NTSB report - ILS and ATC. How does it all come together?

M wrote:

I don't understand your calculation. At 2.5 miles from the touch-down
zone (assuming that's what it is), the GS should be about 750 feet
above the touch-down zone elevation. The pilot was way below the
glideslope.

3 degree G/s = 318.44 feet per mile. 2.5 (318.44) + 46' TCH = 842 feet.

"Sam Spade" wrote in message
news:A%Slg.179411$bm6.90388@fed1read04...

3 degree G/s = 318.44 feet per mile. 2.5 (318.44) + 46' TCH = 842 feet.


All these calculations assume the full ILS was used. The narrative refers
to a 376' minimum altitude, which was the localizer MDA at the time of the
accident.

Steven P. McNicoll wrote:
"Sam Spade" wrote in message
news:A%Slg.179411$bm6.90388@fed1read04...

3 degree G/s = 318.44 feet per mile. 2.5 (318.44) + 46' TCH = 842 feet.



All these calculations assume the full ILS was used. The narrative refers
to a 376' minimum altitude, which was the localizer MDA at the time of the
accident.


I doubt anyone knows whether he was using LOC or ILS minimuma.

The NTSB doesn't even understand the concepts:

"The ILS 36 has a minimum approach altitude of 376 feet above ground
level (AGL). The cloud ceiling was at 500 feet AGL. After the accident,
the ILS 36 was taken out of service to be tested. It was flight checked
on December 24, 1997, with no anomalies found."

What does "minimum approach alitude" refer to?

What does "376 feet above ground level" refer to?

If the field office investigator can't sort oout MDA, DA, and HAT, I
don't expect to figure out much about his or her's view of how the
approach was being flown.

"Sam Spade" wrote in message
...

I doubt anyone knows whether he was using LOC or ILS minimuma.

The NTSB doesn't even understand the concepts:

"The ILS 36 has a minimum approach altitude of 376 feet above ground level
(AGL). The cloud ceiling was at 500 feet AGL. After the accident, the ILS
36 was taken out of service to be tested. It was flight checked on
December 24, 1997, with no anomalies found."

What does "minimum approach alitude" refer to?


It could only be an MDA.



What does "376 feet above ground level" refer to?


At the time of this accident 440 MSL was the MDA for the S-LOC 36, that's
376 feet above the TDZE of 64 feet.

Steven P. McNicoll wrote:
"Sam Spade" wrote in message
...

I doubt anyone knows whether he was using LOC or ILS minimuma.

The NTSB doesn't even understand the concepts:

"The ILS 36 has a minimum approach altitude of 376 feet above ground level
(AGL). The cloud ceiling was at 500 feet AGL. After the accident, the ILS
36 was taken out of service to be tested. It was flight checked on
December 24, 1997, with no anomalies found."

What does "minimum approach alitude" refer to?



It could only be an MDA.


How do you conclude that?

A decision altitude is a minimum approach altitude, too, in a broad use
of a term that lacks any official definition.

Besides, no one has any way of determining whether the pilot was flying
the LOC or ILS profile.


What does "376 feet above ground level" refer to?



At the time of this accident 440 MSL was the MDA for the S-LOC 36, that's
376 feet above the TDZE of 64 feet.


Yes, but "above ground level" is a term of ignorance. Above ground
level at the crash site, at the runway, or at the DA point, or along the
entire length of the final approach segment where the LOC DMA could
resonably apply?

Sam Spade wrote:

Yes, but "above ground level" is a term of ignorance. Above ground
level at the crash site, at the runway, or at the DA point, or along the
entire length of the final approach segment where the LOC DMA could
resonably apply?

MDA

"Sam Spade" wrote in message
news:A5Vlg.179419$bm6.137774@fed1read04...

How do you conclude that?

A decision altitude is a minimum approach altitude, too, in a broad use of
a term that lacks any official definition.


The term would be "decision height" in the US, not "decision altitude".
It's an MDA because nothing else fits. The DH (Decision Height, the height
at which a decision must be made during an instrument approach where an
electronic glideslope is provided to either continue the approach or to
execute a missed approach) for the full ILS RWY 36 was 264 MSL, 200' above
the TDZE (Touchdown Zone Elevation, the highest elevation in the first 3000'
of runway) of 64'. The MDA (Minimum Descent Altitude, the lowest altitude
to which descent is authorized on final approach in execution of a standard
instrument approach procedure where no electronic glideslope is provided)
for the ILS RWY 36 to straight-in localizer minimums was 440 MSL, 376' above
the TDZE.

Think of an MDA as an altitude to be maintained while a DH is an altitude to
be flown through.



Besides, no one has any way of determining whether the pilot was flying
the LOC or ILS profile.


Yes, I already pointed that out.



Yes, but "above ground level" is a term of ignorance.


Not at all, the term is used quite often in aviation.

Steven P. McNicoll wrote:
"Sam Spade" wrote in message
news:A5Vlg.179419$bm6.137774@fed1read04...

How do you conclude that?

A decision altitude is a minimum approach altitude, too, in a broad use of
a term that lacks any official definition.



The term would be "decision height" in the US, not "decision altitude".
It's an MDA because nothing else fits.

I can't make such an inference from an NTSB report that fails to use the
FAA definitiona, thus creating vagueness where precision is required.

As to the US, the FAA is in transition from DH to DA so they can
harmonize with the rest of the world. You need to catch up on your
reading; i.e., AIM 5-4-5-4:

4. Chart Terminology
(a) Decision Altitude (DA) replaces the familiar term Decision Height
(DH). DA conforms to the international convention where altitudes relate
to MSL and heights relate to AGL. DA will eventually be published for
other types of instrument approach procedures with vertical guidance, as
well. DA indicates to the pilot that the published descent profile is
flown to the DA (MSL), where a missed approach will be initiated if
visual references for landing are not established. Obstacle clearance is
provided to allow a momentary descent below DA while transitioning from
the final approach to the missed approach. The aircraft is expected to
follow the missed instructions while continuing along the published
final approach course to at least the published runway threshold
waypoint or MAP (if not at the threshold) before executing any turns.

The DH (Decision Height, the height
at which a decision must be made during an instrument approach where an
electronic glideslope is provided to either continue the approach or to
execute a missed approach) for the full ILS RWY 36 was 264 MSL, 200' above
the TDZE (Touchdown Zone Elevation, the highest elevation in the first 3000'
of runway) of 64'. The MDA (Minimum Descent Altitude, the lowest altitude
to which descent is authorized on final approach in execution of a standard
instrument approach procedure where no electronic glideslope is provided)
for the ILS RWY 36 to straight-in localizer minimums was 440 MSL, 376' above
the TDZE.

Think of an MDA as an altitude to be maintained while a DH is an altitude to
be flown through.

Thanks for the flying lesson.

Having said that there is no logical reason for the NTSB investigator in
this report to have focused on the HAT of the sraight-in LOC MDA rather
than the HAT of the precision DA. Both should have been discussed since
the pilot could have been flying either the NPA or PA profile.





Yes, but "above ground level" is a term of ignorance.



Not at all, the term is used quite often in aviation.


But, not in reference to approach and landing minimums other than HAA
and HAT, which have precise definitions and are not valid as AGL values
anywhere along the final approach course (excepting CAT II RAs, which
are not applicable to this accident).