Re: Cleared for the approach and altitude

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Thanks Ron, I was wrong. I guess I meant to say is that at 5000 feet
msl on the g/s, you are probably before the feather, and outside the
"safe" g/s signal distance (depending on airport altitude). And as
you pointed out, perhaps below the terps altitudes even if the signal
was accurate.
Stan

On Tue, 24 Sep 2002 10:34:02 -0400, Ron Rosenfeld
<ronrosenfeld@nospam.org> wrote:

>On Wed, 11 Sep 2002 23:07:13 GMT, pstanley55@hotmail.com wrote:
>
>>Starting descent at 5000 feet on the g/s is fine, but be aware of the
>>significance of the feather on the instrument app chart. This is
>>where you can rely on g/s and loc signal integrity.
>
>Not so. The beginning of the feather (Jepp Charts) indicates the FAF for
>the precision approach. However, signal integrity is assured over a much
>larger area. The feather is usually starts about 5 NM from the threshold.
>The localizer is usually good up to 18 NM from the antenna, and the glide
>slope should be good to at least 10 NM.
>
>More importantly, there are a very few approaches where following the GS
>down from a higher altitude may result in an inappropriately low altitude
>under certain conditions. However, examination of the chart should reveal
>this anomalies. If I recall correctly, there may be step-down fixes
>between the IAF and the FAF which may keep you above the GP under certain
>conditions of atmospheric pressure. The problem is that the upper limit of
>an underlying CZ expands and may occasionally encroach on the GP -- since
>the GP is a fixed point in space, and the upper limit of a CZ depends on
>the altimeter in the a/c.
>
>
>References (AIM):
>
>1-1-9.b.5. The localizer provides course guidance throughout the descent
>path to the runway threshold from a distance of 18 NM from the antenna
>between an altitude of 1,000 feet above the highest terrain along the
>course line and 4,500 feet above the elevation of the antenna site. Proper
>off-course indications are provided throughout the following angular areas
>of the operational service volume:
>
> (a) To 10 degrees either side of the course along a radius of 18 NM
>from the antenna; and
>
> (b) From 10 to 35 degrees either side of the course along a radius
>of 10 NM.
>
>1-1-9.d.3. The glide path projection angle is normally adjusted to 3
>degrees above horizontal so that it intersects the MM at about 200 feet and
>the OM at about 1,400 feet above the runway elevation. The glide slope is
>normally usable to the distance of 10 NM. However, at some locations, the
>glide slope has been certified for an extended service volume which exceeds
>10 NM.
>
>
>
>Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)