[ARC5] Where Does Air Track Fit?

[Jack Antonio]

On 4/27/2014 10:16 AM, Robert Eleazer wrote:
> I have a piece of equipment, Glide Path Receiver, Type CDE-46120, part of Aircraft Radio Instrument Landing Equipment Model ZA, the other components of which are listed on a separate nameplate.  This set was made by Air Track for the Bureau of Ships!  Yes! Ships!  Contract date is 15 March 1940.  In addition to the nameplate, it is stamped "PBY-5A" in yellow paint on the case.
>
> Anyone have any info on this set?  Of course College Park is where James H. Doolittle made the first blind instrument landing, so instrument landing equipment made there is especially interesting.  (However I think the first blind drunk landing probably was made during WWI.)
>
>


The ZA was an early ILS system. Glide path indication was provided by 
the unit you have, basically
a TRF receiver at about 90 Mc. Localizer was done at LF or MF, using an 
RU or ARA or ARC-5 receiver,
whose audio output fed a converter to drive the indicator.

Indication was to a cross needle indicator, which looks just like the 
I-101 used by the BC-733 and ARN-5 set.

There is a book, "Blind Landings" (I will look up the author if there is 
any interest), which describes this
set, and its problems in implementation. This book describes ILS systems 
from the early days, all the
way to a controversy concerning implementing glide slope/localizer 
systems vs. radar GCA systems
in the early 50s(which I had never heard of before).

According to this book, the glide path to follow was highly dependent on 
the ground conditions. Wet versus
dry would produce different glide slopes, from steep to shallow. So, the 
main application was on
seaplanes, where the "ground" was always wet. Information on Mike Hanz's 
website seems to
confirm this, as ZA installations look to be confined to seaplanes and 
amphibians.

But I've never seen any information on where the "ground" equipment was 
installed, to provide a
glide slope for a water "runway".

According to the book, the localizer was dependent too much on 
propagation conditions, and
was not reliable.

I have a manual for the ZA, but trying to scan it would probably destroy it.

I have a pretty complete ZA set, but haven't had the time to build it up 
as a set.  I probably won't
power any of it up since there is no signal source to listen to, but 
just as a display set.

Jack Antonio WA7DIA/4