SDF?

[Tlewis95]

Im new to IFR and was wondering what an SDF approach is.

Thanks!

[Ron Natalie]

Tlewis95 wrote:
> Im new to IFR and was wondering what an SDF approach is.
>
> Thanks!

The AIM is your friend. If you are a pilot, you should have one.
It's in chapter 1-1-10. A SDF (Simplified Directional
Facility) essentially a localizer type facility but it has a wider
(6 or 12 degree) course width. It also might not be aligned with
the runway. I can't recall ever actually seeing one in real life,
but I'm sure people will pipe up with their favorites.

This is different from an LDA, which is a localizer that just isn't
aligned with a runway. We've got an LDA here into National Airport.
It even has a glide slope, it just doesn't take you anywhere near
the airport.

[G Farris]

In article >,
says...
>
>Im new to IFR and was wondering what an SDF approach is.
>

Look it up in any book, and you'll find probably a full paragraph, indicating
the amount of printing ink the publishers wish to squander on this approach -
the SDF (Simplified Directional Facility, IIRC) is like a LOC approach, except
instead of being aligned with a friendly runway it's aligned with a big old
tree or communications antenna several degrees off the extended centerline.
Lateral precision is reduced, compared with a LOC, and MDA is correspondingly
higher.

There are very few of them left - SME (Somerset KY) was one of them, until a
KingAir took out a communications tower a few years back.

I think you can pretty much bank on them being phased out entirely pretty
soon, though I wouldn't want to put a time scale on that.

G Faris

[John R. Copeland]

"Ron Natalie" > wrote in message =
m...
> Tlewis95 wrote:
>> Im new to IFR and was wondering what an SDF approach is.
>>=20
>> Thanks!
>=20
> The AIM is your friend. If you are a pilot, you should have one.
>=20

And even if you don't have one, you still can read it on the web.
http://www.faa.gov/ATPubs/AIM/index.htm
---JRC---

[Ron Natalie]

G Farris wrote:

>
> Look it up in any book, and you'll find probably a full paragraph, indicating
> the amount of printing ink the publishers wish to squander on this approach -
> the SDF (Simplified Directional Facility, IIRC) is like a LOC approach, except
> instead of being aligned with a friendly runway it's aligned with a big old
> tree or communications antenna several degrees off the extended centerline.
> Lateral precision is reduced, compared with a LOC, and MDA is correspondingly
> higher.

The above is the definition of an LDA.

[G Farris]

In article >,
says...
>
>G Farris wrote:
>
>>
>> Look it up in any book, and you'll find probably a full paragraph,
indicating
>> the amount of printing ink the publishers wish to squander on this approach
-
>> the SDF (Simplified Directional Facility, IIRC) is like a LOC approach,
except
>> instead of being aligned with a friendly runway it's aligned with a big old
>> tree or communications antenna several degrees off the extended centerline.
>> Lateral precision is reduced, compared with a LOC, and MDA is
correspondingly
>> higher.
>

>The above is the definition of an LDA.

Well, no. The LDA has the same characteristics as a localizer, but is not
aligned with the runway. The SDF has reduced lateral precision, and may not be
aligned with the runway.

G Faris

[Andrew Sarangan]

For all practical purposes, you can treat the LDA and SDF as a poorly
designed Localizer approach. LDA is not aligned with the runway, and
SDF may or may be aligned and has a larger course width. Here are some
examples: LDA/DME-18 @ TVL, LDA-C @ VNY, SDF10 @ DWU



(Tlewis95) wrote in message >...
> Im new to IFR and was wondering what an SDF approach is.
>
> Thanks!

[DH]

I have shot many SDF approaches. The difference is it's either 6 or 12
degrees and you don't know which. As long as the needle is in the center it
doesn't matter. Usually you are aligned with the runway, but it may not
align you with the runway, as are some ILS approaches. There is NOTHING
wrong with these approaches.

"Andrew Sarangan" > wrote in message
om...
> For all practical purposes, you can treat the LDA and SDF as a poorly
> designed Localizer approach. LDA is not aligned with the runway, and
> SDF may or may be aligned and has a larger course width. Here are some
> examples: LDA/DME-18 @ TVL, LDA-C @ VNY, SDF10 @ DWU
>
>
>
> (Tlewis95) wrote in message
> >...
>> Im new to IFR and was wondering what an SDF approach is.
>>
>> Thanks!

[Ron Natalie]

DH wrote:
> I have shot many SDF approaches. The difference is it's either 6 or 12
> degrees and you don't know which.

Of course you don't know what the angular course width of a real localizer
is either, but it's going to be narrower than 6 degrees.

[Gerry Caron]

"Ron Natalie" > wrote in message
m...
> DH wrote:
> > I have shot many SDF approaches. The difference is it's either 6 or 12
> > degrees and you don't know which.
>
> Of course you don't know what the angular course width of a real localizer
> is either, but it's going to be narrower than 6 degrees.
>
To be picky; it will be 6 degrees or less, down to a minimum of 3 degrees.

