Determination of DA(H)

[shazapis]

Hello,

I am trying to find any regulatory reference to the need to add 50 feet to the MDA(H) of an NPA in order to determine the DA(H) for the CDFA technique.

I have had no luck thus far, although everybody tells me (referencing their ops manuals though, not a regulation) that this is indeed a requirement when flying a NPA using CDFA.

Any assistance will be greatly appreciated

Regards,

Spiros Chazapis
Athens, Greece

[BOAC]

You must not descend below MDA so you need to add something! Whether it is 50/30/or???.

[shazapis]

Hello,

Yes I know it makes perfect sense from an operational standpoint.
What I am looking for though is a specific reference in a regulatory document (by any source, FAA, ICAO, EASA, whatever).

Spiros Chazapis
Athens, Greece

[BOAC]

The 'regulatory document' says you must not descend below MDA. Your company SOPs will then tell you what you need to add - it's er - common-sense?

[shazapis]

Hello again,

No, I have been told that there is a specific requirement, originating from a regulation, that a minimum of 50 feet MUST be added to the published MDA(H), plus any additional SOPs/type specific/operator specific/whatever factor.

Actually, I have seen this with my own eyes but, alas, I can't seem to find it in my (large and messy) document library.

Please realize I am not making this up and I do have operational experience (I am a RW pilot). Also, forgive me if occasionally some of the things I write make no sense (not being a native English speaker can be a pain)...

Spiros Chazapis
Athens, Greece

[punk666]

Its an EU-Ops requirement to add 50ft to the MDA.

As mentioned above, you cannot decend below the MDA so when you start your go-around the aircraft will still decend around 30-40 feet before it will start to climb away...this 50 feet is a buffer.

With the DA(H) its the latest altitude you can start a go-around or I should say make the decision to go-around.

Make sure you read the plates as some NPA now use DA(H) instead of MDA.

[shazapis]

Hello,

Thank very much for the reply. It is exactly what I've been looking for.
Do you know if EU-OPS is available online ? (I am military and we do not have immediate access to EU-OPS)

By the way, do you know if there is a way to determine (ideally in the cockpit) whether a procedure is published by the authority with a DA(H) (and therefore already includes the 50 ft - am I right?) or if it is just a chart conversion by Jepessen or some other publisher (they specifically state that they do not add anything to MDA(H) in order to determine the DA(H).

Regards,

Spiros Chazapis
Athens, Greece

[BOAC]

Shaza - your English is fine! In other threads here about this some have said that their company says add 30 or 40 feet depending on type/height loss in the g/a..

punk - do you have a para reference for that?

[reynoldsno1]

Make sure you read the plates as some NPA now use DA(H) instead of MDA.

These are LNAV/VNAV APV procedures, and the DA is determined using methodology similar to that used for ILS - it is not just a case of adding 50ft to an MDA for these procedures.

[Nightrider]

Late in 2008 Jeppesen placed a Notam in their manuals to explain the procedure, the changes from MDA(H) to DA(H) and the requirements an operator has to follow. Not sure if it is still in place.

[rudderrudderrat]

Hi Nightrider,

Was this the explanation from Jeppesen you referred to?

jeppesen.com/download/aopa/dec99aopa.pdf

[Checkboard]

For approaches, the surveyor surveys the area and establishes an Obstacle Clearance Height (OCH) for the approach.

The regulator then determines an appropriate overall System Minima for each type of approach - this is the minimum altitude that an operator may authorise their crews to descend to on that type of approach.

The operator then looks at their training program, equipment and experience in an area of operations and determines the authorised minima for each approach (which in the vast majority of cases is the same as the greater of the system minima/OCH - and this is the number Jeppesen place on their charts, unless you have an operator-specific chart).

The Commander then sets the minimum for the approach on the day. This is the charted number in the vast majority of cases, but the commander has the right to say (for example) "On today's approach, with this weather, this terrain and these MELs, we shall add 200 feet to the published minima before making a missed approach and diverting."

From EU-OPS (available on-line at: EU-OPS):

Appendix 1 (Old) to OPS 1.430
Aerodrome operating minima

2. Minimum descent height. An operator must ensure that the minimum descent height for a non-precision approach is not lower than either:

(i) The OCH/OCL for the category of aeroplane; or

(ii) The system minimum.

3. Visual reference. A pilot may not continue an approach below MDA/MDH unless at least one of the following visual references for the intended runway is distinctly visible and identifiable to the pilot:

(i) elements of the approach light system;

(ii) the threshold;

(iii) the threshold markings;

(iv) the threshold lights;

(v) the threshold identification lights;

(vi) the visual glide slope indicator;

(vii) the touchdown zone or touchdown zone markings;

(viii) the touchdown zone lights;

(ix) runway edge lights; or

(x) other visual references accepted by the Authority.

