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Airbus Within 6ft of the Ground nearly 1 mile Short of Runway

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Airbus Within 6ft of the Ground nearly 1 mile Short of Runway

Old 18th Oct 2022, 17:31
  #261 (permalink)  
 
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Originally Posted by MechEngr
and GPS measures absolute altitude
Doesn't GPS actually measure relative, rather than absolute, altitude - that's to say relative to a reference ellipsoid that approximates the earth's surface ?
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Old 18th Oct 2022, 18:17
  #262 (permalink)  
 
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Originally Posted by DaveReidUK
Doesn't GPS actually measure relative, rather than absolute, altitude - that's to say relative to a reference ellipsoid that approximates the earth's surface ?
I can't speak for specific applications, but I have a GPS tracker system that I use in my high power rocketry. When I power it up, it reads that altitude of the launch site relative to MSL. There is a button that I then push that resets that altitude to zero so that subsequent readings are relative to the altitude of the launch site. The GPS can then be used to determine things like max altitude of the flight (and speeds - although during the ascent the speeds change to rapidly that the update rate of the GPS makes it less than completely useful).
As MechEngr notes, if that's how the system normally works, it would require a pretty detailed terrain map to reliably determine altitude to the local ground level.
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Old 18th Oct 2022, 19:26
  #263 (permalink)  

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Originally Posted by tdracer
if that's how the system normally works, it would require a pretty detailed terrain map to reliably determine altitude to the local ground level.
In which case all that needs to be done is align the GPS '0' to the same reference zero that has been in use since forever to calculate elevations and altitudes for the standard old-school aviation data-set? Within the original scope of the thread - not it's the altitude which was wrong already, no need to evaluate height.

My personal favourite is to mandate the ANSPs to publish radio-height at the 1000' AAL checkpoint for every IAP. Darn easy, GPWS, EGPWS and ACAS also started mandatory for big aeroplanes only. I mean, if the issue is flying into terrain and RAs exist, why insist on devising another tool or gadget instead of learning how to utilize the full potential of what we already have?

For the aeroplane discussed, an electronic comparison cross-check between FCU BARO REF and MCDU APPR PG seems a no-brainer.
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Old 19th Oct 2022, 01:03
  #264 (permalink)  
 
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Originally Posted by DaveReidUK
Doesn't GPS actually measure relative, rather than absolute, altitude - that's to say relative to a reference ellipsoid that approximates the earth's surface ?
I think there are several datums that are available for reporting, including the GPS default ellipsoid WGS-84 (apparently), but a GPS nav unit is initially calculating a 3D position based on the orbits of the GPS satellite constellation. The report should be consistent for a consistent location, such as a if one is on a radio tower or mountain peak. The pressure altitude will vary and the difference with some other fixed location will vary for those fixed locations.

The more I look at it the more I don't want to look at it. https://geodesy.noaa.gov/GEOID/index.shtml It starts to glaze over the brain when considering that we live on a lumpy blob that is changing shape in ways that are measurable, but not reliably so from any location on the planet. Worse, where the satellites are is affected by the lumpy gravity of that lumpy blob. Gah!

There appears to be a project to convert to using the constellation directly as the reference; there is also a project to generate and equi-potential (they call it orthometric) model that includes differences in local gravity that is very useful in predicting water flow and flood plains. https://geodesy.noaa.gov/GRAV-D/pubs...2007_12_19.pdf

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Old 19th Oct 2022, 10:52
  #265 (permalink)  
 
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Originally Posted by ve3id
I used that video in my Air Cadet radio class yesterday and the 12-14 year old cadets immediately picked up the mistake!
Easy when you know what to look for
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Old 25th Oct 2022, 23:18
  #266 (permalink)  
 
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Originally Posted by India Four Two
I've been following Mentour Pilot for a couple of years. That was without doubt his best video to date. Very informative - even a non-pilot would understand what happened.
While I found the video from Mentour Pilot to be useful, it has left me wondering if his videos sometimes don't include important information such as this quote from post #4 on this thread: "9 seconds between minima and TOGA". Isn't that of significant importance.
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Old 26th Oct 2022, 09:34
  #267 (permalink)  
 
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Originally Posted by punkalouver
While I found the video from Mentour Pilot to be useful, it has left me wondering if his videos sometimes don't include important information such as this quote from post #4 on this thread: "9 seconds between minima and TOGA". Isn't that of significant importance.
To repeat - slightly edited - my earlier comment (post #133).
"the preliminary report seems to be clear that ...the crew flew straight through (what they believed to be) the MDA at a constant descent rate of 12 ft/sec, without having any visual references. It appears that the need for a go-around was not manifested for a further 6 seconds (72 ft further descent), when the Captain disconnected the autopilot and made a nose-up input, but a full go-around was not initiated for a further 3 seconds when TOGA was applied. So even if the altimeters had been set correctly obstacle clearance would have been significantly infringed – at the lowest point the aircraft would have been 123 feet below the correct MDA, apparently in full IMC. From the Captain’s actions (autopilot disconnect and stick back and then TOGA power 3 seconds later) it seems likely that he was not mentally prepared for a go-around.

