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alphacentauri
You could argue the same point with an ILS approach. Work those same numbers with a Cat II. |
Yes, but the concept of protection on an ILS is different than for an NPA. There is no such thing as a minimum obstacle clearance for an ILS, rather a set of surfaces to which obstacles are not allowed to penetrate. If they do penetrate then you derive a DA from the penetration. This is where lack of understanding from a procedure design point of view is leading people to the false conception that an MDA can be used as a DA, they are two totally different concepts, based around two different types of approach design criteria
If you go around on a CAT II, especially below 161ft it is widely accepted that your wheels may touch the ground. Would you like to do that off an NPA to an aerodrome with no HIALS? |
Its not the the airplane touching the runway that i worry about. It is when you hit something else that it becomes a problem.
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Alpha,
Well stated, this coupled with the condition of most State's obstacle databases... I am wondering what 757 is using for vertical guidance? If it is baro-vnav, lower temperatures will get you down to a 2.5 degree GPA , thats 260 feet low at the FAF, and you dont even know it. |
That's the whole concept of an ILS - that is so precise that you will not hit anything but the runway.
Hence, the reason that you have to make a go around is that you don't have visual reference to make the flare and the roll out. With CAT2/3 ground equipment, it's so precise that it's acceptable that that you touch the runway during the go around as well. Assuming of course you made a stabilized approach and made the go around due lack of contact. Making a go around at CAT2 min with full scale deflections is maybe not such a good idea. :ouch: |
Here is Boeing take on the matter by the way:
When specifically authorize by the appropriate regulatory authority, approaches may be flown to the following minima: • a published VNAV DA(H) • a published MDA(H) used as a decision altitude. When either of the above minima are not specifically authorized, use the MDA(H) specified for the instrument procedure. Note: If using an MDA(H), initiating a missed approach approximately 50 feet above MDA(H) may be necessary to avoid descending below the MDA(H) during the missed approach, if required for the procedure or by the regulatory authority. For my part this is only if the minimum is listed as a DA on the chart. |
The ILS is assumed to have a 200 foot ROC....that is the surface we use for obstacle penetration, the 34:1 surface is the visual surface for obstacles...
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Cosmo
In the FAA, authorization to use DAs is a OpSpec under HBAT 99-08, so it won't be on a chart, but the company manual. This probably has been updated, but FAA authorizations are based on it. And, it must be a commercial operator under FAR 121, 125, or 135. |
GF,
I am in Europe. But for the sake of the argument, let's take USA. You fly from Miami to somewhere in Bogota. How can the FAA allow you to go below minimum during a go around in another country? The same for EU, all fine and well within EU OPS states, but what about when I fly to e.g. the middle east? There is a big world outside US and EU. |
That's the whole concept of an ILS - that is so precise that you will not hit anything but the runway. It is possible that the A/C will miss the landing area when doing CAT II hence the requirement for a visual segment. |
Even when it is precise (or accurate, which would be more useful ;)) there is also the issue of reliability, which with the lower systems requirements for the less accurate options also leads to a need for pilot involvement.
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Cosmo,
Didn't say the FAA could, it is true only in the US |
I'm lost
Think I'll divert - this is getting too complicated for mortals like me! Go Around Flaps ! :O |
This was posted by JimL over in the rotorheads forum, but is very applicable here...
Safety Reminder Message from Eurocontrol (dtd. 03/02/2010): SYNOPSIS EUROCONTROL has been advised of concerns about the use of Decision Altitude/Height (DA(H)) instead of Minimum Descent Altitude (MDA(H)) as the aerodrome operating minima (AOM) on some non-precision approach charts produced by Jeppesen for countries applying “EU Ops”. This has become a source of confusion and has implications for aircraft operators. ANALYSIS Commission Regulation EC 859/2008 dated 20 August 2008, EU Ops 1.430(d) 2 (applicable from 16 July 2011) states that “all non-precision approaches shall be flown using the continuous descent final approaches (CDFA) technique”. EU Ops, 1.435.9 defines CDFA as, “A specific technique for flying the final-approach segment of a non-precision instrument approach procedure as a continuous descent, without level-off from an altitude/height at or above the Final Approach Fix altitude/height to a point approximately 15m (50ft) above the landing runway threshold or the point where the flare manoeuvre should begin for the type of aircraft shown”. Moreover, Appendix 1 (New) to OPS 1.430, states that, “the missed approach, after an approach has been flown using the CDFA technique, shall be executed when reaching the decision altitude (height…”. Note: Additional CDFA guidance material is currently under preparation. Jeppesen only publish DA(H) on CDFA-based, non-precision approaches where the equivalent national AIP minima is shown as an OCA(H). Where national AIP minima is shown as a MDA(H) or for non-CDFA-based, non-precision approaches, Jeppesen continues to publish MDA(H). ICAO PANS OPS definitions: Minimum Descent Altitude/Height (MDA(H)): “a specified altitude or height in a non-precision approach or circling approach below which descent must not be made without the required visual reference”. Decision Altitude/Height (DA(H)): “a specified altitude/height in a precision approach or approach