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Wizz Air A321 CG was off the chart

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Wizz Air A321 CG was off the chart

Old 10th Oct 2020, 06:33
  #41 (permalink)  
 
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bentbanana

Do I understand correctly that the A320 has 3 cabin zones and the A321 has 4 cabin zones?

This being the case, the late reallocation of an A320 load to an A321 would have resulted in Zone D being empty. The 42 pax shown in Zone D on the loadsheet would have previously been seated across Zones A, B & C on the A320. During the change of gauge to A321 there must have been 44 pax moved into Zone D to achieve trim. Evidently these pax were not issued with new boarding passes and a communications breakdown has resulted in their remaining in Zones A, B & C. With additional seats in the first three zones of the A321 there were probably no seat dupes to raise alarm and if there were they were probably just told to sit in the vacant seats in Zones A, B & C. What should have raised alarm was the vacant Zone D but the cabin crew probably assumed that it was deliberate for trim.
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Old 10th Oct 2020, 06:38
  #42 (permalink)  
 
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Originally Posted by sonicbum View Post
I believe they did correct it now.
Yes, it's been corrected to 123 KIAS Vr, although the byline still shows it as "last updated" Thursday afternoon, in the hope that nobody will notice.
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Old 10th Oct 2020, 06:43
  #43 (permalink)  
 
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Originally Posted by Rodney Rotorslap View Post
Do I understand correctly that the A320 has 3 cabin zones and the A321 has 4 cabin zones?

This being the case, the late reallocation of an A320 load to an A321 would have resulted in Zone D being empty.
You understand correctly - see post #25.

From the report:

"Passengers were boarded with their seat allocation for the A320 and therefore were seated within cabin Zones A, B and C. This left the seats at the rear of the A321 aircraft, which has a fourth zone, Zone D, unoccupied. The unusual passenger distribution was not noticed by the cabin crew or dispatcher. The aircraft commander was unaware of the passenger distribution in the cabin but was passed a Load and Trim Sheet for his A321 aircraft, G-WUKG"
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Old 10th Oct 2020, 08:04
  #44 (permalink)  
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A couple of thoughts ..

(a) This being the case, the late reallocation of an A320 load to an A321 would have resulted in Zone D being empty.

Unless a trimsheet be designed to cover multiple models (and that may be both reasonable and feasible for some aircraft) a change in model surely requires a reworked loadsheet ? One presumes an adequate level of competence in those charged with the execution of load control. We have checks and balances and multicrew operations to provide for a high probability of success, providing everyone does a reasonable job. In the simplistic view, the crewmember signing off the completed loadsheet ought to be able to detect such gross errors.

(b) I see some comments regarding the non-intuitive nature of loadsheets. This is especially so with the typical electronic summaries we have seen for many years, now. However, there are various simple ways to get around Murphy's antics ...

I was most impressed with a very simple system we came up with to defeat a lot of these sorts of problems which was implemented for IPEC freight operations in the 80s.

The freight shed did their thing using a normal paper trimsheet - but my comment would be equally pertinent regardless of whatever system might have been used - even an electronic ACARS style sheet such as I was routinely familiar with flying for another operator.

The critical thing was that the IPEC crew then ran an independent check using the load summary to check the trim with a whizz wheel trimsheet. One pilot called the loads in sequence and summed the totals as an independent check. The other pilot ran the whizz wheel to check the trim and the whole exercise took no longer than the time it took the first pilot to call the numbers at a measured pace. In addition, as was typical for freight operations then, one pilot physically ran a can check on weights to detect any gross misloading sequence errors. This is entirely analogous to the cabin senior's running an eye over the cabin and (ideally) then running a quick brief with the cockpit to make sure that the reality matched the storybook to a reasonable degree.

Really, folks, there is no reason, or excuse for, why the load control answers can't be reliably accurate and consistently so.

In the same vein, there is no valid reason why operator training should not ensure that the flightcrew is alert to gross speed schedule it-doesn't-look-quite-right calls. I have no background playing with Airbus but, in another age, we would have picked up alarm bells (on Mr Boeing's products) such as speed schedules encroaching on Vmca/Vmcg regions of the envelope without any undue problem or delay.
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Old 10th Oct 2020, 08:30
  #45 (permalink)  
 
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Originally Posted by vilas View Post
The first comment on the report in Avherald makes it very scary. It could have ended in disaster. The RW is short with no overrun the crew wouldn't consider abort takeoff. The aircraft which is in direct law on ground got airborne only because of the thrust/weight couple created by TOGA. Otherwise they would've overrun with takeoff thrust. Providential escape.
The Captain saved the day by selecting TOGA which provided an UP pitching moment as pointed out by vilas .

