The 51 per cent rule-how does it
apply to purchased projects?
Several aircraft projects have changed hands
recently, and I have been asked about the "51
percent rule." Let's go ahead and review this
aspect of homebuilt aircraft, as I know there are
others out there wondering about the specific
As they say, "majority rules!" What a
beautiful concept it is, useful for everything from
deciding where to go on vacation, to electing
Presidents, to...well...deciding whether or not
an airplane is truly "Experimental."
And how wonderfully useful it is, that this
ancient and simple democratic principle is made
to fit the world of homebuilt experimental
No ifs, ands or buts, if you make 51 per cent
of the airplane it can be licensed in the
Experimental category. Period.
Not even a two-thirds or a three-fifths
majority is needed, just document the fact that
anything over half the amount of work was done
by you for your own entertainment and
education, and you've met the test.
In this application we see a manifestation of
the increasingly rare art of "hands-off"
governance. (Sadly, in many areas of life the
government is seen as more meddling.)
We can thank our own EAA-type "founding
fathers," including Paul Poberezny, Wes Schmid,
and the late Steve Wittman, who helped the FAA
understand that the 51 percent rule is good and is
workable, therefore serving us homebuilders
well for half a century now.
But as with any other "simple" rule, it's the
interpretation of it that counts, or the fear of how
someone else such as a court or a panel of judges
might interpret it in some cases.
So with that in mind, let's examine some
aspects of the 51 percent rule and hopefully
enlighten ourselves a little bit.
Several people working together can do 51
percent of the work. It does not have to be
one lone individual.
"51 per cent of what?"
In its simplest form the so-called "51 per cent
rule" for homebuilt aircraft seems very straight-
forward. If you build at least 51 per cent of an
aircraft, it qualifies for licensing in the
Licensing an experimental aircraft exempts
the design (and the builder of the aircraft) from
having to meet FAA requirements for weight,
design or speed that apply to certified type
aircraft designs such as Piper, Beechcraft,
Cessna, Mooney etc.
For many of us, the most important part of the
51 percent rule is that any maintenance,
modification, repairs, and annual inspections of
that aircraft may be performed by the builder,
who is granted mechanic status (a "repairman
certificate") for that particular aircraft. It does
not have to be performed by an FAA-licensed
The aircraft safety record for homebuilts
appears to still be acceptable enough for the
FAA to believe that "relaxed" governmental
control and compliance will continue to
adequately protect the public from undue danger
caused by Experimentals.
FAR (Federal Aviation Regulations) Part 21
defines two categories of airworthiness
certificates, "standard" and "special." Then they
are broken down even further.
One type of "special" airworthiness certificate
is "experimental," which applies to subcategories
such as these: "...aircraft engaged in...research
and development...to conduct flight tests...for
surveys...sales demonstrations...[or] amateur-
built aircraft." (emphasis added)
Obviously we are interested in the latter. The
pertinent FAR, which is Part 21 Subpart 191(g),
states that amateur-built aircraft are those which
are "...fabricated and assembled by persons
who undertook the project solely for their
own education or recreation."
That seems simple enough, right? Well, it is
simple until you start to think about variations on
this theme, like one airplane, several builders.
|Using this Celerity as an example, do you think that completion from this point on would qualify as 51 per cent? It just depends on how much you add to the project.|
"51 per cent by whom?"
Please note that FAR 21.191(g) says that it's
"persons" (plural) and not "person." That clears
up one thing--It doesn't have to be just one lone
individual completing 51 per cent of the work.
The 51 per cent of the fabrication and
assembly can also be done by you and your best
friend, or by a group of people (i.e.-a high
school class), or it can be performed by you plus
the person you purchased the project from.
Just so long as more than half of the project
was "amateur-built," that's what counts to qualify
the project as an Experimental aircraft.
However, please note that only one person
can get the repairman certificate for that aircraft,
not everybody who worked on it.
Another FAA rule worth noting is that your
possession of an experimental aircraft repairman
certificate does not allow you to go and perform
an annual inspection and certification of your
friend's amateur built aircraft.
In fact, this certification is only valid for the
actual aircraft on which you gained your
certification, not even the exact same airplane
design that your friend has built.
How do you determine 51 percent?
This can be difficult to determine with a great
deal of precision, especially if it is for a project
that you have purchased from another builder.
Of course, if the initial builder kept track of
the hours spent in construction and you do the
same, you would have hard evidence to support
your 51 percent claim.
But oftentimes we don't have that luxury, and
many of us have a difficult time accurately
estimating how much time it is going to take to
build something anyway. (Count me in that
category.) So when we look at somebody else's
work, especially for something we haven't done
before, it's harder for us to figure out if that thing
sitting on the trailer is just barely 49 percent of a
|If you were to do the complete engine, prop, cowling, interior and paint work, it would probably total more than 51 percent.|
I have heard it said that if you put in the
engine, panel, interior and paint, that's about 51
per cent of the work. This may be true, I
honestly don't know. It certainly sounds
reasonable, especially when you talk to
somebody who has done this!
I think that the real world interpretation made
by the FAA would be if you have done enough
of the work for them to feel comfortable that you
have gained the necessary knowledge to do your
own maintenance and inspections.
If it appears that you don't have a clue how
this airplane is built, you're standing on shaky
ground. You cannot build 51 percent of an
airplane and be oblivious as to what makes it
tick, what to watch out for, etc.
