[Milsurplus] AN/APN-1 Mission

[J. Forster]

There seems to be pretty much general agreement that the APN-1 Radio Altimeter
was (almost?) never connected to an autopilot. So what was the thing used for?
There were both Navy and Army versions (the former with one range, the latter
with two) and a LOT of them were produced. Possible applications include:

Ferrying of aircraft? It seems doubtful that it was made just for ferry flights
over water. Did they ferry at high or low altitude?

Long range, low altitude, missions over water to approach below coastal radars?
I wonder about this because the set is CW, and, although low transmitter power
(a fraction of a watt), it transmits a pretty distinctive signal that should be
detectable at 50 miles or so with quite a simple receiver. Because the set
sweeps widely, receiver tuning would not be an issue.

Flights over land where barometric information was not available. The deserts of
North Africa come to mind, but was there much Navy activity there? I don't think
the set was capable of the kind of terrain following tried with the F-111 in
'Nam. It was also clearly down looking, not forward looking.

Part of an ILS. This  does not seem likely as most landing areas would have a
radio and a barometer.

Anybody have any information (or speculation)?

-John