Homebuilt aircraft, also known as
amateur-built aircraft or kit planes, are constructed by persons for whom this
is not a professional activity. These aircraft may be constructed from
“scratch,” from plans, or from assembly kits.
Overview In the United States, Brazil, Australia
and New Zealand, homebuilt aircraft may be licensed Experimental under FAA or
similar local regulations. With some limitations, the builder(s) of the
aircraft must have done it for their own education and recreation rather than for
profit. In the US, the primary builder can also apply for a repairman’s
certificate for that airframe. The repairman’s certificate allows the
holder to perform and sign off on most of the maintenance, repairs, and
inspections themselves. Alberto Santos-Dumont was the first to
offer for free construction plans, publishing drawings of its Demoiselle in
the June 1910 edition of Popular Mechanics. The first aircraft to be
offered for sale as plans, rather than a completed airframe, was the Baby Ace in
the late 1920s. Homebuilt aircraft gained in popularity
in the US in 1924 with the start of the National Air Races, held in Dayton,
Ohio. These races required aircraft with useful loads of 150 lb and engines of 80
cubic inches or less and as a consequence of the class limitations
most were amateur-built. The years after Charles Lindbergh’s transatlantic flight
brought a peak of interest between 1929 and 1933. During this period many
aircraft designers, builders and pilots were self-taught and the high accident
rate brought public condemnation and increasing regulation to
amateur-building. The resulting federal standards on design, engineering, stress
analysis, use of aircraft-quality hardware and testing of aircraft brought
an end to amateur building except in some specialized areas, such as racing.
In 1946 Goodyear restarted the National Air Races, including a class for
aircraft powered by 200 cubic inch and smaller engines. The midget racer class
spread nationally in the US and this led to calls for acceptable standards to
allow recreational use of amateur-built aircraft. By the mid-1950s both the US
and Canada once again allowed amateur-built aircraft to specified
standards and limitations. Homebuilt aircraft are generally small,
one to four-seat sportsplanes which employ simple methods of construction.
Fabric-covered wood or metal frames and plywood are common in the aircraft
structure, but increasingly, fiberglass and other composites as well as full
aluminum construction techniques are being used, techniques first pioneered
by Hugo Junkers as far back as the late World War I era. Engines are most often
the same as, or similar to, the engines used in certified aircraft. A minority
of homebuilts use converted automobile engines, with Volkswagen air-cooled
flat-4s, Subaru-based liquid-cooled engines, Mazda Wankel and Chevrolet
Corvair six-cylinder engines being most common. The use of automotive engines
helps to reduce costs, but many builders prefer dedicated aircraft engines, which
are perceived to have better performance and reliability. Other engines that have
been used include chainsaw and motorcycle engines.
A combination of cost and litigation, especially in the mid-1980s era,
discouraged general aviation manufacturers from introducing new
designs and led to homebuilts outselling factory built aircraft by five to one.
In 2003, the number of homebuilts produced in the USA exceeded the number
produced by any single certified manufacturer.
History The history of amateur-built aircraft
can be traced to the beginning of aviation. Even if the Wright brothers,
Clément Ader, and their successors had commercial objectives in mind, the first
aircraft were constructed by passionate enthusiasts whose goal was to fly.
=Early years=Aviation took a leap forward with the
industrialization that accompanied World War I. In the post-war period,
manufacturers needed to find new markets and introduced models designed for
tourism. However, these machines were affordable only by the very rich.
Many U.S. aircraft designed and registered in the 1920s onward were
considered “experimental” by the CAA, the same registration under which modern
homebuilts are issued Special Airworthiness Certificates. Many of
these were prototypes, but designs such as Bernard Pietenpol’s first 1923 design
were some of the first homebuilt aircraft. In 1928, Henri Mignet
published plans for his HM-8 Pou-du-Ciel, as did Pietenpol for his
Air Camper. Pietenpol later constructed a factory, and in 1933 began creating
and selling partially constructed aircraft kits.
In 1936, an association of amateur aviation enthusiasts was created in
France. Many types of amateur aircraft began to make an appearance, and in 1938
legislation was amended to provide for a Certificat de navigabilité restreint
d’aéronef. 1946 saw the birth of the Ultralight Aircraft Association which in
1952 became the Popular Flying Association in the United Kingdom,
followed in 1953 by the Experimental Aircraft Association in the United
States and the Sport Aircraft Association in Australia.
