Re: Korean Air 801 crashed on approach to Guam

Date:         08 Aug 97 05:41:21 
From:         lstone@wwa.com (Larry Stone)
References:   1 2 3
Next article
View raw article
  or MIME structure

In article <airliners.1997.1717@ohare.Chicago.COM>,
"[non-spam]jfmezei"@videotron.ca wrote:

>Could someone put this missing glide slope in perspective ?

It may be a factor but on its own it is not the cause.

>Just how important is it to a landing in darkness with little or no
>visibility ? What other instruments/information would have been
>available to the pilot to help him stay on track to the runway ?

The glide slope provides vertical navigation inofrmation. Precision
instrument approaches include both horizontal and vertical navigation
aids. "Non-precision" aprroaches (such as a VOR approach) do not include
vertical navigation aids.

Most airports have multiple instrument approaches. A full ILS includes
both a glide slope for vertical information and a "localizer" for
horizontal information. Most ILS approaches, as published, also incluse
localizer-only minimums for use when the glide slope is inop.

>Is it plausible that the missing glide slope would have resulted in the
>plane being much lower than it should have been in its approach ?

Only due to pilot error. A non-precision approach, including an ILS
localizer-only approach, will have higher descent minimums than a
precision approach. You do not go below those minimum altitudes until you
have the runway in sight and are in position to make a normal landing.

>How common is it for the glide slope to be inoperational for airports
>that handle 747s on a daily basis ? Is this a no-brainer for pilots when
>it is missing, or does this require a lot more attention ?

Yes and yes. It should be a no-brainer but it does require more attention
to fly a non-precision approach. Unfortunately, evidence from other
incidents suggest that many airline pilots get so used to flying easy
approaches day in and day out that when something is down, they're thrown
for a loop.

--
-- Larry Stone --- lstone@wwa.com
   http://www.wwa.com/~lstone/
   Schaumburg, IL, USA