The 50' addition to the MDA referred to above is applied by the operator (and is a pseudo standard) as part of step three above. The regulatory requirement is both to "not continue an approach below" AND an "operator must ensure that the minimum descent height for a non-precision approach is not lower than" (which is why most operators specify 50' addition) however there is no regulatory reference which specifies that "50 feet" shall be used.

You are, of course, legally bound to follow your OPS manual procedures.

[Nightrider]

rudderrudderrat no, it was a notam.

[rudderrudderrat]

Hi,

The NOTAM I seem to remember read like something like this.
(copied and pasted from the link (11) posted above.)

"Using the MDA as a DA
There are many aircraft today that are equipped with vertical navigation equipment and are capable and authorized to fly the computed descent angle on non-precision approaches. Because of this capability and the airlines’ desire to use more of the capability in their FMSs, the FAA issued a Joint flight Standards handbook bulletin for Air Transportation (HBAT) and General Aviation (HBGA). The Bulletin number is HBAT 99-08 and HBGA 99-12 and is applicable to operators under FAR 121, 125, 129, or 135.

The profile view with KENDO as the FAF shows a slightly different depiction of the descent angle. Instead of a dotted line, there is a dashed line from the FAF down to the MDA. Note that the dashed line stops at the MDA and is followed by a small arrow that curves up at the MDA. This shows that the MDA can be used as a DA(H).

Once the statement is made that the MDA can be used as a DA(H), a lot of explaining is necessary. And a lot of conditions must be met.

There is a small ball flag with the number “1” at the bottom of the dashed line. The ball flag refers to the note that states, “Only authorized operators may use VNAV DA(H) in lieu of MDA(H).” First, special approval from the FAA is necessary for each operator to gain this new benefit. And - the approval is only for certain airplanes used by the operator. And the big “IF.” The MDA may be used as a DA only if there has been a visual segment obstacle assessment made for the straight-in landing runway. The FAA has stated that there has been an obstacle assessment when the runway has a VASI or PAPI as a visual guidance system indicator, an electronic glideslope, or an RNAV approach published with a decision altitude.

Since an obstacle assessment has been made, the FAA has authorized the DA since it is assumed that a momentary descent will be made below the DA during the execution of a missed approach."

[Nightrider]

My memory failed me, it was a Briefing Bulletin, sorry. Here is the text, found after digging a lot:

AERODROME OPERATING MINIMUMS ACCORDING TO EU-OPS 1
General Information
The European Union published the . 2nd Amendment of EU-OPS 1 (Annex III to Regulation 3922/91)
This EU-OPS 1 is the replacement of JAR-OPS 1 and contains a new method to determine Aerodrome Operating
Minimums (AOM). The new method will become the European Standard on 16 July 2011 at the latest.
According to ICAO Doc 9365-AN910 (Manual of All Weather Operations) and Annex 6 to the Convention on International Civil Aviation it is the operator’s responsibility to establish Aerodrome Operating Minimums which need to be approved by the responsible authority.
The Appendix 1 (new) to OPS 1.430 describes the method which has to be used by all European Operators and within the European Union (EU).
Jeppesen will support your operations by replacing the current JAR-OPS AOM with the new Standard. Due to the huge number of airports (1000+) and procedures (5000+) the conversion could only be done on a step by step basis.
It is our intent to have all procedures revised to the new Standard AOM by 16 July 2011 for all airports within
– European Union member states,
– European Aviation Safety Agency (EASA) member states,
– Joint Aviation Authorities (JAA) member states and
– for other states where the currently used JAR-OPS AOM will be replaced.
In May 2008 we asked commercial operators about their plans for this EU-OPS implementation. The following items are directly related to the results of that survey:
a. All non-precision approaches will be reviewed to show CDFA (Continuous Descent Final Approach) profile and minimums.
b. In case of CDFA only, a DA(H) is shown instead of the previously published MDA(H). The missed approach point is still shown according to state source but the missed approach initiation arrow is moved to the point where the DA(H) is reached.
c. Jeppesen charted AOM do not include an add-on when current MDA(H) is replaced by DA(H). Pilots are reminded to check their operator’s Flight Operations Manual or similar documents whether they have to apply an add-on or not.
d. For CDFA profiles, Jeppesen will show DME vs altitude bands, distance vs altitude bands or timing vs altitude tables. If not provided by the State source those altitudes will be calculated by Jeppesen.
e. Non-CDFA profiles and minimums will be shown in exceptional cases only and may be combined with CDFA
profiles and minimums.
f. For CAT I operations with full approach light system (FALS) Jeppesen will include RVR values below 750m together with the higher values. Pilots are reminded to check their operator’s Flight Operations Manual or similar documents to fulfill the requirements for using the lower RVR values.
g. Lower than standard CAT I minimums are charted on request on customer tailored charts.
h. Other than standard CAT II minimums will be charted if the procedure is approved for such operations by the state of the airport.
i. Circling minimums must not be lower than the minimums of preceding instrument approach procedure. If circling MDA(H) and/or visibility must be raised due to higher straight-in values, only one set of circling minimums is shown which relates to the highest straight-in minimums.
Legend and ATC Pages
Jeppesen is currently reviewing the final version of this EU-OPS to replace the current ATC-601 (JAA AOM)
pages with a summarization of the new EU-OPS Aerodrome Operating Minimums.
In addition we will update the current Introduction 171 – 173 (JAR-OPS 1 AOM) pages to explain how the new minimums and the CDFA profiles are depicted on Jeppesen charts.
Conversion Plan
The publication of the new Standard of AOM will be done along with normal chart revision activity. It is planned
to convert all procedures of an affected airport at the same time.
We will create special minimums pages, numbered 10-9S (similar to current 10-9X JAR-OPS pages), as an interim solution.
Jeppesen will maintain or create JAR-OPS 1 minimums pages on customer request only.
Please contact your Jeppesen customer service representative for any special requirements, such as airline tailored minimums, airborne equipment considerations or your conversion priorities.
Charts with JAR-OPS label
The JAR-OPS label on Jeppesen approach and airport charts indicates that the minimums correspond to the rules described in Appendix 1 (old) to OPS 1.430 of the EU-OPS 1.
Future Outlook
The FAA will also publish new minimums which will be harmonized with the EU ones.
Jeppesen’s intention is to replace the current ECOMS and JAR-OPS Aerodrome Operating Minimums with the future harmonized version on a world-wide basis.

