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Old 7th Dec 2017, 17:12   #41 (permalink)

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Originally Posted by India Charlie View Post
This seems to be an “Airbus specific” issue, very probable in the SIA incident. If this was the case, kudos to the crew for realising that the FMGS was giving them wrong information and taking evasive action.
You read me wrong, IC. The FMS took the THY all the way down the runway, almost resulting into RNAV autloland. The fact of the aircraft landing on the runway edge was blamed on the THR COORD being wrong (they were). What I mean to say, is RNAV on modern day (Airbus) A/C = precision within 10 m. Sorry for the confusion.
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Old 8th Dec 2017, 03:27   #42 (permalink)
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Originally Posted by MATELO View Post
Just a question from SLF.

What would the possibility be of the pilots using the wrong input dial for the go around height. ie 3000ft and instead using the heading selector 300 making the aircraft turn.

Is this at all possible or would the auto-land function over ride any manual inputs.
When engaged in NAV mode, no input from the HDG or ALT selector can make the a/c climb/descend or turn.

If it was an FMC assisted VOR approach (which I think it must have been), the a/c would be in NAV mode and following the track drawn by the FMC inbound to rwy 09, till the crew had the rwy in sight at which point they would disconnect the A/P and take manual control of the a/c. Highly unlikely that the a/c would be in ‘managed’ mode (A/P engaged w/ HDG/ALT selected) on a VOR approach, that too a few miles from touchdown, but then I may be wrong...?
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Old 8th Dec 2017, 08:00   #43 (permalink)
 
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Which brings me back to the point of why the crew would not trust their nav system and leave it engaged until solid confirmation of the visual reference of the target runway. To disconnect early on approach, and make such a significant track change towards a runway for which they must have been very high on profile, seems questionable. At SIA they must have come from another LNAV/VNAV GPS/FMC a/c and so they should have had trust in the basic system. Why the rush, or is there another reason?
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Old 8th Dec 2017, 08:22   #44 (permalink)
 
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India Charlie. Thank you. (both with your reply and not treating me with contempt)
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Old 8th Dec 2017, 09:36   #45 (permalink)
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Do you mean that the crew were being familiarised with the rwy 09 app (with a deliberate deviation to show them Juhu)?

Definitely not, more a case of using a developing situation to illustrate possible future problems to be avoided and recovering the situation before any risk to flight safety.


Quote:
FMC aircraft don’t suffer from ‘radial instability’ on VOR approaches.

Is that the way it is for you today misd-agin ? I have no Airbus experience but when we flew the VOR approach to Mumbai it was PF on HSI raw data and PNF on MAP, no such thing as RNAV approach to Mumbai 09. Take my word for it, the radial needle would dither from side to side, the radial would often appear 'bent' and eventually it was the mark one eyeball that brought things to a satisfactory conclusion. As I said in a previous post, I hope all this has long since been sorted out by now.
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Old 8th Dec 2017, 14:02   #46 (permalink)
 
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Mateo - no. Not in the automation mode being used. In other automation modes? Yes.

There are mistakes that can be made, like selecting 300 kts and a 250 heading vs 250 kts and a 300 degree heading. That occurred during a low altitude missed approach due to failure of the preceding aircraft to clear the runway. Simple manual flying while the PM fumbled with the automation inputs made it a non issue.

But the track of SIA 422 is not consistent with the mistake you mentioned. And VOR approaches arenít flown in heading mode. If they were in heading mode, and switched the heading to 105(+/-) the turn would make sense. But there is no altitude setting of 1050 that would explain the mistake you mentioned.

And the missed approach altitude would have been set earlier and changing the heading selector, or changing the altitude selector, would not have changed the automation mode the aircraft was in.
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Old 9th Dec 2017, 06:13   #47 (permalink)
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"Definitely not, more a case of using a developing situation to illustrate possible future problems to be avoided and recovering the situation before any risk to flight safety."

I don't think I follow you parabellum, "developing situation..." meaning what?

