Figure 12-5.Main gear door latch mechanisms.
through the actuated dump valves. Nitrogen from
another bottle actuates the shuttle valves on the up lock
cylinders. Nitrogen flows into the up lock cylinders and
causes them to disengage the up locks. As soon as the
up locks are disengaged, the main gear extends by the
force of gravity. Fluid on the up side of the main gear
cylinders is vented to return through the actuated dump
valves, preventing a fluid lock. When the gear fully
extends, the down lock cylinders spring extends its
piston and engages the down lock.
LANDING GEAR COMPONENTS
Learning Objective: Identify components of a
landing gear system.
Various mechanical and hydraulic components
make up a landing gear system. The components
discussed in this chapter are representative of those
found on most naval aircraft.
LANDING GEAR DOOR LATCHES
Landing gear hydraulic system maintenance is
similar to the other types of hydraulic system
maintenance. This system is inspected for internal and
external leakage as well as proper operation during
inspections. While performing operational checks, you
must inspect the complete landing gear installation for
adjustments, clearances, and sequence of operation.
The adjustment of latches is one of your prime
concerns. A latch is used in hydraulic systems as a
device designed to hold a unit in a certain designated
position after the unit has traveled through a part of its
cycle. For example, when the landing gear is retracted
in some landing gear systems, each gear is held in the
up position by a latch. The same holds true when the
landing gear is extended. Latches are also used to hold
the landing gear doors in the open or closed positions.
There are many variations in designs of latches. All
latches are designed to accomplish the same thing, They
must operate automatically, at the proper time, and hold
the unit in the desired position.
The main landing gear forward door is held closed
by two door latches. As shown in figure 12-5, one latch
is installed near the front of the door and the other near
the rear of the door. To lock the door securely, both locks
must grip and hold the door tightly against the aircraft
structure. The principal components of each latch