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AirAsia flies to Melb instead of KL . Navigation error

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AirAsia flies to Melb instead of KL . Navigation error

Old 8th Sep 2016, 14:02
  #61 (permalink)  
 
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Whatever happened to "It's all an aid to DR"?
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Old 8th Sep 2016, 14:43
  #62 (permalink)  
 
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Originally Posted by Hogger60 View Post
How many cockups is this for AAX in Aussie airspace in the past few years??

I would hope CASA would be taking a very close look at them and soon.
Bloody hope so

Just 25min ago local XAX213 almost taxied over the pushout tug and engineer who was still standing by to show the bypass pin, they got taxi clearance and were on their way, engineer had to do the bolt, it was very close
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Old 8th Sep 2016, 15:13
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What about FMGC Fuel prediction , or expected landing fuel at destination ?
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Old 8th Sep 2016, 15:21
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Originally posted by RAT 5
From early comments on here it would seem they still had No.2 ADIRU. Will someone say if this is enough to give correct info to either PFD, or whatever ABus call it.
The Capt would have lost all attitude and air data when ADIRU 1 was cycled OFF. The FO's PFD would have continued displaying data from ADIRU 2, but the heading info would have been wrong. The Capt was unable to select data from ADIRU 3, because it had also been cycled OFF. However, he could have selected a copy of the data displayed on the FO's PFD to be displayed on his side by using the EFIS DMC selector. Whether he did that or not is unclear. Attitude, heading and air data from ADIRU 1 could also have been restored to the Capt's PFD when the FO subsequently completed the IR ALIGNMENT IN ATT MODE checklist.
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Old 8th Sep 2016, 15:45
  #65 (permalink)  
 
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Buzzbox: thank you. So their technical knowledge seems to have been lacking. Firstly the attempt to realign in the air, and then how to recover sufficient display data to allow a safe return to Sydney.
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Old 9th Sep 2016, 00:11
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Originally Posted by Algol
But no. Now we discover that if the GPS doesn't agree with the INS's it will effectively vote itself out of the system, and the only warning you'll get is one single chime after it has thought about it for ten minutes (or more)! Incredible.
I read somewhere that this is the same for 747-400s (at least the part about the GPS being voted out).

According to the report, the aircraft in the incident did throw up a warning about position mismatch during the preflight, but the captain forced through it. i.e. the basic position comparison (which looks at both latitude and longitude).

Originally Posted by RAT 5
So their technical knowledge seems to have been lacking. Firstly the attempt to realign in the air, and then how to recover sufficient display data to allow a safe return to Sydney.
That was my initial impression, too, but if you read the report, they did eventually follow the QRH to get the aircraft into basic attitude mode. With limited visibility for a return to Sydney, basic attitude mode may have been insufficient to meet regulatory requirements/airline SOPs (?)
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Old 9th Sep 2016, 00:32
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And why did entering the wrong coords cause a terrain alert?
Because one of the modes of EGPWS Warnings works of the database with terrain data. That DB is used in connection with the aircraft POSITION that needs to be ENTERED. So, if you enter a wrong position happened to be close enough to some mountains, and then try to fly the AC, EGPWS SHOULD trigger "terrain terrain" warning.
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Old 9th Sep 2016, 00:48
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Originally posted by NSEU
With limited visibility for a return to Sydney, basic attitude mode may have been insufficient to meet regulatory requirements/airline SOPs (?)
They certainly couldn't have flown an RNP or any other type of 'new age' approach, but radar vectors to an old-fashioned ILS should have been easily doable once the attitude and heading information was restored. That said, I suspect the crew was a bit 'gun shy', given they didn't really understand what had occurred.
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Old 9th Sep 2016, 05:18
  #69 (permalink)  
 
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Surely a pair og GPS's in agreement are more reliable than even 3 INS's?
But no. Now we discover that if the GPS doesn't agree with the INS's it will effectively vote itself out of the system
Some problems relying solely on GPS:
  • Multiple GPS units share common failure points (e.g., the satellite signals) so they are not independent -- two units may simultaneously fail in the exact same way
  • Common integrity monitoring algorithms can't detect all failure scenarios -- they can report acceptable integrity when the data is actually garbage
  • GPS signals are subject to interference, jamming and spoofing
Also when the first aviation GPS systems were being designed back in the mid-1980s and early 1990s, we did not yet have the full GPS constellation launched in space, and the US DOD was actively degrading GPS signals via Selective Availability (SA).

