[Milsurplus] SCS-51 ILS - Airborne Components

[Mike Morrow]

Clete wrote:

>Do I remember the SCS-51 I maintained in the late
>40's had 5 channels; V, W, X, Y, Z?   Localizer
>and Glide Slope were paired frequencies, and still
>are.  We still tune in the Localizer, and get the
>Glide Slope in a package deal.

The 110 mc BC-733 localizer receiver appeared first, and is a six channel
set (RC-103).  Its BC-732 control box has a frequency select switch marked
U, V, W, X, Y, Z.  The receiver output goes to the horizontal pointer on the
cross-point indicator I-101.  The vertical pointer was initially unused.

When the 330 mc AN/ARN-5 glide slope receiver appeared a little later, it
was as the single channel R-57/ARN-5.  In short order, the three channel
R-89/ARN-5A replaced it.  Channels are selected by the same BC-732 control
box that controlled the BC-733, such that glide slope channel 1 was selected
when localizer channel U or V was selected, etc.  Later models of the
AN/ARN-5 went to six channels, but I believe that no model later than the
R-89 appeared before WWII ended.  The output was sent to the vertical
pointer of the I-101.

The AS-27/ARN-5 combined localizer/glide slope antenna has both a
folded-back (ram's horn) dipole for the localizer, and a short linear dipole
for the glide slope receiver.  On WWII-era aircraft, the AS-27 and the the
LP-21 ADF antenna are often the most obvious RF structures.

The other associated landing device was the 75 mc marker beacon receiver.

This system has to be *THE* outstanding success story of WWII-era
electronics.

I've just about completed my system electrically except for the connectors.
Mechanically, I'm still looking for the FT-292 and 293 mounts for the BC-732
and 733.

Most folks don't care too much about this type of gear, but it represents a
really important part of the technical history of avionics.

You have to hand it to the WWII-era USAAF avionics development folks.  In
contrast to the USN, they had excellent ADFs (SCR-269 and AN/ARN-7) and an
excellent ILS...systems that were used essentially unchanged for decades
after the war for both military and civilian flight.

Mike / KK5F