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positive numbers were chosen by placing the
datum line on the nose of the aircraft. Some
manufacturers prefer to use a datum located
somewhere between the aircraft’s nose and
the leading edge of the wing.
(5) This kind of datum will set up a system
of positive arms (items located aft of the datum) and
negative arms (items located forward of the datum).
(6) When working a weight and balance
problem with negative and positive moments, subtract
the sum of all negative moments from the sum
of all positive moments to reach a ‘‘total moment’’
for the aircraft.
18
AC 90-89A 5/24/95
SECTION 9. PAPERWORK
‘‘It is harder to write a lie in a logbook than tell one, because your eyes see it and your fingers feel
it.’’ Bob Moorman, Ultralight Instructor (1994)
1. OBJECTIVE. To have the proper documentation
and paperwork to conduct the flight test.
a. Weight and Balance: The weight and balance
for the aircraft should be carefully done. The
gross weight and CG range should be determined
prior to every flight.
b. Airworthiness/Registration/Operating
Limitations/Placards/Weight and Balance: Must be
on board, or the aircraft is not legal to be operated.
c. Checklists: In addition to the assembly/airworthiness
checklist previously discussed in section
7, the builder should prepare the following checklists:
preflight; take-off/cruise; before starting;
descent/before landing; starting the engine; after
landing; before takeoff; securing the aircraft; and
emergency procedures. A checklist to cover the
above procedures may seem a tedious task, but it
will only be the size of a 5x8 card -- similar to a
checklist for a Cessna 150 or a Piper PA-28-140.
NOTE: The amateur-builder should anticipate
several revisions to the checklists.
d. Flight Manual: It is imperative a flight
manual describing the anticipated performance of the
aircraft be written by the aircraft builder/kit manufacturer.
The manual will be revised several times during
the flight test phase until it accurately reports
the aircraft’s performance.
e. Maintenance Records (logbooks): Operators
of amateur-built aircraft are required to only
record the yearly condition inspections in accordance
with the aircraft’s operating limitations. The FAA
recommends, however, that every amateur-built aircraft/
ultralight owner record in the aircraft’s
logbooks all inspections and maintenance performed.
This will create an aircraft’s maintenance history and
will be invaluable in spotting trends.
19
5/24/95 AC 90-89A
SECTION 10. POWERPLANT TESTS
‘‘Don’t short-change the engine tests or you won’t be around to give your grandkids a ride.’’ Dick Koehler,
A&P Instructor (1994)
1. OBJECTIVE. To ensure that the engine has
been properly run-in and is safe to operate in all
rpm ranges.
a. An engine pre-oil and cold compression test
can be conducted as follows:
(1) Remove the rocker-box covers and one
spark plug from each cylinder.
(2) Using an external oil pump, or by rotating
the propeller in the direction of rotation, pump
a substantial supply of oil up from the sump into
the rocker arms.
(3) When the engine is pre-oiled, run a
cold compression test of each cylinder.
(4) The results will serve only as an initial
bench mark for comparing other compression tests
taken after the engine has been run-up to operating
temperature.
b. New/newly overhauled engine run-in procedures:
(1) Most amateur-builders start with a new
or newly overhauled engine and proceed to ‘‘run it
in’’ on the airframe. This practice is followed due
to lack of access to a test cell or a special ‘‘club’’
propeller that is specifically designed to aid in engine
cooling during run-in. There are pros and cons to
using an airframe to run in an engine, but the best
advice has always been to follow the engine manufacturer’s
instructions. These instructions are found
either in the manufacturer’s overhaul manuals, service
bulletins, or service letters. Following the manufacturer’s
instructions is especially important if the
engine has chrome cylinders which require special
run-in procedures.
(2) Also, before running-up the engine, be
certain that it has the proper grade oil in the sump.
Some new and newly overhauled engines are shipped
with a special preservative oil to prevent corrosion.
20
AC 90-89A 5/24/95
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