MDA
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.
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lowering the nose to commence the descent (bunt)
This is so confusing....could this not be done from level flight at any altitude?
....say for example, the MDA.
....say for example, the MDA.
. Not to mention that it goes against the philosophy of a stabilised approach.
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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.)
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.)
Last edited by Jetdriver; 31st Aug 2013 at 15:44.
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.
Originally Posted by roulishollandais
the pilot may think he is allowed to pass D10.0 aswell at 3000' or 2000', D7.0 aswell at 2000' or 1300'.
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.
Originally Posted by roulishollandais
BUT it is possible that the pilot descending the CDA does the same fatal mistake...
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@ 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.
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.
Last edited by roulishollandais; 31st Aug 2013 at 10:23.
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Originally Posted by Captain Bloggs
Originally Posted by roulishollandais
BUT it is possible that the pilot descending the CDA does the same fatal mistake...
WHY? HOW?
Yes! SIMPLE! But they did NOT and crashed (unless altimeter mistake and other founding of the Enquiry).
WHY? HOW?
WHY? HOW?
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.
Last edited by AerocatS2A; 31st Aug 2013 at 11:25.
Originally Posted by roulishollandais
When experienced pilots are crashing after many many correct NPA approaches, are these approaches step by step or CDA,
Originally Posted by roulishollandais
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.
A brain-reset is required; remove all concepts of D and D and 15% and start with a clean slate.
Last edited by Capn Bloggs; 31st Aug 2013 at 11:28.
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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.
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.
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Originally Posted by underfire
What is the reference for 15% slope for obstacle clearance?
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)
Last edited by Jetdriver; 4th Sep 2013 at 10:08.
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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!
Didactic problems are the true "human factor".
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!
Didactic problems are the true "human factor".
Last edited by roulishollandais; 4th Sep 2013 at 09:55.
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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.
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.
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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.
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.
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@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.
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.
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This is to verify/validate the location and altitude of the fix.
Note the straight steps at the fix locations, not a 15% taper:
OCS surface straight lines, hence the confusion:
Note the straight steps at the fix locations, not a 15% taper:
OCS surface straight lines, hence the confusion:
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Just use VNAV, RNP, and treat MDA(H) as a DA(H)
While authority views on this still may vary globally, and operator's policies still widely vary, and notwithstanding obsolete criteria still in TERPS and Pans-Ops, from a scientific and safety perspective, the issue of the potential minor momentary descent slightly below MDA(H) during a properly executed G/A is completely irrelevant. Both the FAA/JAA/Industry AWO HWG recognized this now over two decades ago (e.g., Theo Van de Ven's RLD paper) as well as even FAA's signed AC120-29A, which acknowledged this situation with language such as:
“Go-Around” Transition To A Missed ApproachWhen Using a DA(H) or MDA(H).
When using minima based on this appendix in conjunction with a DA(H), flightcrew procedures for timely initiation of a go-around and anticipated altitude loss below the DA(H) during the momentary transition to a go-around are assumed to be the same as those specified for ILS, MLS, or GLS. The procedures used may be as specified by the operator or by the aircraft manufacturer, as applicable.
When using minima based on this appendix in conjunction with an MDA(H), it is recognized that the missed approach path following a stabilised approach may momentarily descend below MDA(H) while initiating the missed approach. This momentary and slight descent below MDA(H) during the transition to a missed approach is considered acceptable and is assumed to typically result in a displacement below MDA(H) of 50 ft. or less.
“Go-Around” Transition To A Missed ApproachWhen Using a DA(H) or MDA(H).
When using minima based on this appendix in conjunction with a DA(H), flightcrew procedures for timely initiation of a go-around and anticipated altitude loss below the DA(H) during the momentary transition to a go-around are assumed to be the same as those specified for ILS, MLS, or GLS. The procedures used may be as specified by the operator or by the aircraft manufacturer, as applicable.
When using minima based on this appendix in conjunction with an MDA(H), it is recognized that the missed approach path following a stabilised approach may momentarily descend below MDA(H) while initiating the missed approach. This momentary and slight descent below MDA(H) during the transition to a missed approach is considered acceptable and is assumed to typically result in a displacement below MDA(H) of 50 ft. or less.