On 12/18/2009 12:30 PM, leee wrote:
> I live beneath the turn-in point for clockwise approaches on 05 at
> Stanstead Airport (EGSS)
I assume that was supposed to say runway 04 at Stansted.
^^ ^^^^^^^^
> and most airliners, up to 747s and MD-11s,
> are lined up on the glideslope by about 7.5 nm out from the
> threshold.
Turn point? Lined up?
I thought the topic of this thread was GS range.
GS is not the same as LOC. Anecdotes about "turning"
or "lining up" don't tell us much about the GS.
> In view of what seems to happen at EGSS, I would say that the 14nm
> range & 5000ft altitude seem about right.
According to the authoritative NATS charts, the final
approach fix is at 6.6DME which is about 5.5nm from
the touchdown zone, and occurs at an altitude of
2500 feet, no higher, no lower. For this approach,
GS intercept should occur at the FAF, no earlier, no
later.
The turn onto the localizer, for a no-vector approach,
is 3 or 4 nm farther out than that. The altitude
should be 2500 although 3000 might arguably be tolerated.
Radar-vector procedures will be somewhat more variable,
but not wildly different.
Bottom line: The standard 10nm GS service volume should
be more than plenty for the EGSS RWY 04 approach.
More generally: Limiting the GS service volume to 10nm
or thereabouts is a significant departure (if you'll
pardon the expression) from previous FGFS behavior, but
it is not wrong. It is a feature, not a bug.
References:
http://www.nats-uk.ead-it.com/aip/current/ad/EGSS/EG_AD_2_EGSS_7-14_en.pdf
http://www.nats-uk.ead-it.com/aip/current/ad/EGSS/EG_AD_2_EGSS_8-1_en.pdf
=========================================
Worrying about GS service volume seems off-scale
unimportant relative to other issues. For starters,
Stansted has a reversible ILS. The code to handle
reversible ILSs in FG has been broken for years, and
actually got worse recently.
The code to make it possible to fly at airports with
reversible ILSs has been available for a long time.
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