to performing the external and internal hydraulic
electric contact rings. See figure 8-23, Preliminary
balance has been obtained when the propeller
shows no tendency to tilt, or when tilting maybe
stopped or reversed by the addition of the lightest
External and Internal
balance washer to one or more blades on the light
Hydraulic Leakage Test
side of the propeller.
After you have determined the amount of
Before you begin the propeller test, first verify
washers to install, remove the propeller from the
that the propeller test equipment has been
balancing stand, Disassemble the propeller until
inspected, serviced, and properly assembled. This
the light blades have been removed. Install the
must be done prior to the installation of the
required washers on the blade balance plugs.
propeller. Install the propeller on the test equip-
Reassemble and reinstall the propeller on the
ment in accordance with the appropriate technical
balancing stand. Recheck the preliminary balance
publication before beginning the hydraulic leakage
and obtain the final balance check, as previously
After the hydraulic fluid is warmed up,
exercise the propeller between the high and the
After you obtain final balance, remove the
low blade angles several times to purge air from
special head screw taped on the dome assembly.
both the test equipment and propeller system.
Remove the dome assembly from the propeller,
Purging will avoid erratic operation during the
using care not to disturb the 45-degree setting of
external and internal leakage tests.
the rotating cam. Remove the balancing arbor
from the propeller.
Remove the propeller from the balancing
stand. Remove the deicer contact ring assembly
and the packing seal ring with its preformed
packing. The propeller must be reassembled prior
Attempting to initiate a decrease in pro-
peller blade angle when the propeller is in
a range from about 60 degrees to 15
degrees may cause the pitchlock to engage
or cause damage to the ratchet teeth. If it
becomes necessary to stop in this range,
first increase the blade angle to above the
pitchlock range, and then proceed to a
decreased blade angle.
EXTERNAL LEAKAGE TEST
The test equipment used to supply the various
pressures and flow requirements is the hydraulic
propeller test stand GS1221. With the test stand
maintaining 150 psi, cycle the propeller blades
between a low blade angle and a high blade angle
until a total of eight cycles are completed. No
external leakage is permissible during the cycling.
If any external leakage occurs at the junction
of the barrel half seals and the blade packings,
eliminate the leakage by separating the bar-
rel halves and adding zinc chromate putty,
MIL-P-8116, to the junction. You must control
the amount and location of the putty to prevent
it from getting into the barrel cavity. Leakage
from the blade bores can be eliminated by
replacing the blade preformed packing. The
complete external leakage test must be rerun after
Figure 8-23.-Propeller suspended for balancing.