Walt,
No-one is afraid of talking about it - just put 'PRC112' or 'ARS6' into Google and see how much is open-source. Eg.
AN/ARS-6(V) Personnel Locator System (PLS) (United States) - Jane’s Military Communications
The RDU is a very basic display that gives very raw left or right of nose indications and appox DME. Also, it is in front of the LH Seat NHP/PNF and so is definitely not something many people, as HP/PF, would want to blindly follow in IMC towards culmulo-granite at high speed, if your theory is correct.
OTOH, what is known is that UK Chinooks had CPLS fitted around the time of the crash as a STF - BUT there is no record of STF or SD paperwork, even in a secret sub-section of the RTS. Records should be kept, even if the capability was sensitive (which it probably was then, as the system used crypto-variables). Ultimately, this further shows how immature was was the design process and EMC trials of the HC2. To my mind, this creates even more doubt!
flipster
Thank you Walt for helping us find the information.