacturing floor, technicians man a screen-festooned control room that would make NASA envious. Computers monitor and record thousands of processes for continuous analysis, ferreting out new ways to improve the manufacturing process and also for, well, CYA purposes.

Product liability insurance costs are a very real problem for engine and component manufacturers in particular, admits TCM President Bryan Lewis. Given that engines are generally replaced at intervals of less than 18 years, they do not benefit much from the General Aviation Revitalization Act of 1994, which provides a statute of repose — basically an 18-year statute of limitations — to general aviation manufacturers. Someday all of those stored bits and bytes of data associated with each engine may well prove that the engine was not negligently manufactured, no matter how convincing the plaintiff's attorney might be. The data analysis will more likely prevent any defects from creeping in in the first place and it will help isolate them if they do sneak in.

With the advancements in machining and careful manufacturing processes, today's engine is a "super-conforming product," says Lewis. Every part is consistently in the center of the factory specification limits.

Take those connecting rods, for example. Forty-five parameters are measured on each and every connecting rod. The data are stored and compared to others to ensure that none strays from the center of the factory spec.

When it comes time to finagle those rods into an engine, they are not the only items carefully chosen to match their counterparts. Technicians match everything from valve springs to fuel injectors to pistons (also balanced to within 2 grams across a set of six) to ensure that the resulting engine runs as smoothly as possible.

Once an engine kit is prepared, it does not move down an assembly line. Instead, a team of four technicians assembles it using very modern lifts and powered wrenches — the way you might imagine a team assembling a very expensive and fine piece of equipment, which is what an aircraft engine is, after all.

"Oh, sure," you may think, "horizontally opposed, aircooled engines have been around for many decades; they're crude compared to my car engine. Why not something new?"

As has been discussed before on these pages, to date, no other type of engine has proven in the long run to be more efficient and durable than those that we have today. Recognizing that, TCM has focused on improving the engines to increase reliability. And it appears to be working. According to Terry Horton, TCM's manager of product field performance, the new manufacturing techniques and trend analysis have resulted in a significant drop in warranty claims.

Show me the electrons

The one area ripe for improvement on these engines is the way pilots manage the power output. To that end, TCM has been leading the charge with FADEC — full authority digital engine control. TCM's PowerLink was the first general aviation FADEC approved as part of an aircraft type certificate — with the Liberty XL2. The system, which uses redundant computers to control ignition timing, fuel flow, and a host of parameters, provides greater power, better fuel specifics, and — presumably — longer engine life; it's too new to know for sure. It is available aftermarket for Beechcraft Bonanzas and Barons, with other models in the works.

FADEC is what Lewis calls "a game changer" when it comes to service and maintenance. Eventually, through FADEC and a wireless Internet connection, service technicians in Mobile will be able to troubleshoot your engine operation as you run it up anywhere in the world. The system records dozens of operating parameters for trend analysis to predict problems before they become problems.

TCM has extensively tested a diesel engine and continues to look at various horsepower options to determine the best fit for the market. The engine under consideration now is a six-cylinder configuration with a 17-1 compression ratio that will put out between 300 and 350 horsepower at 55 inches of manifold pressure and 2,200 rpm. With 360 cubic inches of displacement, the engine is projected to have a brake-specific fuel consumption of about 0.35 pounds of fuel per horsepower per hour, which is in line with what modern diesel engines in other applications put out.

The company is partnered with Honda for the development of a more conventional engine. That project engine is going through an extensive redesign.

TCM is conducting extensive testing on alternative fuels, such as unleaded, high-octane auto fuel, seeking a replacement for avgas. During a recent factory tour, TCM demonstrated in a test cell how an IO-520 with low-compression cylinders and retarded timing would run fine on auto fuel without detonation.

TCM has no plans to certify its small turbine engines that currently power cruise missiles. These engines are designed to be started and run only once — there is no round-trip ticket for a cruise missile; the demands of FAA certification would require an entirely new engine.

It's a long way from the 1906 auto engines to the 1920s start of aircraft engine manufacturing to today's FADEC-controlled, highly efficient GA engines. With its recent investments in new systems and manufacturing techniques, TCM appears set to be a strong player in aviation's second century.


E-mail the author at thomas.haines@aopa.org.