Re: loss of glideslope

Date:         30 Mar 99 01:53:30 
From:         "David A. Domino" <>
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In article <airliners.1999.314@ohare.Chicago.COM>, David Lybäck <> wrote:
> I wonder how often it happens (e.g. during heavy precip., esp. snow),
> that you loose glideslope indication during approach.
> It must be a rather difficult mental switch to suddenly start using
> other mean of navigation during approach; can you actually continue with
> only localizer, dist., and radar alt, and make a cat i-iii without
> glideslope ?

In more than 30 years of flying, I have never experienced loss of glideslope
information for any of the reasons you describe. Which is not to say it
can't happen, only that it would be a rare occurance. And it's a good thing
since there is no alternate means of completing a precision ILS approach
without it. In other words there is no alternate method using any of the
navaids you suggest. In some circumstances, an ILS approach may be continued
as a non-precision approach if localizer-only minima are published, which
would typically be substantially higher than those for a full ILS.  However,
if the the weather conditions actually required descent to full-ILS minima,
the only possibility after loss of glidelsope would be a missed approach and
diversion to an alternate airport. The point at which you would abandon the
approach might vary, depending on the operating regulations under which the
approach is conducted, and where in the approach procedure you happened to
be at the time of the failure, but absent an improvement in the weather, you
wouldn't be landing at the original destination.

David A. Domino