2 NDB approach

[pensador]

Who knows the max. vertical and lateral deviations on the glide path during 2NDB approach? any formulas?

[Daysleeper]

What glidepath!

NDB approaches are non precision, there may be a list of advisory altitudes (or heights), there may be minimum altitudes (or heights) at certain points and then there will be a Minimum descent altitude below which no part of the aircraft may pass unless the appropriate visual references are in sight.


Max lateral deviation is 5 degrees, though I can't lay my hand on the exact reference for that as I'm in the garden!

[pensador]

How does measure this 5deg.?

[philc1983]

You obviously can't go below the MDA (or circling minima, if that is necessary for your approach) or any stop altitudes that are detailed on the plate. If none you are quite allowed to descend to your MDA and maintain that until you reach the MAPt or you become visual with the runway.

In terms of lateral errors permitted you must maintain a QDM/QDR that is +-5 degrees of the designated approach. For example if the inbound QFU is 270 (all magnetic unless stated on plate) your needle on the RMI/RBI cannot deviate more than those 5 degrees either side. So it's your instruments that measure and show you this.

[BOAC]

Phil - caution - I don't feel we are talking to a pilot here.

If none you are quite allowed to descend to your MDA and maintain that until you reach the MAPt or you become visual with the runway. - may be correct in Russia but not under JarOps

[Christo]

How does measure this 5deg.?

If your QDM to the beacon is out by more than 5 deg to the approach path.

It's also easier to look at the plate. I've attached Wonderboom's 2NDB. You will -see that you start at +- 6000' once established. You can descend to 5100' at WB and then continue to the MAPt at WR.

http://www.caa.co.za/resource%20center/Charts/AERONAUTICAL%20CHARTS/W/FAWB_WONDERBOOM/NDB_01/FAWB_BREAKCLOUD%202%20NDB%20RWY%2029_NDB-01_20NOV2008.pdf

[King Julian]

I don't see any wrong with Phil's post. This system is practiced in the NZ & Oz.
You can descent up to your MDA and continue it till the MAPt. or till you become visual.

And as stated by Phil lateral is 5 deg on both sides
And even though vertical is limited to the MDA, I've seen many renowned operators go a bit below, say nothing more than 50-70ft to catch a glimpse of the ground to go for an approach.

Hope this helps.:ok:

KJ

[BOAC]

I don't see any wrong with Phil's post - have another look? It is not 'wrong', just not complete. Do you know if Pensador flies only in 'NZ and OZ'?

[Skipping Classes]

BOAC, can you point exact place in JAR-OPS (or EU-OPS for that matter) where it does not allow you to descend to the MDA once all the other altitude constraints on the approach have been met/passed?

If you are talking about CANPA, which is mandatory by many operators, as far as I know it is not mandatory under JAROPS.

SC

[FE Hoppy]

ops 1.430

All non-precision approaches shall be flown using the continuous descent final approaches (CDFA) technique unless otherwise approved by the Authority for a particular approach to a particular runway. When calculating the minima in accordance with Appendix 1 (New), the operator shall ensure that the applicable minimum RVR is increased by 200 metres (m) for Cat A/B aeroplanes and by 400 m for Cat C/D aeroplanes for approaches not flown using the CDFA technique, providing that the resulting RVR/CMV value does not exceed 5 000 m.

There are of course plenty of exceptions.

[Pilot Positive]

No glide path as such Pensador - only the one you construct - as its a Non-precision approach.

I prefer to attain a Constant Path Descent as definately not comfortable with sitting at Minimum Descent Altitude (MDA) early or even going below MDA unless fully visual.

Use check heights or Rate Of Descents indicated on your Jeppie or Aerad plates to monitor the glide/target profile and get your PNF to call out deviations as you go... :cool:

[Chris Scott]

Quote from Pilot Positive:
Use check heights or Rate Of Descents indicated on your Jeppie or Aerad plates to monitor the glide/target profile and get your PNF to call out deviations as you go...

