OK. At last I think that I know where the question originates and where Keithl, is basing his answer on.
Let's look first at the LOC........a single LOC with a backcourse and say a front course of 270deg serving runway 27.
The 150Hz lobe will over lie the runway and to the north of the runway and appraoches from both ends.
The 90Hz lobe will overlie the runway and to the south of the runway and approaches.
The LOC indication produced in the cockpit is not an indication of aircraft position or of heading required to intercept or of direction to turn or of anything else. The LOC indication is a simple indication of which lobe is being received the strongest.
In this case, the arrow head represents an east-west line through the aircraft with the arrow pointing 270deg. The beam bar simply tells the pilot if they are in this case NORTH of the centerline (150Hz dominant) or SOUTH of the centreline (90Hz dominant).
Regardless of where the arrow is pointing on the HSI, the arrow points 270 and the indication of being N or S of the centerline is correct. Thus it is not necessary to set the arrow to any particular direction to deduce this information.
However, provided the arrow is set to the inbound FRONT course, situational awareness will be improved because the display will be intuitive regardless of where the aircraft is and regardless of the desired tracking inbound/outbound/front/back.
So using the HSI or for that matter, the OBS, it does not matter what the arrow is set to for LOC tracking, the indication will be the same (confusing as that may be to the pilot).
Moving on to the VOR.
First of all, the VOR compares the current radial from the VOR station and after checking the "desired" course TO or FROM the station displaces the beam bar appropriately. Unless the arrow is set to an appropriate number then this comparison is meaningless.
While Keithl is incorrect to make a sweeping statement saying that it does not matter where the arrow is pointing, He is correct to say that when using a HSI, provided that either the arrow head OR the arrow tail is set to the required track, the beam bar will show the correct position of the aircraft relative to the desired radial.
Replacing the runway above with a VOR station and making our desired radial the 090/270 through the VOR. Our aircraft is N of the 090/270 radial. NW or NE it matters not.
Once again, the arrow and tail represent an east west line through the aircraft and the beam bar tells the pilot the position of the desired radial in relation to the arrow line.
Let's look at the position with the arrow set to 270. The beam bar will show that the desired radial is SOUTH of the aircraft. This is the true position.
With the arrow set to 090, the beam bar still shows that the desired radial is SOUTH of the aircraft.
However, without the TO/FROM flag, it is IMPOSSIBLE to know if the aircraft is NE or NW of the VOR.
Consequently, without the TO/FROM flag, a further instrument must be looked at and the information absorbed in order to maintain situational awareness......extra workload.
Now we can see that whan making a VOR approach by tracking outbound anlong the final approach track and then completing a procedure turn to establish inbound, Keithl is technically correct to say that the final approach inbound course can be set from the very start on a HSI.
However, the system Keithl relies on is that the slaved compass system MUST BE OPERATING.
Failure of the slaved compass throws the idea out the window.
Furthermore, if the approach is made using an OBS then what Keithl suggests will not work.
Also, some automatics will have problems with the procedure Keithl describes.
So to be safe........when using the VOR always point the arrow in the desired direction!.......it's "failsafe"
Regards,
DFC