Helicopter Non-Precision Approaches
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Helicopter Non-Precision Approaches
There is much debate at the moment in my corner of the training world about non-precision approaches, and I would be grateful if anyone could give me a definitive "textbook" answer to put this to rest:
Jeppesen charts in USA still show "traditional" non-precision approaches with MDA and missed approach point.
In Europe, however, these all seem to have disappeared to be replaced by big-jet style continuous descent profiles with a decision altitude.
Some believe that you can still fly this approach in a helicopter in the "traditional" manner, treating the DA as an MDA. Others say that you must fly it as published on the chart. There is debate as to whether there should be a helicopter type allowance to add on before it is acceptable to fly it as a DA.
Please dont give me another opinion, because I have heard lots! Just need the chapter and verse!
Many thanks in anticipation,
Plod
Jeppesen charts in USA still show "traditional" non-precision approaches with MDA and missed approach point.
In Europe, however, these all seem to have disappeared to be replaced by big-jet style continuous descent profiles with a decision altitude.
Some believe that you can still fly this approach in a helicopter in the "traditional" manner, treating the DA as an MDA. Others say that you must fly it as published on the chart. There is debate as to whether there should be a helicopter type allowance to add on before it is acceptable to fly it as a DA.
Please dont give me another opinion, because I have heard lots! Just need the chapter and verse!
Many thanks in anticipation,
Plod
I don't think there is a definitive text-book answer to this one - unless there is a step fix, you can theoretically fly straight down to MDA and continue to the MAP.
As you state, it has become fashionable to favour the CDFA because it makes the go-around easier (less trim changes) on a FW but really makes no difference to a RW.
If you have a HTA for a DA then you also should apply it for a MDA anyway - the difference will be that you can dip below a DA as you start your go-around but not a MDA.
As you state, it has become fashionable to favour the CDFA because it makes the go-around easier (less trim changes) on a FW but really makes no difference to a RW.
If you have a HTA for a DA then you also should apply it for a MDA anyway - the difference will be that you can dip below a DA as you start your go-around but not a MDA.
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CDFA
In FAA land it appears to be defined thus:
http://www.faa.gov/documentLibrary/m...%20120-108.pdf
I remember reading something similar for JAA/EASA land about 18 months ago, but can't for the life of me find it.
http://www.faa.gov/documentLibrary/m...%20120-108.pdf
I remember reading something similar for JAA/EASA land about 18 months ago, but can't for the life of me find it.
A subject dear to my heart! We - or should I say, my operator until yesterday 
- adopted the CDFA NPA concept when we introduced the S92s. We add 50 ft to the MDA and treat it as a DA (ala FW) though, depending on the location of the MAPt and the VPATH coding, the MAPt may come first. Every approach is thus flown in the same manner with the same sight picture at the bottom - ILS, NDB, VOR, RNAV. Many NPA approaches are now approved - and published - as allowing the MDA to be used as the DA. This reflects the fact that the approach is being flown at approx 3° (5.2%), rather than the assumed 15% gradient used for OCH calculations by ICAO Doc 8168.
The fundamental misunderstanding amongst many pilots who argue against this concept is that somehow the MAPt relates to the ability to land from the approach - it does not. The MAPt is the first point from which the Missed Approach Criteria are defineable, and in no way implies that a safe approach can be made from - or just before - that point. Consider an NDB approach, with the MAPt at the NDB in the mid-field with an MDH of 650 ft - how can you safely conduct an approach and landing from that point? Dump the collective, and practically enter autorotation? Turn downwind and descend - back into IMC possibly?
I could go on, but I have a plane to catch.....
