lock secures it in the down position. At this time, the
figure 13-3. When the landing gear is down and locked,
cockpit position indicator shows the down wheel, and
wheels appear on the indicator.
the transition light on the control panel goes out.
During the emergency extension, cockpit indications
on the indicator and the lighting of the transition light
If the landing gear fails to extend to the down and
are the same as during normal landing gear extension.
locked position, each naval aircraft has an emergency
When the landing gear control handle is actuated in
method to extend the landing gear. Emergency
the emergency landing gear position, a cable between
extension systems may vary from one aircraft to
the control and the manually operated nitrogen bottle
another. The methods used may be the
opens the emergency gear down release valve on the
auxiliary/emergency hydraulic system, the air or
bottle, as shown in the schematic in figure 13-4.
nitrogen system, or the mechanical free-fall system. An
Nitrogen from this bottle actuates the release valves on
aircraft may contain a combination of these systems.
the other three bottles so that they will discharge.
For example, the main landing gear emergency
Nitrogen flow from the manually operated bottle
extension may be operated by the free-fall method and
actuates the dump valves. This action cause the shuttles
the nose gear by the auxiliary/hydraulic system
within the shuttle valve on the aft door cylinders, and on
the nose gear cylinder, to close off the normal port and
The nitrogen storage bottle system is a one-shot
operate the cylinders. The nose gear cylinder extends
system powered by nitrogen pressure stored in four
and unlocks the up lock and extends the nose gear. The
compressed nitrogen bottles. See schematic in figure
nitrogen flowing into the aft door cylinders opens the
13-4. Pushing in, rotating clockwise, and pulling out
aft doors. Fluid on the closed side of the door cylinders
the landing gear control handle actuates the emergency
and the up side of the nose gear cylinder is vented to
gear linkage connected to the manually operated
return through the actuated dump valves. Nitrogen from
release valve on the nitrogen bottle. The release valve
another bottle actuates the shuttle valves on the up lock
connects pressure from the bottle to each release valve
cylinders. Nitrogen flows into the up lock cylinders and
of the remaining three bottles. The compressed
causes them to disengage the up locks. As soon as the
nitrogen from the manually operated bottle repositions
up locks are disengaged, the main gear extends by the
the shuttle valve in each of the other three nitrogen
force of gravity. Fluid on the up side of the main gear
bottles and permits nitrogen pressure to flow to the
cylinders is vented to return through the actuated dump
extend side of the cylinders. When the up lock hooks
valves, preventing a fluid lock. When the gear fully
are released, the main gear drops by gravity, and the
extends, the down lock cylinder's spring extends its
nose gear extends by a combination of gravity and
piston and engages the down lock.
nitrogen pressure. Each gear extends until the down
Figure 13-3.--Landing gear warning and position indicator.