On the simulator, it looks like the GPS sensing was
also reversed so that while on "gps" tracking in the
vectors to final mode that the HSI read correctly--
while dialed to the front course heading--as it would
be in anticipation of the BC approach.

I don't have a Garmin 530 but a KLN 94 and a King/Bendix HSI; however,
in any case it is important to distinguish between the GPS based
approaches and the actual ground navigation equipment based
approaches.

For example, I can select and load a LOC BC approach on my GPS (I get
a warning that this is for monitoring only since there are no LOC
based overlay approaches). If I were to fly this approach on the GPS,
i.e. have the information to the HSI coming from the GPS and "GPS" on
the HSI source annunciator, I would have to set the LOC front course
outbound or back course inbound on the HSI course bearing pointer.
That would give me correct sensing.

On the other hand, if I fly the BC LOC approach based on the NAV radio
(no GPS involved here), i.e. the information to the HSI coming from
the NAV source and "NAV" on the HSI source annunciator, I must set the
HSI course bearing pointer to the LOC front course inbound for correct
sensing.

I hope that's not too confusing and may answer your question.

Gerd (ATP since Monday)
T182 C-FDOW