So regardless of the altimetry issue, we have a prima facie serious breach of AOM in that the aircraft descended far below the indicated MDA without the Captain having seen visual cues which should already have “been in view for sufficient time for the pilot to have made an assessment of the aircraft position and rate of change of position in relation to the desired flight path.” (ICAO definition of reqjired visual reference)."
To repeat: it's "DECISION to land or go around height/altitude", not "start looking for cues altitude".



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Old 15th Jul 2024, 17:11
  #268 (permalink)  
 
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Final report now out....
34938.pdf (skybrary.aero)
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Old 15th Jul 2024, 18:25
  #269 (permalink)  
 
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Not updating to the latest software standard

"Transmission of incorrect altimeter setting (QNH) by air traffic service, near-collision with ground during satellite approach procedure with barometric vertical guidance."

"As per design (!!!), there was no on-board ground proximity alert (TAWS) during the event. In their statements, the crew indicated that they had not been aware of this proximity with the ground."

"The aeroplane was configured for landing and in a standard rate of descent, so no TAWS basic and reactive mode alerts or warnings were triggered. Furthermore, the GLIDE SLOPE alert is not available for barometric approaches. Lastly, since the predictive Premature Descent Alert (PDA) mode includes an inhibition zone before the runway to avoid untimely alerts on each landing, and as the EGPWS software version was an old version and did not use GNSS positioning, no alert was generated, despite the aeroplane's low height."

"… an EGPWS equipped with a more recent software version and using GNSS positioning, would have generated a "TOO LOW TERRAIN" caution alert at a height above ground of approximately 200 ft RA, i.e. approximately 15 s before the lowest point at 6 ft RA.
Although aircraft and TAWS manufacturers have encouraged operators to update the TAWS on their aeroplanes to more recent standards and to use GNSS positioning, Airbus and Boeing estimate that there are still around 1,600 aeroplanes in service equipped with EGPWS that would not generate an alert in the circumstances of this serious incident."

Updating to the latest software standard - operator responsibility !
1600 aircraft …
and EGPWS / TAWS is probably the most successful safety technology ever!
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Old 16th Jul 2024, 05:25
  #270 (permalink)  
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This raise the question of installation such safety enhancements .upgrades: should they really be optional and cost money to install ?

Any idea of the price range of such update on an A320 ?
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Old 16th Jul 2024, 07:15
  #271 (permalink)  
 
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Originally Posted by ATC Watcher
This raise the question of installation such safety enhancements .upgrades: should they really be optional and cost money to install ?

Any idea of the price range of such update on an A320 ?
Does it imply hardware change or 'just' a software update?
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Old 16th Jul 2024, 09:54
  #272 (permalink)  
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I seem to recall reading the report said updating the aircraft in question to a later version would involve hardware and wiring changes.
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Old 16th Jul 2024, 10:37
  #273 (permalink)  
 
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Software issues are really a second or even third order protection. Pilots have rad alt so why not monitor the bloody thing? Software is your last resort, not a regular go to.
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Old 16th Jul 2024, 10:40
  #274 (permalink)  
 
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Originally Posted by mustafagander
Software issues are really a second or even third order protection. Pilots have rad alt so why not monitor the bloody thing? Software is your last resort, not a regular go to.
Obviously correct but if a hole in the proverbial cheese can be filled with relatively little work/money it should be high priority IMHO
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Old 16th Jul 2024, 12:36
  #275 (permalink)  
 
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From the report - ITM Controller:
"She subsequently discussed the serious incident with other controllers who were also unaware of the importance of the QNH for certain RNP approaches [Note: Several other controllers questioned by the BEA during the investigation indicated the same lack of awareness]."

Question for ATC ers on here? is it POSSIBLE that experienced (or even new) Controllers are not aware of how QNH is used?

Broader question: how has this not happened before if the info is not seen as critical?
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Old 16th Jul 2024, 14:38
  #276 (permalink)  
 
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A software update should be routine. The 218 version was a major change specifically to address the low approach situation - many years ago. Even without a hardware change for nav accuracy, the 'nav' positional environment around CDG (DMD/DME) should have been sufficient with the modified software.
Database updates should be done regularly, minimising nuisance alerts for new airports and addining protection from new obstacles.
Hardware changes to improve 'nav' positional accuracy might be more difficult; some versions of EGPWS have a built-in GPS receiver.

