MDA for CONSTANT DESCENT NPA

[piratepete]

I know this has been industry-wide practice now for a long time, but can anyone quote me either ICAO or Jeppesen reference to the requirement to add 50 feet to the published MDA for a NPA when flying the now-standard constant descent angle approach technique, to allow for the height loss on a go-around on say a category C airplane?.Also any decent paper on this subject written by ICAO or other professional source explaining the logic behind this practice (for training purposes).Many thanks Pete.

[411A]

...when flying the now-standard constant descent angle approach technique,

Now standard, with whom?
At our mob, we still dive and drive....works good, lasts a long time (properly applied, of course).:rolleyes:

[PT6A]

Standard in Europe 411.....

Pete, it's in our ops manual and charts (we have company charts from LH Systems)

PT6

[PT6A]

NON – PRECISION (NON-ILS) APPROACH :
1. Non-Precision Approach will be carried out in the CANPA
Profile (Constant Angle Non-Precision Approaches) with VNAV
or V/S mode. Detailed description of CANPA is given in Part
‘C’.
2. CANPA procedure does not involve leveling out at MDA &
Missed Approach is initiated after reaching DDA (Derived
Decision Altitude). Levelling out at MDA will only be carried
out in special Approaches, eg. CANARASI R/W 13 at JFK
where special briefing is required.

VNAV APPROACH
“LNAV / VNAV or LOC / VNAV is the preferred method for
accomplishing non-ILS approaches that have an appropriate vertical
path defined on the FMC LEGS page. (V/S may be used as an alternate
method and is given subsequently).” The A/C is equipped with RNP /
ANP Alerting System. However, VNAV DA(H) will not be used. Use DDA
(Derived Decision Altitude, which is arrived at by adding 50’ to the MDA).
The following should be ensured :-
1) Appropriate Vertical Path defined on the FMC Legs Page is
the same as the published Vertical Path.
2) The Glide Path from FAF to R/W coded in the FMC
Navigation Database, is the same as the published Glide
Path and is between 2.750 & 3.770.
3) Atleast one GPS or one DME is operational.
4) Such approaches may be flown provided RNP being used
is equal to or less than RNP specified for the approach.
Following RNP values must be ensured [Prog Page 4
(B777-300ER/LR) & 3 (B747-400) of FMS CDU and can
also be cross checked on ND] :
VOR - DME / VOR / NDB : 0.5
RNAV / RNAV GPS : 0.3

[backofthedrag]

My understanding is that one may not descend below the MDA , without visual reference ; therefore the habit of adding 50 feet for a Cat C aircraft will hopefully ensure that in the event of a Go Around , initiated at the 50 foot point , the a/c will not go below MDA ( and you will not fail your check ).
With a DH , the missed approach must be INITIATED at or before the DH and a subsequent sag below DH is acceptable.

[BOAC]

pp - we've had this discussion recently here! Have a look here (http://www.pprune.org/questions/371214-mda-changed-da.html). Note the link (http://redirectingat.com/?id=42X487496&url=http%3A%2F%2Fwww.jeppesen.com%2Fdownload%2Fbriefbull%2Fa bb_jep_08_D.pdf) to the Jepp info. There is more bedtime reading here (http://www.google.co.uk/url?sa=t&source=web&ct=res&cd=5&ved=0CCEQFjAE&url=http%3A%2F%2Fwww.transportstyrelsen.se%2FGlobal%2FRegler %2FLuftfart%2FSubpart_E_background.pdf%3Fepslanguage%3Dsv&ei=IGhES8icLcS14QayuOGqCA&usg=AFQjCNEn3DDcy1PAr7LZI7xg7jalcLEOwQ&sig2=rzTWTJ7DOvgFlZ2OfwhyHQ) As '737jock' says, there is now the option in EU-OPS anyway of establishing a DA for an NPA which will not cause the a/c to descend below a safe obstacle clearance during a g/a. It will be company specific in the OM and some may take a while to change. Note the 'divers and drivers' are required to increase min RVR for their approaches.

As 'backofthedrag' says the whole definition of 'MDA' was that you could not go below it in a g/a and hence the (various) additions for different a/c in different OMs (50' in my lifetime). MDA was an abbreviation for Minimum DESCENT altitude ( not DECISION). Obviously a change to a 'real' DA will need a review of the figures used. It will certainly make like easier at the sharp end.

I believe implementation of the new system has to be sometime in 2011.

Like many things 'European' it is riddled with scope for confusion!

[fireflybob]

Surely the "add-on" depends on the a/c type? On the B737-200/300 it was 35 ft (defined I believe somewhere in the AFM). For CAT A types we used 10 ft and then also added the max pressure error correction of 50ft, the latter also specified in the AFM.

[despegue]

My company does not add this 50' to an MDA. In some cases, and these are the cases where the weather is on the limit, during this 50' you will see the rwy and a G/A is not necessary. If not, there is still enough margin to safely execute the G/A. I had already tons of NPA's where this was the case.

[Wizofoz]

My company does not add this 50' to an MDA. In some cases, and these are the cases where the weather is on the limit, during this 50' you will see the rwy and a G/A is not necessary. If not, there is still enough margin to safely execute the G/A. I had already tons of NPA's where this was the case.

