[Milsurplus] Naval Aviation Navigation

[sdaitch at ibb.gov]

Ed hit on something that I had not thought to mention, regarding
radio configuration.

With a real TACAN radio in an military aircraft, it is a one box process, where the radio operator has to set up only one frequency/channel and the display will indicate bearing and distance information.

In older civilian aircraft, the DME was almost always a separate radio unit, and would only display the DME information, and was channeled by a phantom VOR frequency.  That is, the navigation chart showing the civilian compatible DME side of the TACAN would give a VOR frequency to set the DME unit, to channel properly.  There was a DME channel pairing for about half of the TACAN channels, so the civilian side of the house could use some of the DME portion of TACAN nav aids.

Bear in mind that in a VOR site, there is one VOR transmitter.
A VOR-DME has a VOR TX and the DME transponder system - two systems
A TACAN has the TACAN bearing transmitter and DME transponder system - two systems
A VORTAC has three systems, the VOR TX, the TACAN bearing TX and the DME transponder system.

73
sheldon
WA4MZZ




----- Original Message -----
From: Ed Zeranski <ezeran at ezeran.cnc.net>
Date: Wednesday, March 15, 2006 0:07 am
Subject: RE: [Milsurplus] Naval Aviation Navigation

> Mac, the antenna wouldn't have to rotate and produce
> the azmuth information if all you wanted is DME.   On
> a VORTAC the VOR antenna rotates a heart-shaped
> pattern which makes the azmuth info.
> 
> 	Yep. In the base TACAN sets I worked on the antenna was 
> stationary but the
> parasitic elements spun. The triggers for the main and aux bursts were
> generated by iron slugs in an aluminum plate that rotated with the 
> 900 rpm
> spinning parasitic drum. As the little iron bits passed through 
> coils they
> generated the triggers. Distance interrogation came from the 
> aircraft and
> that only happens when the flyer turns on the DME part of his set. 
> We had an
> old ARN-21 mounted in our truck as a monitor. Civilian aircraft 
> can monitor
> the mil sites and the mil TACANS were on the aircharts. The 
> civilian use put
> an FAA AZ accuracy requirement on land based mil TACANS.
> 
> EdZ
> 
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