Cost is relative; plus or minus 6ft from ground level.

A significant point is the limitations in risk assessment, a reminder that we cannot foresee every eventuality. Need to rethink beliefs about threat detection and safety management.
With hindsight, Baro/GPS approaches should only be authorised when monitored by a EGPWS of similar or better capability in positional / alerting accuracy.
Check your aircraft configuration, mod state, and software revision. If no EGPWS/GPS, and software revision, then no Baro RNAV approaches.

Also to remind us of the subtle differences across RNP systems, non precision vs precision accuracy and associated risk assessments.

Procedures - scan the Rad Alt; as I recall, no approach path, precision or non- precision, should be less than 250 ft agl before minimum altitude.
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Old 16th Jul 2024, 14:45
  #277 (permalink)  
 
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Originally Posted by Maninthebar
From the report - ITM Controller:
"She subsequently discussed the serious incident with other controllers who were also unaware of the importance of the QNH for certain RNP approaches [Note: Several other controllers questioned by the BEA during the investigation indicated the same lack of awareness]."

Question for ATC ers on here? is it POSSIBLE that experienced (or even new) Controllers are not aware of how QNH is used?

Broader question: how has this not happened before if the info is not seen as critical?
It probably has happened before just not quite as spectacularly. The analysis states neither the pilots nor ATCOs had any idea how serious it actually was in the immediate aftermath, or really what had even happened.

From my point of view I know how QNH generally is used, but I was surprised that there was absolutely no effective form of crosscheck between what the ATCO said and what the reality was - on either end. Definitely not looking to excuse a potentially grave error (even if easily made as a misspeak) by the ATCO, but in terms of the system as a whole you’d think something else would catch that. A single transposed digit in this scenario shouldn’t be enough to cause a CFIT.

As mentioned in the report both the Netherlands and the UK have QNH/mode S error highlighting on the radar, which would have flagged it very early in and made it a non-event. I was surprised that wasn’t more widespread for something that seems fairly simple. The pilots had the QNH written down from the ATIS but neither challenged it despite being 10hPa off. There’s a few holes all lined up, but it seems like another hole or two needs implementing.
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Old 16th Jul 2024, 19:52
  #278 (permalink)  
 
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Originally Posted by slast
To repeat - slightly edited - my earlier comment (post #133).
"the preliminary report seems to be clear that ...the crew flew straight through (what they believed to be) the MDA at a constant descent rate of 12 ft/sec, without having any visual references. It appears that the need for a go-around was not manifested for a further 6 seconds (72 ft further descent), when the Captain disconnected the autopilot and made a nose-up input, but a full go-around was not initiated for a further 3 seconds when TOGA was applied. So even if the altimeters had been set correctly obstacle clearance would have been significantly infringed – at the lowest point the aircraft would have been 123 feet below the correct MDA, apparently in full IMC. From the Captain’s actions (autopilot disconnect and stick back and then TOGA power 3 seconds later) it seems likely that he was not mentally prepared for a go-around.

So regardless of the altimetry issue, we have a prima facie serious breach of AOM in that the aircraft descended far below the indicated MDA without the Captain having seen visual cues which should already have “been in view for sufficient time for the pilot to have made an assessment of the aircraft position and rate of change of position in relation to the desired flight path.” (ICAO definition of reqjired visual reference)."
To repeat: it's "DECISION to land or go around height/altitude", not "start looking for cues altitude".
The report was interesting reading but I didn’t see much mention of this, which for me as well was one of the big issues. They were flying a NPA and if it had been an NDB with the correct QNH and they’d been 5degs off to one side (within limits) and had a near miss with a church spire because they bust minima, that would be the headline. The AP was in and they had basically one job to do which to look out of the window and go around approaching MDA if there wasn’t an adequate visual reference.
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Old 16th Jul 2024, 23:48
  #279 (permalink)  
 
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At least Airbus has amended the FCOM to ask the pilots to preselect the destination QNH in the standby altimeter during descent preparation following this incident. Personally, as a safety net, I have always preselected on my barometric reference selector as well since I started flying Airbus. I remember some captains back in the days telling me: "Don't do that it can trigger a TCAS RA!".... No it can't. If only one of these 2 pilots have done it, this incident would most certainly have been avoided.

For those interested, Mentour Pilot made a nice video about this incident:
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Old 17th Jul 2024, 14:30
  #280 (permalink)  
 
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Not to mention confusing and conflicting terminology.
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