So you're saying that you initiate a G/A AT MDA and knowingly go below MDA because there is "enough saftey margin"?

[PT6A]

The DDA is required for CANPA.

[BOAC]

My company does not add this 50' to an MDA. - see what I mean about confusion. As written there that company is operating illegally. A minimum is a minimum!

[Tee Emm]

knowingly go below MDA because there is "enough saftey margin"?

I realise this will cause an uproar, but realistically 50 feet is going to make stuff-all difference in terms of flight safety in a go-around from an MDA on a non-precision approach. The lowest MDA I know of is probably around 350 feet and if for decades the normal published MDA has been used from where a go-around is commenced (whether dive and drive or a constant angle descent) I doubt if there are hundreds of aircraft spread over the countryside simply because they went below a MDA by 50 feet on an instrument go-around. Isn't it all really a storm in a tea cup? Having said that I realise there is a question of legality.

[despegue]

The MDA has been designed decennia ago when aircraft were still driven by props. In these times, you descended to MDA and kept that altitude until visual or at the MAP nowadays, nearly all companies do a CDA. based on the DME/altitude readings on the profile. it is therefore considered that an MDA is in fact a DA.
As previously mentioned, the DA and MDA will be the same in the new procedures. No need to add this 50'.
Operating illegally?! Don't make me laugh! Our OM is approved by a major EASA state and my company is well known for its good standards.

[Rapid D]

Now standard, with whom?
At our mob, we still dive and drive....works good, lasts a long time (properly applied, of course).

Dive and drive is stone-age. Is "your mob" the "fly it like a 200 mob?"

LNAV/VNAV or CANPA is much more stable/safer way to go. Drive and drive "not applied properly" = GPWS warning now and then.

[rudderrudderrat]

Hi despegue,

What aircraft are you operating?

If you are using dive and drive to MDA then you must have commenced the level off before so that you didn't sink below MDA. (at MDA + 50 say?)

We can't satisfy the stable approach criteria with the level segment below 500 feet AGL so we must use a continuous descent profile.

[Denti]

Even LNAV/VNAV is old now, the newfangled thing for boeings is IAN. Everything is flown with identical procedures and indications, be it ILS, GLS, or any kind of NPA.

That said we do not add 50ft to the MDA, however we have to initiate the go around latest 50 feet above an MDA, if a DA is used instead no added safety margin is needed. Sadly the 50' above an MDA thing is put into a small note that is very easy to miss, simply bad presentation in our present manuals.

[piratepete]

PT6 and BOAC, thanks kindly for that info.I know most operators have the procedure in their ops manuals also AFM has the actual 'aircraft allowance' but where else is this CANPA information published.Sorry im currently working somewhere I cant access a Jeppesen manual, and my current employer has never heard of this stuff (dont laugh), perhaps 411A is the DFO here, and has banned any discussion of the dreaded "constant descent NPA", cheers Pete.

[toby320]

Hi, guys I understand diference exist on a DA and MDA but I never see in a paper those 50 feet that you are talking about, and the initial post is asking about a reference to find these matter.
toby

[411A]

Dive and drive is stone-age

Yup, and it suits this stone age guy just fine, thank you.:rolleyes:

Quote:
My company does not add this 50' to an MDA.

- see what I mean about confusion. As written there that company is operating illegally. A minimum is a minimum!

Illegally...nonsense. They don't add 50 feet, and apparently don't descend below MDA without visual reference.
We do exactly the same at our mob.
50 feet is for the uninformed.
Or those that can't fly level at MDA.

[BOAC]

and apparently don't descend below MDA without visual reference - read his post again?My company does not add this 50' to an MDA. In some cases, and these are the cases where the weather is on the limit, during this 50' you will see the rwy and a G/A is not necessary. - and in others? Yes - he could well descend below M Descent A without visual reference. I cannot see how you arrive at your conclusion!

[PT6A]

Not to mention flying level at low altitude... breaking out and diving for the runway = unstable approach...

When we have the tools to do it better why do it the old way?

Not an issue for my company as if the airport does not have an ILS we have a company RNP approach with CAT 1 like minimums...

PT6A

[B4MJ]

BOAC has it right in post #7, the links are all good information and 'dive and drive' (as it's commonly known) will be a thing of the past in a few years (or maybe decade where 411A works) except for circling approaches.

FAA currently requires 50' to be added to any CANPA MDA UNLESS the OPERATOR has been granted permission to use the published MDA without adding 50'.

For dive and drive everyone uses the published MDA - no 50' additive.

For CANPA everyone adds 50' to the published MDA unless special permission has been received from FAA to delete the 50'. (It's said FAA was initially concerned that the newfangled CANPA would be so unfamiliar to crew they might become confused and not respect the "absolute floor" of the MDA as they were long accustomed to doing for dive and drive approaches:))

BUT, if an individual operator has trained it's pilots to FAA satisfaction, then that carrier MAY receive permission from the FAA to delete the 50' additive. Then you get to use the published MDA the same as someone who does the now frowned upon (except for circle approaches) dive and drive. Only your flight department will know if your operation has been granted permission by the FAA to delete the 50'.