The other thing they could have done was to move the trim wheel to increase UP stabilator (the stabilator is frozen at the TO Trim setting in direct law until airborne).

When you run out of elevator authoriy (or up/down pitch stick control authority) in an all-moving-tail (all-flying-tail) aircraft (most airliners), in any phase of flight, you must manually move the stabilator to regain control.

The same applies to datum trim aircraft (which then need to be re-trimmed).
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Old 10th Oct 2020, 08:43
  #46 (permalink)  
 
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Originally Posted by DaveReidUK View Post
You understand correctly - see post #25.

From the report:

"Passengers were boarded with their seat allocation for the A320 and therefore were seated within cabin Zones A, B and C. This left the seats at the rear of the A321 aircraft, which has a fourth zone, Zone D, unoccupied. The unusual passenger distribution was not noticed by the cabin crew or dispatcher. The aircraft commander was unaware of the passenger distribution in the cabin but was passed a Load and Trim Sheet for his A321 aircraft, G-WUKG"
Interesting, we only have 3 zones for both 320 (1-10, 11-20, 21-31] and 321 (1-10, 11-25, 26-39).

So we could use all the 320 data (Zone, Underfloor, Fuel) and enter it into our 320 e Loadsheet by mistake, and if pax sit in their assigned seat, this forward CofG is still a problem as the zones might appear correct, but 5 rows of zones 3 are actually sitting in zone 2 and the last 8 rows are still empty.

Once again it comes down to the Cabin Crew to eyeball the cabin and recognise a problem and the Pilots to check the paperwork, carry out the cross checks and be vigilant to the 320/321 differences.

I havenít flown for 6 months, or studied, and am racking my foggy brain to try to remember any other mitigators for this problem
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Old 10th Oct 2020, 08:56
  #47 (permalink)  
 
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Strikingly similar to this: Incident: Jetstar A321 at Melbourne on Oct 29th 2015, difficulty to rotate aircraft for takeoff

Incident: Jetstar A321 at Melbourne on Oct 29th 2015, difficulty to rotate aircraft for takeoff
By Simon Hradecky, created Thursday, Dec 3rd 2015 16:12Z, last updated Friday, Jan 18th 2019 17:46ZA Jetstar Airbus A321-200, registration VH-VWT performing flight JQ-976 from Melbourne,VI to Perth,WA (Australia), was accelerating for takeoff from Melbourne's runway 16 when the crew needed to apply nearly full back pressure on the side stick to rotate the aircraft. The aircraft climbed out to safety, the flight crew requested cabin crew to count the passengers on board and note down their seat distribution. The results were recalculated and the flight crew found, that the aircraft had been outside the aircraft's loading limits. The passengers were redistributed within the cabin to bring the center of gravity back into the aircraft's envelope. The flight continued to Perth for a safe landing.

On Dec 3rd 2015 Australia's TSB rated the occurrence a serious incident and opened an investigation, the final report is being estimated for October 2016.

On Jan 18th 2019 the ATSB reported that the investigation was discontinued. The ATSB argued that the organisational context within the operator had changed significantly in the last 3 years and any finding would thus no longer match the current situation.

In the event summary the ATSB stated: "It was later established that passenger seating allocations had been determined using the seat map for an A320 instead of an A321." After reseating 6 passengers to the aft cabin the crew recomputed weight and balance and proceeded for an uneventful remainder of the flight.
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Old 10th Oct 2020, 09:26
  #48 (permalink)  
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Interesting, we only have 3 zones for both 320 (1-10, 11-20, 21-31] and 321 (1-10, 11-25, 26-39).

Entirely a matter for the operator and the weights engineering folks to determine how their loading systems are designed. The problem here appears to be that the relevant folks didn't recognise the mistakes made which ought to have been recognised at the time. Mistakes are part of the experience and we have to accept that they will occur - trapping mistakes before they become somewhere between embarrassment and catastrophe is the essence of what we do.
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Old 10th Oct 2020, 09:46
  #49 (permalink)  
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Originally Posted by pineteam View Post
Never understood why it was there at the first place. Good thing they finally removed it. This aircraft can be flown entirely without checklist in my opinion especially the newer models where you have an Ecam warning for everything. All the important items are displayed on the Ecam memo. Gotta love Airbus for that.
I understand itís there because a few people have tried to land in OP DES.
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Old 10th Oct 2020, 16:40
  #50 (permalink)  
 