[savi]

Hello,

When you fly NPA as CDFA, you may use MDA/H as the DA/H with no height add-on.

(EU-OPS Operator - the minima calculated in accordance with Appendix 1 (New))


AIRBUS - Flight Operations Briefing Notes
From Non-Precision to Precision-like Approaches

The nature of the minima’s, MDA(H) or DA(H):
The MDA(H) being a minimum descent altitude, no altitude loss below the MDA(H) is allowed during the approach and go-around; this implies to either:
− Level-off at the MDA(H) - step-down / dive-and-drive technique - until visual references are acquired:
− Initiate the go-around above the MDA(H) - constant descent-angle technique - if no visual references are acquired, in order not to “duck under” the MDA(H).
This is obviously not required when the applicable minima is a DA(H), which is a decision altitude; if no visual references are acquired when reaching the DA(H), a go-around must be initiated at DA(H)

[BOAC]

Originally Posted by savi

you may use MDA/H as the DA/H with no height add-on.

- no. Read the note again!

Initiate the go-around above the MDA(H) - constant descent-angle technique - if no visual references are acquired, in order not to “duck under” the MDA(H).

[411A]

Quote:
Initiate the go-around above the MDA(H) - constant descent-angle technique - if no visual references are acquired, in order not to “duck under” the MDA(H).

Much consternation, it seems.
All this can be avoided, of course, if one uses a sensible alternative, dive/drive....IE, fly a short level segment, from which a go-around does not require adding an altitude 'buffer'.

It would appear that certain companies/regulatory authorites have made all this much more complicated than it actually needs to be.

No surprise there.
After all, how else would they justify their salaries?

[BOAC]

Seems to be an American thing 411? From Jeppesen:

There are many aircraft today that are
equipped with vertical navigation equipment
and are capable and authorized to fly the
computed descent angle on non-precision
approaches. Because of this capability and
the airlines’ desire to use more of the
capability in their FMSs, the FAA issued a Joint
flight Standards handbook bulletin for Air
Transportation (HBAT) and General Aviation
(HBGA). The Bulletin number is HBAT 99-08
and HBGA 99-12 and is applicable to
operators under FAR 121, 125, 129, or 135.

My Bold

and

Most aviation authorities and industry leaders
have recognized the safety benefits that will
be gained by reducing the number of nonprecision
approaches that don’t have vertical
guidance. The addition of vertical guidance
should help to reduce the number of CFIT
(controlled flight into terrain) accidents.
Recently, the NTSB has recommended that
aircraft with onboard capabilities for vertical
guidance should be required to use them
during non-precision approaches. They have
also recommended that within 10 years all
non-precision approaches approved for air
carriers should incorporate constant-angle
descents with vertical guidance from
onboard systems.

Which FAR do you fly under? Have you seen the bulletin?

[EMIT]

The famous 50 ft

411A, if you want to fly level at MDA, how high above MDA do you have to start levelling off, in order not to sag through it, would about 50 ft be a nice estimate?
In that way the margin discussion turns into a storm in a bowl of dust.

The 50 ft have just become a sort of industry standard figure for most types (not all, e.g. the famous MD-11 does not require that margin, lightning fast acceleration on Go Around apparently)

Am not gonna chastise you for the D/D technique, it's just that the trend in regulation and in many outfits is moving away from it and today's avionics make it possible to achieve good results with the "artificial glidepath" technique, an accurate present position is the basic element that makes it possible (yes, some aircraft types had that already eons ago).