with vertical guidance at which a missed approach must be initiated if the required visual reference to continue the approach has not been established”. Obstacle Clearance Altitude/Height (OCA(H)): “The lowest altitude or the lowest height above the elevation of the relevant runway threshold or the aerodrome elevation as applicable, used in establishing compliance with appropriate obstacle clearance criteria”. The DA(H) value shown on the Jeppesen charts is at least equal to the published national AIP OCA(H)) minima for a non-precision approach. Importantly, however, the DA(H) published on the Jeppesen charts does not include any add-on to account for any height loss during the initiation of a missed approach. This is not mentioned directly on the charts, but it is described in the Jeppesen Briefing Bulletin JEP 08-D and in the legend pages to the Jeppesen Airway Manual. EU Ops 1.430 (a)1 states that, “an operator shall establish, for each aerodrome planned to be used, aerodrome operating minima…” YOUR ATTENTION IS REQUIRED Aircraft operators are invited to: Note the issue above specifically with a review of the need to consider the requirement for an add-on factor to account for height loss at missed approach initiation. Share their operational experiences. It is critical to flight safety that pilots brief the DA(H) or MDA(H) (as appropriate) so that there is no ambiguity as to what minimums are being used irrespective of the type of approach being flown. FURTHER READING Commission Regulation EC 589/2008 (EU Ops) dated 20 August 2008. SKYbrary - EU-OPS ICAO Doc - 8168 PANS OPS Jeppesen Airway Manual Jeppesen Briefing Bulletin JEP 08-D - 26 Sep 08 at http://www.jeppesen.com/main/corpora...b_jep_08_D.pdf Draft Implementing Rule for Air Operations of Community Operators (EASA NPA 2009-02B) (CDFA Guidance pages 155-165). EASA - European Aviation Safety Agency For more information contact, EUROCONTROL Safety Alerts Coordinator, Richard Lawrence at: [email protected] |
I am reading this thread as a result of studying non-precision approach practices, because of the UPS BHM accident in Aug, 2013, where they hit obstacles after descending visually below the MDA to attempt to land.
Any my US -121 airline, for a non-precision approach (which we normally fly a CDMA), if there is a published glidepath on the approach chart (jeppesen) and a published glidepath in our FMS database, we are to set the MDA as the DA. Consequently, when going around we will go below the MDA. If there is NOT a published glidepath, then we must add 50' to the MDA, which should keep up as above the MDA if we go around. |
In many countries the DCA has made mandatory to add 50ft.
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we always round up to the next 100 for the mda. mainly for the altitude alerter once we leave the mda with a visual on the runway the alerter is set to missed approach alt
and while the constant rate of descent is preferred, we sometimes use the so called dive and drive if we want to get in. |
Are there ever times when you DON'T want to get in? What's the point of flying an approach differently depending on whether you really want to get in or not? Shouldn't you fly the approaches the same way every time? After all they are not there for fun, if you are doing the approach you presumably would like to land off it.
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we sometimes use the so called dive and drive if we want to get in |
Gentleman, i'm shocked.
Has the house of flight safety declined to a wh*re house, where everybody is doing what suits himself? The definition of an MDA / MDH has not changed, not as far as i know, how come it is handled differently than before? |
Franzl, they are just kids playing now. No proper knowledge at all.
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aerocat and boac
I simply meant the following: sometimes the dive and drive technique allows you to see the runway and maneuver around clouds that might otherwise be in the way of a constant descent. if there is a cloud at the mda in the exact place that the constant descent leads you to, then you don't get in. if you get to the mda early and DO NOT LEAVE THE MDA until it is safe to do so, you might observe the runway and a way to it that the constant descent would not allow you to see. I DO NOT, say again, DO NOT advocate leaving the MDA until the runway can be safely made. But the harsh reality of non precision approaches simply means the clouds have to be out of the way...flexibility, crew coordination, precise understanding of the particular approach, airport environment and the like all are part of the equation. and for the record I do not steepen an approach to a runway if the runway is seen ''too late''. I also remind you all that circling or non straight in approaches also have an MDA and even with the restrictions airlines now impose of basic vfr to circle, observations at MDA on the early side (or basic vfr equiv for certain airline ops ) aid in the approach. oh, and just in case...sometimes, in odd situations, a non precision apch may get you in while an ILS leaves you in the cloud for the same runway... |
Understand what you're saying, though the point of a constant descent approach is to hit the MDA on profile (ie 2w/2r on PAPI), so if you can't get in off the CDA because there is cloud on profile at the MDA then you shouldn't be getting in off the dive and drive either if, as you say, you are not leaving the MDA below or above profile.
oh, and just in case...sometimes, in odd situations, a non precision apch may get you in while an ILS leaves you in the cloud for the same runway... |
we have some exceptions to your company's rule.
lining up on final at at least one airport here requires maneuvering at low altitude. |
Originally Posted by Aerocat
so if you can't get in off the CDA because there is cloud on profile at the MDA then you shouldn't be getting in off the dive and drive either if, as you say, you are not leaving the MDA below or above profile.