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AAIB investigation to Airbus A321-231, G-WUKG Slow response to aft side stick control input at rotation, London Luton Airport, 16 January 2020. Evidently the rotation problem was due to not correcting the passenger seating when the 321 was subbed for the 320.]
https://assets.publishing.service.go...WUKG_10-20.pdf
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Old 10th Oct 2020, 16:45
  #51 (permalink)  
 
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Check Airman

The original design concept of the A320 was that it would never have any QRH or paper checklist and that it would only fly in managed modes. For self-explanatory reasons, none of that materialised, especially given that all the 1980s technology available back in the day was not even close to what we have now.
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Old 10th Oct 2020, 17:40
  #52 (permalink)  
 
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Have flown the A320 for a while with an operator SOP that had no check lists between after start and parking checklist, and generally a silent flightdeck philosophy. Works very well indeed. But there is many ways to fly the same plane.
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Old 10th Oct 2020, 19:30
  #53 (permalink)  
 
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Originally Posted by john_tullamarine View Post
Interesting, we only have 3 zones for both 320 (1-10, 11-20, 21-31] and 321 (1-10, 11-25, 26-39).

Entirely a matter for the operator and the weights engineering folks to determine how their loading systems are designed.
Zone D on the Wizz A321ceo is, in effect, a virtual zone that simply designates those row numbers (31-39) that are present on the A321 but not on the 30-row A320.

It's hard to see how there can be any physical demarcation between the 28" pitch seats in Zones C and D, respectively, other than at most a curtain - which would be pretty pointless in an all-Y layout.

In which case, the criticisms being levelled at the cabin crew amount to them failing to twig the significance of the fact that only the first 6 rows of the 14-row cabin aft of the E/E were occupied, which seems a tad unfair.





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Old 10th Oct 2020, 21:49
  #54 (permalink)  
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The critical consideration, though, is that the OM loading system protocols must define, adequately, differences between, and procedures for, different models to avoid screw ups. How this might best be done in a matter for the ops management, tech services, and weights engineering folks.

Point is that, if there be no formal protocol to avoid problems, then problems will arise as surely as day follows night.

I can't comment on the Airbus as I have no background, either flying or engineering, with the aircraft. However, when it comes to weights engineering work, an aircraft is an aircraft is an aircraft and differences are unremarkable.
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Old 11th Oct 2020, 11:21
  #55 (permalink)  
 
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In one of my previous operator (UK), for every flight the cabin crew were doing a counting of number of passenger per zone and the number one was giving me a paper with the 4 zone and each number of pax per zone.
it was really easy to check now with the load sheet the number of total passenger and each zone, easy to spot if passenger moved or was a mistake.

Most of the time some passenger had moved and sometimes when it was clearly impacting the CG to my experience we would ask the CC to move some passenger, for example, 3 pax from zone A to D ...

My last operator, we don't do that and it is even not mandatory to tell me the full number of pax on board (it depends of the destination, what I don't really understand)

If it would be mandatory for all EU (world) operator to do what I just said above with mandatory CC counting, this kind of incidents with CG would be unlikely to happen. But as always in the world, until we don't have a big crash at the end of the runway with media coverage and the world been shocked, nothing will change ...
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Old 11th Oct 2020, 12:47
  #56 (permalink)  
 
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So, who else is doing load sheets with Excel tables?
(Very intrested for my personal no fly list)
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Old 11th Oct 2020, 14:04
  #57 (permalink)  
 
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Fly Be used to a few years ago
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Old 11th Oct 2020, 14:07
  #58 (permalink)  
 
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Would you prefer manual loadsheets? Those are definitely error-proof.
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Old 11th Oct 2020, 18:12
  #59 (permalink)  
 
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In a way yes, because I would expect a second pair of eyes looking over those.
Over the years I have seen many Excel "applications". I have even seen a closed loop simulation in Excel - albeit only with fixed step solver.
They all had one thing in common: The were perfecly good when they were working. However if somebody inserted a row, broke a link or Excel would not update a cell for some unknown reason (which I have experienced) they would fail - and the failure could only be discovered by critical awareness of the individual before the screen.
Add the possibility of these copy and paste errors as we've seen here.
So yes, perfecly inadequate for loadsheets.
QED

Last edited by BDAttitude; 11th Oct 2020 at 18:27.
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Old 11th Oct 2020, 19:21
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The mark one eyeball, and experience, comes into play here.
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