So I think the engineers & regulators decided to take a very conservative approach in preferring the "proven" IRS (incidents like KAL007 notwithstanding). SA was not turned off until May, 2000.

What about FMGC Fuel prediction , or expected landing fuel at destination ?
Prior to takeoff, fuel prediction is only based on the entered flight plan & departure runway -- not the aircraft position -- so it would appear correct to the crew.

radar vectors to an old-fashioned ILS should have been easily doable once the attitude and heading information was restored
I believe they restored (partial) attitude & heading information only after the decision to divert to Melbourne was already made.
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Old 9th Sep 2016, 06:06
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Originally posted by peekay4
I believe they restored (partial) attitude & heading information only after the decision to divert to Melbourne was already made.
Possibly so, but the report says "The flight crew continued their attempts to restore the flight guidance and navigation systems while in the Sydney area. The FO then carried out the IRS ALIGNMENT IN ATT MODE checklist from the QRH, restoring some ND and PFD functions..." So it seems they were still in, or very close to the Sydney area when those functions were restored. They were certainly much closer to Sydney than Melbourne! The weather in Sydney at the time was 10k vis, light rain showers and a cloud base of 1,700ft, so they would have been visual well above the minima.

Last edited by BuzzBox; 9th Sep 2016 at 06:20.
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Old 9th Sep 2016, 07:50
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It is a worry, why can't you just hard tune the ILS and fly a good old fashioned Instrument Approach, all that you need is the compass, altimeter, vor/ils and you are good to go.
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Old 9th Sep 2016, 08:00
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It is a worry, why can't you just hard tune the ILS and fly a good old fashioned Instrument Approach, all that you need is the compass, altimeter, vor/ils and you are good to go.
Ollie, that's exactly what they could have done, once they'd realigned the IRSs in ATT mode and restored their attitude and heading info. It'd be a tad difficult without those!
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Old 9th Sep 2016, 08:11
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Well having never tried to depart with the IR's aligned 6,000 nm away!! I for one am glad it was them and not me. We can all learn from their initial stuff up and now have a good refresh on exactly what works in that situation and how to get good data back.

Thanks Air Asia.....
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Old 9th Sep 2016, 08:11
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"Children of the magenta line" jokes even though the old captain has over 20k hours

Once some people find a scapegoat they always fall back on it.
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Old 9th Sep 2016, 08:30
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PROG page and entering the active runway in the field will show bearing and distance from the threshold. Useful as a gross error check.
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Old 9th Sep 2016, 08:32
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What would have happened had the FO turned off the No 2 IRS thingee?
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Old 9th Sep 2016, 08:52
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What would have happened had the FO turned off the No 2 IRS thingee?
Capt & FO would lose all attitude, heading and air data on their PFDs & NDs. Data could be recovered by realigning the IRs in ATT mode, with the heading updated periodically from the standby compass.
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Old 9th Sep 2016, 09:36
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I couldn't see anything but strange the Australian regulator has not imposed any conditions on the AOC? They were pretty quick to ground the Tiger Airways operation with numerous restrictions and then the implications were shown.

We're gambling with lives now...
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Old 9th Sep 2016, 10:35
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What SBY attitude display is there on A330? Is there a good old basic AH lurking somewhere in the corner, or is it all TV screen stuff?
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Old 9th Sep 2016, 11:19
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Old A330s have a basic AH, but newer aircraft have an Integrated Standby Instrument System (ISIS). It's basically a souped-up AH plus ASI/altimeter and ILS scales combined into one instrument and displayed on a small screen. The ISIS has its own gyros and air data module, so it's independent of the other aircraft systems.

Last edited by BuzzBox; 9th Sep 2016 at 12:01.
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