Yes! And, if you're a lucky Airbus driver, use the "bird": with or without the FD (subject to your SOPs). If using AP, you'll have to anticipate the start of the descent, due to the time/distance taken for the AP to achieve the push-over.

Levelling off at the MDA in a large aeroplane, and - having become visual at, say, 400 ft aal - catching the right moment to start down again, can be a nightmare, particularly at a "black-hole" airfield. :eek:

One thing to bear in mind with the continuous descent is that, if you are not planning to level off at the MDA (and why would you want to in a big jet?), you must go-around from a suitable margin above MDA, to avoid going below it during the G/A.

Chris

[flyboyike]

If only I were smart and had any idea what an NDB approach is...

[FE Hoppy]

One thing to bear in mind with the continuous descent is that, if you are not planning to level off at the MDA (and why would you want to in a big jet?), you must go-around from a suitable margin above MDA, to avoid going below it during the G/A.


er....... not always the case anymore. As you may find that DH is published rather than MDA and in this case it should be treated as a DH and a certain height loss below is accounted for in the procedure.

[Two's in]

I've seen many renowned operators go a bit below, say nothing more than 50-70ft to catch a glimpse of the ground to go for an approach.

...would that quote fit on a headstone?

[pensador]

Sorry for question: What do the abbreviations QFU, QDM/QDR mean? For me they are new!

[gusting_45]

Why worry about NDB approaches. NDB's will all be gone the way of the dinosaurs very soon (at least in the modern world), and good riddance to them.

[FE Hoppy]

QDM Magnetic bearing to a station
QDR Magnetic bearing from a station
QFU Magnetic bearing of the runway in use

[Chris Scott]

gusting_45,

I seem to have been hearing that argument since the 'Sixties! Unfortunately, some poor sods still have to do them for real. If you don't:
(a) count yourself spoilt:
(b) don't bother to come on this thread? :rolleyes:

FE Hoppy:

I assume you are right, but the basic principle would still apply; and the DH (or decision altitude?) would have to be type-specific, to cater for different flare performances. If I remember correctly, ILS DHs are normally predicated on the use of a radio altimeter, requiring suitably flat terrain. In the case of non-precision approaches, the latter is often not available, so any decision height/altitude would presumably be associated with a barometric altimeter?

[Some of us are old enough to remember when DHs were first introduced on ILS approaches! Prior to that, in the UK at least, we only had CH (critical height); the ILS equivalent of MDA. We even used to level-off at critical height on an ILS. NOT a good idea, as I'm sure most of our readers are aware, particularly on a jet... :eek: ]

Chris

[Pilot Positive]

Why worry about NDB approaches.

Because some of the smaller airports cant afford a nice ILS or a even VOR??? :rolleyes:

Somethings are better than nothings ;)

[pensador]

FE Hoppy thanks a lot!

[411A]

How does measure this 5deg.?

It is accomplished using the installed Radio Magnetic Indicator (RMI)...and if you don't know what this is, you have no business doing NDB approaches...:ugh:

[Don Coyote]

FE Hoppy

The minima is still a no go below height on a non-precision approach. This Briefing Bulletin (http://www.jeppesen.com/main/corporate/documents/aviation/notices-alerts/hubwatch/BriefingBullentins/abb_jep_08_D.pdf) from Jeppesen has some information; take particular note of point c.

it has caused some confusion by calling it a DA(H) but you still cannot go below it.

[rudderrudderrat]

Hi Don Coyote,

Thanks for the Jepp Ref. I've checked para "C" and our Ops manuals agree with FE Hoppy. We don't add anything to a "DA" - but we add 50ft to a "MDA".

[Don Coyote]

rudderrudderrat

That is correct as your manuals will currently written in accordance with approach calculations based on Appendix 1 (Old) to OPS 1.430; the DA associated with a NPA are calculated in accordance with Appendix 1 (New) to OPS 1.430. The New rules will come into effect by 2011.

Approach chart producers are having to update all minima in accordance with the new rules and for a while you will see minima as JAR-OPS and EU-OPS. The EU-OPS minima are calculated using the new rules.

