Marco Leon wrote:
I like reading Richard Collins's stuff but he was a bit of a wise-ass in
that exchange. It seems to me the fundamental issue is their preference to
the Jeppesen way of charting step down segments versus the NACO way. I'm
surprised you didn't stress the underlining of the segment altitudes as
NACO's way of identifying the level-off altitudes in a LNAV-only approach as
opposed to the Jepp way of depicting the step-downs visually with the line.

That said, with the advent of LPV and the increased frequency of one chart
showing both precision* and non-precision approaches, Jeppesen's method will
create less confusion to the average pilot (especially in bumpy IMC). In a
pure "legalese" view, you are correct in that the NACO chart is not charting
the approach "incorrectly." However, I think they have a legitimate gripe in
taking issue with the way NACO charts the step-downs in GPS approaches with
mixed LPV-LNAV/VNAV-LNAV minima. What makes their case a bit stronger is the
fact the WAAS GPS units will default to the LPV approach as long as the
HAL/VAL is within limits and (at least in the 430/530 series) there is no
way of manually choosing the LNAV-only approach. Therefore the majority of
the time the approach will be flown closer to the Jeppesen visual
representation rather than the NACO's representation.

Using the CRQ RNAV(GPS) RWY 24 chart you used in the email exchange, a
typical LPV approach will have the aircraft level-off at 3,100 ft between
KANEC and JABAL with glideslope intercept occurring at JABAL. The NACO chart
shows this transition only with the [thin] lightening bolt whereas the Jepp
shows it quite clearly with the visual step down depiction. Like you stated,
neither way is wrong but Jepp is just clearer IMO.

Question for you. You say that the sloping outside JABAL is "advisory only."
Given the typical GPS T-configuration, would anyone be expected as standard
practice to actually intercept the glideslope at KANEC? Also, If you're on
the glideslope at JABAL, your altitude should be 3,100 feet (or close to it)
correct? Therefore, if you choose to follow the advisory glideslope at
KANEC, would your altitude be 3,800 feet? If one can not expect to
cross-check their altitude at KANEC with the depicted altitude of 3,800 ft.,
it would be another misleading representation (notice I didn't say
"incorrect").

I look forward to your point of view.

Regards,

Marco
Last first: LPV IAPs are indeed precision IAPs.

And, let me add, my entire professional life has been with Jeppesen charts.

But, I work with TERPS and the FAA a lot. NACO charts are the FAA's
method of charting IAP source. So, if they were wrong, they need to be
called on it. But, if is an issue of style, and Collins feels strongly
enough about it, he is welcome to attend the semi-annual FAA/Industry
Aeronautical Charting Forum, even submitting an issue paper in advance.
(His attendance has been mentioned to him before).

At CRQ let's say I am flying the terminal routing from OCN. I would not
receive an LPV G/S on a Garmin 400/500W series navigator until crossing
KANAC at 3800. the LPV G/S would be a full fly-up because the G/S at
KANEC would be just over 5100. (So, there is no cross-check info for
that provided by either Jepp or NACO, nor should there be.) I can
choose to maintain 3800 until G/s intercept (just over 2 miles prior to
JABEL, or descend to 3100 to intercept at JABAL. Will the G/S be
precisely 3100 at JABEL? That depends on altimeter error, just like
with an ILS.