Not quite.

First one has to remain mindful that only aircraft on the South side of ZEDAG will fly the Hold In-Lieu of Procedure Turn (HILPT).

http://i202.photobucket.com/albums/a...psb6f228df.png

Aircraft arriving on the NoPt side do not utilize the pattern -- the TAA has already provided consideration to descent gradient as well as course alignment.
6300' minimum within 30 nm, then 4300 from 4nm to the IF (ZEDAG).

The minimum holding altitude at ZEDAG is 4300, indicated by the underscore.

http://i202.photobucket.com/albums/a...ps3d3f6951.png

The 4300' value is only a chance coincidence with the inner NoPT TAA sector on the North side.

The obstacle clearance assessment template for the HILPT is vastly different from the the TAA obstacle evaluation criteria.

Thanks for the link you sent, Zeffy.

"Aircraft arriving on the NoPt side do not utilize the pattern" does not really answer my question "If I want to join the hold from that inbound, what then?" - I am thinking 'outside' the RNAV procedure as for this aircraft. Should I then abandon the RNAV chart and fly the LOC/DME hold at INDRA? IE Is the ZEDAG hold PURELY for the RNAV procedure and not for 'general' holding?

I see, out of interest from your link, that the ACTUAL MSA inbound ALMOST to ZEDAG from the south-east is only 1800' becoming 4100' at ZEDAG.

Why simple, basic MSAs are not published on the RNAV chart escapes me!

Aterpster - where did Jepp get 2725' for the dominant obstacle from?

You don't want an MSA. If you had one, which goes out to 25 miles, it would be at the higher altitude which is unnecessary. With the magic of GPS showing distance from a waypoint you can descend once past the higher terrain that may be for example, 15 miles from the airport. Plus, in the U.S. the MSA is an emergency only altitude, so the approach would be much more restrictive in terms of letting down within 30 miles.

"If you had one, which goes out to 25 miles, it would be at the higher altitude which is unnecessary." - not so - see the post you have replied to - 1800/4100?

MSAs are not operational altitudes in the U.S. Terminal Arrival Areas (TAAs) appear on a fairly small percentage of FAA RNAV instrument approach procedures. TAAs are operational altitudes and are considered the equivalent of feeder routes. RNAV IAPs with TAAs do not have MSAs published.

ZEDAG is the course reversal hold for this IAP (RNAV RWY) 19 and it is also the missed approach holding pattern for the RNAV Rwy 01 IAP.

There is no way that ATC can get anyone onto this procedure at less than 5,000 because of the Anchorage Center's MIA. A pilot entering the procedure must be at not less than 5,400 if entering the south TAA or not less than 6,300 if entering the north TAA.

As to the spot obstacle Jeppesen shows on the RNAV 19 chart, they do that in-house using their own topographical data. The source I have is the U.S. 1:50,000 topo map for that area. I'll post the significant portion of that topo chart.

This is the Jepp "2750" terrain point. As you can see it is not 2,750...not quite. The FAA chart shows 2,550 at approximately the same location. These cartographic features are not from procedure source; rather they are added by the various chart makers for reference only.
Nonetheless, this is the general area where the BE1900 crash. 2,000 won't get you through that area, and their true altitude was surely lower than 2,000 because of cold station altimeter error.



http://i201.photobucket.com/albums/a...ps57eb6733.jpg

MSA - TAA - MSA - MEA - MOCA
 

I got to the impression that because of differences for the used similar sounding abbreviations - e.g. MSA - on the two sides of the pond, a bit of a confusions has started and there is talking about two different items. Here in good old Europe it´s all ICAO !!
To solve that, read this:
SKYbrary - Minimum Sector Altitude

aterpster, the difference in shown heights of the mountains could also come from a different charting base. Normally it all should be WGS 84, but could it be possible that some people still use other geo ref systems or simply stick to old procedures ?

Annex14:

You make a good point. Most U.S. Geological Survey charts are referenced to NAD 27. So, if anyone is using a paper topo they would not be using WGS 84. The GIS program I use has corrected the bitmap USGS topos to WGS 84. No doubt that the FAA procedures design department uses obstacle data predicated on WGS 84.

But, the chart makers, for terrain point reference data? Beats me.

Having said that when Jepp adds color terrain contours they appear to be WGS 84 compliant.

And, of course, the FAA sectional visual charts are WGS 84 compliant, as are similar charts in developed nations.

Interesting, when important elevations are not agreed. All other things being equal, if Mr X impacts 50' below the top of a 2750' spot height charted at 2550', is the chart provider liable?

BOAC:

They would probably be sued, but with a couple of good expert witnesses for the defense, the defense would (or should) prevail. The segment and TAA altitudes are all correct and "shout" on paper to not descend below 4300 in that area. And, it is higher than 4300 if not in the holding pattern, but in that sector or area.