Your operator should specify that you can only use the old minima (JAR-OPS)until all your approaches are calculated in accordance with Appendix 1 (New) to OPS 1.430. Once that is done, you will only be able to use the new minima; at which point the entry in your Ops manual will be clarified to state that you have to add 50' to all non precision approaches (i.e. MDA & DA) in order to not go below the minima. For precision approaches the DA will be treated as it currently is i.e. you initiate the GA at DA and pass slightly below it.

I apologise that it is all a bit confusing but I do not make the rules!

[rudderrudderrat]

Hi Don Coyote,

at which point the entry in your Ops manual will be clarified to state that you have to add 50' to all non precision approaches

Does this mean that sometime after 2011, we'll be adding 50 ft to all NPA minima (either DA or MDA) again? If so then I'm really confused.

A MDA is a minimum descent Altitude - i.e. don't go below.
A DA is the point I make the decision to continue or not, and since I have a ROD - I'll subsequently sink up to 50 feet below my DA. So what's the point of publishing a NPA DA then?

[Don Coyote]

Apparently it is down to a misunderstanding by the service providers who produce the charts. Because the minima is based on a continuous descent profile, they call the minima (under the new rules) a DA even though it is a non precision approach. For a non precision approach (under the new rules)you will still be unable to pass below the minima regardless of whether it is a MDA or DA; hence the requirement to add an amount appropriate to your aircraft (nominally 50')

Essentially nothing will change in that currently just add 50' to all minima for non precision approaches (currently only MDA), after the change, just add 50' to all non precision approaches (either MDA or DA).

The important point is to make sure that you are using the correct minima (either JAR-OPS or EU-OPS) dependant on what your operator is currently approved to use. There are no DA minima for JAR-OPS approaches so if your operator has not changed and you have a minima shown as a DA for a non precision approach then you are using the wrong minima.

[rudderrudderrat]

Hi Don,

This link is for LGW GNSS 26L (http://merrowresidents.org.uk/jeppcharts/LGWGNSS26L) and is under JAR-OPS, it is a NPA and has both DA and MDA published (depending on whether you have vertical guidance or not).

Can you explain why?

[FE Hoppy]

@Don Coyote,

How do you reconcile this statement from ops 1 (annex 1 (new) to 1.430 c, 2) with your plus 50ft?

The missed approach, after an approach has been flown using the CDFA technique, shall be executed when reach- ing the decision altitude (height) or the MAPt, whichever occurs first. The lateral part of the missed approach pro- cedure must be flown via the MAPt unless otherwise stated on the approach chart.

[FlightDetent]

Apparently it is down to a misunderstanding by the service providers who produce the charts. Because the minima is based on a continuous descent profile, they call the minima (under the new rules) a DA even though it is a non precision approach. For a non precision approach (under the new rules)you will still be unable to pass below the minima regardless of whether it is a MDA or DA; hence the requirement to add an amount appropriate to your aircraft (nominally 50')
With all due respect, I do suggest that you do not appreciate the full picture. The chart providers have very good understanding of regulatory changes in OPS procedures and that is why they correctly show DA for EU-OPS (appendix new to 1.430). As you correctly say, unless you are approved for such operations by local CAA you should not be using those charts.

If, on the other hand, you have the approval, there are two possible solutions. The classical approach/approval that you describe would have you add an increment (i.e. 50 ft) and treat NPA DA as an MDA and there is nothing wrong with that. Other possible approval will allow you to use DA with no additionals and operate with "decison" at DA (and duck under during go around) as opposed to classical "level off" at (M)DA. Extensive reading and good understanding of Doc 8148 both volume I and II is required to find out that the obstacle distance on NPA with DA is in fact still greater than o.d. on an ILS with DA. And nobody disputes DA on ILS, we'll agree to that.

