Safe & Arm Device, FCDCA Signal Interrupter

The FCDCA Signal Interrupter is a Safe & Arm devices that has a very simple theory of operation. In the safe position the two Explosive Leads (Boosters) are rotated out-of-line with their respective ordnance ports. A mechanical safing pin (key) prevents the device from moving from the out-of-line position (arming)—even if an arm command is applied. Once the safing pin is removed and an arm command is applied, the Explosive Leads (Boosters) are brought into mechanical alignment with their respective ordnance ports.

The Interrupter is designed to prevent explosive stimulus from transferring or propagating through the device when in the safe position and to allow it to transfer or propagate through the device when in the armed position. The input stimulus is provided by an input explosive (an FCDCA end tip or equivalent) that is initiated by command independent of the Safe and Arm; i.e. the Safe and Arm does not generate an explosive signal; rather, it responds to an explosive signal. It either stops the explosive signal or transfers the explosive signal depending upon the commanded state (safe or armed) or the Safe and Arm. The safing key cannot be removed when arm power is applied to provide additional safety.

The Safe and Arm uses a classic rotating barrier to accomplish the mechanical arming and safing of the explosive train. The input and output explosive devices are installed in either side of the Safe and Arm along a common axis or ‘line-of-sight.” A cylindrical shaft or “barrier” is placed between the two explosives. In the safe position, the shaft is rotated so that the explosive lead is 90° with respect to the explosive train, effectively blocking the path between the input and output explosives. In the armed position, the barrier is rotated so that the explosive leads are aligned with the input and output explosives.

Redundant explosive trains are provided; each is designed to function independent of the other in that detonation of the input explosive train #1 will not initiate the output of train #2 nor will it render train #2 inoperative. It should be noted the design could easily be modified to a single explosive train by simply deleting the design elements associated with the second explosive train.