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Thai Air B777 Melbourne NDB approach

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Thai Air B777 Melbourne NDB approach

Old 7th Feb 2008, 04:32
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Thai Air B777 Melbourne NDB approach

"On 4 November 2007, a Boeing Company 7772D7 aircraft, registered HS-TJW, was being operated on a scheduled passenger service from Bangkok, Thailand, to Melbourne, Vic, with 17 crew and 277 passengers on board. During a non-directional beacon (NDB) non-precision approach to runway 16 at Melbourne Airport, the aircraft descended below the segment minimum safe altitude at 6.8 distance measuring equipment (DME, a measure in nautical miles). Soon after, the crew received two enhanced ground proximity warning system (EGPWS) cautions. The crew then levelled the aircraft and conducted a visual approach and landing on runway 16.
The investigation is continuing."

Full report here...

http://www.atsb.gov.au/publications/...727_prelim.PDF
HIGH n MIGHTY is offline  
Old 7th Feb 2008, 05:22
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I was led to believe that modern a/c like the 777 and some of the newer generation airbus's do not have ADFs on them....
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Old 7th Feb 2008, 06:00
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all Boeings do I think but the new gen Airbusses (Airbi.??) dont. Caused a few dramas the few months the ILS was out Im told...
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Old 7th Feb 2008, 07:19
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all the latest Airbus i flew, had a single ADF on them, so still able to fly ndb approaches.
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Old 7th Feb 2008, 07:58
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Not to MEL 16!! It requires 2 ADF.
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Old 7th Feb 2008, 09:05
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nope it does not .
in the old days it was a twin locator approach, not anymore.
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Old 7th Feb 2008, 09:19
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one adf

Why do airlines/manufacturere penny pinch on the relatively small extra cost of a second ADF. There are may instances of incidents/accidents caused by the lack of a second one. The USAF 737 fatal at Dubrovnik being just one. Trying a twin locator (ADF) approach with only one is iffy to say the least.
Or am I just behind the times?
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Old 7th Feb 2008, 09:36
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The Jepp chart now states DME and both NDBs required even though its now an NDB rather than a Twin Locator.... Now, whether that means both need to be monitored simultaneously or not is another question..
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Old 7th Feb 2008, 09:37
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No go-around ?
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Old 7th Feb 2008, 10:02
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There wouldn't be any NDBs in Australia today (and for quite some years now), saving tens of millions of dollars a year in maintenance and upkeep, if some nameless person in Canberra hadn't screwed up royally when writing the GPS specs of the J model Herc.

But that's another story...

Non precision approaches in big aeroplanes are seen to be so incredibly dangerous by some airline managements that they forbid their aircrews from practising them on the line. (Not just NDBs, but VORs and LLZRs as well.) Total exposure to NPAs is once every six months in the sim - unless a line pilot has to do one for real on the line because a precision approach is not available.

I don't know if Thai follow this... shall we say rather remarkable practice. However, when aircrew who aren't allowed to practise have to do an NPA in anger, their management wonders why they sometimes get it wrong.
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Old 7th Feb 2008, 10:46
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Join Ryanair, and you will likely shoot a NPA every or every other day. All flown in VNAV now though so no massive rates of descent in V/S, which is where the danger lies.

They are not dangerous if you are well trained, diligent and practise regularly.
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Old 7th Feb 2008, 11:06
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Hello everyone, first time post!
NPA are normal ops on charter flights, I fly either A330 and A321 both equipped with two ADF extremely usefull for landing in places like Boavista, Capoverde or Banjul, Ghambia. If you are trained its fun tough!
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Old 7th Feb 2008, 11:38
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The crew reported that the approach briefing included an intention to conduct a constant angle approach path using the vertical navigation (VNAV) mode of the automatic flight control system
If they did indeed use VNAV and it flew them low there'd better be some flack-jackets issued for the database boys in Jepp...

