Localizer Back Course vs. ILS

[ilsub]

Hello.
My home base airport (KOSU) has ILS 9R approach and NDB 27L approach.
My question is,
Can they have Localizer Back Course 27L?
I am wondering if the signal is always avaialble on the reverse
side of Localizer. Or should there be something extra to have
Localizer back course?

I tested the signal while landing on runway 27L, and it seemed that
the signal was available. But there is no published instrument
approach like Localizer back course 27L approach.

Can you give me input on this?
I think Localizer Back course would be more accurate than NDB
approach.

Thank you.
Ilsub Jung

[Bob Gardner]

Not always. AIM 1-1-9 cautions against using the back course signal unless
an approach has been authorized. At some locations, the back course is
screened off in some way to make it unavailable (don't know the details). I
would be reluctant to fly the back course in actual IMC just because it
exists.

Bob Gardner

"ilsub" > wrote in message
om...
> Hello.
> My home base airport (KOSU) has ILS 9R approach and NDB 27L approach.
> My question is,
> Can they have Localizer Back Course 27L?
> I am wondering if the signal is always avaialble on the reverse
> side of Localizer. Or should there be something extra to have
> Localizer back course?
>
> I tested the signal while landing on runway 27L, and it seemed that
> the signal was available. But there is no published instrument
> approach like Localizer back course 27L approach.
>
> Can you give me input on this?
> I think Localizer Back course would be more accurate than NDB
> approach.
>
> Thank you.
> Ilsub Jung

[Ron Natalie]

"Roy Smith" > wrote in message ...

>
> A proper "flight check" involves an FAA aircraft filled with fancy
> electronics which checks the signal for strength, accuracy, etc, not
> just on the centerline, but also at the edges of the approach corridor.
> The "test" you did yourself just isn't good enough.

The loc offset for 9R is 5 degrees, pretty close to the max allowed (5).
The back course might point you off into some obstacle.

You could always get a GPS there are GPS approaches to both ends of
the runway :-)

[[email protected]]

ilsub wrote:

> Hello.
> My home base airport (KOSU) has ILS 9R approach and NDB 27L approach.
> My question is,
> Can they have Localizer Back Course 27L?
> I am wondering if the signal is always avaialble on the reverse
> side of Localizer. Or should there be something extra to have
> Localizer back course?
>
> I tested the signal while landing on runway 27L, and it seemed that
> the signal was available. But there is no published instrument
> approach like Localizer back course 27L approach.
>
> Can you give me input on this?
> I think Localizer Back course would be more accurate than NDB
> approach.
>
> Thank you.
> Ilsub Jung

Back courses are more often not available to flight inspection tolerances
for approaches because of shielding of the antennas to make the front
course perform to requirements.

[[email protected]]

Greg Esres wrote:

> <<The loc offset for 9R is 5 degrees, pretty close to the max allowed
> (5).>>
>
> TERPS says that any localizer that's more than 3 degrees off will be
> identified as an LDA. Where does your 5 degrees figure come from?

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

[Greg Esres]

<<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.

[[email protected]]

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.

[Greg Esres]

<<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.

[Ron Natalie]

"Greg Esres" > wrote in message ...
> <<The loc offset for 9R is 5 degrees, pretty close to the max allowed
> (5).>>
>
> TERPS says that any localizer that's more than 3 degrees off will be
> identified as an LDA. Where does your 5 degrees figure come from?
>
The number in the parens is a typo. Second, I made a mistake. When I
looked up the runway heading, I didn't notice that I was reading the true
runway heading. Add in the 5W variation at OSU and the runway heading
is precisely aligned with the localizer course. Never mind :-)