Figure 13-2.--Nose gear up cycle schematic.
cylinder. The down lock cylinder disengages the down
is a schematic that shows the fluid flow in the nose gear
lock, and the nose gear cylinder starts to raise the nose
up cycle. This system contains a selector valve, flow
gear. As the gear is raised, the nose gear doors are
regulators, priority valves, check valve, actuating
closed by mechanical linkage. When the gear is fully
cylinders, and the necessary hydraulic tubing that
retracted, the up lock mechanism engages the nose gear
routes hydraulic fluid to and from the required
to lock it in the up position. The up lock mechanism is
components.
mechanically actuated through linkage connected to
When the landing gear handle is in the UP position,
the nose gear.
a circuit is completed from the landing gear handle
As soon as the down lock mechanism is disengaged
circuit breaker, through the landing gear up switch, to
and the gear starts to retract, the pilot's position
the selector valve. The selector valve is electrically
indicator displays change from a wheel to a barber pole,
positioned to direct pressure into the landing gear up
and the transition light on the landing gear control panel
lines and to vent the down lines to return. Fluid flows
comes on. As soon as the gear is up and locked, the
from the selector valve, through a flow regulator to the
transition light goes out and the position indicator
up side of the nose gear cylinder. Fluid also flows
changes from a barber pole to UP, as shown in
through another flow regulator to the down lock
13-3