And if you really want to know what the course width is, you can look it up
(along with every other bit of data) at the FAA flight inspection (AVN) web
site:

http://avnwww.jccbi.gov/datasheet/

[Andrew Sarangan]

"DH" > wrote in
:

> I have shot many SDF approaches. The difference is it's either 6 or
> 12 degrees and you don't know which. As long as the needle is in the
> center it doesn't matter. Usually you are aligned with the runway, but
> it may not align you with the runway, as are some ILS approaches.
> There is NOTHING wrong with these approaches.
>
> "Andrew Sarangan" > wrote in message
> om...
>> For all practical purposes, you can treat the LDA and SDF as a poorly
>> designed Localizer approach. LDA is not aligned with the runway, and
>> SDF may or may be aligned and has a larger course width. Here are
>> some examples: LDA/DME-18 @ TVL, LDA-C @ VNY, SDF10 @ DWU
>>
>>
>>


Actually I don't know why they make a big deal about it because the
approach chart clearly shows the alignment of the final course with the
runway. Why not call all of them LOC approaches, and leave it to the pilot
to figure out the extent of the misalignment?

[jharper aaatttt cisco dddooottt com]

So what exactly is the point of an SDF versus a normal
localizer? Is it cheaper? Or what?

In fact a lot of these approaches are a bit bizarre.
The LDA @ TVL makes perfect sense. If the localizer was
aligned with the runway, they'd have to make a big tunnel
through the mountains to the east of the lake. That would
be expensive, so a non-aligned localizer is a good idea -
especially since the MDA is >1000' AGL so you've got plenty
of time to line up with the runway.

The LDA @ VNY is a Terpster's joke. By coincidence the
ILS @ BUR happens to cross the end of the VNY main runway,
and the BUR OM is actually on VNY. So it's a case of "charting
it because it's there". I can't imagine that anyone would
actually use it (other than for practice), especially since
VNY has a perfectly fine ILS.

As for the SDF @ DWU, I can't see anything which makes this
better than a LOC approach...?

John

Andrew Sarangan wrote:
> For all practical purposes, you can treat the LDA and SDF as a poorly
> designed Localizer approach. LDA is not aligned with the runway, and
> SDF may or may be aligned and has a larger course width. Here are some
> examples: LDA/DME-18 @ TVL, LDA-C @ VNY, SDF10 @ DWU
>
>
>
> (Tlewis95) wrote in message >...
>
>>Im new to IFR and was wondering what an SDF approach is.
>>
>>Thanks!
>

[Bob Moore]

"jharper wrote

> As for the SDF @ DWU, I can't see anything which makes this
> better than a LOC approach...?

After my retirement from PanAm, I instructed at DWU for about
six years. I can offer the following speculations.

The SDF was initially purchased, installed, and maintained by
the Ashland Oil and Refining Corp. for use by their fleet of
Citations and Falcons. The installation and maintenance costs,
flight checks, etc. may have been much less for an SDF. Now
that Ashland has moved the Corporate Headquarters to the CVG
area, there is/has been talk about removing the SDF due to a
lack of funds available to the Airport Board for maintenance.

Another problem may have been the multiple hills along the
approach course that may have interfered with the required
precision for a true LOC installation.

Sure wish that I had a nickle for every SDF approach that I
conducted there with an instrument student! :-)

Bob Moore

[Doug]

The LDA at Juneau has higher minimums than the NDB. They use the same
approach path. Go figure.

"jharper aaatttt cisco dddooottt com" <"jharper aaatttt cisco dddooottt com"> wrote in message news:<1099637784.56510@sj-nntpcache-5>...
> So what exactly is the point of an SDF versus a normal
> localizer? Is it cheaper? Or what?
>
> In fact a lot of these approaches are a bit bizarre.
> The LDA @ TVL makes perfect sense. If the localizer was
> aligned with the runway, they'd have to make a big tunnel
> through the mountains to the east of the lake. That would
> be expensive, so a non-aligned localizer is a good idea -
> especially since the MDA is >1000' AGL so you've got plenty
> of time to line up with the runway.
>
> The LDA @ VNY is a Terpster's joke. By coincidence the
> ILS @ BUR happens to cross the end of the VNY main runway,
> and the BUR OM is actually on VNY. So it's a case of "charting
> it because it's there". I can't imagine that anyone would
> actually use it (other than for practice), especially since
> VNY has a perfectly fine ILS.
>
> As for the SDF @ DWU, I can't see anything which makes this
> better than a LOC approach...?
>
> John
>
> Andrew Sarangan wrote:
> > For all practical purposes, you can treat the LDA and SDF as a poorly
> > designed Localizer approach. LDA is not aligned with the runway, and
> > SDF may or may be aligned and has a larger course width. Here are some
> > examples: LDA/DME-18 @ TVL, LDA-C @ VNY, SDF10 @ DWU
> >
> >
> >
> > (Tlewis95) wrote in message >...
> >
> >>Im new to IFR and was wondering what an SDF approach is.
> >>
> >>Thanks!
> >