Walter
To keep things simple, I tried to avoid technical detail. You describe the system accurately, although it is unclear if the MoD had PRC-112s with embedded GPS in 1994. Or if the variant capable of auto-entry of waypoints existed then. We have probably read the same material. Additionally, last month a Government/MoD publication carried a quite detailed article on ARS-6/PRC-112 (in the context of GPS jamming/spoofing, explaining why DME was retained in AYD-1) which led the reader to believe the UK had the system. I received this in the post at home, so one assumes its open source.
For our purposes, the important thing is the voice comms, antennae and the level of installation design, trials and acceptance work which would be necessary. If the MoD wanted to install such a system, the first questions would be (a) Do we have the real estate? (b) Is there an existing UHF Homer? (c) If so, does it share one of its antennae with a UHF radio?
The first is obvious – you need physical space to host the ARS-6; Tx/Rx, Control Display Unit, Remote Display Unit, Antenna Switching Unit and the Homing Pair of Antennae with their phase-matched feeders. And, on the ground, the TS-4360 Test Set to aid maintenance.
The second and third determine the complexity of the installation design and trials. This is the area requiring input from a host of MoD and Industry sources, which I think would be difficult to hide.
A palletised solution sounds simple, and indeed is from the maintainers point of view. They have a pallet, they follow (hopefully) simple (hopefully) instructions, and in short order the a/c has a different capability/role. But, a lot of work goes into simplifying such an installation. The pallet in this case would only hold the Tx/Rx and ASU and would, I suggest, be pretty adjacent to the (hard mounted) external antennae. But where are the CDU and RDU? They must be in the cockpit or cabin, being operated by aircrew. They are not standalone in the laptop sense – they need to be hard-wired to the ARS-6 Tx/Rx and a/c intercom (and perhaps a data bus if one exists). If they were hand held (and they are not designed to be) there would have had to be some serious thought, trials and approvals behind the safety implications of wander leads.
You mention 243MHz. The system operates across 225-300MHz (3000 channels in 25kHz steps). This is the whole point – it is an advance over a simplistic, non-LPD UHF Guard system, and why new antennae are required. I don’t know what other frequency band you are referring to but a VHF homing system needs substantially larger antennae, usually mounted either side of the cockpit area. Similarly, so would a PRC-112 VHF equivalent.
Walter, I am not saying your theory is impossible. I know you understand the way the system works. I am trying to articulate the relative complexity of process and procedure required to procure, install, use and maintain ANY such kit. To achieve this in 1993, the aircraft and equipment project offices in PE (and perhaps AML) would be involved, over a sustained period of time. SY, due to crypto. Won’t go further here, except to say this is not one guy in an office. DOR(Air) and RAFSC would have to demonstrate a requirement to secure funding. Again, not just one office. In industry, the aircraft DA (Boeing) and equipment DAs (ARS-6, PRC-112, Intercom, Radio) would be involved. Boscombe Down. RAF units. Publications to be amended. Aircraft to be fitted “for but not with”. And so on. The point I and others are making is that it would be very obvious to anyone concerned with Mk2 that such a system was fitted; and the paper trail voluminous. Yes, one can hide or destroy, but we have been assured by more than one Ppruner who was stationed at Aldergrove that the kit wasn’t there. I think you have to accept their word.
The reason I don’t dismiss your theory entirely is because some of the above process and procedure can be circumvented by the SEM route. But, and this is a point I’ve made often, the inherent risks and resultant problems caused by MoD’s use (abuse) of SEMs are well known, and wholly related to their equally well known failures regarding airworthiness. In my opinion, this last is already beyond all doubt on ZD576, whereas your theory is just that – a theory. That is why I think this thread should concentrate on known facts which can undermine the MoD’s position, with theories discussed elsewhere.
Regards