SOME COMMENTS ON DR. EDWARDS BLOG POST OF NOVEMBER 13, 2022:
1. Airliners have a "minimum equipment list" that must be operational before they depart on a commercial flight. In the 1971 time frame, it appears that NWA had to have at least two operational radio transceivers for voice communications. These transceivers would be wired to be completely independent of each other so that if one failed for some reason the other would still be operational. They would have different power sources and different antenna systems. Consequently, the two transceivers could both transmit and receive at the same time. In the case of NWA 305, it appears that one transceiver was used for communicating with air traffic control, and the other transceiver was used for communicating with the ARINC ground stations.
Several years ago, Fred Poynter of the WSHM and I were informed by ARINC personnel that a typical large airliner today has as many as five transceivers.
2. Poynter's group at the WSHM did a detailed analysis of the ARINC teletype transcripts that the George Harrison family loaned to them and they concluded that there were missing teletype transcripts. And if I remember correctly, the existing transcripts indicated that the phone patch with NWA was established through the ARINC system before the airliner even landed in Seattle at about 5:30 PM PST. Several weeks ago, I suggested that Chaucer get a copy of the WSHM analysis from them but he has apparently not done so.
Further, it appears that teletype transcripts were also routinely made of the voice transmissions over the ARINC system. And according to Chaucer, Carr apparently told him about some of these transcripts that have not been released.
3. With several decades of experience in the military and as an Aeronautical Engineer in the DOD, I can categorically state that the dashed lines in the Seattle ATC transcripts mean that sections of those transcripts have been redacted. This is irrefutable despite any hopes to the contrary.