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A380 low at Melbourne

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A380 low at Melbourne

Old 2nd Aug 2016, 07:42
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Bit off topic but recently read an interesting (but incomplete) dissertation on the FMS and the whimsicalities of some systems when dialling up waypoints. Mention was made of how the Helios 737 flew to Athens and entered a holding pattern (presumably via the correct sector entry at the holding fix). However that got me wondering what would happen when you weren't enroute to a destination and overflew that way-point which had no associated instrument appch and/ or onwards waypoint in the same direction beyond that waypoint. What would that FMS do as far as onwards tracking/heading goes? It surely wouldn't orbit that way-point. Would it just maintain locked to its last track or heading? If so and turbulence/cloud deflected it from that track/heading, what tracking could be expected?
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Old 2nd Aug 2016, 12:55
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It will maintain the desired track. Track, by definition, is corrected for wind.
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Old 2nd Aug 2016, 15:53
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Originally Posted by WeeWinkyWilly
However that got me wondering what would happen when you weren't enroute to a destination and overflew that way-point which had no associated instrument appch and/ or onwards waypoint in the same direction beyond that waypoint. What would that FMS do as far as onwards tracking/heading goes?
On some planes I've flown if you overfly the last waypoint into a discontinuity the aircraft will go into a heading (not track, I believe) hold, altitude hold mode.

On others, like the A310/A306, seems like the autopilot kicks off with an aural warning (to wake up the pilots ).
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Old 2nd Aug 2016, 16:56
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Like all this "magic," vendors have different methods of implementation. In my view, having the autopilot disconnect is not good safety engineering. Aural warning, yes. Disconnect, no.
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Old 2nd Aug 2016, 17:56
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Over here in FAA land, the feds are now offering this conservative guidance about last minute changes to an approach:

b. POIs will work with their operators to ensure that operators have procedures that explicitly state that any changes to an approach after the initial briefing should be re-briefed in accordance with accepted crew briefing procedure. Last-minute runway or approach changes should be accepted only if pre-briefed as a backup to the planned approach. The PM should update the FMC to reflect an approach change, and verify with the PF that the new approach is properly set up in the aircraft. If time does not allow for re-brief and verification of proper FMC/cockpit setup, the flightcrew should ask for extended vectors or holding until briefing/setup can be accomplished.

c. POIs will also work with their operators to develop information about how the FMS could provide an incorrect presentation in the lateral and/or vertical profiles if waypoints are incorrectly entered, or a route discontinuity exists that is not corrected before conducting an approach.
http://www.faa.gov/documentLibrary/m...N_8900.311.pdf

I don't know how EK does it these days. And we won't know for a while if a botched route mod or mode selection caused this MEL altitude bust.

Seems like some operators, like Air Canada, had a rule that you couldn't do any button pushing on the FMS below 10,000 feet and if there was a runway or approach change, you would go to raw data. Of course, these days on approaches like the one discussed above at MEL, there is no raw data, at least not in the traditional sense of ground based navaids.

And, I've seen the other extreme in years past where the sim instructor would have the PNF typing all the way down to the runway to demonstrate proficiency with last minute route mods and runway changes that were very unlikely in the real world. For training, of course...
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Old 3rd Aug 2016, 15:21
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Unlikely to be a modification to the approach as the RNP AR with RF leg is not permitted to be modified.

And generally once ATC (in Australia) clears you for the approach they will expect you to do exactly as it says on 'the tin'.

As I said this is flown in NAV/DES and there is a whole section in the FCOM about how to fly these approaches; which we are required to have a look at as part of the arrival briefing before TOD. Personally I don't like the NAV/DES way of doing it and I have seen finger trouble with these more than once!
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Old 3rd Aug 2016, 20:19
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To my knowledge no-one has yet posted the weather at the time. Will this who know please do so. i.e. were they visual or IMC?
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Old 3rd Aug 2016, 21:23
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White Knight:
Unlikely to be a modification to the approach as the RNP AR with RF leg is not permitted to be modified.
There are three choices offered in the FMS when this approach is selected, all of which begin at IAFs, LAVER, SUDOS, or GOOLA. If the SUDOS IAF is selected all inbound RFs drop out of the approach. Since the scant report states he was 28 KM south, presumably he was cleared off-route to SUDOs and presumably told to maintain 3,000 (or, at or above 3,000) until crossing SUDOS.

