Figure 8-21.-Valve housing assembly (adjustments).
feather opens the air start beta switch to re-
Fuel Governor, Pitchlock, and
Reverse Horsepower Checks
energize the air start relay. Now the blades are
cycling around the air start blade angle to stabilize
The purpose of the fuel governor check is to
the propeller speed and engine speed. These
be sure that the fuel control governor will limit
stabilized speeds prevent a NTS condition from
the engine speed if the propeller governor fails.
occurring during an air start. The air start blade
The pitchlock check makes sure that the propeller
angle for unfeathering cuts out ground unfeather-
pitchlock will engage to prevent the propeller from
ing when you depress the pressure cutout override
going to a lower blade angle. The reverse
(PCO) button. This button is usually adjacent to
horsepower check will ensure that the reverse
the feather button. Depressing the PCO button
horsepower will operate normally.
prevents the blades from cycling around the air
start switch. The PCO button allows the blades
NTS Check On Shutdown
to go to a lower blade angle setting.
With the engine running at low rpm, place the
NOTE: Stopping a decreasing blade angle
NTS/feather valve check switch in the NTS check
during ground operations may cause a
position. Turn the fuel/ignition switch to OFF.
problem. If stoppage occurs above the low
NTS action should develop and illuminate the
pitch stop, do not, under any circum-
NTS light. If unsuccessful, maintenance action
stances, attempt to decrease the blade angle
is necessary.
any further.
Increase the blade angle before trying a
PROPELLER BALANCING
decrease, so the pitchlock teeth will disconnect.
AND LEAKAGE TESTS
The pitchlock teeth will engage upon release of
Accomplish all propeller balancing in a
the feather button. Failure to increase the blade
horizontal plane using the propeller balancing
angle will cause damage to the pitchlock teeth.
8-23