For pilots flying under FAA rules the answer is in the column you select on the Jepp approach chart . Some airports have both a LNAV column with MDA and a LNAV/VNAV column with a DA. If you are using the column with MDA minimums AND you are using CANPA, and you don't have permission from the FAA to delete the 50'; - you WILL add 50' to the published MDA.

If you're using the column with DA minimums you fly to the DA.

That's for FAA. The links in post #7 explain what the rest of the world does.

[411A]

Not to mention flying level at low altitude... breaking out and diving for the runway = unstable approach...


We don't 'dive' toward any runway, we apply normal descent techniques to the runway.
In addition, we often circle at 600 feet (the lowest we can go with our heavy jet) and you simply cannot apply CANPA for these ops.
In fact, this was mentioned earlier, here...
Levelling out at MDA will only be carried
out in special Approaches, eg. CANARASI R/W 13 at JFK
where special briefing is required

It would therefore appear that the fine art of circling and/or actually finding the runway during non-precision approaches is lost on the younger crowd...and many of the older crowd as well, who have apparently lost their skill somewhere along the line.
All this is in line with the general lack of hand flying/handling skills that we often see today.

[PantLoad]

The CDA (Constant Descent Approach) is the result of technology...the ability to select a prescribed descent angle. It is a huge advantage for pilots when executing non-precision approaches....especially in large aircraft.

Some authorities allow the CDA to the MDA, without allowing for inertia; some do not. FAA is a case of an authority who does not. My old company required adding 50 feet to the MDA to allow for a go-around without busting the MDA. Other agencies, other airlines may have different SOPs.

411A....you can hand-fly this type of approach, or you can couple it. My old company's SOP required the autopilot....but that was our SOP. But, I ask you, what's the difference of flying a rate-of-descent or descent angle?

Fly safe,

PantLoad

[rudderrudderrat]

But, I ask you, what's the difference of flying a rate-of-descent or descent angle?

Changes in ground speed are automatically accounted for.

[TCASfail]

Hi folks,

when reaching DA we make a decision. After a decision for a G/A it is physicaly imposible to go without descending below DA. That is allowed! The allowed hight loss depends on the A/C category.

To descent below a MDA is not yet allowed. That´s what I know. So I add 50 ft as well.

But: meanwhile you can find some Jepessen NPA charts with a DA published not a MDA!!!

I can´t find any rule within the EU OPS that allows a descent below such a published DA for a NPA.

Doe´s anybody know where we can find such a rule?

[411A]

But, I ask you, what's the difference of flying a rate-of-descent or descent angle?




We do both at our mob, as the situation dictates.
The idea is to have the longest possible time to find the runway, and thereafter land, using normal rates of descent whilst doing so.
I can appreciate why some airlines use CDA, especially larger ones with possibly quite junior First Offciers, however...we have experienced F/O's with good experience on type (L1011) and therefore can indeed fly level at the MDA and/or circle at the MDA, and actually land at destination, rather than diverting.
All it takes is practise.
I suspect the real reason why airlines today do not use dive/drive (and/or circling) is it takes training time and this equates to proper funding...so the easy way out is CDA
Therefore, all the diatribe about CDA being somehow 'safer' is nonsense.
It is only safer for those that do not know how to do otherwise...properly.

[lospilotos]

In my airline the SOP for CDA is to fly it on automatics, set the MCP ALT to the MDA rounded up to the nearest hundred feet, not to get extra margin but since you only can set the MCP ALT in hundreds. Hence the MDA is not busted and the desicion is made already on the ALT ACQ (737NG) mode change. If not visual then, wait for the ALT HLD and then execute the go-around. Obviously this has the effect that some approaches could have lead to successful landings instead of G/As, when the weather is right down to the minima. Not saying this is the way to do it, just saying they way it is done...

[rudderrudderrat]

Hi 411A

all the diatribe about CDA being somehow 'safer' is nonsense.

Would you consider it "safer" to fly an ILS by ignoring the glide path and diving to the "LOC only MDA", fly level to your MAP and then Land?

The dear old TriStar is still my favourite of all I've flown. CAT IIIB 75m No DH in the 1970s - PFM.

But if our modern NAV FMS is able to generate a pseudo "glide path" for our NPA (VNAV, FINAL APP or whatever it's called) as vertical guidance then we can use the published DA on the procedure. If we can't generate vertical guidance (LNAV, NAV only) then we use MDA limits. (+ 50 for us)

[411A]

Would you consider it "safer" to fly an ILS by ignoring the glide path and diving to the "LOC only MDA", fly level to your MAP and then Land?


If said glidepath was OTS, dive/drive would be my option.
The dear old TriStar is still my favourite of all I've flown. CAT IIIB 75m No DH in the 1970s - PFM.


As it is with many older pilots...Lockheed manufactured a fine airplane that was far ahead of anyone else.
A true gentlemens airplane.
Indeed....PFM.

[BOAC]

TCASfail - I went to a lot of trouble to provide you with that information. Please read it! The 'rules' are there for you to see.:mad:

Horses and water?

PS It would be nice if all this obfuscation about 'dive and drive' was left for a different thread since it has nothing to do with the topic!

[PantLoad]

I've done both the 'dive 'n drive' and the CDA.....most of my flying career was dive 'n drive. Both work fine. Of course, dive 'n drive was the only option on my own airplane....back when I owned one.

