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Detonator Impact, Inertial Switch SA-3/A, BC-706a for Radio Sets SCR-595,-695 and ABK IFF System

Federal Manufacturing

Detonator Impact, Inertial Switch SA-3/A, BC-706a for Radio Sets SCR-595,-695 and ABK IFF System


Here is a rare example of a WWII-era Detonator Impact / Inertial Switch used in the Identification Friend or Foe Radio System SCR-595 and -695 (or ABK as termed in US Navy aircraft).  This system was deployed across most aircraft of the US Army Air Force and Navy, including B-17, B-24, B-29, P-51, and P-38.  In the event of a crash that would risk this equipment getting into the hands of the adversary, this Inertial Switch would trigger upon impact and ignite the explosive charges installed within the cabinet of this radio system. 

From a WWII Navy Radar Operator’s Manual:

“There is always the possibility of aircraft being forced down or shot down with the ABK itself still in an undamaged or repairable condition. To guard against this contingency, a detonator is installed in every ABK unit. This detonator or "destructor" is an explosive charge inserted into the side of the cabinet. When exploded, it can destroy the insides of the unit so completely that it is impossible for the enemy to determine what the resulting wreckage originally was.  Composed of thermite, the charge can be set off without rupturing the case, and though the terrific heat melts everything already blown up, it cannot injure the pilot who sets it off nor can it damage or set fire to the plane. It does a thorough job of guarding the security of this important IFF unit.

“The designers made certain that the detonator would function regardless of the fate of the crew of the airplane. The pilot has two switches {i.e.,the BC-765} to push to explode the demolition charge if he must land on hostile ground, so that the foe is rewarded only with a picture of destruction when he attempts to investigate IFF. If all the crew are killed, an impact switch does the job for them. It sets off the destructor when the plane crashes...."

Also see the excerpt from the P-51H Erection and Maintenance Manual dated 1945 which describes how to reset the switch, and a page from the P-38L Erection and Maintenance Manual dated 1945 illustrating the installation of the switch.  

It is 'experienced' cosmetically, but in good shape otherwise. The detonator spring does trigger the switch mechanically, and can be reset.  

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