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

Steven P. McNicoll wrote:
"Mike" wrote in message
. ..
Using trigonometry, I get ~ 785ft 2.5 miles out from the touch down zone,
so your method is pretty accurate. Here's my calculation:

Assuming:
Distance = 15,000 ft
Slope: 3 degrees

Height = Distance * sin(Slope) = 785.04 ft.


A 3 degree glidepath descends 318 feet per nautical mile. 318 x 2.5 = 795.


Sorry, the original calculation was based on bad data. 15,000 feet is
not 2.5nm as stated in the original post.

1nm = 6,076ft
2.5nm = 15,190ft
Elevation = 15,190 * sin(3-degrees) = 795 ft


--
Mike

Mike wrote:
Steven P. McNicoll wrote:
"Mike" wrote in message
. ..
Using trigonometry, I get ~ 785ft 2.5 miles out from the touch down
zone, so your method is pretty accurate. Here's my calculation:

Assuming:
Distance = 15,000 ft
Slope: 3 degrees

Height = Distance * sin(Slope) = 785.04 ft.


A 3 degree glidepath descends 318 feet per nautical mile. 318 x 2.5 =
795.

Sorry, the original calculation was based on bad data. 15,000 feet is
not 2.5nm as stated in the original post.

1nm = 6,076ft
2.5nm = 15,190ft
Elevation = 15,190 * sin(3-degrees) = 795 ft


Sorry for the double post. Last send just "hung" so I resent thinking it
didn't send the first time.

--
Mike

Mike wrote:
Steven P. McNicoll wrote:

"Mike" wrote in message
. ..

Using trigonometry, I get ~ 785ft 2.5 miles out from the touch down
zone, so your method is pretty accurate. Here's my calculation:

Assuming:
Distance = 15,000 ft
Slope: 3 degrees

Height = Distance * sin(Slope) = 785.04 ft.


A 3 degree glidepath descends 318 feet per nautical mile. 318 x 2.5 =
795.

Sorry, the original calculation was based on bad data. 15,000 feet is
not 2.5nm as stated in the original post.

1nm = 6,076ft
2.5nm = 15,190ft
Elevation = 15,190 * sin(3-degrees) = 795 ft


The TCH is 46 feet, so the G/S is 842 feet about TDZ at 2.5 miles from
the threshold.

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.