But, the past few years of my flying I did CDA. I prefer it, without question, to the dive 'n drive procedure.

Just my opinion....

But, the original topic...we did add 50 feet to the MDA and made it sort of a DH...i.e. we flew it like a precision approach. Works great.

rudderrudderrat....yes, you are quite correct. Thanks for adding that.
This is the beauty of the technology.

Personally, I loved hand-flying the approaches. (Not SOP.....but, I did it in VMC.) With the precision the Bus allows, you can really fly a nice approach using Selected Guidance and 'The Bird'. 411A....brings tears to the eyes of us old guys.

Fly safe,

PantLoad

[Mansfield]

I think 411A is being slightly disingenuous to the younger crowd...unless he has already pointed out that thanks to the marvelous feature incorporated in the 1011 known as DLC (Direct Lift Control), he can make the vertical navigation changes with little change in pitch attitude once landing flaps are set...he doesn't really "dive", he "sedately sinks" and then drives. It is the Cadillac, and always will be.

The fifty foot addition likely has more to do with the approach design criteria. In many cases, the authorities may not have the data to substantiate the missed approach obstacle clearance requirements if the missed approach climb begins at an altitude below the MDA. It is not that it can't be done; just that they have not done it. I note that my current employer adds fifty feet to any non-ILS approach flown with either constant rate or constant angle procedures, unless it has a published VNAV DA. I imagine that some authorities may have different interpretations.

When I look at the confusion generated by the introduction of constant angle, VNAV procedures, I often wonder if more error potential has been introduced than was removed. Nonetheless, the dive and drive technique has a poor history worldwide with respect to CFIT. I also imagine that a VNAV coupled constant angle approach will lead to far fewer misses over time, simply because the captain will be satisfied that the airplane is in a position to land more often than with earlier techniques.

In any event, as I often remarked to trainee pilots years ago, the term "non-precision" in non-precision approach refers to the accuracy of the signal in space...not to your flying technique...whichever one you choose, in this case.

[Tee Emm]

Just had a peek at my trusty Boeing 737-300 FCTM and at page 5.33 is says "set the MDA (H) using the baro minimums selector...if required to use MDA (H) for the approach minimum altitude, the barometric minimums selector should be set at MDA + 50 feet to ensure that if a missed approach is initiated, descent below MDA(H) does not occur during the missed approach.

So for Pistol Pete - I guess if your ops people say they have never heard of this 50 feet addition it maybe they either haven't read the advice in their Boeing FCTM or they ignore it. Could be their local culture of course. Of course they may be operating another type where the automatics are so advanced, the 50 feet additive is not a factor?

[captseth]

No Published DA requires the height loss derived decision altitude which adds 50' to the MDA. If it is published LNAV/VNAV, it has a DA so no DDA required.

Coincidentally dealing with these issues right now with my Air Taxi company, here in the US so it's FAA rules. APV approval not a problem, LNAV/VNAV should not be an issue for us either, but the DDA would be new to our type of operations so I'll let you know how it goes if anyone is interested.

[Rapid D]

It would therefore appear that the fine art of circling and/or actually finding the runway during non-precision approaches is lost on the younger crowd...and many of the older crowd as well, who have apparently lost their skill somewhere along the line.
All this is in line with the general lack of hand flying/handling skills that we often see today.


The pilots most likely to bend metal (or worse) today are guys like yourself who claim all their "Chuck Yeager-lke" flying skills are better than technology and avionics available. Like Ice-man said, guys like you are "dangerous". I'm sure the Korean Air 747 captain who hit Nimitz Hill in Guam back in late 90's on non-precision approach doing dive and drive was very comfortable in his hand flying/handling skills and was a big fan of doing the dive and drive if "handled properly'. Dive and drive worked out great for them until they hit Nimitiz Hill and killed everyone when it was not "handled properly."

There are plenty of other examples in aviation history of dive and drive NP approaches resulting in fatal accidents. A constant descent approach, either VNAV or other derived constant angle approach is so much more stable and yes SAFER. I can't find anywhere where such an approach in itself has resulted in an accident. I can find plenty where your favored dive and drive has resulted in accidents.

I am sure your are a great stick, but shouldn't procedures be in place for us average Joe's?

Give it up man. Get an Iphone too :)

[PantLoad]

Why we make personal attacks against people here....our fellow airmen...is beyond me.


PantLoad

[411A]

Why we make personal attacks against people here....our fellow airmen...is beyond me.


As a long time contributor to PPRuNe, in my view it is from those that simply do not have the skills necessary to complete the task, therefore attack those that do.:}

[extreme P]

Give it up man. Get an Iphone too.

Early in the year but that has to go down as a front runner for funniest post of 2010.

CDA is better than dive and drive in every regard. If anybody has info regarding a crash from a CDA approach please post now.

411A, have you ever done a CDA approach? L1011 may have been the best newfangled flying machine ever built but the relentless march of technology cannot be slowed. Enjoy your iphone.

[Panama Jack]

As far as I know, there is no ICAO or Jepp reference-- it is up to what your company works out with your regulator.

At my present employer we add a 50' buffer to the MDA for protection during the go around maneuver (since the aircraft will continue descending a few feet from momentum).

