FUEL GOVERNOR AND PROPELLER
signal to the propeller governor, and vice-versa,
PITCHLOCK TEST SWITCH. --Four two-
until some corrective action is taken.
position (TEST-NORMAL) switches, one for
ANTS INOP warning light illuminates when
each propeller, are on the engine check panel.
the 45-degree air start blade angle circuit energizes.
The air start blade angle system limits negative
Upon placing a switch to TEST, the propeller
speed-bias servomotor receives a continuous
NTS fails. The blades, upon reaching 45 degrees,
overriding signal. The signal drives the mechanism
full travel toward decrease pitch. This resets the
energize the air start blade limit circuit, which
propeller governor to a speed of 106 percent
drives the feather valve to the feather position.
RPM, permitting a ground check of the pitchlock
The blades moving toward the feather position
open the circuit, de-energizing the feather solenoid
and fuel governor functions.
valve. The result of this action is a cycling of the
blades around the air start blade angle switch. For
ground unfeather operation, bypass the air start
Feathering aligns the propeller to the airstream
blade limit switch by actuating the feather pump
to minimize drag during engine shutdown con-
pressure cutout override switch while unfeathering
ditions. Feathering is started by pulling the engine
emergency shutdown handle, autofeathering, or
depressing the feather switch button. The feather
valve ports hydraulic fluid to increase pitch on
A hydraulic, speed-sensitive pitchlock
the propeller blades. This action bypasses all other
mechanism is in the propeller assembly to prevent
overspeeding. It is completely automatic and
NORMAL FEATHERING. --To accomplish
prevents further decrease in blade angle when
normal feathering, pull the engine emergency
engaged. Automatic engagement occurs in two
shutdown handle. Pulling the handle mechanically
ways: by loss or control oil pressure and when
positions the feather valve and electrically
RPM exceeds 103.5 percent. The pitchlock
energizes the feather button solenoid. Also,
governor, sensing the overspeed, allows the
current goes to the auxiliary pump and to the
pitchlock teeth to engage, which prevents further
feather valve solenoid, which hydraulically
decrease in blade angle. Due to teeth design, the
positions the feather valve to feather the propeller.
blade angle can increase if the normal governing
When the propeller fully feathers, oil pressure
control is restored.
buildup operates a pressure cutout switch, causing
BLOCKOUT RANGES. --There are two
the auxiliary pump and feathering solenoid to
blade angle ranges where pitchlock does not
de-energize. The feathering button light then goes
operate. One range is from plus 17 degrees to
minus 14 degrees. This allows for RPM surges as
Feather Pump Pressure Cutout Override
blade angles reduce during approach and landing.
Switch. --There is a push-button switch next to
The second is blade angles between 57 degrees and
each feather button. Actuating the override switch
86 degrees (full feather). This is necessary to
bypasses the feather pump pressure cutout switch.
decrease blade angle for air starting. Blade angles
This permits continued operation of the feather
will be less than 57 degrees at 405 knots or limit
pump if the feather pump operation finishes
before the propeller reach the full feather.
PITCHLOCK RESET. --A reset system will
Feathering Switches (Buttons). --Four guarded
reset pitchlock up to 109 percent RPM at blade
feather switches (buttons), one for each engine,
angles above 10 degrees with the power lever
provide an alternate method for feathering the
below 28-degree coordinator position. This
109 percent RPM setting of the pitchlock is
propellers. Pressing a button to FEATHER cuts
momentary. It is necessary when the power lever
off fuel electrically, and energizes the feather
moves very rapidly into the beta range and blade
solenoid and the feather pump motor to feather
angle reduction is not quick enough. Pitchlock
the propeller. The propeller unfeathers when the
reset comes into use during an aborted takeoff
button goes to the unfeather position. The center
position is for normal propeller operation. A light
or landing. In this condition the increase in fuel
scheduled will cause engine speed to increase
in the feather button illuminates when the circuit
above 103 percent RPM.
to the feather pump is energized.