And generally once ATC (in Australia) clears you for the approach they will expect you to do exactly as it says on 'the tin'.
If they were cleared off-route to SUDOS, they would have been "on the tin," as you characterize it. But, anything less than 3,000 would presumably have violated the "pre-tin" portion of the clearance.
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Old 4th Aug 2016, 06:49
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If you listen to ATC Live, you will hear that they were recleared off the STAR to "direct PIERS".
PIERS is 14nm to run to the runway and 6nm before SUDOS. Refer Ports Nine P STAR
(14nm = 26 kilometres)
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Old 4th Aug 2016, 12:53
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Trent 972:
If you listen to ATC Live, you will hear that they were recleared off the STAR to "direct PIERS".
If they crossed PORTS at 9,000, and been on a VNAV path, they should have crossed PIERS at 4,900, or so.
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Old 4th Aug 2016, 15:51
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Originally Posted by Trent 972
If you listen to ATC Live, you will hear that they were recleared off the STAR to "direct PIERS".
PIERS is 14nm to run to the runway and 6nm before SUDOS. Refer Ports Nine P STAR
(14nm = 26 kilometres)
Later in the recording, which scans several freqs and misses a lot of the transmissions, you hear EK407 acknowledge a clearance to maintain 2000 feet. Then possibly a truncated approach clearance readback. After that you hear EK407 call approach again, perhaps from on the ground to discuss the incident.

EK407 checks in at 3:22 in this recording:

http://archive-server.liveatc.net/ym...2016-0930Z.mp3
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Old 4th Aug 2016, 20:38
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Back to my question: what was the Wx? IF VMC and insight, all this playing around with FMC approaches for X or Y or Z and being vectored off the expected approach etc/etc. If you want to fly via automatics why not just use basic modes; if confused why not go manual? Rule No. 1. If confused DO NOT connect FMC to autopilot and then ask "what's it doing now."
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Old 5th Aug 2016, 13:44
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RAT 5:
"
Back to my question: what was the Wx? IF VMC and insight, all this playing around with FMC approaches for X or Y or Z and being vectored off the expected approach etc/etc. If you want to fly via automatics why not just use basic modes; if confused why not go manual? Rule No. 1. If confused DO NOT connect FMC to autopilot and then ask "what's it doing now."
Absolutely! And, that goes even more so for RNP AR approaches where special training is supposedly required.

Having said that the STAR they were on melds perfectly with the RNP AR approach at issue.
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Old 5th Aug 2016, 19:27
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RAT 5, the problem with that argument is that if you can't use the automatics properly in VMC, what hope do you have in IMC?

If you've been taken off the approach, then fine, basic modes or manual flight.

But they weren't.
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Old 5th Aug 2016, 23:26
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I would like to think that an RNP AR crew that must be specifically trained and qualified on the ins and outs of RNP AR would not screw up one, especially this one that is designed and set-up so perfectly.

Then again, Turkish Airlines really messed up at VNKT and so did Nepal's aviation authority. But, I'm confidant the Australians don't have QC issues.
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Old 6th Aug 2016, 00:00
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Watch it on Webtrak:

WebTrak

Click the Historical tab, then choose 14 July, 7 40 PM.

Interestingly, it looks like they descended to and maintained 2500ft. The didn't climb back to 3000 as stated by the ATSB.
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Old 6th Aug 2016, 00:39
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It will be interesting to read the final report, which will be accurate. At present, too little info, too much "static."
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Old 6th Aug 2016, 04:33
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Originally Posted by Capn Bloggs
Watch it on Webtrak:

WebTrak

Click the Historical tab, then choose 14 July, 7 40 PM.

Interestingly, it looks like they descended to and maintained 2500ft. The didn't climb back to 3000 as stated by the ATSB.
I agree, looks like somehow they went down to 2500 feet early and then picked up the descent path at MEXUN.

Hopefully the ATSB report will have distances in nautical miles instead of kilometers since that is what is on the charts and instruments the pilots were using.
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Old 6th Aug 2016, 22:45
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Webtrak displays altitude referenced to Standard. So you need to know the QNH to see what their actual altitude is.
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Old 6th Aug 2016, 23:40
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Originally Posted by Capt Fathom
Webtrak displays altitude referenced to Standard. So you need to know the QNH to see what their actual altitude is.
From the Webtrax Help tab, Other (emphasis mine):

Remember that the aircraft's altitude is displayed. Altitude is relative to mean sea level and not your home location. However if you know the elevation of your home location then you can work out how high above your location the aircraft is at a particular time (the height with reference to your location). You can find more discussion of Altitude in Aviation on Wikipedia.
And Webtrax certainly knows the QNH, it is given as 30.4 [sic] inHg, must be another Oz format I'm not too familiar with.

As a crosscheck, EK407 altitude on rollout is 453 feet, in close agreement with the upwind threshold elevation of 432 feet.
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