command sequencing system operates twin firing pins
ensure location of the catapult in the correct cockpit
in the ejection gun initiator to fire the explosive charge.
(fig. 2-5). An interference arm mounted on one of the
The resultant gas pressure and the heat operate the
guide rail brackets ensures that the correct main beam
ballistic latches in the barrel and fire the secondary
assembly is installed. A cross-beam secured to the
cartridge as the piston extends. The catapult is water
barrel provides an anchorage point for the RH ballistic
sealed, having seals fitted to the initiator, the secondary
manifold quick-disconnect lanyard.
cartridge, the breech, and the guide bush.
The top end fitting of the barrel has a square
aperture, the barrel latch, through which the plunger of
the top latch mechanism fitted on the seat main beam
The barrel is a built-up structure consisting of a
protrudes when the seat is installed on the catapult. A
light alloy tube with an accurately lapped bore that has
guide bush, fitted in the internal diameter of the top end
permanently attached top and bottom end fittings; a
fitting, is secured by three dowels that are sheared by
housing towards the bottom end contains the secondary
the head of the piston striking the guide bush. The
cartridge. Five brackets support two guide rails bolted
piston then separates from the barrel and the guide bush
on diametrically opposite sides of the tube. The bottom
remains on the piston.
end fitting incorporates the lower mounting bracket for
attaching the catapult to the aircraft and studs for
Two ballistic latches are attached to the bottom end
attachment of the ballistic latches. The upper mounting
fitting by studs and nuts. Each latch comprises a body,
consists of a bracket clamped on the barrel towards the
internally drilled to form a cylinder and containing a
Figure 2-5.--Interference devices, forward and aft seats (SJU-17(V)2/A).