Loc Back Course

mhcasey

mhcasey

Well-Known Member
If a runway has a front course going both directions (i.e. - ILS 17 and ILS 35), will there ever be a procedure turn depicted? It seems easy enough if there is just one front course...track the back course outbound for the procedure turn. But with a front course heading both directions, would I get reverse sensing on the way outbound, or normal sensing? Or is this just something that doesn't really exist?

Example: Suppose KAUS had a procedure turn depicted for ILS 17L. I fly outbound heading 350. The needle swings left. I was under the impression that with a localizer, it really doesn't matter what you set the OBS to. If I set it to 350, would I be right of course? Likewise, if I set 170, would I be left of course (reverse sensing)?
 
Heading outbound on a backcourse gives normal sensing anyways. But If there are two front courses, there is no backcourse.
 
I think I see what's confusing you. KAUS uses the same LOC frequency for both 17L and 35R. In that case, the tower controls which runway gets the front course at any given time. If they are landing 17L and the wind shifts, they throw a switch and the front course changes to 35R. The identifier changes as well, so you know you are getting the correct indication.

It doesn't matter what you set the OBS to.

Does that answer your question?
 
To clarify that answer consider the following fictional airport examples:

A) runways 36 and 18 have the same frequency and different identifiers, therefore there are two sets of antennae providing localizer and glideslop signals. Someone in the tower has to physically flip a switch to select the active approach.

B) runways 9 has a full ILS and 27 has a localizer backcourse approach. These will be on the same frequency with the same identifier. There is only one set of antennae.

C) Runways 36 and 9 have different frequencies and different identifiers. There are two sets of antennae, just like example A, but there is no need for a switch to activate either approach; both may be on at the same time. You might be inclined to fly the front course for the opposite approach while outbound on the procedure turn rather than accepting reverse sensing. DO NOT DO SO.

The critically important thing to remember:

Consider example C: If there are two separate localizers, one for each end of the pavement, neither may be exactly lined up with the runway centerline. If, in this example, there was an obstruction to the west of each approach course, the designers of the approaches could offset the final approach course up to 3 degrees. So, if each approach course was offset 3 degrees to the east of the runway centerline and you elected to follow an opposite front course outbound rather than tracking the correct front course with reverse sensing, you could be up to 6 degrees off course to the west...towards the obstacles.

Always fly the courses as they are depicted. There is always a reason for the selection of these courses though not always obvious.
 
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