We've gone back to the research "lab" and this is the answer to

your flying IFR with a GPS

1. As stated earlier (below) AIM, paragraph 1-1-21, lists the
"preferred" FAA method for flying IFR with a GPS. That "preferred"
method includes a statement, in AIMs, "hand-held GPS devises are not
authorized for IFR flight."

2. The same paragraph in the AIM refers to GPS having or meeting the
requirements of TSO C-129 and AC 20-138.

3. Like you, EAA has not found any FAR that states "hand-held" GPS
devices shall not be used for IFR flight. EAA even went to FAA
headquarters for further guidance.

4. The answer or bottom line:

As an experimental amateur-built aircraft you must certify your
aircraft and all the equipment on board the aircraft (per 91.319(b))
that: (1) Your "aircraft is controllable throughout its normal range
of speeds and throughout all the maneuvers to be executed; and (2) The
aircraft has no hazardous operating characteristics or design
features."

That certification is accomplished when you sign your experimental
amateur-built aircraft airworthiness application (FAA Form 8130-6),
and verified through the phase I test flights and the resulting
logbook sign-off - as required by your FAA issued operating
limitations.

The test flight hours listed in your operating limits are recommended
minimums, so if you need more hours to complete your aircraft's
"certification" for flight into IFR conditions (must be done VFR),
including "certifying" your IFR equipment (GPS, etc.) you need to
extend those hours to meet your requirements. You may even need to go
back to the FAA FSDO or MIDO to modify your test flight area in order
to fly GPS (or other NAVAID) approaches. If you can certify your
hand-held GPS as "having no hazardous operating characteristics or
design features throughout all the maneuvers you will be executing",
per the FAA "guidance" listed in TSO C-129 and AC 20-138, then just
make a logbook entry stating that fact.

If the GPS system you are using was added after you completed your
initial phase I test flights or you purchased a used experimental
amateur-built aircraft and added a GPS system, then you must:

1. Per your operating limitations determine if the change or addition
of the GPS and its antenna's meet the "major change" rule. If they
do, comply per your operating limitations. If not, or in either case,
as the owner of the experimental amateur-built aircraft you are still
responsible for certifying your GPS (or other NAVAID) as "having no
hazardous operating characteristics or design features throughout all
the maneuvers you will be executing" and making the appropriate
logbook entry stating that.

2. To "certify" your new installation requires you to place your
aircraft into a test flight phase to prove the installation of the
system and it's effect on the aircraft's other systems are safe, and
will not pose a hazard to persons or property on the surface. The
test flight must be done in VFR conditions, with no visibility
reducing devices (foggels, etc.), no passengers, and flown on actual
GPS approaches. You make the determination of the test flight hours
necessary to make that determination.

3. Once the test flights are finished and you make the appropriate
logbook entries certifying to the airworthiness of the system, you
place yourself back into the phase II normal flights.

4. There is no requirement for the FAA to approve or sign-off your
GPS system. As the owner of an experimental amateur-built aircraft,
that is your responsibility.

Your amateur-built aircraft's operating limitations contains
references to FAR's that must be complied with or met "with the scope
and detail" of those FAR's. This is no different, the TSO and the AC
are the FAA "guidelines" for GPS operations within the National
Airspace System, and you must certify that your GPS system meets those
guidelines and your aircraft is in a condition for safe operation and
will not be a hazard to persons/property on the ground or other
aircraft operating within the National Airspace System.