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Old 10th Aug 2006, 20:56
  #2530 (permalink)  
walter kennedy
 
Join Date: Sep 2003
Location: Perth, Western Australia
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tecumse
You wrote:
<<Again, while I can’t absolutely discount your theory (on the use of AN/AYD-1 Personal Locator System), for it to be valid would require the AN/ARS-6(V) in the aircraft to have been pre-loaded with the unique crypto ID of the actual AN/PRC-112s borne by the troops on the ground.>>
Are you sure that you are not getting confused with more modern systems? – and perhaps, for the system of the vintage we are referring to, confusing the ground equipment having a unique code that identifies it with needing to know that code to interact with it at all?
Your interpretation of how this system worked would have rendered it just about useless – I think that you will find on further inquiry that any contemporary PRC112 operating in DME mode within range would have been detected although the caller ID may not have been recognized! – you would still have got accurate range and approximate bearing – which would have cropped up automatically as just another waypoint on the a/c’s nav display.
Regarding voice communication – again, think 1994 – the system allowed AM voice communication (not, presumably, encrypted) – this went through the intercom system (just plugged in somewhere handy I suppose) and, say, if a pilot had selected UHF guard on his intercom, he would have been able to communicate with the person on the ground through the ARS6 unit without having to do any other switching etc – and wasn’t the handling pilot’s intercom in just such a position for which there is no other clear explanation? UHF wouldn’t have been the frequency of choice for a distress call at their altitude in that location, would it?
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The rest of your description of the system, the work involved in fitting the onboard equipment, is a surprise – are you familiar with the fit for the Bosnian conflict period (1995)? – these sets of equipment were delivered “palletized” for the easy transfer between the RAF’s HC2 Chinooks – I understood that this implied the (small) uhf antennas must have been on the same module/ pallete – how else could they have been transferred “easily”? Perhaps you could find out the configuration for that period and clear this up? – it could hardly be a great state secret by now with new technical advances. I thought I had sent you the relevant information I had some time ago. The sales pitch from the manufacturer (in the public domain) implied a largely self contained system with simple interfaces as one option/ variant to the deluxe tailored fit – still giving approximate bearing as well as range – this is at odds with your description of the work involved. Please check out the following extract from manufacturers blurb that puts it rather succinctly:
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
VARIANTS/UPGRADES
The AN/ARS-6(V) can operate as a stand-alone system that can be installed on any aircraft with connections limited to aircraft power and the voice intercom system. It can also be installed as a data bus system using ARINC 429 or MIL-STD-1553 bus controllers and displays that support an integrated cockpit design.
When PLS is installed as a data bus system, range and steering data can be automatically transferred to the onboard navigation system. This sets the survivor's position as a "way-point."
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>.
Spelling it out, if the 47D that the HC2 was based upon had that bus and a slot for plugging into that bus in the nav racks the stand alone variant ARS6 would be very much a “plug in” – I am sure that the manufacturer would give you all the technical detail that you ask for – don’t be shy – and you would of course already have confirmed the bus in the HC2 before writing your last post, wouldn’t you?
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You wrote:
<<Taken with categorical assurances from people who were there (Aldergrove) that ZD576 wasn’t AYD-1 enabled,>>
I don’t understand “AYD enabled” – in my understanding of the system, it was fitted or it was not, the basic architecture of the HC2 Chinook was the same as the 47D in this area and the on board equipment was designed to interface simply with the 47D – that is, there should not have been any preparation required to fit the module. Again, when you come back with a convincing description of the 1995 fit, I may well be corrected.
Do you mean that you have had these assurances from the ground crew who actually did the work on the nav racks just before that final flight? – this would be excellent stuff – if they swore that such a module was not fitted, great, end of story. I am surprised, though, if it was they whom you were referring to – the work that they did (without paperwork) seems to be only vaguely understood – one would have thought that they would have been brought to the inquiries to testify as to what exactly in detail that they did bearing in mind that they had worked on the nav equipment just before a flight that flew into a mountain.
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Anyway, I hope you are not mistaken because I thought that you had the relevant technical background to clear this up. If you are correct then this line of inquiry is indeed finished and I would be grateful for that – I am pursuing this as a matter of obligation rather than self gratification.
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