The term “homebuilding” became popular in the mid-1950s when EAA founder Paul
Poberezny wrote a series of articles for the magazine Mechanix Illustrated where
he explained how a person could buy a set of plans and build their own
aircraft at home. The articles gained worldwide acclaim and the concept of
aircraft homebuilding took off.=Technology and innovation=
Until the late 1950s, builders had mainly kept to wood-and-cloth and steel
tube-and-cloth design. Without the regulatory restrictions faced by
production aircraft manufacturers, homebuilders introduced innovative
designs and construction techniques. Burt Rutan introduced the canard design
to the homebuilding world and pioneered the use of composite construction. Metal
construction in kitplanes was taken to a new level by Richard VanGrunsven in his
RV series. As the sophistication of the kits improved, components such as
autopilots and more advanced navigation instruments became common.
Litigation during the 1970s and 1980s caused stagnation in the small aircraft
market, forcing the surviving companies to retain older, proven designs. In
recent years, the less restrictive regulations for homebuilts allowed a
number of manufacturers to develop new and innovative designs; many can
outperform certified production aircraft in their class.
An example of high-end homebuilt design is Lancair, which has developed a number
of high-performance kits. The most powerful is the Lancair Propjet, a
four-place kit with cabin pressurization and a turboprop engine, cruising at
24,000 feet and 370 knots. Although aircraft such as this are considered
“home-built” for legal reasons, they are typically built in the factory with the
assistance of the buyer. This allows the company which sells the kit to avoid the
long and expensive process of certification, because they remain
owner-built according to the regulations. One of the terms applied to
this concept is commonly referred to as “The 51% Rule”, which requires that
builders perform the majority of the fabrication and assembly to be issued a
Certificate of Airworthiness as an Amateur Built aircraft.
A small number of jet kitplanes have been built since the 1970s, including
the tiny Bede Aircraft BD-5J.=Future trends=
Van’s Aircraft and Aircraft Kit Industry Association President Dick VanGrunsven
was asked about the future of the kit aircraft industry in a wide ranging
interview in KitPlanes magazine in December 2012:
I don’t expect to see dramatic changes in the industry within the next ﬁve
years. Ten years; who knows—it’s too dependent on fuel prices, FAA policy,
etc. Overall, I think our industry will continue to mature, particularly as AKIA
is successful in growing and having a positive inﬂuence on the professionalism
of its industry members and on the builders/pilots of its products. With
concern over fuel prices, we might see a trend toward lower-powered aircraft
intended more for pure sport ﬂying rather than the trend toward
cross-country aircraft, which has been the norm over the past 30 years. I would
expect that toward the end of that period, there might be some design
ventures into electric-powered aircraft, but only if battery technology improves
signiﬁcantly. We might see more motorglider-type homebuilts, tied both
to high fuel prices and emerging electric-propulsion technology.
What we do at Van’s could mirror some of the above thinking. Unfortunately, I
don’t see the growth potential that there was in the 1980s and 1990s. There
seems to be a shrinking pilot base from which to draw people to build kits.
Plus, with demographic changes, there is possibly a diminishing interest in, or
ability to undertake, aircraft building as a pastime. Hopefully, EAA and AOPA
initiatives to interest more people in learning to ﬂy will help create a larger
market for our airplanes. Emerging markets such as China and India
could also boost demand for our products, but entire infrastructures
will need to be formed before small players like us could beneﬁt.
Building materials Homebuilt aircraft can be constructed
out of any material that is light and strong enough for flight. Several common
construction methods are detailed below.=Wood and fabric=
This is the oldest construction, seen in the first aircraft and hence the best
known. For that reason, amateur-built aircraft associations will have more
specialists for this type of craft than other kinds.
The most commonly used woods are Sitka spruce and Douglas fir, which offer
excellent strength-to-weight ratios. Wooden structural members are joined
with adhesive, usually epoxy. Unlike the wood construction techniques used in
other applications, virtually all wooden joints in aircraft are simple butt
joints, with plywood gussets. Joints are designed to be stronger than the
members. After the structure has been completed, the aircraft is covered in
aircraft fabric. The advantage of this type of construction is that it does not
require complex tools and equipment, but commonplace items such as saw, planer,
file, sandpaper, and clamps. Examples of amateur-built wood and
fabric designs include: The classic Pietenpol Air Camper, a
homebuilt that has been built since the 1920s.
The Bowers Fly Baby, a low-wing monoplane which has been popular since
the 1960s. The Ison miniMAX
=Wood/composite mixture=A recent trend is toward wood-composite
aircraft. The basic load carrying material is still wood, but it is
combined with foam and other synthetic materials like glass- and carbon fibre.