Jeppesen lost at Durovnik because of a shadow box issue with one of the NDBs. But, that had an operational nuance.

dubrovnik
 

Please pm, explain "shadow box " , and which / when,.. was that a Britannia in early 60s?
I landed there the next day and visited the site. I seem to remember an unusual approach , (ILS working, but notammed as out of service) , taking 4 approach markers instead of 3, which could have lead to incorrectly crossing them each at the height specified for the next.
They CFIT about the inner marker , querying on the RT about 'ground fog' when they lost sight of the runway , it was a gin clear night and they were below the trees

wily:

1996 CFIT of US Air Force 737 carrying Clinton's Secretary of Commerce Brown. Because of the war the ILS was missing in action. So, the approach was a dual NDB approach. Jeppeson designates the primary nav aid with a shadow box. That was messed up in this case, or at least so alleged in the lawsuit that followed.

It's been a long time. I am sure you can Google it.

Actually, I think they stuck terrain beyond the airport. The 737 flown only had 1 ADF onboard when dual ADF was required.

Back to AK.....

That would be why the FAA adds a 2,000-ft "cushion" in the published minimum safe altitudes - that, plus the possibility/probability of altimeter calibration errors, or imprecise barometric information, etc.

As in this case, where the high point was 2,250, and the minimum safe altitude was 2,050 feet higher (4,300').

- I think you are looking at different charts to the rest of us. Try ours - FAA or Jepp, which ever you believe.

Try 2550' (or 2750') to taste, and 6300'? (or 4100', or....). Nice and easy, isn't it?

It would appear that the TAA figures bear no resemblance to 'min safe' altitudes, since according to the FAA LOC/DME R19 it is 'safe' at 4100' over that peak.

gf:

The arrow indicates the point of impact:

http://i201.photobucket.com/albums/a...psfff71728.jpg

BOAC:

TAA "apples" and holding pattern "oranges." The outer TAA area of 6,300 covers vastly larger topography than does the holding pattern. In any case, the TAA inner area is 4,300, the same altitude as the holding pattern, because the same terrain controls for both the inner area and the holding pattern.

Although the 6,300 area goes out 30 miles for the pilot, the obstacle assessment area extends out an additional 4 miles. That is a lot of real estate.

OK, my bad - the FAA cushion is more like 1,500 feet.

That doesn't change the important part of my point - if the pilot stays at the charted safe altitude of 4300 feet (or even 4100 feet), the disparity between 2550 feet or 2725 feet as the highest terrain point is really irrelevant.

if you're so low that a geographical elevation error of 50, or even 250 feet, makes the difference between safe passage and a crash - you're far too low in any event. At least in IMC - we'll acknowledge that there are visual approaches that cut things that fine.

- not the point of my post! Don't think anyone would disagree. Is the Pope a Catholic?.................and I won't ask about bears.......................

Edit to add: Incidentally - I suspect your 'cushion' will be 1000' even in FAA land, so I assume there is a 3100' peak somewhere within 25nm north of Dillingham.

Thanks for the chart, aterpster.

The DBV Approach is almost like the one in Trabzon, Turkey...When I flew a jet (727) full of passengers into there at night and/or low vis conditions...I always kept in mind one thing...If everything starts to go south...TURN RIGHT!!! Over the Black Sea...Maybe not correct, but if you lose situational awarness...at night, in IMC, Over the sea is better than towards the mountains....

As has been beaten to death here on this thread by many of us "greybeards"...if you're not sure where you are at, IMC or at night being at 2,000' is not the time or place to try to figure it out....

- my post was about ACTUAL MSAs, not some 'TAA' figure - out of interest, why 4300'for TAA when MSA is 4100'? What are the criteria for TAAs?

TAA criteria are in Vol. 4 of Order 8260.58

FAA AFS-420 web site hosts all TERPS Orders on this page.

Thanks again, Zeffy - I could not find any reference to the ROC for TAA procedures (mind you, I got dizzy with all the maths................) Overall it seems odd that the hold at INDRA (1 nm inside ZEDAG) is considered safe at 3800' and yet when we switch to TAA procedures it jumps to 4300'. I assume there is a different (increased) ROC since the terrain is no less 'challenging'.

Incidentally, I see that 8260.19E at 2.74 calls for 200' to be added as an AAO which may account for the 200' discrepancy we see between the FAA and Jepp chart 'spot heights' (basically to allow for the 199' mast), and 2750' + 1000' gives us the 3800' hold, I guess.

Just glad I never had to construct procedures..........................

Sorry for the diversion and back to the accident.

Yes, the criteria are not for the faint of heart.:)

In a very small nutshell: ROC values for TAAs are the same as for airways.:ok:

BOAC:

Chart makers don't use AAO for reference obstacles.

But, the designers made additives to the holding pattern's minimum ROC of 1,000, probably for precipitous terrain and, more important at this location, cold station altimeter errors.

- I was talking ROC not reference obstacles, and Jepp seem to have added 175' (to the reference obstacle)

BOAC:

I was speaking of both in the total context of this aspect of the RNAV 19 procedure. I have no idea how Jeppesen came up with the value they show.

NTSB Report

Accident Docket

ATC Factual