However, my previous employer did not add the buffer. When I asked about it, they replied that they had discussed the issue with the regulator and it was felt that it was not necessary-- given that the location that the aircraft would reach the MDA was in the location which it would normally have continued the descent (close to the runway, with sufficient terrain clearance). I was satisfied with that explanation.

[411A]

Enjoy your iphone.
My First Officer has one, as does the Flight Engineer.
They stare at them endlessly, with seemingly poor results.
When push came to shove, up in Russia, they couldn't even call out, nil signal....however, my trusty Nokia worked just fine...with AT&T worldwide roaming.

So, a pox on the iphone.:}

[extreme P]

Question remains, have you ever done a CDA approach?

[411A]

Question remains, have you ever done a CDA approach?
Yes, at one airline.
Didn't think much of 'em, either.
Dive/drive works far better.
Of course, if you're not skilled, better stick with CDA.

[extreme P]

Dive/drive works far better.

Why is that?

[BOAC]

Dragging this lurching vessel back to a CDA - do we have a definitive, logical explanation from 'them's what regulates' as to whether or not the 'old' MDA is to be re-calculated (raised?) to derive a DA and if so by whom? Is it now accepted that it was an unnecessary restriction to forbid descent below such? Do the readers here consider the matter has been adequately addressed in terms of ensuring that the change is clearly presented and everyone understands? Any ATC procedure folk to comment?

I hesitate to mention 'D&D' :sad: but obviously there is no need for any recalculation of MDA there, only the mandated increase under EU-OPS in minimum RVR for such. This leads to further confusion - can a D&D now use the new DA? Will this DA be 'safe' for terrain clearance when, unless there are further restrictions, strictly speaking there would be nothing stopping a death-defying D&D 'dive' from FAF straight down to the 'new' DA several miles out? Will we have to retain 2 sets of figures on Jepps etc?

[rudderrudderrat]

Hi BOAC,

can a D&D now use the new DA - I don't think so.

I've only seen DA published on NPA charts with published Lateral & Vertical guidance. If there is no Vertical guidance then a MDA is published.

The only reason we are allowed to sink below the DA during the GA, is because we'll be on profile. The D&D aircraft will be further away from the runway when it reaches it's MDA and will be closer to the obstacles which are considered.

[411A]

Why is that?
If you are truly interested (rather than being argumentative) my reasons are aptly described in post number 28.
All that is necessary is to actually read and understand.

With regards to dive/drive, Harry Truman said it best...'can't stand the heat, stay out of the kitchen.'
The 'new' way seems to be CDA, however....being quite a lot older, and have successfully used dive/drive over many years, we stick with what we do best, the old fashioned way.:)
And, what's more, the concerned regulatory authority has no objections whatsoever.

[Spooky 2]

This is pretty easy to understand if you leave the flamming and insults out of it.

In the US, the FAA will allow you to treat the MDA as a DA if your training provides for VNAV approaches in lieu of the the dive and drive method of descent. Some here want argue that the D&D is better, or in some cases they just feel more comfortable with it. So be it. That not witstanding there volumes of data that show the VNAV or IAN approach is superior in every way to the D&D method. You can argue along with all the insults, but the data will still prove your wrong on this topic.

If on the other hand your not approved for VNAV along with using the MDA as a DA, then you will continue to use the MDA as your final descent altitude. I believe that the OpsSpec for this is B036, but don't bet the farm on that.

As others have noted the additional 50' was imposed on the operator so that they would not descnd below the MDA on a go around. In the case of Boeing the 50' is applied to Boeing aircraft from the 737 to the 787. No differences within the fleets.

[rudderrudderrat]

Hi 411A

being quite a lot older, and have successfully used dive/drive over many years

I bet you're not older than me! I'm now using CDA NPA with FMS (FMGS) generated vertical profile - something my dear old TriStar couldn't do. If your FMS could provide an accurate VNAV profile - I bet you'd use it too. It's PFM (well almost).

However, if you can't do VNAV approaches I can see the advantage of the extra time you'd have at MDA up to your MAP, and the brilliantly clever DLC giving instantaneous change in VS.

Horses for Courses.

Regards
Last Memory items for 2nd Eng Failure.

[411A]

However, if you can't do VNAV approaches I can see the advantage of the extra time you'd have at MDA up to your MAP, and the brilliantly clever DLC giving instantaneous change in VS.



Exactly....you've got the message.

[beerdrinker]

I fear I have to reply (not as a young first officer but a 20K+ hours ex Check Airman on two types of wide bodies) to 411A's dated opinions on Dive & Drive.

It was considered many moons ago to be a potentially dangerous manoeuvre by Aviation Authorities around the world for a number of reasons including the fact that it encouraged dirty dives towards the threshold and deep landings.

Most MAP's are very close to the runway threshold. If you do a Dive and Drive approach you dive to around 500ft agl (typical NPA MDA) and then drive towards the MAP peering out of the window for a sight of the runway. You see it and and dive towards the runway, with a potentially dangerous rate of descent, risk landing deep and running out of runway.

Modern thinking is for a stabilised approach from 1000 ft agl. There is no way an approach is stabilised when one makes a power on. approach flap, level flight at 500 ft agl, sees the runway, then makes a sudden power rduction to get the dive started, select landing flap, and dive for the runway and then have to apply power to stabilise the approach, before actually going into the flare, power reduction and land.