- adopted the CDFA NPA concept when we introduced the S92s. We add 50 ft to the MDA and treat it as a DA (ala FW) though, depending on the location of the MAPt and the VPATH coding, the MAPt may come first. Every approach is thus flown in the same manner with the same sight picture at the bottom - ILS, NDB, VOR, RNAV. Many NPA approaches are now approved - and published - as allowing the MDA to be used as the DA. This reflects the fact that the approach is being flown at approx 3° (5.2%), rather than the assumed 15% gradient used for OCH calculations by ICAO Doc 8168.The fundamental misunderstanding amongst many pilots who argue against this concept is that somehow the MAPt relates to the ability to land from the approach - it does not. The MAPt is the first point from which the Missed Approach Criteria are defineable, and in no way implies that a safe approach can be made from - or just before - that point. Consider an NDB approach, with the MAPt at the NDB in the mid-field with an MDH of 650 ft - how can you safely conduct an approach and landing from that point? Dump the collective, and practically enter autorotation? Turn downwind and descend - back into IMC possibly?
I could go on, but I have a plane to catch.....
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I must admit its the first time I hear something about this procedure.
I haven`t flown IFR for quite a while now but when was this procedure introduced? I have never seen an approach like this on the charts I used. (or maybe overlooked it)
Nevertheless, although I don't see anything wrong with the procedure, I can't find the big (or even a small) benefit.
212man, I use your post to explain my point of view.
Correct me if I missed or misunderstood something.
As long as I stay above the MDA I can (legally) descend / climb however I want!? The MAPt defines the point I have to start the climb out (at least) and the MAP. (I can start the climb way before the MAPt but have to track to the MAPt to start the MAP in regards of turns etc.)
So why do they have to be approved for this?
The following applies for day operations:
Consider clouds broken at 650ft. You fly the 3° approach and there is this cloud layer right at the place you reach your "DA". You see nothing
(at 700ft!, cause you added 50ft for the DA. You are allowed to dip under the DA but you are not allowed to plan it. Actually, the approach would be a waste of time, because you already know you won't become visual before you start the approach) and start the MAP (or at least the climb).
The second in sequence is a guy flying the "dive and drive" procedure.
Lets assume the clouds did not move to give both the same situation.
After a quick (no autorotation of course) descent he reaches the MDA far before the MAP. He starts to cruise at 650ft and (because of the BKN cloud layer being at 650ft) he is lucky to find a "hole" in the clouds, descents further below MDA (now visual) and performs a visual approach.
Now lets assume he did not get visual on his way to the MAPt but gets visual at the MAPt. (The NDB is midfield) He descents below the MDA as far as possible (remains the required ground clearance) and performs a circling approach.
Visibility requirements should be considered, too. If you don`t find the requested VIS you start the MAP even if you are outside the clouds.
I understand your point, but we are still in the helicopter section, aren't we?
Circling with a helicopter is... well... not that difficult. You can slow down legally to 60 KIAS (CAT H) or 70 KIAS (CAT A).
Again, in my eyes its legal but not really practical or even safer.
I haven`t flown IFR for quite a while now but when was this procedure introduced? I have never seen an approach like this on the charts I used. (or maybe overlooked it)
Nevertheless, although I don't see anything wrong with the procedure, I can't find the big (or even a small) benefit.
212man, I use your post to explain my point of view.
Correct me if I missed or misunderstood something.
We add 50 ft to the MDA and treat it as a DA (ala FW) though, depending on the location of the MAPt and the VPATH coding, the MAPt may come first. Every approach is thus flown in the same manner with the same sight picture at the bottom - ILS, NDB, VOR, RNAV. Many NPA approaches are now approved - and published - as allowing the MDA to be used as the DA. This reflects the fact that the approach is being flown at approx 3° (5.2%), rather than the assumed 15% gradient used for OCH calculations by ICAO Doc 8168.
So why do they have to be approved for this?
The fundamental misunderstanding amongst many pilots who argue against this concept is that somehow the MAPt relates to the ability to land from the approach - it does not.
The MAPt is the first point from which the Missed Approach Criteria are defineable, and in no way implies that a safe approach can be made from - or just before - that point.
