Figure 12-3.–Landing gear warning and position indicator.
light goes out and the position indicator changes from a
barber pole to UP, as shown in figure 12-3. When the
landing gear is down and locked, wheels appear on the
indicator.
EMERGENCY SYSTEMS
If the landing gear fails to extend to the down and
locked position, each naval aircraft has an emergency
method to extend the landing gear. Emergency
extension systems may vary from one aircraft to
another. The methods used may be the auxiliary/
emergency hydraulic system, the air or nitrogen system,
or the mechanical free-fall system. An aircraft may
contain a combination of these systems. For example,
the main landing gear emergency extension may be
operated by the free-fall method and the nose gear by
the auxiliary/hydraulic system method.
The nitrogen storage bottle system is a one-shot
system powered by nitrogen pressure stored in four
compressed nitrogen bottles. See schematic in figure
12-4. Pushing in, rotating clockwise, and pulling out the
landing gear control handle actuates the emergency gear
linkage connected to the manually operated release
valve on the nitrogen bottle. The release valve connects
pressure from the bottle to each release valve of the
remaining three bottles. The compressed nitrogen from
the manually operated bottle repositions the shuttle
valve in each of the other three nitrogen bottles and
permits nitrogen pressure to flow to the extend side of
the cylinders. When the up lock hooks are released, the
main gear drops by gravity, and the nose gear extends
by a combination of gravity and nitrogen pressure. Each
gear extends until the down lock secures it in the down
position. At this time, the cockpit position indicator
shows the down wheel, and 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 are the same as during normal landing
gear extension.
When the landing gear control handle is actuated in
the emergency landing gear position, a cable between
the control and the manually operated nitrogen bottle
opens the emergency gear down release valve on the
bottle, as shown in the schematic in figure 12-4.
Nitrogen from this bottle actuates the release valves on
the other three bottle so that they will discharge.
Nitrogen flow from the manually operated bottle
actuates the dump valves. This action cause the shuttles
within the shuttle valve on the aft door cylinders, and on
the nose gear cylinder, to closed off the normal port and
operate tie cylinders. The nose gear cylinder extends
and unlocks the up lock and extends the nose gear. The
nitrogen flowing into the aft door cylinders opens the aft
doors. Fluid on the closed side of the door cylinders and
the up side of the nose gear cylinder is vented to return
12-4
