Desert Dingo #120: “I thought the track went down the middle of McMurdo Sound” is not necessarily inconsistent with “I thought the track went direct to McMurdo Station”. The statements would be inconsistent if the witness knows that a direct track from Cape Hallett to McMurdo Station goes over Ross Island (ie, does not go down the middle of McMurdo Sound). In order to know that a direct track from Cape Hallett to McMurdo Station goes over Ross Island, you need a map showing Cape Hallett, McMurdo Station and Ross Island.
The Radio Navigation Chart (McFarlane p81) is of small scale, does not identify Ross Island by name and, in any event, is what it says it is: a map for radio navigation purposes.
NZMS135 (McFarlane pp 90,91) is a topographical map showing all three positions, and containing an inset map of the area around McMurdo Station. But this map was not available at the briefing. The map used at the briefing was a photocopy of the inset (McFarlane p37). The inset does not show Cape Hallett, so the map can’t be used to picture the track from Cape Hallett to McMurdo Station in relation to Ross Island.
The point is that it was possible for a pilot attending the briefing to leave with the impression that the track was direct to McMurdo Station, and that this track would take the aircraft down the middle of McMurdo Sound, with Ross Island to the left.