Consider an NDB approach, with the MAPt at the NDB in the mid-field with an MDH of 650 ft - how can you safely conduct an approach and landing from that point? Dump the collective, and practically enter autorotation? Turn downwind and descend - back into IMC possibly?
Consider clouds broken at 650ft. You fly the 3° approach and there is this cloud layer right at the place you reach your "DA". You see nothing
(at 700ft!, cause you added 50ft for the DA. You are allowed to dip under the DA but you are not allowed to plan it. Actually, the approach would be a waste of time, because you already know you won't become visual before you start the approach) and start the MAP (or at least the climb).
The second in sequence is a guy flying the "dive and drive" procedure.
Lets assume the clouds did not move to give both the same situation.
After a quick (no autorotation of course) descent he reaches the MDA far before the MAP. He starts to cruise at 650ft and (because of the BKN cloud layer being at 650ft) he is lucky to find a "hole" in the clouds, descents further below MDA (now visual) and performs a visual approach.
Now lets assume he did not get visual on his way to the MAPt but gets visual at the MAPt. (The NDB is midfield) He descents below the MDA as far as possible (remains the required ground clearance) and performs a circling approach.
Visibility requirements should be considered, too. If you don`t find the requested VIS you start the MAP even if you are outside the clouds.
I understand your point, but we are still in the helicopter section, aren't we?
Circling with a helicopter is... well... not that difficult. You can slow down legally to 60 KIAS (CAT H) or 70 KIAS (CAT A).
Again, in my eyes its legal but not really practical or even safer.
The only problem with the CDFA concept is that you end up with situations like the one 212man describes, where the MAPt is at the beacon in a difficult place to make a landing from if you do happen to get the references. Not only do you not get to the minima but converting to a visual approach to land is made more difficult.
What is wrong with flying an approximate 3 degree approach but adjusting the RoD (but complying with any step-fixes) so that you get to MDA a reasonable distance before the MAPt? That way you can fly the approach to the actual minima and have the opportunity of gaining the required visual references in stable level flight (probably using the alt hold) before the MAPt.
It seems a nonsense to apply FW techniques to RW just for the sake of commonality when there is no real benefit - this procedure is all about removing trim changes and the potential for CFIT from FW approaches - really not applicable to RW.
The idea that all approaches then look the same is really dumbing down what pilots get paid for - can't imagine this will be used in the offshore environment where that extra 50' will make the difference between getting to the rig (and keeping everyone happy) or going home or diverting.
The MAPt is where the calculated obstacle clearance planes guarantee terrain clearance if the MAP is followed - one could argue that if you are still descending as you pass the MAPt (even if you have added 50') you will be below the obstacle planes (albeit probably briefly) as you initiate the go-around - this is not the case if you come in level and go-around from that configuration at the MAPt.
What is wrong with flying an approximate 3 degree approach but adjusting the RoD (but complying with any step-fixes) so that you get to MDA a reasonable distance before the MAPt? That way you can fly the approach to the actual minima and have the opportunity of gaining the required visual references in stable level flight (probably using the alt hold) before the MAPt.
It seems a nonsense to apply FW techniques to RW just for the sake of commonality when there is no real benefit - this procedure is all about removing trim changes and the potential for CFIT from FW approaches - really not applicable to RW.
The idea that all approaches then look the same is really dumbing down what pilots get paid for - can't imagine this will be used in the offshore environment where that extra 50' will make the difference between getting to the rig (and keeping everyone happy) or going home or diverting.
The MAPt is where the calculated obstacle clearance planes guarantee terrain clearance if the MAP is followed - one could argue that if you are still descending as you pass the MAPt (even if you have added 50') you will be below the obstacle planes (albeit probably briefly) as you initiate the go-around - this is not the case if you come in level and go-around from that configuration at the MAPt.
Crab - CDFA means Constant Descent Final Approach. i.e. it is the nominal 3 degree approach you describe. The problem with an awkward MAPt I was referring to was the traditional 'step down' or 'dive and drive' all the way to the MAPt concept. Why do I want to be in "stable level flight"? I want to be in a stable approach, surely? My discussion was only related to Onshore published procedures and has no relevance to offshore ops.
