[Milsurplus] Interphone question

[Mike Hanz]

Jack Antonio wrote:

> In a typical WWII heavy bomber installation,
> were the gunners jackboxes wired to allow
> them access to the command radio?


Nope - or to be more accurate, they generally had no ability to key the 
transmitters.  On some aircraft they were allowed to transmit on the VHF 
(plane to plane) radio alone.  It seems to have depended on the 
operational unit.

> I thought they were, but in a movie I saw
> over the holidays, there was a scene where
> the radio op was instructed to "rig up
> an extension so the General could talk
> on the command radio", the General using
> the top turret to observe formation flying.


Yup.  :-)

Normally, *transmitting* on either the command or liaison radio was 
reserved for the pilot, copilot, or radio operator.  The pilot had 
ultimate responsibility for who transmitted at any given point.  I think 
it was in part to minimize the problem of "oops" that including everyone 
on a crew of ten times a thousand in a big raid would have created in a 
radio silence environment.  The policy seems to have been universally 
shared with both AAF and Navy multi-place aircraft, one of the few times 
they agreed on anything....

Not to change the subject too radically, but a good friend of mine 
recently asked me a question that I had sort of taken for granted in the 
use of the interphones on WWII aircraft.  His question revolved around a 
puzzling remark I had made on my web page  - about the use of an 
interphone amplifier to raise the gain of WWII aircraft receivers enough 
to drive, for example, a speaker.  He correctly observed that this 
wasn't intuitively obvious from the aircraft wiring diagrams...he was 
looking at BC-347 usage in a B-29...and he is right.  Except for the 
RL-24 system, which presaged the complexity of the later systems, it was 
only in the AIA-3 and later (AIC-3, AIC-4, and AIC-5, etc.) that the 
concept of driving the assembled earphones using the amplifier from more 
than a single source was introduced.  Up until that time the amp was 
pretty much restricted to raising the output of the crew microphones.  
Of course, that later approach complicated switching far beyond the 
original concept and ultimately required more than one amplifier to do 
the job with enough flexibility, as you can see in the AIC-5 control box 
at http://members.cox.net/aaf-radio-2//Interphone_systems.html.  The 
AIC-4 pictured earlier on that page had a pretty basic combiner for 
radio and microphones, leaving the guy in charge to select which radios 
would be included in the mix.

73,
Mike