Examples of wood-composite designs include:
Ibis experimental aircraft project, designed by Roger Junqua
KR series of homebuilts designed by Ken Rand
PIK-26 designed by Kai Mellen=Metal=
Planes built from metal use similar techniques to more conventional
factory-built aircraft. They can be more challenging to build, requiring
metal-cutting, metal-shaping, and riveting if building from plans.
“Quick-build” kits are available which have the cutting, shaping and
hole-drilling mostly done, requiring only finishing and assembly. Such kits
are also available for the other types of aircraft construction, especially
composite. There are three main types of metal
construction: sheet aluminium, tube aluminium, and welded steel tube. The
tube structures are covered in aircraft fabric, much like wooden aircraft.
Examples of metal-based amateur aircraft include:
The Murphy Moose, Rebel, Super Rebel and Maverick, produced by Murphy Aircraft.
The Vans RV-4, RV-8, RV-10 and other models produced by Van’s Aircraft, are
the most popular metal homebuilt aircraft.
Chris Heintz’s Zenith CH601 Zodiac and Zenith STOL CH701
=Composite=Composite material structures are made
of cloth with a high tensile strength combined with a structural plastic. The
fabric is saturated with the structural plastic in a liquid form; when the
plastic cures and hardens, the part will hold its shape while possessing the
strength characteristics of the fabric. The two primary types of composite
planes are moulded composite, where major structures like wing skins and
fuselage halves are prepared and cured in moulds, and mouldless, where shapes
are carved out of foam and then covered with fiberglass or carbon fiber.
The advantages of this type of construction include smooth surfaces,
the ability to do compound curves, and the ability to place fiberglass or
carbon fiber in optimal positions, orientations, and quantities. Drawbacks
include the need to work with chemical products as well as low strength in
directions perpendicular to fiber. Composites provide superb strength to
weight. Material stiffness dependent upon direction allows for advanced
“elastic tailoring” of composite parts. Examples of amateur craft made of
composite materials include: Canard designs such as the VariEze and
Long EZ designed by Burt Rutan The pusher propeller Cirrus VK-30
designed by Jeff Viken and the Klapmeier brothers
The Europa XS family of British two-place monoplanes designed by Ivan
The safety record of homebuilts is not as good as certified general aviation
aircraft. In the United States, in 2003, amateur-built aircraft experienced a
rate of 21.6 accidents per 100,000 flight hours; the overall general
aviation accident rate for that year was 6.75 per 100,000 flight hours.
The accident rate for homebuilt aircraft in the USA has long been a concern to
the Federal Aviation Administration. At Sun ‘n Fun 2010 FAA Administrator Randy
Babbitt said that homebuilts “account for 10 percent of the GA fleet, but 27
percent of accidents. It’s not the builders [getting into accidents], but
the second owners. We need better transition training.” It is important to
note that in the USA a person may receive flight instruction, including
primary flight training, in an experimental aircraft that he/she owns
from any CFI willing to provide such training.
A study released in 2012 by the US National Transportation Safety Board
concluded that homebuilt aircraft in the US have an accident rate 3-4 times
higher than the rest of the general aviation fleet. Almost 10% of homebuilt
accidents occurred on the first flight and 9% of first flights by purchasers of
used homebuilts resulted in accidents. The study also identified that
powerplant failures and loss of control in-flight accidents were much higher
than the same rates for certified aircraft.
Most nations’ aviation regulations require amateur-built aircraft to be
physically marked as such, and extra flight testing is usually required
before passengers can be carried. Culture
The largest airshow in the world is the Experimental Aircraft Association’s
annual EAA AirVenture Oshkosh airshow in Oshkosh, Wisconsin, which takes place in
late July and early August. Other annual events are the Sun N’ Fun Fly-In, which
occurs in the early spring in Lakeland, Florida, and the Northwest EAA Fly-In in
Arlington, Washington. These events are called a fly-in as many people fly their
homebuilts and other aircraft into the airport hosting the show, often camping
there for the duration. Both events last a week. Takeoffs and landings at these
shows number in the thousands. See also
Aircraft design process Ultralight
Special Airworthiness Certificate Heathkit
Kit car References
External links Experimental Aircraft Association
Light Aircraft Association, the representative body in the United
Kingdom for amateur aircraft. FAA Advisory Circular 20-27G:
Certification and Operation of Amateur-Built Aircraft