Thanks FD - a clear and helpful explanation. It was the 'silly idea' of flying an ILS in FPV that was really confusing me! Didn't realise you poor deprived folk could not F Dir a VOR radial (or presumably couple?).
You will no doubt recall from your 737 days that the HDG/TRK selection was only Pin selectable by avionics, but that NPAs were a 'doddle' and flown using the track line as a 'sheepdog' on the Nav display to 'corral' the NDB pointer, which removed any mag variation or IRS errors.
As an aside, the WORST 737 IRS error I ever had was 122kts on stand caused by an incorrect 'part number' IRS unit.
Fearing less now...
