Flying Mag Clueless about LPV and NACO

Airbus wrote:
In article , says...


Airbus wrote:

In article , says...


John T wrote:


Oh, I did write them about it.

They erected a giant stone wall.





Maclellan says some readers took him to task for claiming that an LPV was flown
exactly like an ILS. He and Collins surmised that some of the confusion could
be attributed to charting ambiguities on NACO charts. This indeed seems to be a
pet peeve of theirs, as Collins goes into it in one of the Sporty's videos as
well, and uses the same DMW approach as an example, if I recall.

The gripe seems to be that the profile view in the NACO chart does not show a
stepdown, as the Jepp does, neatly intercepting the glideslope from below. In
purely graphical terms, they have a point. An architect would agree it's
misleading, and the continuous, sloping line on the NACO chart suggests a fixed
descent rate from the IF would have you magically intercept the glideslope at
the right place and altitude and even on the correct slope, which of course is
not true, and is not the way it's flown.

You argue this is a conventional depiction, unchanged from the way they have
always depicted ILS's and simply knowing the convention allows the pilot to fly
it correctly and intercept at the right altitude at the lightning bolt. You
certainly have a point as well, but if it were that clear and simple perhaps
there would have been fewer confused readers writing to Mac because they didn't
understand how to fly the approach.

We don't know what those readers wrote, but perhaps he has some reason to
believe their confusion stems in part from an imperfect charting convention,
which could stand some clarification.

Readers are often confused. It is the duty of the editors to have
sufficient knowledge to help their readers out. If the editors don't
possess sufficient knowledge in fundamental technical areas, such as the
case in point, then they should seek out expert advice, perhaps in this
case from both the flight procedures experts at the FAA and the charting
experts at NACO.

They apparently missed the point that the NACO altitudes with an
underscore govern in any segment other than a precision final approach
segment. They also apparently misunderstood the cartographic license
that Jeppesen used for the feather and that NACO uses in a more advisory
sense, and not at all on NACO LPV charts.

I also took the trouble to show them a Jepp and NACO charting of a
strictly non-precision RNAV IAP (first F70, then at "their" airport
DMW.). But, that seems to fly right over their collective heads. And,
they made no effort to be fair or make rebuttals, observations, and
perhaps (yegads!) ask some reasonable questions.

As you can see, as a paid subcriber I tried to help, but only revceived
rude treatment at their hands.

The NACO sloping line is cartographic license. They have done it this
way for years. It does not govern. The segment underscored altitudes
govern. Look at the NACO chart for the ILS 25L at LAX for an example of
an extended ILS profile.

Unlike Jeppesen, who mostly sets its own standards, NACO is governed as
to charting specs by an inter-government panel (FAA and military "IACC")
who established government charting specifications to the nth degree.
These guys aren't a bunch of numbskulls so they presumably had their
good reasons for going with the sloping but *advisory* provfile line
many years ago.

Flying Magazine, just like other aviation user groups, has the
semi-annual FAA/Idustry Aeronautical Charting Forum available to air its
technical concerns about instrument procedures and all forms of
charting. I recommened that to Collins as a venue open to him several
years ago when he ignorantly and incorrectly critized FAA procedure
design. But, that went unanswered and unheeded.

As a reader, I find their ignorance in this area understandable,
although it brings into question their editorial standards. But, as to
their unwillingness to listen or seek expert advice, I do not have much
understanding of that.

On Fri, 02 May 2008 07:25:22 -0700, Sam Spade
wrote:


They apparently missed the point that the NACO altitudes with an
underscore govern in any segment other than a precision final approach
segment.

Right. The underscore should _always_ grab a pilot's attention.

As you can see, as a paid subcriber I tried to help, but only revceived
rude treatment at their hands.

I don't think they even bothered to try to understand your point.

The NACO sloping line is cartographic license.

Just as it does where course reversals are depicted. I've never seen
a course reversal depicted where the slope made sense, so I always
read it as Cross "X" @ NNNN, descend to NNNN and cross "Y", then
descend to NNNN to cross "Z". I never assume the slope to mean
anything other than "descend", as opposed to "level" as depicted for
holds and some procedure turns.

I don't see why the "FLYING" folks were so confused.

On Fri, 02 May 2008 07:35:13 -0700, Airbus wrote:

The gripe seems to be that the profile view in the NACO chart does not show a
stepdown, as the Jepp does, neatly intercepting the glideslope from below. In
purely graphical terms, they have a point. An architect would agree it's
misleading, and the continuous, sloping line on the NACO chart suggests a fixed
descent rate from the IF would have you magically intercept the glideslope at
the right place and altitude and even on the correct slope, which of course is
not true, and is not the way it's flown.

It always seemed pretty obvious to me based on the crossing altitudes,
but again, I don't have much experience with Jepp charts.

When one section of the continuously sloping line descends 200-400
feet, and the other (after the lightning bolt) goes from say, 2200 to
400 AGL, it's obviously not to scale.

Kind of like the 10 MN ring...