end of the body. A gas tube machined in the upper part
gas passage through the unit body connects the
of the cartridge ensures even distribution of gas
cartridge breech to the lower end of the start switch
pressure when the cartridge fires.
plunger.
The static lanyard assembly comprises a lanyard
Barostatic Release Unit
precoiled into a cylindrical container with special
fittings swaged onto each end. The upper end fitting has
The barostatic release unit (BRU) is located on the
a wedge-shaped disconnect device, which engages with
RH main beam of the seat and contains an impulse
the lower end of a spring-loaded firing pin positioned
cartridge CCU-102/A. The CCU-102/A normally is
below the cartridge. The lower end fitting protrudes
initiated by the sequencer to supply gas pressure to
through the lower end of the body and is retained by a
release the upper and lower harness locks and fire the
shear pin. When the seat is installed on a catapult, the
secondary cartridge in the parachute deployment rocket
protruding lower end fitting fits in one of the
motor. If the sequencer fails, the BRU cartridge will be
catapult-mounted ballistic latches.
fired by mechanical operation of the BRU.
The start switch is a series of metal sleeves and
The BRU (fig. 2-15) consists of a body containing
insulated sections, installed vertically to form an
the impulse cartridge, a barostat assembly, and a
electrical switch assembly. An internal plunger has a
4-second time delay mechanism.
short gold-plated section with piston head at its lower
BAROSTAT.--The barostat consists of an aneroid
end, and is partially sleeved with insulation. A shear pin
capsule housed in the release unit so that a peg attached
prevents movement of the plunger before operation.
to the capsule may engage a starwheel in the delay
The impulse cartridge is percussion-operated by
mechanism. At altitudes in excess of the barostat rating
the firing pin and is screwed into a breech at the upper
(14,000-16,000 feet), the peg engages the starwheel
Figure 2-15.--Barostatic release unit.
2-14