Stallion, your point about 'descending through a hole' is understandable, but dooes not meet the 'Required Visual References' criteria and should you subsequently be faced with going IMC again will leave you poorly placed. Similarly, your circling suggestion could be bad news - why weren't you visual before the MAPT? Maybe because the cloud was thicker and lower before that point, and now you are turning and descending towards it! With broken cloud, there is always the possibility of encountering that unwanted 'okta' at the DA, regardless of the type of approach - PA or NPA (I know NPAs have an MDA - before anyone jumps on that).
I'd write more but I'm using a knackered keyboard in an airport lounge with very slow internet, so my enthusiam is waning! Besides, I hung up my flying suit yesterday, so what do I know anymore!
Stallion, your point about 'descending through a hole' is understandable, but dooes not meet the 'Required Visual References' criteria and should you subsequently be faced with going IMC again will leave you poorly placed. Similarly, your circling suggestion could be bad news - why weren't you visual before the MAPT? Maybe because the cloud was thicker and lower before that point, and now you are turning and descending towards it! With broken cloud, there is always the possibility of encountering that unwanted 'okta' at the DA, regardless of the type of approach - PA or NPA (I know NPAs have an MDA - before anyone jumps on that).
I'd write more but I'm using a knackered keyboard in an airport lounge with very slow internet, so my enthusiam is waning! Besides, I hung up my flying suit yesterday, so what do I know anymore!
Last edited by 212man; 1st Aug 2013 at 09:12.
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Thanks for all the posts so far.
For those flying across the water, please note what I said in the original post - the problem does not arise in the States, because NPAs are still published by Jeppesen in the traditional format. The problem is in Europe, where these approaches have been replaced.
I can see there is real split opinion in this community, which reflects the situation I have at work. We can see the advantages and disadvantages of flying with CDFA, and with the "dive and drive". We know how we have flown in the past, and what technique we like. BUT.... what is legal? - If a published approach is depicted with a CDFA and a DA, can we unilaterally decide to "dive and drive" and elect to treat the published DA as an MDA?
Is there anybody out there from EASA/CAA etc with a definitive answer?
For those flying across the water, please note what I said in the original post - the problem does not arise in the States, because NPAs are still published by Jeppesen in the traditional format. The problem is in Europe, where these approaches have been replaced.
I can see there is real split opinion in this community, which reflects the situation I have at work. We can see the advantages and disadvantages of flying with CDFA, and with the "dive and drive". We know how we have flown in the past, and what technique we like. BUT.... what is legal? - If a published approach is depicted with a CDFA and a DA, can we unilaterally decide to "dive and drive" and elect to treat the published DA as an MDA?
Is there anybody out there from EASA/CAA etc with a definitive answer?
Last edited by Non-PC Plod; 1st Aug 2013 at 10:10.
212man - what is easier, fly a level last 1/2nm with the height hold in following the crappy NDB in marginal weather looking for the references or flying a constant descent to 50' above the MDA and then having to initiate the go around?
I don't personally like the full dive and drive profile and we tend to do what I was advocating earlier - the difference between it and a CDFA approach is that you get to MDA and level before the MAPt rather than fly a CDFA to the MAPt.
JimL is most likely to be the guy in the know as far as the 'legality' of how you fly it.
I don't personally like the full dive and drive profile and we tend to do what I was advocating earlier - the difference between it and a CDFA approach is that you get to MDA and level before the MAPt rather than fly a CDFA to the MAPt.
JimL is most likely to be the guy in the know as far as the 'legality' of how you fly it.
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My "dive and drive" example is a little drastic. Just wanted to make my point clear. I prefer a smooth decent too. But when the weather is critical I wan't to be at the MDA as soon as possible.
I might be wrong on this, but when I have the "requested" 2,5km (for example) at 650ft, runway environment in sight and in the circling area I meet the required visual references?
