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should be visually inspected, positive in operation,
and securely mounted. The friction lock on both controls
should be checked for operation. Each control
should have full movement with at least a 1⁄4 inch
of ‘‘cushion’’ at the full travel position. The control
cables should be firmly attached to the fuselage along
each 24 inches of their runs to prevent whipping
of the cable and loss of cable movement at the other
end. Control cables with ball sockets should have
large area washers on either end of the bolt connection.
This will ensure the control will remain connected,
even if the ball socket fails and drops out.
j. Static system: The best procedure to check
the altimeter for leaks and accuracy is to have the
entire static system checked in accordance with FAR
Part 43, appendix E, at an FAA-approved repair station.
12
AC 90-89A 5/24/95
4. FIELD CHECK. Two people are needed to
accomplish the following field check that will enable
an amateur-builder to detect if the aircraft’s
instrument system is leaking: (Note: This field check
is not an accuracy check.)
a. Airspeed check: Slip a long rubber hose
over the pitot mast (surgical tubing is recommended).
As one person reads the airspeed, the other should
very slowly roll up the other end of the tubing. This
will apply pressure to the instrument. When the airspeed
indicator needle reaches the aircraft’s approximate
recommended cruise speed, pinch the hose shut,
and hold that reading. The airspeed needle should
remain steady for a minute if the system is sound.
A fast drop off will indicate a leak in the instrument,
fittings, lines, or the test hose attachment. NEVER
force air in the pitot tube or orally apply suction
on a static vent. This will cause damage to the
instruments.
b. Altimeter/vertical speed check.
(1) To check the static side, apply low suction
at the end of the static vent port. The easiest
way to gain access to the static system is to remove
the static line at the static port. If there are two static
ports, tape the unused port closed. Next, get two feet
of surgical tubing, seal one end, and tightly roll it
up. Attach the open end to the static line and slowly
unroll the tubing. This will apply a suction, or low
pressure, to the static system.
(2) The altimeter should start to show an
increase in altitude. The vertical speed indicator also
should indicate a rate of climb. The airspeed may
show a small positive indication. When the altimeter
reads approximately 2,000 feet, stop and pinch off
the tube. There will be some initial decrease in altitude
and the vertical speed will read zero. The altimeter
should then hold the indicated altitude for at
least a minute. If altitude is lost, check for leaks.
(3) IMPORTANT: The above airspeed and
altimeter field checks should not be considered the
equivalent of airspeed or static system accuracy tests
as certified by a certificated repair station, but a
check of the system for possible leaks. These checks
do not take into consideration the pitot tube and static
ports located on the airframe. The FAA recommends
the builder not deviate from the designer’s original
plans when installing the pitot and static system.
c. Fuel system: Since 1983, more than 70 percent
of the engine failures in amateur-built aircraft
were caused by fuel system problems. Many times
the direct cause of engine failure was dirt and debris
in the fuel tank and lines left behind during the manufacturing
process.
(1) Before the aircraft’s fuel tanks are
filled, the amateur-builder should vacuum any manufacturing
debris from each tank and wipe them down
with a ‘‘tack’’ cloth (available from a paint supply
store). Next, the system should be flushed with aviation
grade gasoline several times in order to remove
any small or hard to reach debris from the tanks
and lines. The fuel filter/gasolator screen/carburetor
finger screen should also be cleaned. The amount
of time spent ‘‘sanitizing’’ the fuel system will provide
big safety dividends for the life of the aircraft.
(2) When filling the tanks, place the aircraft
in the straight and level cruise position. Add
fuel in measured amounts to calibrate the fuel tank
indicators. While allowing the aircraft to sit for a
short time to observe for possible leaks, inspect the
fuel tank vents to see if they are open and clear.
Check that the fuel tank caps seal properly. If there
are no leaks and the fuel system has an electric boost
　
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