HF
Thanks for the acknowledgements regarding the HF. It relieves me after having some posts deleted from the prior thread, and to me they were hardly less valid.
Why have ACMS? Why have ACMS reporting via ACARS? It's to reduce delays on the turnaround. So yes, dual HF, being required for overwater flight, will be reporting to the ACMS and linking via ACARS. It's common sense that a Failed HF won't be transmitting its own failure, btw.
Here's what I replied to a PM from a doubter: Cut the wires between the HF transceivers in the fuselage and the HF antenna couplers in the fin, and the HF will send a Fail message to ACMS. The coupler is actively tuned to resonance with the antenna each time the frequency is changed, and reports Tune in Progress and Tuned to the transceiver before transmit is allowed.
If you've used airborne HF, you know the Tune Tone. It's quite short, however, with the new electronically tuned couplers of the last ten years, but still occurs.
GB