Arming is the same in any case. A regulator in the fuze
converts the applied voltage to the required level and
polarity. It is then applied to the energy storage unit and
the 2.6-second timer. If the weapon decelerates, the Mk
31 safety device senses the deceleration and causes the
retard switch to close. At 2.6 seconds, the timer
completes its cycle and transfers the voltage to the
rotor-actuating bellows. The bellows operate and turn
the rotor to the armed position.
If the weapon does not decelerate, the retard switch
does not close. The 2.6-second timer continues to run.
At 3.8 seconds, the Mk 31 safety device causes the
voltage to transfer to the input of the rotor-actuating
bellows. At 10.0 seconds, the bellows operates and
turns the rotor to the armed position.
FMU-152/B ELECTRONIC BOMB FUZE
The FMU-152/B is an advanced fuze system for
use in general purpose and penetrating unitary
warheads. The FMU-152/B provides safing, in-flight
cockpit selection, and multifunction and multiple delay
arming and fuzing functions. The FMU-152/B is a
hardened target capabilities that provide arming and
fuzing functions for general purpose and penetrating,
unitary warheads. The FMU-152/B system operates in
three fuze mission phases: the pre-release, pre-arm,
and post-arm phases. The pre-release phase
includes all fuze functions performed prior to the point
at which the weapon is released from the delivery
aircraft. The pre-arm phase includes all fuze
functions occurring between weapon release and
weapon arming. The post-arm phase includes all fuze
functions after the weapon is armed.
FMU-143E/B ELECTRIC TAIL FUZE
The FMU-143E/B fuze (fig. 1-7) is used with the
GBU-24B/B. It is initiated by the FZU-32B/B initiator,
which is used to generate and supply power to arm the
fuze. The safe condition is verified by the presence of a
safety pin or arming wire through the pop-out pin (gag
FMU-139 (SERIES) ELECTRONIC BOMB FUZE
The FMU-139 (series) electronic bomb fuze (fig.
1-8) is an electronic impact or impact-delay fuze. It is
used in Mk 80 series general-purpose bombs, including
laser-guided bombs. The arming times are in-flight
selectable, and the functioning delay must be set during
weapon assembly. There are three arming times (2.6,
5.5, and 10.0 seconds) and four functioning delay
instantaneous). Only 2.6/60, 2.6/25, 2.6/10, and
2.6/inst high drag arm/delay switch positions are
authorized for Navy/Marine Corps use. The low drag
arm time switch should always be in the X position. The
low drag arm time rotary switch is positioned at X for
shipping, storage, and all FFCS (fuze function control
set) use. The FMU-139 fuze differs from the Mk 376
fuze in that the gag rod and arming wire housing are
located in the center of the faceplate (fig. 1-9).
ARMING SAFETY SWITCH MK 122 MOD 0
The Mk 122 Mod 0 arming safety switch (fig. 1-10)
connects the fuze control circuits of the bomb in the
aircraft to the electric fuze circuits in the bomb. This
switch provides an open circuit and a RADHAZ shield
to prevent electromagnetic radiation from entering the
While the weapon is loaded, the coaxial cable of
the switch is plugged into the receptacle of the aircraft's
electrical arming unit. When the bomb is suspended
from the rack, the lanyard is attached to a fixture on the
rack or pylon. Upon bomb release, the lanyard pulls the
lanyard pin and closes the fuze circuit. The lanyard is
long enough so the weapon separates from the bomb
rack suspension hooks before the lanyard pin is pulled
from the switch. This ensures that the fuze does not
receive charging voltages in case of weapon release
failure. The coaxial cable is longer than the lanyard,
which permits sufficient time for the charging voltage
to pass from the electrical arming unit on the aircraft to
the fuze electric circuits on the bomb before the cable is
pulled free or breaks from the arming unit receptacle.
NOTE: The Mk 122 Mod 0 switch must be
installed and removed in a RADHAZ-free
MK 43 MOD 0 TARGET DETECTING DEVICE
The Mk 43 Mod 0 target-detecting device (fig.
1-11) is a proximity nose element that gives airburst
capability for electric-fuzed Mk 80 (series) bombs.
The Mk 43 Mod 0 element is compatible with all
electric tail fuzes and is identified by the dark green
color of the nose cone. A thermal battery powers its
internal circuitry. The thermal battery is initiated by
+300 volts dc or by the striker rod.
The Mk 43 is initiated mechanically (striker rod)
only when a delay airburst is desired. This is the
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[Avionics Today 02-24-2015] Marion Blakey will be leaving her post...