Localizer Back Course vs. ILS

Greg Esres wrote:

One pertains to course width, the other to course offset.

No, I don't think so. A localizer can be 3-6 degrees in width, so
that goesn't jibe with either my figure or Ron's.

Well, here are the pertinent TERPS criteria. There is no criterion for
a 5-degree offset. It goes from LOC to LDA at 3 degrees offset, and a
back course cannot be offset at all, nor can a back course have a course
width in excess of 6 degrees:

901. USE OF LOCALIZER ONLY. Where no usable glidepath is available, a
localizer-only (front or back course) approach may be approved, provided
the approach is made on a LOC from a FAF located within 10 miles of the
runway threshold. Criteria in this section are also applicable to
procedures based on localizer type directional aids (LDA). Back course
procedures shall not be based on courses that exceed 6° in width and
shall not be approved for offset LOC.
{New-2002-24 902 Revised May 15, 2002}
902. ALIGNMENT. Localizers which are aligned within 3° of the runway
alignment shall be identified as localizers. If the alignment exceeds
3°, they will be identified as LDA facilities. The alignment of the
course for LDA facilities shall meet the final approach alignment
criteria for VOR on-airport facilities. See chapter 5, paragraph 513,
and figure 48.

There is no criterion for a 5-degree offset. It goes from LOC to
LDA at 3 degrees offset,

And that was the substance of my original post. I asked Ron where he
got the 5 degree figure. He said 5 degrees was the maximum offset for
a LOC.