On that point (and never trusting Bill Gates oops I mean computers in general) it is interesting that two profile points, 8DME and 7DME, are not printed on the approach chart. How on earth is a crew supposed to easily monitor the VNAV (or do it themselves) if the chart hasn't got the complete profile on it? The two that are not there cover the height the aircraft got to when the EGPWS went off. "Thanks for nothing, system." Really nice pic of the runway though...
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Old 7th Feb 2008, 11:48
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Firstly: most current 777's have 2 ADF's fitted. However the next bunch of 300ER's at CX will NOT come with ADF's

Second: I'm pretty sure the 16 Twin Loc app in MEL is not in the Honeywell FMC database. You can build the legs if you want to and use L Nav ( monitoring the raw data for tracking ) BUT you cannot use Vnav for the arrival. Only Data base approaches can use V Nav for guidance. ( ILS's VOR/DME GPS etc all ok, there are no NDB approaches at all in a Boeing FMC )
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Old 7th Feb 2008, 12:23
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...but in this instance you can select the ILS - and use it as an overlay. LNAV VNAV should then work, with appropriate raw data and profile height checks.

I dont see why the honeywell FMC cant be as flexible as the smiths FMC.

Smiths you can just build rwy extension and waypoint on waypoint, plug some altitudes in and watch LNAV VNAV fly it for you.
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Old 7th Feb 2008, 12:37
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Smiths you can just build rwy extension and waypoint on waypoint, plug some altitudes in and watch LNAV VNAV fly it for you.
But would you really fly an approach that you've "built" down to minimums and be the first one to see if it works? Or doesn't.
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Old 7th Feb 2008, 12:40
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in this instance you can select the ILS - and use it as an overlay. LNAV VNAV should then work, with appropriate raw data and profile height checks.
I dunno about the legality of that, Blueloo! VNAV below the MSA using an different approach to that being flown? Duck heads, over.
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Old 7th Feb 2008, 12:42
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Does the 777 have the "Green Arc" showing descent point like the 757/767? I use that in VS a lot. (Yes, I know I'm a danger to myself and humanity in general for using vert speed. I fully expect the police to be at my door anytime now... )

Descending below the min alt. for a given segment on a NPA can be done by anyone not paying attention. Certain individuals go below G/S without a peep from the other seat, too. TC
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Old 7th Feb 2008, 13:05
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Even if, as they were, joining the V-Nav (FMC calculated glidepath) from above the initial MCP Alt window should have had 4000' until 12D when 3000' would have been entered until 9D and so on.

The FMC should be an aid, with the MCP Alt window still protecting the the crew from the "embarrassment" of FMC mistakes..

Last edited by woodpecker; 11th Feb 2008 at 20:30.
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Old 7th Feb 2008, 22:37
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"But would you really fly an approach that you've "built" down to minimums and be the first one to see if it works? Or doesn't. "

Most probably not would be my answer at this stage.

- my thoughts - if no non-precision approach - or overlay as appropriate is in the database why could you not build an LNAV track to replicate the approach. Your choices - a blank map and raw data - in a big boeing using HDG SEL and VS. Or build an LNAV track - let it fly LNAV monitoring raw data - you now have a display for situational awareness, and you shouldnt have to fiddle with the HDG knob every few seconds when the wind changes, or you havent got the HDG/drift quite right....



Capn Bloggs:
Remember you still must monitor raw data. The approach must be flown ie Alt constraints etc as per the NDB chart - (or company requirements) - all VNAV and LNAV are doing is reducing the workload, to allow you to monitor and manage the approach - an ILS overlay which has the same exact lateral tracking should be fine (the melbourne ILS overflys BOL and ROC) - and as ILSs tend to fly 3 degree approaches then VNAV should be appropriate.


Woodpecker:
"Passed the Cb, we were cleared present position direct to the VOR"

I must have missed something in the cleareance - or was it "cleared to the VOR to resume the STAR"?

I am not familiar with the area you are talking about - the terrain ATC or otherwise.

If you are cleared direct - surely you are no longer on the STAR. Which presumably means the Atl constraints are no longer valid. So you need minimum safe altitudes from somewhere.....the original STAR constraints may not protect you if you are off track - they may in fact be higher.
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