Making your case
The best and most prudent course for you the
builder (or in some cases, for you as the
"completer" of an existing project) is to start
keeping records of what you do and how much
time you spend doing it.
Begin logging your time and tasks right away,
and take lots of photos to document what you
have done. Nothing talks like hard evidence.
Also keep track of your material and component
Of course, as with so many things in life, the
computer can be used for this purpose. Just be
sure that you periodically download a hard copy
and stash it somewhere in the unlikely case that
your old PC goes belly-up!
Some airplane builders go so far as to start a
Web site about their airplane building project
and document things as they go along, for all to
see. Usually this isn't kept up to the same detail
as a logbook, but it would serve as additional
You can easily keep track of your tasks and
hours on your computer, using Word, Excel, or
some other common format for updating the
builder's log. You might want to make entries
each time you check your email for example.
Of course, you can just as easily write it all
down in a log book or spiral notebook. Some do
it scrapbook style, pasting in progress photos as
they go along.
Regardless of how you keep track of your
work, don't ever feel that you are piling up too
The worst thing is to cause an inspector to
question your work or your intentions, simply
because you didn't document everything thoroughly!
So write down all that hard work so that the FAA
inspector evaluating your project is "...looking AT it,
not looking FOR it!"
Never put an inspector in the position of having to
make a decision on the merits of your argument
without having proper documentation at hand.
Celerity and Marathon
builder construction videos
to go digital
The old boy runs out of excuses...
For some of us Neanderthals out there, and I
include myself in the category, change comes a
little harder. Herewith is my confession.
While a lot of you guys are jumping right up
and becoming the very first kids on the block to
try out the very latest whiz-bang items, I prefer
to sit back and wait.
Wait for what? Oh, wait for the prices to
come down, for one thing. And wait for the bugs
to get ironed out, for another.
Then I also have old sayings on my side such
as this jewel of a maxim, "Never buy the 'A'
model of anything!"
I didn't own a home computer until it seemed
that most of my friends had one, and then I
didn't start using the Internet for some time after
When GPS came out, I decided to wait
awhile. I am still waiting to use one for the very
first time. Of course there is also the plain old
preference factor at work here--with my degree
in geography, I still love my old paper maps
I used a flight simulator while getting my
instrument rating (in 1983) but have resisted
putting flight sim on this newer laptop that's
sitting in front of me. Heck, this computer might
have come with Flight Sim already programmed
into it, I wouldn't know! I remember that when I
had flight sim loaded on my old PC I played
around with it a little bit, but I am not really the
video game type.
And EFIS? What's that stuff all about?
Actually I do know just a little tiny bit about
electronic flight instrumentation systems, but
that's about it.
I did finally purchase one of those newfangled
digital cameras last year and I have been able to
make good use of it. It's one of those things I
wish I had bought sooner!
However, I don't have one of those cell phone
thingies that will take pictures, much less a color
cell phone display with color TV-like pictures!
Need versus want
I guess what it comes down to is that I have to
have a real need for something before I feel
compelled to buy it and try it.
It is not enough that something "new"
reportedly does a particular task extremely well,
it just doesn't make any difference to me in a
practical sense unless I actually need that degree
of improvement. And of course, I have to be
able to afford it.
I got a call from an Englishman the other day
asking about our airplane designs. While
discussing the builder's videos, this gentleman
mentioned that VHS videotapes are often hard to
play. (Especially since the Europeans adopted a
format that is different from VHS!) I guess there
isn't a similar problem with DVD's.
Also, the quality of the VHS videos suffers a
bit when making copies of the tapes, while
digital videos are theoretically as perfect as the
Another advantage with DVD's is that they
cost considerably less to send through the mail,
and they also take up less shelf space for our
builders. (Our builders who have a DVD at
home, of course.)
A final selling point is that you can now
purchase a decent DVD recorder (or "burner")
for less than a hundred dollars.
So I guess I have run out of excuses and at
this point I feel that I need to upgrade the
construction videos that Larry and I have made,
using what for me is this very latest technology.
Fellow builder Don O'Rourke of Tucson
volunteered to make digital master DVD's of the
construction videos from the original hand-held
camera videocassettes, after which I will be able
to make copies for our builders.
Of course, I'll need to do some computer
updates also so I can not only make copies but
also manipulate the material and make changes
as needed. This might take a little time.
If you want to get a DVD copy of any
construction video, or a new DVD set, just give
me some time to get everything set up and then I
will be able to provide them to you.
But first I want to do a little editing and so
forth. I hope to make the new product a little
more user-friendly, and possibly even a bit more
attractive than the old VHS videos.
Is this your big year?
Are you REALLY ready?
I know that several of you builders are getting
tantalizingly close to taxiing out for that First
Flight. As the big day draws near and as you do
final preparation on your airplane, be sure that
you too are personally prepared for this event.
If you're going to do your own test flying, be
sure that you have taken advantage of EAA's
Flight Advisor program to evaluate your skills
and make sure that you are up to the task.
Also, try to get some time in a high
performance airplane--not a 150 or a Cherokee,
but something more like Van's RV or similar to
prepare you for the lighter control feel.
Don't be like the local pilot a few years back.
While taxiing out in his newly purchased
experimental aircraft, he joked to the tower, "I'm
going to learn how to fly this thing or die
trying!" Guess what? He died trying.
So be careful out there, you hear? Yours for
safe skies! Ed.
© 2010, Mirage Aircraft, Inc, Tuscon, AZ