The SMDC and FCDC segments act as the plumbing for the emergency egress system. They provide all internal and external jettison initiators with manifolds and one-way transfers to all explosive charges. Some S-3A aircraft have been modified to incorporate FCDC in place of the SMDC at the four locations where the canopies and/ or hatches meet the airframe. The use of the FCDC alleviates the installation problems encountered with SMDC. The SMDC and FCDC focus extremely high velocity and pressures onto the ends of adjacent SMDC segments. The high reaction speed of 8,000 to 9,000 feet per second makes the SMDC very difficult to unintentionally detonate from extraneous sources such as sawing, filing, drilling, and hammering because the speed of these operations does not approach the 8,000 to 9,000 feet per second requirement. From the standpoint of manufac-turing and maintenance personnel, the system is virtually inert when safety pins are installed.

Figure 2-16.- Hatch/ canopy detonating cord assembly.

The ends of the SMDC, while in storage or not connected in the aircraft, must be capped at all times. Any scaring or deformation of the transfer tip is cause for rejection. Any deformity here will affect the direction the blast force will travel. The tips of the SMDC act as both donor and acceptor to receive and transfer the charge from one SMDC segment to another. The tips contain Hexanitrostilbene II (HSN II) while the cord charge itself is Hexanitrostilbene I, a less sensitive material.