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Drain this out and reservice the engine with the correct
oil before starting.
c. Used engine run-in procedures: Some amateur-
builders install a used engine from a flyable aircraft.
The same checks and adjustments used on a
new or newly overhauled engine should be conducted.
New and used engines require special
attention to engine cylinder baffling to ensure cylinder
cooling is within the engine manufacturer’s
cylinder head temperature specifications.
d. Pre run-in checks:
(1) Before beginning the powerplant tests,
inspect the engine and propeller carefully. All fuel
and oil line connections should be tight. Check the
torque on the engine mount attaching bolts. Be certain
that there are no tools, hardware, or rags laying
between the cylinders or under the magnetos.
(2) Check for the proper amount of oil in
the engine and that the dip stick gives an accurate
reading of the oil quantity. Be advised that some
engines were mounted on an angle in type certificated
aircraft. These engines have a special part number
oil dip stick, which corrects for the different
angle of oil in the crankcase. The same engine,
mounted level in a amateur-built aircraft with the
original dip stick, will not show the correct oil quantity.
e. Test and Support Equipment:
(1) A cylinder head temperature gauge
(CHT) is needed to ensure that all cylinders are
receiving the proper flow of cooling air.
(2) On the newer aircraft engines, the cylinders
are drilled and tapped to accept a bayonet
type of CHT thermocouple probes. For older engines,
the thermocouple is designed like a spark plug
washer and fits under a spark plug. It can be installed
in any cylinder, either under the top or bottom spark
plug.
(3) Each type of CHT design can have
multiple thermocouples which are connected to a
selector switch in the cockpit. The pilot then selects
the cylinder he wants to monitor. This also is an
excellent troubleshooting tool for identifying fouled
plugs and bad ignition leads.
(4) If there is only one CHT thermocouple,
attach it to the rearmost cylinder on the right side
of the engine (as viewed from the cockpit) and runup
the engine. Run the same test on the opposite
rearmost cylinder to be certain the hottest running
cylinder was selected. Calibrated oil pressure and oil
temperature gauges also are needed to test the
accuracy of the engine instruments installed in the
aircraft.
(5) The following support equipment is
needed: 50 feet or more of tie-down rope, tie-down
stakes, two chocks for each wheel, fire extinguisher,
assorted hand tools, safety-wire, cotter-pins, ear and
eye protection, grease pencils, logbooks, clip board,
pen and paper, a watch to time the tests, rags, and
manufacturer’s instructions.
f. Safety Precautions: Before the first engine
run, ensure the aircraft is tied down, brakes on, and
the wheels are chocked. The builder and flight test
team should wear ear and eye protection. All flight
test participants should be checked out on fire extinguisher
use and operation. During engine runs, do
not allow anyone to stand beside the engine, or inline
or close to the propeller. Making minor adjustments
to a running engine, such as idle and mixture
settings, is a very dangerous procedure and should
be done with great care by experienced individuals.
g. The First Engine Run:
(1) The first start of the engine is always
a critical operation. The engine should be pre-oiled
in accordance with the manufacturer’s instructions.
For aircraft using other than FAA-approved oil pressure
and temperature gauges, the FAA recommends
attaching an external calibrated oil temperature and
pressure gauge to the 4 cycle engine in order to calibrate
the engine instruments. After priming the
engine and completing the starting engine checklist
items, the first concern is to get an oil pressure reading
within the first 20 to 30 seconds. If there is no
oil pressure reading -- shut down.
(2) There are three common problems that
would cause low or fluctuating oil pressure.
(i) Air in the oil pressure gauge line:
This is easily fixed by loosening the line connection
near the oil pressure gauge and squirting oil into
the line until full. Another option is to use a preoiler
to provide the pressure and carefully bleed the
air out of the line near the oil gauge by loosening
the B-nut that connects the oil line to the gauge.
21
5/24/95 AC 90-89A
(ii) A misadjusted oil pressure relief
valve: Cleaning the pressure relief ball, checking for
　
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