"Peter Bjoern" wrote in message
...

I have an original AAF Technical Order 30-100 "Instrument Flying
Basic and Advanced" published on 15 January 1944.
Btw. it looks like a kind of predecessor to the later AFM 51-37.

/\/\/\/\/\/\/\ LOTSA GOODSTUF SNIPPED \/\/\/\/\/\/\/

The third part (T.O. 30-100F-1) covers the Army Air Forces Instrument
Approach System. Dated 10 November 1943.

This is nothing less than an ILS system, complete with localizer,
glide path and marker beacons. The frequencies used are even the same
as used today, though there were only six frequencies available for
the localizer, named channels U,V,W,X,Y and Z in the area 108.3 to
110.3 MHz or megacycles as they used then. The glide path was using
frequencies around 335 mc and the marker beacons 75 mc just as today.
The airborne equipment is a receiver control box to tune the desired
channel and the well known crossed-needle instrument with the blue/yellow
zones.

I don't know how widely available this system was, but at least it
was known and developed as early as November 1943 and considered
important enough to place in the instrument flying manual.

Not very widely available, but others have commented as you did about the
longevity of the system developed way back then. One of them is Roger Mola
of Aviation International News who, incidentally, won the Northrop Grumman
Award for the Best Breaking News Submission ( for 'Shutdown of National
Airspace system was 'organized mayhem' ).
And he comments on dates and such of the ILS family development, at the
US Centennial of Flight Commision website:
http://www.centennialofflight.gov/index.cfm (my notes in brackets below):

(SIX LOCATIONS IN 1941)
The instrument landing system (ILS) incorporated the best features of both
approach lighting and radio beacons with higher frequency transmissions. The
ILS painted an electronic picture of the glideslope onto a pilot's cockpit
instruments. Tests of the system began in 1929, and the Civil Aeronautics
Administration (CAA) authorized installation of the system in 1941 at six
locations. The first landing of a scheduled U.S. passenger airliner using
ILS was on January 26, 1938, as a Pennsylvania-Central Airlines Boeing 247-D
flew from Washington, D.C., to Pittsburgh and landed in a snowstorm using
only the ILS system.

(ILS REMAINS UNCHANGED)
More than one type of ILS system was tried. The system eventually adopted
consisted of a course indicator (called a localizer) that showed whether the
plane was to the left or right of the runway centerline, a glide path or
landing beam to show if the plane was above or below the glide slope, and
two marker beacons for showing the progress of approach to the landing
field. Equipment in the airplane allowed the pilot to receive the
information that was sent so he could keep the craft on a perfect flight
path to visual contact with the runway. Approach lighting and other
visibility equipment are part of the ILS and also aid the pilot in landing.
In 2001, the ILS remains basically unchanged.

(NINE LOCATIONS BY 1945, TEN UNDERWAY)
By 1945, nine CAA systems were operating and 10 additional locations were
under construction.

(ARMY INSTALLING 50)
Another 50 were being installed for the army. On January 15, 1945, the U.S.
Army introduced an ILS with a higher frequency transmitter to reduce static
and create straighter courses, called the Army Air Forces Instrument
Approach System Signal Set 51. In 1949, the International Civil Aviation
Organization (ICAO) adopted this army standard for all member countries. In
the 1960s, the first ILS equipment for fully blind landings became possible.

Cheers.