Given the number of times this scenario is actually encountered, CDAs are better. No worries about bumping into/off/thru limiting steps. |
thanks capn blogg
originally, these approaches were called, ''cloud breaking approaches'' I also recall at one time, apchs were based on visibility and ceiling...now of course most are just visibility. |
oh, by the way...some ILS approaches have higher mins than some localizer only for the same runway...interesting huh?
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flarepilot:
oh, by the way...some ILS approaches have higher mins than some localizer only for the same runway...interesting huh? |
oh, by the way...some ILS approaches have higher mins than some localizer only for the same runway...interesting huh? |
Europe once again shows its anarchist face against UNO/ICAO system. They contest the laws, the logic, the reality of the ground's and obstacles' limits. Please don't fly out of Europe and don't transport not European passengers. (But once again what is "Europe" and which "Europe" - ICAO European region, European Union of 28 sovereign Countries, Eurozone, Benelux, Geographic zone from Atlantic to Oural? ?) Watch Europe's crazy history ! Aviation safety and travel freedom needs to have only one system based on international worldwide treaties in ICAO. Millions People died during worldwide Wars to get SUCH FREEDOM in a SAFE world.
Constant descend angle method once again shows its ideologic agressive and limited private conception. Dive and drive method respects the actual ground's shape irregularities and is building approach procedures at minimum price with minimum descend (and not decision) altitude. Dive and drive concepts are build on experience of pilots, not on insurance rates and off-shor Banksters connected to Kings and Queens European Countries. Dive and drive method respects operational mathematical analysis rules where TWO sorts of parameters - and not only ONE - are used differently : 1. variables who state Limitations ("constraints"), and 2. adjustables variables who increase performance, wealth, optimization. In the approach design the first are mandatory couples distance/altitude (true altitude not baro dependant indicated altitude or angle), the latter are used to verify the path (tables in NPA) but are not mandatory. I would like to refer too to the existence of the 15% rule of obstacle clearance in NPA procedures design : The captain of the F-GGED crash flew it (220 kts, 3300 FT/mn) but could not see he had to stop at 3660 FT until the FAF ar 7 NM DME to STR VOR, as the AF/ATLAS chart did not show the FAF position where altitude is mandatory. Appearant "Constant" descend angle method just ignores it.... as it decides to ignore MDA is ground- minimal. |
@ RetiredF4
I'm shocked too! |
capn blogg
check out KRNO, reno,nv usa...both ILS 34L and LOC DME 34L look under cat a and b...loc dme has lower vis req than ILS |
... some ILS approaches have higher mins ...
Although not a direct comparison, an old NPA to Zurich 29 had visibility minima where it was impossible to see the runway at 'MDA' when on the approach path.
The then procedure design assumed level flight to MAP, from which if the runway was seen resulted in a 6 deg flight path. Unfortunately it took a tragic CFIT accident to alert the authorities to this and change the procedure, and ultimately to install an ILS. IIRC this accident also strengthen the case for EU CDA regulation and procedure review by ICAO; perhaps other authorities have yet to learn, adopt CDA, or implement the MDA concept. |
roulishollandais
"Millions People died during worldwide Wars to get SUCH FREEDOM in a SAFE world." I was not aware that WW1+2 were about the right to fly NPAs in a certain way. Thank you for enhancing my education. |
Originally Posted by Flarepilot
check out KRNO, reno,nv usa...both ILS 34L and LOC DME 34L
look under cat a and b...loc dme has lower vis req than ILS |
http://155.178.201.160/d-tpp/1309/00346I16R.PDF
http://155.178.201.160/d-tpp/1309/00346L16R.PDF Lower mins, both ceiling & viz, for all cats, ABCD + additional E on the LOC, both straight-in and circling, versus the ILS. Why would anyone fly the ILS in preference other than to avoid reading the note about glider activity? Long live the NPA. :) There is an LPV with even lower mins ceiling wise, lower viz than LOC for CD, higher viz than LOC for AB. Go figure. http://155.178.201.160/d-tpp/1309/00346RX16R.PDF |
I assume it is the different slope that raises the minima although that is a mighty jump to 7SM! I guess it must be the 6361' or 6219' that does for the ILS. Why put in a 3.1 ILS??
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True the LOC is 3.49 VDA to 55' TCH....but both the ILS & LPV are 3.10 degrees to a 63' TCH??
Identical slope & TCH and the LPV gets you ~1200' lower mins than ILS. Terps 102? :) |
Ah - didn't look at the LPV plate.....................yes, strange. Interesting too that the ILS does not refer to the MALSR, but since it appears little more than a 'cloudbreak'..........................
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dear capnblogg
you are welcome...and thanks for the civil conversation...so many say things are not so. I grew up flying in nutty mountainous / special airports all over the USA...go figure. Reno, Lake Tahoe , Truckee...all mountainous with unique stuff unique stuff back east too. all i'm saying is that whenever anyone says NO...well, you have exceptions somewhere. and I could tell you stories about ...well, that would just garner someone calling me a liar and i'd rather be a flyer than a liar. folks, you can also check certain notes about papi not being useable more than six miles out due to terrain...and I mean TERRAIN. |
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