The CDA, aided by timing and /or distances brings one down to MDA from where, if the runway is in sight, the constant (safe) rate of descent can be continued down to a landing in correct area of the runway.

The CDA either in modern aircraft with VNAV help automaticaly or manually, or older aircraft with basic instruments is the safer way to fly NPAs and that has also been recgnised by the FAA.

BD

[Spooky 2]

Well said Beerdrinker. The D&D cannot hold a candle safety wise to a well executed VNAV type approach whether it be coupled or handflown. The record books are full of accident reports utilizing the D&D methods. I realize for various reasons some would choose the D&D over the more stabilized VNAV concept, be it their particular equipment or other issues but one cannot argue with the safety, economy and overall sucess of the VNAV/IAN approach concept. :ok:

[rudderrudderrat]

Hi 411A I've left a PM.

Most MAP's are very close to the runway threshold. If you do a Dive and Drive approach you dive to around 500ft agl (typical NPA MDA) and then drive towards the MAP peering out of the window for a sight of the runway. You see it and and dive towards the runway, with a potentially dangerous rate of descent, risk landing deep and running out of runway.

What's the difference if your stop watch timed CDA NPA leaves you slightly higher than the ideal profile so you only see the runway at your DA (MDA + 50?) just before your MAP?

I would suggest that both crews should GA from that position.

[FE Hoppy]

I think you will find that your charts have the extra height built in to the MDA. You just don't realise what you are doing.

you cannot fly a "precision like" CDA to the old MDA and then go around. You must descend below MDA in that case and this is not allowed.

I would suggest comparing your company minimum on one of these approaches with a standard MDA from a company who dive and drive.

[Spooky 2]

FE Hoppy, I can only speak to the Jepp plates, but if there is a DA posted in lieu of an MDA, that's what the operator is approved for REGARDLESS of their OpsSpecs. If on the otherhand there is an MDA and the operator has the "OpsSpecs approvals" that opertor can use the MDA as a DA and use that value. IF, the opertor does not have the approval, they must add the 50' to the MDA and use that new value. That 50' is not shown anywhere in the Minimums block and it's simply an operators specific limitation.

That may be what you just wrote, but for some reason I did not understand it that way. :ok:

[411A]

If you do a Dive and Drive approach you dive to around 500ft agl (typical NPA MDA) and then drive towards the MAP peering out of the window for a sight of the runway. You see it and and dive towards the runway, with a potentially dangerous rate of descent, risk landing deep and running out of runway.


In actual fact, this is totally not in agreement with our ops.
We start an 800 ft/min descent at the final fix (and if landing straight in, select landing flaps, which includes DLC, as noted before by another poster), level off at MDA and look for the runway.
If it is not in sight until close in, we don't 'dive' for said runway, we don't land long, we go missed approach.
However, if the runway is in sight at a reasonable distance, a normal descent is commenced toward the runway.
Quite simple actually, IF you know what you are doing.

Clearly many here don't, therefore I would suggest that they stick to CDA.

In the L1011 however, it works like a charm.
No problems whatsoever.

[Meikleour]

Beerdrinker:
As a contemporary of you I applaud your efforts here but 411A has never knowingly admitted to changing his mind. in over 7,000 posts!! That says it all really.

[galaxy flyer]

I cannot resist posting, sorry. Why when given the choice between having an ILS-like presentation thru, LNAV/VNAV (or LPV) approach with a charted DA, would any professional pilot choose a "dive and drive" NPA? The minimums are the same, if you follow the "dive and drive" technique to a visual descent point, the distance from runway when the decision has to be made, is the same. There is no reason not to use the simpler and safer approach method, other than an attachment to old ways.

Flying the F-100C down final at 185 KIAS, with a 3" MM-3 AI and raw data, was challenging and made for a fast crosscheck, is that a valuable skill anymore? NO. It is the 21st Century, use the stuff that is proven safer and more reliable.

GF

[777AV8R]

'Beer' and 'Galaxy' have come as close as anyone to explaining this thread. I too have 20K+ and am an active checkpilot on the B777. I too have flown the L1011. Time to move on.