Of course, this possibility does exist.
But in the real world you probably have the actual weather at the aerodrome from the ATIS or TWR. The location of the TWR controller is most likely very near at the MAPt (near the runway) so he should be able to give you a pretty clear picture of the weather and therefore the possibility to get IMC or not during circling.
And again... we are flying helicopters. Circling is not a traffic pattern.
It could also mean that the approach is not aligned with the runway, so I wouldn't need to turn back into IMC.
Back to the legal stuff, DA or MDA:
Non PC-Plod, could you post a picture of the chart?
Haven't seen one of those approaches before.
but dooes not meet the 'Required Visual References' criteria
Similarly, your circling suggestion could be bad news - why weren't you visual before the MAPT? Maybe because the cloud was thicker and lower before that point, and now you are turning and descending towards it! With broken cloud, there is always the possibility of encountering that unwanted 'okta' at the...
But in the real world you probably have the actual weather at the aerodrome from the ATIS or TWR. The location of the TWR controller is most likely very near at the MAPt (near the runway) so he should be able to give you a pretty clear picture of the weather and therefore the possibility to get IMC or not during circling.
And again... we are flying helicopters. Circling is not a traffic pattern.
It could also mean that the approach is not aligned with the runway, so I wouldn't need to turn back into IMC.
Back to the legal stuff, DA or MDA:
Non PC-Plod, could you post a picture of the chart?
Haven't seen one of those approaches before.
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Plod -
I have not seen a published approach where a non-precision approach, depicted with CDFA, has a Decision Altitude (DA). I would expect to see a published Minimum Descent Altitude (MDA) as it is non-precision.
As far as I am aware, the legal bit is clear, at a DA(Precision Approaches) a decision is required, and if a go-around is the decision then you will descend below that DA quite legally during the process. The MDA(Non-precision approaches) is the MDA, and is a not-below altitude unless you have the required references.
There are exceptions to these under certain circumstances, but in general, this is the legal situation as I see it.
HH
I have not seen a published approach where a non-precision approach, depicted with CDFA, has a Decision Altitude (DA). I would expect to see a published Minimum Descent Altitude (MDA) as it is non-precision.
As far as I am aware, the legal bit is clear, at a DA(Precision Approaches) a decision is required, and if a go-around is the decision then you will descend below that DA quite legally during the process. The MDA(Non-precision approaches) is the MDA, and is a not-below altitude unless you have the required references.
There are exceptions to these under certain circumstances, but in general, this is the legal situation as I see it.
HH
Which type of NDA are we talking about here?
The NDA is just that.....Non-Precision.
Legally, (at least in the USA), you can descend to the MDA at the FAP and fly the final approach at that altitude. That method is generally frowned upon by most.....whereas the descend expeditiously so as to arrive at MDA slightly before the MAPT.
We have to discuss what determines the MAP.....a Beacon or Time....before we can adequately discuss the methodology of using a Vertical Descent Criteria, in my view.
If using an approach where the MAPT is a Beacon then Vertical Guidance might well be appropriate. If the Beacon is behind you.....and Time is the determining factor....we would have to rethink what we are trying to achieve.
I prefer to get down to the MDA and fly at MDA to the Missed Approach Point....with the goal of getting visual in time to locate the point of landing, hopefully do so in a position to land straight in....or nearly straight in without having to circle to land. Remembering Circling to Land requires a higher MDA.
A NPA does not mean you will be aligned to the Runway in use.....and also does not mean the Airport will be in front of you.
Now that we have GPS.....knowing our position and track is much more precise even if limited to NPA use.
Which also begs the question.....are we talking about a GPS Overlay or GPS NPA?
Could we be a bit more precise about our Non-Precision?
The NDA is just that.....Non-Precision.
Legally, (at least in the USA), you can descend to the MDA at the FAP and fly the final approach at that altitude. That method is generally frowned upon by most.....whereas the descend expeditiously so as to arrive at MDA slightly before the MAPT.
