Lycoming Engines - The Homebuilder's Favorite?

EXTERNALLY, ONE PITTS looks very much like another. So do the VariEzes, Emeraudes, Baby Aces, Acro Sports and just about all other homebuilts you see in flight. Under those cowlings, though, there is a world of difference. Under the cowlings lies the reason for the difference in performance and fuel consumption.

One Pitts can be pulled up into a vertical climb and held there until it becomes a small speck hardly visible from the ground. Another, in the same antic, will stall and fall after a faltering climb of several hundred feet.

Of course, we realize that there is a difference in performance between airplanes and properly attribute it to the engine installed. Although the brand of engine under the cowl is a relatively insignificant factor in obtaining high performance, horsepower is not. Obviously, the more important of the factors is the horsepower of the powerplant installed. So, are builders going for performance and power, or for fuel economy? What do you think?

At some point during the construction of each of my homebuilts, I would begin to wonder a lot. I wondered what size engine I needed. I wondered what make of engine I should try to buy, and even wondered what kind of engine other builders were using in similar airplanes. When you get right down to it, there is often but a small difference in engine weight-to-power that makes one engine better suited to a particular design than any other.

An engine that is too heavy affects weight and balance as well as performance. An engine that is too powerful may tear itself out of the aircraft, or at the very least be so thirsty as to gulp up all the fuel you can carry in less time than it takes to get lost. Indeed, there is a very small choice among powerplants for one best suited for your project.

Speaking of power, you may be surprised to learn that homebuilders have in the past (up to 1979) preferred the larger horsepower engines, the Avco Lycoming in particular. The 3 engines ranking highest in popularity (largest number in use by homebuilders) are the 160 hp, the 140 hp and the 180 hp Lycomings. (See Table 5) Amazing!

With all the interest in and display of automotive conversions at Oshkosh, I was led to believe that a large number of homebuilts were flying around powered by economical easily converted auto powerplants. Alas, it simply is not so. Not so, at least, according to the official data contained in FAA's latest Census of U. S. Civil Aircraft for the Calendar Year 1979. Yes, 1979. Actually, you wouldn't expect to get more up-to-date data this soon, would you?

Publishing governmental reports is a complex process and these things take time. After all, there were well over 250,000 aircraft that had to be censused (censed? . . . counted, and although that number is somewhat smaller than the national debt - which is tabulated more frequently and more accurately, I might add - it still taxes the agency's reporting prowess).

At this point you may already suspect that I am somewhat less than pleased with my trip through the statistical data presented in that Census of Civil Aircraft, Calendar Year 1979. Your suspicions are well founded.

This report shows a grand total of 251,516 aircraft . . . all air carriers and general aviation aircraft like rotorcraft, gliders, blimps, balloons, and not in the least, the amateur built aircraft.

A separate section of the Census report provides a detailed shred-out of the 11,448 individual amateur-built aircraft making up part of the total air fleet of 251,516. However, after laboriously reviewing the report, I could only identify 9870 of the aircraft as homebuilts. Why such a discrepancy?

Frankly, in my opinion, the report is a substandard official document. It is spotted with omitted essentials and erroneous groupings. For example:

Would you believe that the hundreds of Volkswagen-engine powered aircraft, built and flying, are all powered by 36 hp engines? That's right, 36 hp. You and I know that such a documentation is ridiculous because only a few builders have ever installed the early model small 1340cc VW engine in their aircraft. Most existing VW-powered homebuilts have the larger basic 1600cc engine, or a more powerful conversion developing up to 80 hp (some even more). The difference between 36 and 85 is considerable and can only reflect indifferent statistical reporting. But that is not all that is wrong with the data.

An unbelievable number of aircraft are listed as having an UNKNOWN powerplant. Even more unbelievable, the governmental statistician apparently didn't know what engines were installed in hundreds of aircraft manufactured under an ATC (Approved Type Certificate) either. A similar perusal of the Amateur-Built tabulations revealed that as many as 55% of the homebuilts listed had an engine model and horsepower also reported as UNKNOWN. Can you imagine such a lack of data would exist when the FAA requires all manufacturers and homebuilders to provide that information before they will issue a Certificate and Operating Limitations?

But, hold on, amigos, there is more . . . George Meyers of Corpus Christi, Texas, many years ago (early 60s, as I recall) designed and built a perky little biplane called Little Toot. The FAA data correctly reports Meyers to be the manufacturer of the Little Toot. and that the little biplane was a single seater equipped with a Lycoming 140 hp powerplant.

Far be it for me to detract from the recognition accorded to George by the FAA, but . . . I don't believe that George would ever claim to be the manufacturer of a Laser 200, an AVRO 504K, two Woody VJ-22's, 14 MA 4 Lancers, Lincoln Replicas (16 of them) nor the builder of 36 versions of the popular Volksplane VP-1.

Elsewhere the report more accurately lists a large variety of homebuilts with ABCO as the manufacturer responsible for their existence. I've deduced that the term must mean AMATEUR-BUILT . . . (COMPANY?). However, just as I was getting engrossed in the amazing variety of homebuilts I came across 634 amateur-built Pipers, 115 homebuilt Maules and something like 437 homebuilt Cessna A152's and TR182's.

There is no doubt that at least 10,000 of the aircraft are properly registered Amateur-Built (homebuilt) aircraft. But with so many of the listed aircraft being improperly categorized, figuring out how many homebuilts were using a particular engine posed quite a challenge.

Not at all intimidated by such uncertainties, I boldly concluded that most of the more than 3600 (55%) homebuilts reported with UNKNOWN engines of UNKNOWN power were surely equipped with engines just like others reported for the same design. This assumption made it seem reasonable to convert the UNKNOWN engines to known engine types by working with percentages. The method may not be scientific, but it is at least as accurate as the document from which the data was extracted.

In Table 1, Table 2, Table 3, Table 4, and Table 5, I report my findings regarding the identity of the engines (and their power output) that make up the homebuilt fleet.

It is a surprise, I guess that the Avco Lycoming engines are used in greater numbers (almost 2 to 1) over all other manufacturers combined. In second place are the Continental Motors powerplants. These two engine makers, of course, represent all of the major aircraft engine manufacturers we have to choose between. Franklin, now defunct, never did capture much of the aviation market in the United States and the homebuilt tabulations show that graphically.

Perhaps as previously stated, the biggest surprise to me was that Lycoming swept the top three rankings with three of the more powerful engines being used by the homebuilders (see Table 5). I always thought that the most commonly used engine was the 65 hp Continental. I hate to bring this up but the FAA virtually ignored the separate identity of the 65 horse Continentals in its report.

It really means little but what do you think the average horsepower rating would be for homebuilts? 85 hp? 140? 180? Less?

The way I figured it. . . 117 hp.

Notice that the large number of Volkswagen engines in use is a clue that they are coming on strong, considering that their entry into the U. S. aircraft community has been recent when compared to the old-line Lycomings and Continentals. (Table 1)

The McCulloch 72 horsepower engines make such a good showing because of their widespread use in gyrocopters . . . about 70% of the gyrocopter fleet uses a McCulloch engine.

Among the bantam-weight engines I found a couple of Heath AVN powered Heaths still flying.

There is already evidence that, as the tidal wave of fuel efficient ultralights hit the governmental computers, engine identification will become completely a hit-and-miss matter because even the engines on some of these ultralights are being designed and built by individual builders.

Table 1 reflects the large variety of engines in use - about 46 in all. I suspect that some readers will challenge the absence of several engine types. Engines like the Subaru. Citroen, Mazda, Oldsmobile, etc., etc. But, don't blame me. I don't maintain the official records.