My memory isn't 'long enough' to remember when the concept of CDAs came into being, but this isn't something new. In view of a number of disasters and incidents having to do with loss of situational awareness to name only one; industry, technical safety groups, regulators, manufacturers, and training organizations put forth the idea of CDAs. Eventually, Jepp notified users through a Briefing Bulletin, that it would begin publishing charts to include recommended 'Distance/Altitude' on its charts to aid in establishing CDA approaches. These strips would only be published on approaches that could provide adequate obstruction clearance to approximate a 3 degree slope. Furthermore; the 'strips' would closely approximate a glidepath of 3 degrees to the MDA. This was pre-VNAV days. I flew these approaches into Geneva and practiced them regularly and they worked well. (both L1011 and 777 in '97-'98)
I was fortunate to be invited to a Boeing checkpilot meeting in the spring of 2001. We talked of stabilized approaches and then we talked of VNAV approaches in specific. We were informed that Jepp would begin to 'code' all approaches so that VNAV could be used on all non-precision/GPS approaches and that the philosophy was to allow the flight to descend continuously in a stabilized energy condition to the MDA which would closely approximate the Visual Descent Point. All of the VNAV approaches were designed to use full automation but the flight crew could still use the FD in VNAV mode, all the way down to MDA. In fact, it is a fun maneuver to manually fly the VNAV 'all the way down' and watch the PAPI...always 2 white-2 red. Note that I talked of stabilized energy conditions earlier. On a stabilized CDA approach, we have near constant energy conditions all the way to MDA and if conditions permit, through to the beginning of flare, where energy changes.
If conditions at MDA do not permit a landing, only one change of state is required from the CDA and that is of nicely entering TOGA and the energy state changes to go-around.
When practicing a CDA either in VNAV or using FPA or VS using the briefing strip dialogue, the result is usually the same: The aircraft is always stabilized throughout the approach and the runway (conditions permitting) will appear exactly where it should be: at the MDA and the PAPI will be in the correct slope.
Derived Decision Altitudes (DDAs) came about as a result of these approaches NOT being thought of as precision approaches and that the maneuvers weren't as accurate as an ILS approach, thus a 50 ft drop-out cushion was allowed for pilot or autopilot 'dropout'. After years of operational proof, it has been found that the VNAV approaches are almost as good as their ILS companions and some regulators will allow for a CDA DH because the accuracy has been so good. In fact, there has been some talk that we will see VNAV approaches down to 200 ft. minimums.
As far as providing documentation on the 50 ft. DDA, the information has crept through training manuals and company operation manuals and has always been a briefing item during sim training and checks. Boeing's philosophy was that they have wanted to see a VNAV approach that was good to a 200 (h) minimum.

The fact is that CDA approaches, without a doubt is the safest method of performing a non-precision approach to minimums for reasons that I previously stated. Times have changed and most good pilots have changed with it.

[BOAC]

777 - thanks for the useful insight. Do I deduce from your post that the 'new' CDA DA is primarily intended for VNAV ops? Does that imply that the V/S type of CDA may well retain the buffer?

[777AV8R]

BOAC...from my discussion with the senior technical people at Boeing, the intent was to bring VNAV down TO a DH because of the accuracy of the system. The philosophy was referred to as "flying to near ILS limits using VNAV and GPS/LNAV/LOC overlays."

In absence of an integrated/automated VNAV system (AFDS) but using FPA or VS, it would be more correct to use the Derived Decision Height.

Would I bust a candidate for not using a DDH on a VNAV approach? It depends on the training philosophy of the company. What were the standards of training? There are many factors to consider. It would be a good debrief item for sure.

[galaxy flyer]

The Rockwell-Collins system has a VGP function. Arm APP and VNAV, VGP will be armed and captured just like a glide slope. When VGP is captured, the ALT Selector will act just as on an ILS and be set to missed approach altitude. VGP presentation shows a GP down to 50 TCH.

GF

[777AV8R]

Galaxy...I want to fly your airplane!:ok:

[FE Hoppy]

GF, you've described the Honeywell Primus Epic system too! The system is designed to be operated exactly the same for an ILS or non localiser based non-presision approach. The APP button responds to the selected nav source and FMS programmed approach. By either arming LOC/GS or LNAV/VGP

[Denti]

VNAV/LNAV approaches on boeings were obviously designed to be flown using automatics although flight director usage is sufficient. The IAN thingy has the same presentation to the pilot flying any non precision approaches as any precision approach (GLS or ILS for us) and therefore can be easily used flying "raw data", following the flight director or fully autocoupled. If you forget to disconnect the pilot because you think its just an ILS and you do an autoland you will get a warning at 100' with a yellow AUTOPILOT on the PFD and auto-callout "AUTOPILOT". If you set up the system correctly (select the approach from the database, fill in the descend forecast page and press APP when cleared for it) it is a very nice and stable way to fly non precision approaches, besides it nearly removes the difference in SOPs and presentation between precision and non precision approaches.

Of course that could be seen as catering to reduced training and only the low hour pilots, however i do think it is a perfect way to make flying safer and reducing the risk of mishaps and CFITs.

IAN is standard for 737s since 2006, dunno if it is available yet on other boeing types allthough we do know it will be available on the 787 (and boeing promises that you can do operate 737 and 787 in MFF, but thats another thing).

[Spooky 2]

Denti, what is MMF?

[eckhard]

Further to GF and FE Hoppy's posts, the CitationJet 'plus' series has the same feature of VGP during an LNAV/VNAV approach with the altitude pre-select working in the same way as an ILS.

The whole aircraft probably costs the same as the stabiliser screw jack on the other type that I fly (744) but it has better displays and VNAV capabilities. I guess that's 20 years of progress for you.

I always teach guys to try and fly every instrument approach as much like an ILS as possible, so I'm firmly in the CDA camp (+50ft).

[galaxy flyer]

777AV8R

Check your PMs, please

GF

[piratepete]

As the starter of this particular thread, I have read the various posts with interest.The posts from 411a, although highly predictable, and similar to my great-grandfathers, (he flew in the 40s and 50s), and are always good for a laugh.Thank you kindly 777av8r, your post is excellent, ive copied it and handed over to my FTM, if you dont mind by way of explanation of said add-on procedure.Pete.

