[Milsurplus] AN/APN-1 Mission

[Scott Johnson]

It is a low range FM altimeter (shouldn't really be designated APN) so it is 
an aid to approaches, just like FM altimeters are today.  The SCR-718 High 
range j-scan pulse altimeter was used for enroute navigation, especially 
when using a driftmeter. The fact that the APN-1 wasn't coupled to an A/P 
speaks as much to the reliability of the autopilots of the day as it does 
the altimeter.

Scott
----- Original Message ----- 
From: "J. Forster" <jfor at quik.com>
To: "Milsurplus" <milsurplus at mailman.qth.net>; "Wireless-Set-No19 @ 
yahoogroups.com" <Wireless-Set-No19 at yahoogroups.com>
Sent: Thursday, April 06, 2006 10:31 PM
Subject: [Milsurplus] AN/APN-1 Mission


> 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
>
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