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| This article was in the
December, 2006 issue of EAA Sport Pilot Magazine.
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By Jim Busha
Attendees at EAA AirVenture Oshkosh 2006 reported some wild sightings! The
outrageous claims included spotting a black-and-white cow with a thick barn-door-style
wing strapped to its back meandering toward the flight line making airplane noises instead
of mooing. Other concerned and equally panicked individuals spoke of a zebra-striped,
winged metamorphosis of an animal with a short round snout resting comfortably on the
grass just south of the Ultralight Barn.
Although the hot, humid
What the perplexed crowd "down on the farm" saw was another of Gene
Smith's designs called the Backyard Flyer. It was no animal, even though it jumped off the
ground like a jackrabbit with its hind legs on fire and flew like a goose with spoilers.
For the last handful of years, Gene Smith has been bringing new creations to
AirVenture, and this year was no exception. As usual, a crowd quickly gathered around the
ultralight with rapid-fire questions following from young and old alike; all of them
marveling at the ingenuity.
"Normally we bring a two-place trainer to
In reality, the Backyard Flyer is a simple-looking design, almost cartoonish in
nature, and by many accounts resembles an oversized child's toy. But make no mistake, this
airplane, along with its custom powerplant, drew attention from sincere airplane folks.
The Backyard Flyer i Meeting a Need
Gene Smith and his son, Larry, call
"Our engines and propellers are built the old-fashioned way, from scratch, one
at a time," said Gene, a mechanical engineer by trade and a former Air Force F-86
mechanic. He began designing airplanes when he worked for International Harvester. But he
soon found he didn't like city life, so he packed up his family and moved to
"We found that many of our customers wanted a four-stroke V-twin engine for
ultralight flying, with minimal weight and enhanced safety and durability." What Gene
and Larry found to fill that bill is a 38-hp industrial V-twin engine that was primarily designed for the airboat
industry.
When the Smiths laid their hands on the airboat engine and started the modification
process, the end result looked nothing like the original. "We removed the governor,
which is not needed on a propeller drive," said Gene. "We then stripped off the
intake manifold and carburetor because neither are suitable for aircraft use. The engine
doesn't have an adjustable accelerator pump, so we used a Weber carburetor system that is
totally adjustable." He also tuned and changed the emulsion tube along with the
carburetor's main jet. "This engine has a diaphragm accelerator pump, which is very
important for an aircraft engine. When you pump the throttle on a botched landing, you
want a smooth power transition. Without the accelerator pump, you are liable to kill the
engine, and then there's no way but down."
To counter any tooth-rattling
effect, Gene developed a drive that uses a poly V-belt with a slack side idler that is
elastically loaded and drives in one direction only. "I spring loaded the idler on
the slack side," said Gene, "and it holds without slip in the forward direction.
When the propeller tries to resonate (push/pull backward and forward), it breaks one
cycle; when the propeller tries to overrun, the idler moves out and lets the belt slip
just a little, all of which takes care of the shaking."
With the compact Big Twin now running as smooth as a catfish through cool water,
Gene also added another one of his exclusive designs, automatic carburetor heat. Gene has
been using this on most of his VW engines since 1993 and describes the unit as extremely
simple and foolproof. "My design recirculates some of
the exhaust gas from the exhaust pipe into the base of the carburetor. The flow of exhaust
gas is pulled through by manifold vacuum and therefore is full on at idle when you need
the most carb heat and practically closed off at full-throttle settings when there's
little vacuum pressure. The amount of carburetor heat is graduated depending on throttle setting."
While showing his new engine to the throngs of admirers, a concerned ultralight
flier asked about the exhaust gas messing up or fouling the mixture rate. Gene was quick
to explain that fuel, air, and exhaust gas can all live happily inside the carburetor with
one another.
"Exhaust gas is an inert gas," said Gene, "all the oxygen has
already been burned out of it. That is why we can introduce exhaust gas and it doesn't
change the mixture ratio of fuel to air at all. It is basically the same amount of fuel
and same amount of oxygen being mixed at a reduced flow. The only noticeable difference I
found was that the idle speed may increase a little bit." Enter the Backyard
Flyer As Gene and Larry
tweaked the Big Twin engine to their liking, they realized they needed a platform to
showcase it. To save time, money, and energy, the Smiths could have bolted the engine onto
an existing airframe from a kit manufacturer or relied on an already built ultralight. For
most people, that would have been the route of choice, involving the least amount of work.