We have to discuss what determines the MAP.....a Beacon or Time....before we can adequately discuss the methodology of using a Vertical Descent Criteria, in my view.
If using an approach where the MAPT is a Beacon then Vertical Guidance might well be appropriate. If the Beacon is behind you.....and Time is the determining factor....we would have to rethink what we are trying to achieve.
I prefer to get down to the MDA and fly at MDA to the Missed Approach Point....with the goal of getting visual in time to locate the point of landing, hopefully do so in a position to land straight in....or nearly straight in without having to circle to land. Remembering Circling to Land requires a higher MDA.
A NPA does not mean you will be aligned to the Runway in use.....and also does not mean the Airport will be in front of you.
Now that we have GPS.....knowing our position and track is much more precise even if limited to NPA use.
Which also begs the question.....are we talking about a GPS Overlay or GPS NPA?
Could we be a bit more precise about our Non-Precision?
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This is out of the first linked doc:
5. APPLICABILITY. The FAA recommends CDFA for all of the following NPAs published with a vertical descent angle (VDA) or glideslope (GS):
• Very high frequency (VHF) Omnidirectional Range (VOR),
• VHF omni-directional range station/distance measuring equipment (VOR/DME),
• Non-directional radio beacon (NDB),
• NDB/distance measuring equipment (DME),
• Localizer (LOC), Localizer Back-Course (LOC-BC),
• LOC/DME,
• Localizer-type directional aid (LDA),
• LDA/DME,
• Simplified Directional Facility (SDF),
• SDF/DME,
• Area Navigation (RNA V), and
• Global Positioning System (GPS).
5. APPLICABILITY. The FAA recommends CDFA for all of the following NPAs published with a vertical descent angle (VDA) or glideslope (GS):
• Very high frequency (VHF) Omnidirectional Range (VOR),
• VHF omni-directional range station/distance measuring equipment (VOR/DME),
• Non-directional radio beacon (NDB),
• NDB/distance measuring equipment (DME),
• Localizer (LOC), Localizer Back-Course (LOC-BC),
• LOC/DME,
• Localizer-type directional aid (LDA),
• LDA/DME,
• Simplified Directional Facility (SDF),
• SDF/DME,
• Area Navigation (RNA V), and
• Global Positioning System (GPS).
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I have a plate in PDF that shows this situation.....but I am not allowed to post attachments according to the little window below this screen.
Last edited by Outwest; 1st Aug 2013 at 23:51.
Some interesting reading......
http://aeronav.faa.gov/content/aeron...rting_CDFA.pdf
Another pprune discussion about this topic....
Jeppesen Approach Charts Non Precision DA
http://aeronav.faa.gov/content/aeron...rting_CDFA.pdf
Another pprune discussion about this topic....
Jeppesen Approach Charts Non Precision DA
Last edited by SASless; 2nd Aug 2013 at 01:41.
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Sorry, I dont have access to a scanner just at the moment to put an example on here, but I may be able to do so next week. If you have access to Jeppesen charts, look at Rome Fiumicino LIRF for example. All the NDB, VOR and RNAV approaches have a DA, not an MDA. I say again, this is a European thing, and you dont see it in the States.
If JimL has an expert answer, it would be much appreciated!
If JimL has an expert answer, it would be much appreciated!
it seems to me that when using the CDFA procedure. you are not flying the 3.0 angle down to the MAPt, at the MDA. you are flying the angle down to the Threshold. this will put you in a straight line down to the runway when you hit your MDA/DA, however, you will not be anywhere near the MAPt when you hit that target altitude. it seems to be the equivalent of shooting an ILS(with no G/S reference) but making your DH higher as if you were circling. instead of going missed at Station passage, time, or a given fix, you go missed at the MDA/DH. this makes every approach basically the same. you fly the prescribed decent rate based on the angle for the approach and your groundspeed.