[Denti]

@Spooky: MFF means Mixed Fleet Flying. Which means the ability to qualify your crews on two different types and fly them in a mixed operation. Most commonly that is currently done on Airbus types, for example A320 family with A330s, but we had the approval for MFF between 737/757 and 737/767 although we never actually did that.

Interesting to read though that Boeing doesn't offer IAN on the 747 yet, but would expect it on the -800.

[malcolmf]

Something that hasn't been brought up is the engine response time. In a L1011 (I haven't flown one, but have a 747-200) the time to get the engines from a high power, high drag (and noise) situation is relatively low, with a GE 777 ( and other high bypass engines) it would be very significant and you would end up with a very destabilised approach unless you are both very good at it. With the 777 you can have FPA and track select and get a very accurate NPA, limited only by the accuracy of the charts.

[411A]

In a L1011 (I haven't flown one, but have a 747-200) ...
Now there's an interesting response....:rolleyes:

[Spooky 2]

Denti, the 747-8 will have the IAN feature and I would expect to see it available in the 777 fairly soon as well. Thanks for the MFF explanation.

[777AV8R]

GALAXY...

Check PM and personal mail.

Rgds
777

[Jet_A_Knight]

Having a look at the Flight Safety Foundation for recommendations made by their Approach & Landing Accident Reduction campaign might be worthwhile for a few people on here.

Just because someone has done dive & drive and circle to land successfully, doesn't make those methods less of a CFIT risk than a CANPA.

And it's nothing to do with the perceived reduction in 'skill and ability' of 'younger generations'.

Even expert pilots crash aeroplanes.

Approach and Landing Accident Reduction (ALAR) | Flight Safety Foundation (http://www.flightsafety.org/current-safety-initiatives/approach-and-landing-accident-reduction-alar)

or

SKYbrary - Flight Safety Foundation ALAR Toolkit (http://www.skybrary.aero/index.php/Flight_Safety_Foundation_ALAR_Toolkit)

[Centaurus]

and therefore can be easily used flying "raw data", following the flight director or fully autocoupled.

The 737 FCTM recommends the autothrottle be switched off whenever manual flying is attempted unless it is climbing after takeoff. One assumes therefore during a CDA approach hand flown on the flight director as above, the pilot would also be using manual throttles. This usually causes some consternation in automated aircraft, as pilots are so ingrained in using full automatics which of course include autothrottle, that their manual throttle handling becomes a trifle hairy to say the least! In turn their speed control is rusty and inevitably approaches can become unstable. It depends largely on the currency of the pilot on manual flying. If not current or slightly nervous, stick to full automatics

[Denti]

Umm, the same is true for every single approach. But especially the 737 is a shorthaul aircraft on which a crew usually does 4 to 6 landings a day so that every flight crew member gets 2 or 3 landings. The use of autothrottle or not during approaches is something we discussed elsewhere indepth and this thread is mainly about non precision approaches.

The sentence you quote up there just states that it is nice to be able to fly a defacto raw data (non flight director of course) non precision approach much easier in IAN (which you should know and use as a current 737 pilot) than in LNAV/VNAV or heaven forbid LNAV/VS. Nothing in there is about autothrottle usage at all, any current pilot should be aware of how to fly according to his company SOPs and the use of autothrottle or not during manual flight, ours actually use the autothrottle ARM feature for the last 20 odd years without any problem so far.

As for manual flight recency, a lot of that depends on your company atttitude towards it, but i think the following from our SOPs gives me quite a bit of that if i want to:

Continuous use of automatic systems leads to loss of basic knowledge of power settings/pitch attitudes and reduces the ability to fly accurately with a low workload. Pilots should therefore regularly fly the aircraft manually, with emphasis on manual departures/ approaches with and without the flight director.

The problem with allways sticking to automatics if uncomfortable is something that can lead to serious problems with raw data flying when necessary and currently a bad trend in the industry, i would rather avoid an airline that doesn't train its pilots enough to be able to fly raw data at all times.

[fastcruise]

The regulatory approvals for DA and MDA differ, in most of the countries the height lost in case of a goaround is not factored for a MDA. So if you have a chart that states DA for a LNAV/VNAV approach do not add 50 ft, otherwise you would have to add.


Happy Landings

:ok:

[manuel ortiz]

Few years back I was very involved with the CDA topic.

At that time the 50 feet increment was just an arbitrary number that some operators used but in fact the requirement was just to establish an SOP with an increase to MDA to make sure this was not busted during the G/A.
Of course this depends on the altitude loss for each particular aircraft type.
The 50 feet number may be a good one size fits "all" but maybe not required as standard by most regulators.

No increase to minimums was only allowed *if* a DA was published *and* the operator had received authorization for such operations.

Something to keep in mind if you are using Baro VNAV is that most of the FMS's can not be compensated for temperature.
(An ILS GS is not affected by this.)

Operators have been using CDA for more than 25 years with excellent results.(Adding cushion to MDA) Published DA's for NPA's and authorizations for their use is not very old

As an active line pilot/Check Airman with some 32K hours and still a few years to go I celebrate the excellent posts provided here promoting the use of CDA.

Brgds.

Manuel