But Gene and Larry Smith aren't like most people. Both father and son realized they wanted an original Smith-designed
aircraft, one as unique as the engine that would power it.
"We sat down and started from scratch," said Larry. "We sketched out
a design the old-fashioned way, using paper and pencil and no computer. One of our goals
was to stay practical and create an affordable, easy-to-fly, safe ultralight. But our main
goal was to have fun, and I think we achieved all of the above."
Gene and Larry said the wingspan is about 27 feet, and the fuselage length is about
17 feet. They described the wing as a big Hershey bar bolted to an aluminum tube. They
calculated the wing's breaking point at 6g and found that it will withstand 4g with
no deformation. The two best attributes to the Backyard Flyer, according to Gene, are the
engine and the use of the Junkers-style ailerons.
"As an old crop duster pilot, I felt that I had to have a lot of control
authority," said Gene. "That's why the big Junkers ailerons worked so well. I
can pull the stick all the way back into my stomach as I coax the Flyer into a full stall.
The airplane will start to sink, but I have full roll control. That is extremely important
when you're on a base to final turn, as those ailerons keep you from rolling inverted in
case you get too slow. I feel that is a wonderful safety margin to have, noticeable roll
control under full stall conditions."
Beyond the well-proven design of the wing and ailerons, the rest of the Backyard
Flyer retains a utilitarian look and feel. Its construction is aluminum tubing; the main
spar is a 6-inch tube with a reinforcing spar cap on the top and bottom. They also
incorporated a flying tail into the design because it is easier to build, involves few
parts, and is lightweight.
To meet the 254-pound empty weight limit for a Part 103-legal ultralight, they
lightened the flywheel by seven pounds and removed the alternator, ending up at 252
pounds.
One thing that Gene and Larry wouldn't skimp on was the installation of an
emergency parachute; they chose a BRS 600 Soft Pack ballistic chute. "Safety in the
air is a huge issue for us," Gene said. "That's why we created an airplane that
will land comfortably in the 20-30-mph range, have full control in a stall
configuration, and provide the pilot with a recovery backup system in case of a structural
failure or loss of power over rough terrain. With that said, every airplane we build will
have a parachute installed."
When I asked the Smiths about cockpit instrumentation, they both laughed. Gene
responded in his Southern drawl: "It ain't much, partner!" He was right.
Sticking to their claim of simple and plain, the Flyer's steam
gauges consist of an airspeed indicator, Tiny Tach, and an oil pressure gauge located on
the engine, "So you can lean out, feel the wind in your face, and see the gauge from
the cockpit," said Gene. Family Business
Gene and Larry estimate they can build a new, made-to-order Backyard Flyer every
two months for about $12,000 to $15,000, depending on desired equipment. They rely quite
heavily on their workforce, most of which is family. Gene's wife, Juanita, has earned the
nickname "Dopey" because she does most of the gluing of the fabric and is
considered the icon of the building process. Larry's daughter, Alaina, and son, Grant,
assist with gluing and rib stitching. Both are quickly becoming a third generation of
Smith aircraft builders. There is one more employee left to be mentioned, and although his
last name isn't Smith, he is still considered family.
"Shane Starks is our prop maker and finisher," said Larry. "He
creates masterpiece propellers from rough blocks of hardwood." Larry explained how
they became prop makers. "Culver Props built a custom-order prop for my father some
years ago. When he wanted another one, we learned the company was out of business. Instead
of reinventing the wheel, we bought the company and moved everything to Rolla. Since then, we whittle about five custom propellers a
week. We start with a large hunk of wood glued up together, 8-1/2 inches wide, 5 inches
thick, and 51 inches long, and draw an outline on wood in black magic marker and then
attack it with a chainsaw.
By the time Shane is done cutting and smoothing, and all the wood chips and dust
have settled, the result is a handcrafted, finished propeller in perfectly balanced
condition."
When a new Backyard Flyer is built and the last screw tightened, the Smiths perform
a debugging process before it is allowed to leave the nest.
"I like to run the engine at least five to 10 hours to make sure the rings are
seated early on in the break-in process," said Gene. "That is important as it
establishes long life in these engines because they are not babied early on. We also
test-fly the airplane to make sure the rigging is correct and everything is balanced to
specifications. We want to be 100 percent sure everything is working correctly before we
turn the airplane over to its new owner." If you want to have some flying fun with the added knowledge that built-in safety features are the main concern and the idea behind the aircraft's design, pay a visit to the Smith Ranch in Missouri and see for yourself what a truly tamed animal the Backyard Flyer is.
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