The previous requirement to avoid flight below MDA was based on the situation that you continue towards MAPt after reaching MDA. As long as your operator addition was 0 (common case) MDA = OCA or system minimum and flight below OCA clearly must be avoided. The M.O.C. to calculate OCA on NPA is still greater than the margin used for determine OCA for ILS approaches. Nowdays, level flight to MAPt is about to be prohibited. Ergo, you do not need to treat NPA OCH (or system minimum) as an MDA anymore because the level-off is not an option. So the only remaining problem is the go-around "duck under" called height loss by 8168. The margin for precision approaches allows for go around height loss and more. The minimum obstacle clearance for NPA is greater than margin and also is based on wider protection areas. With regard to obstacle distance (my generic term) a go around on a NPA DA (no additionals) is safer than GA on an ILS as was always the case - Doc 8168 vol I and II reveal. Hence the possibility to use DA for NPAs because level flight towards MAPt (which would put you below OCA and is clearly forbidden) is no longer an allowed manoeuvre.

Sincerely,
FD (the un-real)

[King Julian]

I know there is a thread on the crash but my question is relating to the NDB approach they were doing.
Read that they were on an NDB approach as there was no VOR or ILS.
And what bewilders me is that haven't they got an MDA and how can you go below it to such an extent.

[pensador]

Thanks everybody a lot for you comments!!!!

Use check heights or Rate Of Descents indicated on your Jeppie or Aerad plates to monitor the glide/target profile and get your PNF to call out deviations as you go...
Why worry about NDB approaches.
You obviously have never flown in Russia. In 98% of Russia airports when performing 2NDB approach during descend after the FAF you have the ONLY POINT (inner marker) with hight and distant to check your position. The QDM/QDR accuracy is up to 4deg. to the left and right. And now imagine your position at MDH when weather is munimum for 2NDB appr at night!
P.S.: in addition some airports hasnt PAPI light at all
con respecto!

[seilfly]

Excuse me if this is a stupid question, but I have never heared about it before:
What is 2NDB approach, and how is it different from a NDB approach? 2NDB approach containing 2 NDBs in the procedure?

[BOAC]

Probably - I think Ohrid used to have such in days gone by - you 'shuttled' between the two beacons with reversals, hold entries and all sorts of non-magenta line stuff:)

[By George]

I say Mr Seilfly, you American chaps are awfully spoilt, when you travel outside the goold old US of A you will find lots of twin NDB thingys and even worse. What has always puzzled me is they never seem to line up with the R/W. Melbourne in Aus, R/W 16 is a rare exception. When flying in the US on the 'NAV RAD' page there is no NDB to enter manually, always seems odd to me that you lot never use 'em.

[flyboyike]

Heck yes, we're spoiled. In fact, as an airline pilot, I have NEVER shot a non-precision approach in IMC. It's been either a visual or an ILS. My last NDB approach was back in 2001 and that particular NDB has since been deactivated.

[BOAC]

Visuals in IMC - damn - always knew you yanks were good:) Takes me back to RAF Germany low flying days - pulling up at the end to fly an IMC PAR..You would think a country like the US could afford the odd VOR, though?

Twin NDBs procs always used to be a challenge with a single receiver/single pilot.:cool:

[flyboyike]

There are plenty of VORs, but we just don't seem to use them much. In IMC we fly ILS, otherwise a plain old visual.

[seilfly]

Well I am Norwegian; just happen to live in the US for a couple of years. It must be my excellent languageskills that made you think of me as an American :)

I am not a knight of the magenta lines/arrows so I do not know what the NAV RAD page does... but taking the IFR charts into account, there are still a lot of NDBs around in the US... It seems like those NDBs are servicing the small airports, and my impression is that they serve the small, old, airports.

New, small airports seem to get the GPS-approaches and/or a VOR/DME approach based on a VOR/DME waaaaay off the field* (nothing wrong with that) instead of setting up a stoneage NDB at the field. The old small airports seem to be getting the GPS-approaches as well, ready to decommission their NDB at the next breakdown or when the NDBs are withdrawn nationwide (whichever occurs first) :)

* like this one: http://204.108.4.16/d-tpp/1004/05537VDA.PDF - SGR also has an ILS and two GPS approaches

[Pilot Positive]

The old small airports seem to be getting the GPS-approaches as well

We should be so lucky in Europe... :) When will the CAA review this further?

