Upon initial installation, fill the propeller with
publication for the special tool requirements.
hydraulic fluid, Add as much propeller hydraulic
Check for freedom of movement for both power
fluid as possible to the atmospheric sump and the
levers and E-handles. There must be NO binding
pressurized sump. Statically cycle the propeller
tensiometer. Insert rigging pins in slots. Rig pins
several times between feather and reverse. Add
fluid each time the PROP PUMP No. 1 light
should go in with slight finger pressure. Adjust
illuminates. Repeat this procedure until you add
control rod lengths if needed. Remove rig pins.
Check rigging at max reverse, takeoff, and flight
a total of 25 quarts. After completion of the first
idle by comparing coordinator readings and
engine runup, inspect the pressurized sump
inserting rig pins in appropriate engine or valve
capacity. Note the fluid level, using the shoulder
within the filler hole as a guide. If necessary,
housing slots. After mechanical rigging checks
completely fill the pressurized sump.
agree, adjust valve housing assembly for setting
blade angles. See fig 8-21.
If the system was full on the last flight and
After all rigging has been completed, check
is below FULL at the next check, suspect external
for installation of bolts, nuts, and safety wire.
leakage. Make a thorough visual inspection of the
propeller and control to locate the site of the
Torque all bolts and nuts, and safety wire all rod
leakage. Statically cycle the propeller before
ends, as required by the appropriate technical
manual. At this point, you should remove all
checking the fluid level. Do not remove the filler
rigging pins and install the valve housing
cap for at least 10 minutes after operation of the
propeller or actuation of the auxiliary pump. If
atmospheric sump filler cap. Now complete pro-
the fluid level is low at the initial check, run the
peller and engine checks to test for proper
auxiliary pump. Recheck the fluid level. Operating
the propeller into the feather position and back
should be sufficient. If the fluid level is still low,
add the amount required to bring the fluid level
up to that specified by the MIM.
Depressing the feather button in the flight
It is important to check the fluid level in the
station causes normal feathering. This action
control assembly before checking the operating
supplies voltage to the holding coil of the feather-
propeller system. This procedure is especially true
ing switch, auxiliary pump, and feather solenoid.
Hydraulic fluid positions the propeller control
before feathering. Without fluid, the pressure
cutout switch will not operate to stop auxiliary
feather valve to feather the propeller. When the
propeller has fully feathered, pressure buildup will
pump motor operation.
operate a pressure cutout switch. The switch
During static system operation, intermittent
causes the auxiliary pump and feather solenoid
operation from about 75 degrees to air or ground
start positions may cause the pitchlock to engage.
to become de-energized through a relay system.
Decreased pitch operation cannot continue until
Feathering also occurs by pulling the emergency
the pitchlock releases. This disengagement is made
shutdown handle (E-handle). This action mechan-
by moving the propeller toward the feather
ically positions the feather valve and electrically
energizes the feather button holding coil to send
position a few degrees.
the propeller to feather.
Rigging and Adjustment
During the initial engine/propeller installation,
or whenever a fuel control, coordinator, or
To unfeather the propeller, pull the feather
linkage has been replaced, make a complete
button and hold in the unfeather position. This
rigging check. The final propeller control linkage
action causes the auxiliary pump to come on.
rigging and valve housing adjustment is done with
Fluid pressure flows to the decrease side of the
pitch change piston in the dome. This action
the propeller installed. In most cases, when a T56
unlatches the feat her latches. The propeller will
engine is ready for issue (RFI) from an aircraft
intermediate maintenance department (AIMD) to
start to unfeather. Upon reaching the air start
a squadron, the fuel control to coordinator rigging
pitch angle (45 to 48 degrees), the air start beta
has been completed.
switch closes. Closing the switch energizes the air
start control relay. This relay energizes the feather
A minimum of five rigging pins are necessary
valve solenoid, which sends the blades back
to rig and adjust the propeller control linkage and
towards feather. The return of the blades toward
valve housing. Refer to the appropriate technical