"I have no Airbus experience but when we flew the VOR approach to Mumbai it was PF on HSI raw data and PNF on MAP, no such thing as RNAV approach to Mumbai 09. Take my word for it, the radial needle would dither from side to side, the radial would often appear 'bent' and eventually it was the mark one eyeball that brought things to a satisfactory conclusion. As I said in a previous post, I hope all this has long since been sorted out by now."

You said you have flown into Mumbai on both the B767 and B747, and I am assuming that they were both FMC equipped. What was the rwy 09 VOR app like? I assume it was FMC assisted...? Also, could you please elaborate on the 'bent radial'. I am pretty sure all this has been sorted out now, but it would be nice if pilots regularly flying into Mumbai were to give an overview of the current situation.

Last edited by India Charlie; 9th Dec 2017 at 08:31. Reason: Typo
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Old 9th Dec 2017, 08:37   #48 (permalink)
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“Which brings me back to the point of why the crew would not trust their nav system and leave it engaged until solid confirmation of the visual reference of the target runway. To disconnect early on approach, and make such a significant track change towards a runway”

RAT 5, Perhaps they were (over) confident that they could hand fly the approach. What other reason to disconnect automatics...?
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Old 9th Dec 2017, 10:05   #49 (permalink)
 
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Perhaps, indeed, but why would you if you can't see the target on an NPA? Confident that they needed to reposition the a/c off their current erroneous track to the target runway they had visual. Ouch. I still suspect there were 2 heads outside and no-one inside monitoring all the clues that confirmed the error.
They were skilful in bailing out of the first approach, but, as is often said, the skilful pilots uses their skills to avoid......etc
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Old 9th Dec 2017, 21:31   #50 (permalink)
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I don't think I follow you parabellum, "developing situation..." meaning what?
IF IT WAS A TRAINING FLIGHT: Possibly it was starting to go wrong and the TC MAY have allowed it to progress up to the GA point rather than correct earlier so as to illustrate the inherent problems that can be associated with a VOR approach to Mumbai 09, if indeed they were doing a VOR approach.


Several VORs world wide have had a sector notamed as possible fluctuations and if you fly the needles you will be changing heading to compensate, such sectors were usually nominated as unreliable and cautionary notes would be on the Jep. chart. Going back now to 2001, SOP for a VOR approach was PF on HSI and PNF on map and could be flown auto pilot and auto throttle engaged. Blindly following the 'purple worm' was not considered accurate enough, map shift caused by updating could occur. As previously said, hopefully all those problems have been overcome, one way or another, by now, even in India.
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Old 9th Dec 2017, 23:17   #51 (permalink)
 
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Originally Posted by India Charlie View Post
When engaged in NAV mode, no input from the HDG or ALT selector can make the a/c climb/descend or turn.
They will if you pull them...

Quote:
If it was an FMC assisted VOR approach (which I think it must have been), the a/c would be in NAV mode and following the track drawn by the FMC inbound to rwy 09, till the crew had the rwy in sight at which point they would disconnect the A/P and take manual control of the a/c. Highly unlikely that the a/c would be in ‘managed’ mode (A/P engaged w/ HDG/ALT selected) on a VOR approach, that too a few miles from touchdown, but then I may be wrong...?
Why would it have been in NAV mode? It looks like an approach that could be flown as an FLS, so the mode would be APP.

Of course, if it was being flown as an FLS, it makes the deviation even harder to understand.
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Old 10th Dec 2017, 06:36   #52 (permalink)
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An interesting article “Safely Flying Non-Precision Instrument Approaches” in the The Airbus Safety Magazine: http://www.aircraft.airbus.com/compa...ocID%5D=231887
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Old 10th Dec 2017, 06:41   #53 (permalink)
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Originally Posted by mrdeux View Post
They will if you pull them...
I’m sorry I did not clarify that.

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Originally Posted by mrdeux View Post
Why would it have been in NAV mode? It looks like an approach that could be flown as an FLS, so the mode would be APP.