[pensador]

Our experienced pilots always tell me about complex navigation. That includes not only the ILS beam usage during approach but any other navigation means that you have to control your position on the descent trajectiory.
Who knows weather there is a true ILS signal you capture or not!

[LLLK]

The minimum obstacle clearance for NPA is greater than margin and also is based on wider protection areas. With regard to obstacle distance (my generic term) a go around on a NPA DA (no additionals) is safer than GA on an ILS as was always the case - Doc 8168 vol I and II reveal.

This has not been the view of the ICAO Obstacle Clearance Panel (now Instrument Flight Procedures Panel), who are responsible for Doc 8168, whenever someone has suggested that, for CDFA, MDA can equal DA. Also note the safety advisory that EUROCONTROL recently issued:EUROCONTROL - Safety Alerts Board (http://www.eurocontrol.int/safety/public/standard_page/safety_alert_board.html)

[FlightDetent]

LLLK: Thanks, good sir. I stand my argument back until further more reading and research is done.

Sincerely,
FD (the un-real)

[seilfly]

Pensador: The pilots know wether they have tuned the correct ILS or not by making sure they have tuned the correct frequency and then identify the station by confirming the station identifier on that frequency with the identifier on the approach procedure.

-If I understood your post correctly

[BOAC]

pensador refers, I'm sure, to false lobe capture?

[seilfly]

Fly the GS intercept altitude until intercepting the GS, crosschecking your altitude against the approachplate. I.E. on this approach: http://204.108.4.16/d-tpp/1004/00924IL35.PDF (ILS35 to KLAW) if you are on the correct GS beam, your altitude should read 2298ft when passing the OM.

An instructor I flew with a couple of times during primary flight training had experienced false glideslopes once when descending ONTO the GS instead of intercepting it from the GS intercept altitude. He was waaaaay above the 2298ft when passing the OM on the above mentioned approach.

(To explain excactly what I mean... the small font numbers close to the FAF-symbol is the altitude of the point where the GS intersects the FAF DME and/or OM

Other considerations?

[Christo]

You can ID false glideslopes by your excessive rate of descend and by the check heights on the plate.

[john_tullamarine]

experienced false glideslopes

I inadvertently set up a situation in a 737 simulator some years ago (which the crew, unfortunately, managed to blunder/stumble into) where the autopilot merrily and quite cheerfully intercepted a false localiser signal. Interestingly, the crew realised that something was not quite right .. but it still took them a frightening period of time before the penny dropped.

Until the jungle drums got the message to all and sundry, I was able to reconstruct the situation for the training benefit of a reasonable number of crews ..

Message is to use the ILS entry keyhole positively and every time. Shortcuts might well prove to be direct to the smoking hole in the ground.

It's well worth a read of the Air New Zealand B767 fright at Apia ..

[pensador]

seilfly, you are absolutely right about false glideslope catpure.

[pensador]

BOAC. pensador refers, I'm sure, to false lobe capture? But a glideslope beam as well

[Pilot Positive]

False glideslope capture:

Monitor ground speed and anticipate ROD based on the glide requirement. Does it look right? How does altitude look against the DME (the old 300 feet/nm on a 3 degree etc..)? How does altitude compare at the check altitude?

If something is amiss either: Check with ATC, initiate a go-around or if both pilots have confirmed that there is a glide slope issue and the aircraft is no danger and within tolerances at that point, then use raw data, assume LLZ only and use plate info to manually execute the approach :eek: bearing in mind the new MDA.

Depends on your SOPs of course. :ok:

[Don Coyote]

LLLK

Many thanks for the link it explains the issue much better and more convincingly than I did.

Rudderrudderrat

I am sorry, but I cannot explain why it refers to JAR-OPS and has a DA but as the link that LLLK provided, there may be issues with Jeppesen minimas. I am not sure if the same is true of AERAD charts.