False glideslopes -- NZ60

An interesting thread on AirDisaster.com (including video) discusses
the false glideslope indications that nearly did in an Air New Zealand
flight some years ago. This is particularly interesting given that
the FAA no longer seems to require an outer marker or equivalent on
ILS approaches, making it much harder to check for correct glideslope
indications.

http://airdisaster.com/forums/showthread.php?t=83775

Here's an excerpt from an article linked in the 7th post in that
thread that explains why it happened:

"On the night of July 29, 2000, the glideslope sidelobe amplifier was
not operating in Apia. In addition, the ILS ground equipment had been
left in bypass mode following calibration maintenance. This prevented
system transfer to the standby transmitter. No alarm sounded in the
control tower because the cable that fed information to the tower
navigation status displays had been cut during construction. As a
result, the Air New Zealand flight received only the glideslope
carrier wave transmission, which was interpreted by the instruments as
being on glideslope, with no warning indications."

In article .com,
wrote:

This is particularly interesting given that
the FAA no longer seems to require an outer marker or equivalent on
ILS approaches, making it much harder to check for correct glideslope
indications.

That's news to me -- I thought they had only done away with the *middle*
marker, no?

Buck Murdock wrote:
In article .com,
wrote:


This is particularly interesting given that
the FAA no longer seems to require an outer marker or equivalent on
ILS approaches, making it much harder to check for correct glideslope
indications.


That's news to me -- I thought they had only done away with the *middle*
marker, no?

Although the FAA hasn't decommissioned existing OMs, it is no longer a
required check. There are ILSes, for example, where the G/S can only be
cross-checked with DME, yet DME is not required for the full ILS.

The issue that occurred in Oz was the result of bad maintenance
practices. The FAA claims that will never happen here ;-)

LPV does not have this problem.

BTW - I don't seem to see the old inner markers as much as I did 30
years ago. Haven't really even thought about it until just this thread,
but are they actually decommissioning those or just not installing new
ones?


-----Original Message-----
From: Sam Spade ]
Posted At: Tuesday, January 30, 2007 9:04 AM
Posted To: rec.aviation.ifr
Conversation: False glideslopes -- NZ60
Subject: False glideslopes -- NZ60

....

Although the FAA hasn't decommissioned existing OMs, it is no longer a
required check. There are ILSes, for example, where the G/S can only
be
cross-checked with DME, yet DME is not required for the full ILS.

....

Jim Carter wrote:

BTW - I don't seem to see the old inner markers as much as I did 30
years ago. Haven't really even thought about it until just this thread,
but are they actually decommissioning those or just not installing new
ones?

I believe inner markers are mandatory on CAT II approach procedures.
Every CAT II in the western U.S. that I looked up has an inner marker.

On Jan 30, 7:04 am, Sam Spade wrote:
Although the FAA hasn't decommissioned existing OMs, it is no longer a
required check. There are ILSes, for example, where the G/S can only be
cross-checked with DME, yet DME is not required for the full ILS.

Well maybe not technically decommissioned, but the ILS27R at Oakland
was redesigned and they stopped using the outer marker (Cases) in
favor of a DME fix about 1/2 mile away. The outer marker is still
there, and I believe it shows up as a grayed out fan marker on Jepp
plates, but not at all on government plates. Are there others? I'd
guess so.

wrote:

On Jan 30, 7:04 am, Sam Spade wrote:

Although the FAA hasn't decommissioned existing OMs, it is no longer a
required check. There are ILSes, for example, where the G/S can only be
cross-checked with DME, yet DME is not required for the full ILS.


Well maybe not technically decommissioned, but the ILS27R at Oakland
was redesigned and they stopped using the outer marker (Cases) in
favor of a DME fix about 1/2 mile away. The outer marker is still
there, and I believe it shows up as a grayed out fan marker on Jepp
plates, but not at all on government plates. Are there others? I'd
guess so.


In that case the P-FAF was moved to be coincident with the non-precision
FAF, if I recall correctly. And, yes, the Jepp chart still shows the OM
grayed out.

On Jan 31, 2:59 am, Sam Spade wrote:

In that case the P-FAF was moved to be coincident with the non-precision
FAF, if I recall correctly.

Why is that important? I guess its easy to do if you're using DME
fixes, but why do that if you're not going to decommission the outer
marker?

wrote:
On Jan 31, 2:59 am, Sam Spade wrote:

In that case the P-FAF was moved to be coincident with the non-precision
FAF, if I recall correctly.


Why is that important? I guess its easy to do if you're using DME
fixes, but why do that if you're not going to decommission the outer
marker?


It is a current FAA policy. If I ever heard the reason, I don't recall
it now. I do know the tower chief at Oakland got upset over the change,
but national policy ruled.

Are you speaking to outer marker or Compass Locator at the Outer Marker?
Al.

wrote in message
oups.com...
On Jan 30, 7:04 am, Sam Spade wrote:
Although the FAA hasn't decommissioned existing OMs, it is no longer a
required check. There are ILSes, for example, where the G/S can only be
cross-checked with DME, yet DME is not required for the full ILS.

Well maybe not technically decommissioned, but the ILS27R at Oakland
was redesigned and they stopped using the outer marker (Cases) in
favor of a DME fix about 1/2 mile away. The outer marker is still
there, and I believe it shows up as a grayed out fan marker on Jepp
plates, but not at all on government plates. Are there others? I'd
guess so.