On 11/17/2023 10:28 AM, Al Klase wrote:

While we're on the subject, does anyone know what "ZA" was?  Saw a reference to it on an aircraft check-list placard.

Al and the list.

The ZA was the aircraft side of an early ILS system. The system
used LF/MF for localizer and VHF around 90 MHz for glide slope.
The set used an external receiver such as an RU or RAX or AN/ARC-5
for receiving the localizer and its own receiver for the glide
slope. The system was developed by a company called Air Track.
I will have to research what the designation of the ground(or shore based) system was.

According to the book "Blind Landings" (I can't find it right now so
can't name the author) the system wasn't too reliable. According to
the book the glide slope angle varied with the dampness of the underlying ground, and the localizer suffered from day/night issues.
Its use seems to be confined to seaplanes and amphibians. In any event it was not in service for very long, and very few ground installations existed.

Also, from reading the operation manual, getting the airplane lined
up properly to make the landing involved quite a bit of manuevering and
switch flipping. I would guess that it would make a bad weather approach
a lot more stressful.

About the book "Blind Landings", it delves into the developement of instrument landing systems from the interwar period and into the use of radar for GCA.

I do have the components for the ZA, but have not attempted to put it
together as a display. Since I'm on a downsizing kick right now, if
someone would like to have it for making a display, let me know, I think
we could probably work something out.

Jack Antonio
WA7DIA
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