Not at all. We were doing this before the distance/Altitude profiles were introduced into the Australian AIP some years ago.

I now use the charted table (if the VNAV is "not available" ;) ) although it is easier to anticipate whole 100s of feet, especially on the tape altimeter.

The only problem with the charted table is it normally only starts at the MSA, so you have the problem I alluded to above; that of getting the aeroplane into a descent prior to, so that you're not pushing the nose over at the start of the profile. I use 300ft/nm back from the start of the table to get organised.

Ah, the bunch that still fly the quadrapuff have something against using the charted profile, I'd assumed you guys in the faster twin-jet had inherited the same reluctance to change.

Hmm, where I grew up a bunt was specifically lowering the nose with sufficient vigour to produce negative g - not sure my pax would appreciate that!!:O

If it ain't broke, don't f... with it!:)

Sure, but get it wrong from the MDA and you have to go around, get it wrong from 30,000+ feet and you've got 29,000+ feet to fix it ;). Not to mention that it goes against the philosophy of a stabilised approach.

You are not allowed to descend more than 15% to have a constant margin to be protected from obsracles
What is wrong with the step by step schematic is that occasionaly (tired pilot, error, etc.) the pilot may think he is allowed to pass D10.0 aswell at 3000' or 2000', D7.0 aswell at 2000' or 1300'. The red line is the real bottom step by step path. BUT it is possible that the pilot descending the CDA does the same fatal mistake... So charts' drawers would not draw square steps but figure the 15% slopes with the distances. So the confusion is no more possible. The confusing grey zone exist already in the official documents about approach path design.
. (I did a mistake calculating the average position where you cross the CDA path at MDA 490' : The distance to AD is 2.0 NM and not 2.8 NM. Please correct.)

http://i1166.photobucket.com/albums/...psea6c9005.png

The presence or otherwise of a depiction of a 15% descent slope to each step makes no difference to my point. If you remember, you said I cannot claim to only use a constant descent method without any dive and drive, I showed exactly how I fly an approach using constant descent and no dive and drive.

That anybody could confuse the grey "no go" zones is a bit of a concern.

Putting the dive and drive on that chart shows how complex D and D really is. That is the beauty of the chart; start at 10DME at 3000ft, dial in/set up a 3° slope and miss every limiting step on the way down. But most importantly of all, you can check your progress down final before you get to any limiting step. In any case, just get on and stay on the Distance/Altitude table and you will 1/miss every limiting step and 2/arrive at the MDA/DDA 2W/2R on the PAPI.

No. Follow the Distance/altitude table until on the PAPI and you will not run into anything. Simple.

@ AerocatS2A
When experienced pilots are crashing after many many correct NPA approaches, are these approaches step by step or CDA, we have to ask us which wrong idea came in their mind that last flight. It is a problem of pedagogy, of didactic of failure. "Errare humanum est " is the norm, and someone think that replacing human by robots is the solution. But "Errare humanum est" works for automation, systems or SOP designers too. We just changed the reason of the crash. We have then to try to do a walk of empathy beside the thaughts of the person who failed that day. It is the main work of the agencies enquiring and elaborating recommendations not always connected to the day's accident.
We are searching which stimulus or lack of stimulus suggested the crew that action that day . Descending step by step with an altimeter and a DME seems one of the easiest task wanted from pilots. But we know sometimes they failed to achieve it. It is one reason to imagine the CDA "surfing" on the top edge of the steps. And we see they still decided to descend hundred feet under that line (last one Birmingham,AL). WHY? HOW?
I examined many times the AF chart in the Ste Odile crash before I understood how the FAF missing induced the idea that D7,3660' lost the state of mandatory. It got just numbers to eventually help. But that day was not like another day (you know any flight is different) and they descended the 15% slope toward 1440' and crashed at 2620' as their knowing of the bottom of the aproach was wrong. One of the expert said me he ignored the 15% limitation rule and no more came to the trial.. Today the status of CDA is still increased with RNAV or GPS approaches and the grey zone appeared in the books. The charts tried to figure together the CDA and the step by step informations. But the square grey zone is dangerous letting the possibility of confusing the bottom position.
Surely AerocatS2A your seem to have a strong use of your correct method help adequate training. In our times where beancounters consider training is too expensive many pilots are not so clear as you.Andpilots are not enough taught about the 15% slope, its beginning distance and finishing distance and that is confusing in the mind in the unconscious gey zone of the brain. Then these grey square zones may confuse the tired brain not help.

Yes! SIMPLE! But they did NOT and crashed (unless altimeter mistake and other founding of the Enquiry).
WHY? HOW?

