Boxes, boxes, everywhere...

The explosion of avionics on WWII aircraft quickly made control boxes almost unmanageable from a human factors standpoint. It was roughly the equivalent of the 1930's household that had one ceiling light fixture, from which emanated multiple extension cords hanging all over the walls and floor. Add to it the lack of consistency on where the boxes were mounted from aircraft to aircraft, and you had a real mess on your hands. Sometime in 1944, someone had the bright idea of emulating the 19" rack mounting system long used in industry to solve the same problem. The new width standard was 6" to accommodate the smaller control constellation required for each avionics device, but the idea was the same - stack them up and hide all the connecting cables from view and possible contact. The particular control heads shown below were most closely associated with the ARC-5, though they were later used for other sets - a tribute to the effectiveness of the modular concept. About 1950 the width was changed to the 5 3/4" standard still used today, with backlit plexiglass overlays and Dzus fasteners substituted for the panel screws to aid in removal and replacement. Many of the older units were converted to this later format by chopping off a little on the sides and installing the Dzus fasteners. As a result, these early rack panels have become quite scarce.

Three of the 6" rack series boxes

The three control heads above are the C-125 for an ARC-5 receiver, a C-126 (functionally identical to the C-38A/ARC-5, less the ARR-2 control portion) and a C-127 master power/volume control. The C-127 has been modified as mentioned above, and will get returned to its original configuration before mounting. The C-137 was a minor variation of the C-126, so is not shown here.

Another of these boxes used with the AN/ARC-5 is the C-189/ART-13 control head for the C-131/AR autotune mechanism installed on the R-26 and R-27/ARC-5 receivers when paired with an ATC or AN/ART-13 transmitter. That combination was used primarily in the Pacific for aircraft that needed multichannel capability without the requirement for a radio operator to retune the receiver from channel to channel. The original intent with the two autotuned ARC-5 receivers was to replace the 1942 designed RCA ARB with a 12 channel capability that spanned 3-9.1MHz, but judging by the control box designs, the deployment never grew beyond a single receiver 6 channel application. The C-189 below is the fourth variation I have seen, starting with the simple six position double pole switch specified in the preliminary manual, but that first version required jury-rigging some sort of mounting for the switch in the aircraft since it had no container. The other two were nomenclatured C-188/ART-13 (also shown below) and C-254/AR, and used C-87/ART-13 style surface mount boxes. Never produced in large quantities, the C-189 seems to have been the least common, perhaps because the Collins ten channel AN/ARR-15 receiver began being deployed by the end of the war, and that receiver had much greater capabilities as a liaison set than the stopgap C-131/ARC-5 concoction. At the same time, anything fielded in the Navy usually hung on in isolated units for years, especially those that did not enjoy a front line aircraft carrier status...note the 1949 overhaul date on the C-189 and a 1953! date on the C-188.

C-189 autotune control

C-188 autotune control
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