4.22 EXTERNAL STORES SUBSYSTEM (ESS).
The ESS consists of an external stores controller and up
to four pylon assemblies. The external stores controller
commands the pylons to the required elevation angles for
the various fire control modes. The modes are: ground
stow; flight stow; and FCC control.
The ground stow mode articulates the pylons so that the
wing stores are parallel with the ground over level terrain.
The ground stow mode is automatically commanded on
landing when the squat switch goes to ground mode, or in
flight whenever the rocket select switch, RKT, (fig 4-14) is
placed in the GND STOW position. The GND STOW posi-
tion would normally be selected immediately prior to land-
ing on uneven terrain or when making a slope landing.
The flight stow mode articulates the pylons to a single
fixed position so that the wing stores present minimum flat
plate drag area in forward flight. The flight stow mode is
automatically commanded on takeoff whenever the squat
switch goes air mode. The PLT/GND ORIDE switch will
not override the squat switch for these functions. In flight,
the pylons remain in the flight stow mode until missiles or
rockets are actioned, which then places the pylons under
FCC control. Under FCC control the pylons can be com-
manded through a range of +4.9 to 15 degrees. If the for-
ward flight airspeed as sensed by the ADSS is 100 KTAS
or greater, the pylons will remain in the flight stow position
under FCC control and will not articulate. The external
stores controller receives 115 vac power from the No. 1
essential bus and 28 vdc from the No. 2 essential dc bus.
The external stores controller is monitored continuously
by FD/LS; the on command test (test 10-PYLN) will fault
isolate to the LRU.
4.22.1 Pylon Assemblies.
The pylon assembly con-
tains the pylon MRTU, the pylon aerial rocket control sub-
system station director, the ejector rack, and the hydraulic
actuator for articulation (fig 2-2). The pylon MRTU is used
to interface the missile launcher and station director with
the multiplex bus. The ejector rack contains the attaching
lugs for the wing store, the winch assembly for lifting the
wing store, and the ballistic ejector for stores jettison. The
pylon assembly connects to electrical and hydraulic pow-
er when attached to the helicopter wing.
a. Wing Stores Jettison.
Each pylon is equipped
with an electrically operated ballistic ejector to jettison the
attached wing store. Selectable wing stores jettison is ac-
tivated by lifting the guard and pressing the spring loaded
switch for the desired store (fig 2-11). An emergency
stores jettison switch is located on each collective switch-
box (fig 2-26) which when activated will jettison all wing
stations simultaneously. The wings stores jettison re-
ceives 28 vdc power from the No. 2 essential dc bus and
the emergency dc bus; the selectable stores jettison cir-
cuit is protected by the MISSION JETT circuit breaker on
the pilot overhead circuit breaker panel; the emergency
stores jettison circuit is protected by the JETT circuit
breaker on the pilot overhead circuit breaker panel. The
two stores jettison circuits are completely independent.