Well for starters the American charts don't appear to have a distance/altitude profile of the type displayed on the Adelaide chart, so unless they made up their own profile they did not have anything to get on and stay on.

I'm not really sure what is confusing about the grey zones, they are areas you are not permitted to fly. As far as being taught about the 15%, I must say I didn't know about it, but I don't need to know about it as my approach descents are all somewhere around 5%. In fact the descent rate required to break 15% would have to be up over 2000 fpm so I don't see that it is relevant.

Let's not get carried away. What pilots have crashed doing a CDA using the chart type/technique that Aeroscat has posted?

Perhaps that is the problem. As far as I am concerned, the 15% slope stuff is totally irrelevant. I have never ever done D and D and I suspect that that is the problem (not your problem but those who use D and D).

A brain-reset is required; remove all concepts of D and D and 15% and start with a clean slate. :ok:

What is the reference for 15% slope for obstacle clearance?

The ROC is based on segments.
Typical ROC values for en route procedure segments, 1000 feet (2000 over designated mountainous terrain);
for initial segments, 1000 feet;
and 500 feet for intermediate segments.

At the FAF, you have a ROC of 500 feet and it tapers to 200 feet minimum.

These ROC's are nothing along the lines of 15%, with FAS ROC being on the order of 1:40 to GPA.

I see little reason to D & D on the YPAD procedure, in fact I would persuade against this, knowing how the database for man-made obstacles is managed worldwide.

These rules are from the most respected rules around the world, aswell civilian as military. The mandatory rules are, Country by Country, codified on the base of that document [PDF] ICAO Doc 8168 - Vol 2 - PANS OPS Approach ... - Code7700 code7700.com/.../icao_doc_8168_vol2.p... Aircraft Operations. This edition incorporates all amendments approved by the Council prior to 3 October ...

The French Civilian document is published by SIA (Service de l' Information Aeronautique) depending of DGAC in the document known as PRO-MIN. (The two pages are non updated extracts)

http://i1166.photobucket.com/albums/...pse3d73c0c.jpg

http://i1166.photobucket.com/albums/...psaa401818.jpg

Pedagogy
 

That is about how the most important danger of the step by step happens in a bad taught or tired brain happens.
Typical virtual exemple : The pilot at D11 to AD of our (for virtual pilots only) Adeleide's VOR 05 map projects himself to D10 which is 3000' protected but according the square grey zone, seems to be protected at 2000' and then decides to start descending to 2000' to descend more continuasly, and crashes on obstacle a 2700' before beeing at D10 to AD.

Any good formation of NPA gives opportuitty to the student to get aware of that (only) NPA risk.

That risk exists too with no grey zone, only the fix points if the pilot is ignorant of the 15% rule in a bad working brain. It does not need much flight time to learn that for ever, but MUST be well taught and is not enough/well taught.

To improve the NPA about that risk, tables of computed couples [Distance,ALTITUDE] have been edited on the approach charts, keeping fix points limitation. The pilots learned too to reckon themselves such couples and correct pitch and power if you are a liitle in advance or late. Tables are never mandatory. Points are (and the hiden unknown, not taught 15% rule) are mandatory.

The risk continues to exist of confusion with the CDA profile when the brain is little working due to fatigue, bad training, etc. And then you have Birmingham and other crashes after descending under the steps /fix or MDA altitude.

If you draw the 15% slope and learn the pilots the 15% rule the risk of confusion not more exists! Magic! :ok:

Didactic problems are the true "human factor".

roulish,

The 15% is on track, ie horizontal obstacle clearance,
not on slope, which is vertical obstacle clearance.

The 15% is not vertical obstacle clearance as referenced in post about the D & D profile.

H ? V?
 

@underfire
It had a look on the two pages, it is unclear.
Which is the number of the post you refered to ? If it is vertical and horizontal the D number are different, but otherwise it is the same.
Thank you for verifying.

Obstacle assessment areas for procedure design are different than obstacle clearance areas.

http://i41.tinypic.com/110aqmh.jpg

@underfire

I am glad you help to do these rules clear and taught to pilots.

Unless you are at A you may have an obstacle at 15%.

Your picture referes to an isolated obstacle, whose rules are not the same that for a mountain.

I had been in trouble about your vertical and horizontal, but your formulation was not clear. For the moment I stay with my first version.

http://i1166.photobucket.com/albums/...ps1767f2f5.jpg

This is to verify/validate the location and altitude of the fix.

Note the straight steps at the fix locations, not a 15% taper:

http://i41.tinypic.com/2crveao.jpg

OCS surface straight lines, hence the confusion:

http://i40.tinypic.com/2ntfceb.jpg