Of course, if it was being flown as an FLS, it makes the deviation even harder to understand.
I’m not familiar with the new FLS function on the A350. My “knowledge base” comes from the A320. I am however familiar with the IAN approach feature on the B737.
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Old 10th Dec 2017, 21:16   #54 (permalink)
 
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Originally Posted by parabellum View Post
Definitely not, more a case of using a developing situation to illustrate possible future problems to be avoided and recovering the situation before any risk to flight safety.





Is that the way it is for you today misd-agin ? I have no Airbus experience but when we flew the VOR approach to Mumbai it was PF on HSI raw data and PNF on MAP, no such thing as RNAV approach to Mumbai 09. Take my word for it, the radial needle would dither from side to side, the radial would often appear 'bent' and eventually it was the mark one eyeball that brought things to a satisfactory conclusion. As I said in a previous post, I hope all this has long since been sorted out by now.
Been a while since your last flight? I fly all non precision appoaches in LNAV/VNAV. There is no need for a RNAV approach to be in the FMC for this. Just a normal profile for the non prec approach.

This flight looks like they were doing a normal non prec approach, got visual with Juhu, disconnected and turned towards Juhu, discovered their mistake and did a go around. Not that hard to understand that this can happen.
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Old 11th Dec 2017, 02:01   #55 (permalink)
 
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LNAV/VNAV is a Boeing term...and their version of these approaches (at least in the 747-400) is far inferior to the FLS used in the 380 and 350.

Basically, in those aircraft the system produces a synthetic ILS, which is flown and displayed, exactly as per an ILS. It does have to be part of the FMC suite of approaches, but I see nothing on the approach plate that would preclude it from being there.
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Old 11th Dec 2017, 02:17   #56 (permalink)
 
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It wouldn't be the first time Airbus has reinvented something done by Boeing years ago.

Airbus has this new fangled 'Soft Go-Around' technology where the motors throttle back on the go-around to give 2000 fpm climb instead of blasting up at TOGA power. Wow. Where have we seen that before?

Boeings have had that 'feature' since the 757 hit the streets in 1981.

Dynasty and other carriers have pranged a lot of 'buses over the years on those TOGA go-arounds.
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Old 11th Dec 2017, 02:35   #57 (permalink)
 
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It wouldn't be the first time Airbus has reinvented something done by Boeing years ago.
I don't see your point. FLS is a better system.

Quote:
Airbus has this new fangled 'Soft Go-Around' technology where the motors throttle back on the go-around to give 2000 fpm climb instead of blasting up at TOGA power. Wow. Where have we seen that before?
Quite true, and more to the point it's the default go around.

Quote:
Dynasty and other carriers have pranged a lot of 'buses over the years on those TOGA go-arounds.
I don't think TOGA has actually had anything to do with it. The issue was that the autopilot disconnect behaviour in the 300/310 was different once you were in approach mode.

On the other hand though, Boeing auto thrust behaviour seems to have been an issue of late.

Both makers have their good features, as well as plenty of others that make you wonder what they were thinking.
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Old 11th Dec 2017, 02:42   #58 (permalink)
 
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Originally Posted by mrdeux View Post
I don't think TOGA has actually had anything to do with it. The issue was that the autopilot disconnect behaviour in the 300/310 was different once you were in approach mode.

On the other hand though, Boeing auto thrust behaviour seems to have been an issue of late.

Both makers have their good features, as well as plenty of others that make you wonder what they were thinking.
Good points, I agree.

I sheepishly admit to having a couple of Airbus ratings from years ago.
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Old 11th Dec 2017, 06:51   #59 (permalink)
 
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Back to the topic:

Whatever you call it, Iím pretty sure they didnít fly this approach coupled to the VOR. Even if they did, it would not explain this turn towards Juhu.
This is an easy mistake to do and they did correct their mistake as they should do.
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Old 11th Dec 2017, 09:17   #60 (permalink)
 
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can you "couple" the autopilot to the VOR in the A350?
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