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Very interesting article.

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You most definitely haven't heard about Maximum Zero Fuel Weight.

That there's still allowance in the MTOW doesn't mean it's all for cargo.

The highest certified MZFW for the A321NEO family is 75.6t.

Using this and your hypothetical passenger weight and fuel weight,

The A321NEO true cargo will be 6.6t

The A321LR and A321XLR will be 5.6t each.

The MZFW is included in any plane certification for a reason, it's not negligible.

Any further available weight is there to take in more fuel.

Complying with the MZFW will also help you get down to or below the MLW upon reaching your destination. The highest certified MLW of the A321NEO family is 79.2t.

If you carry the full 14t cargo you specified for the A321XLR, you will have a landing weight of about 89t, 10t higher than limit. Your landing weight for the A321NEO will be 88t, 9t higher than limit.

Note that the A321LR, A321XLR will burn between 0.2-0.7t more fuel if flying the Sydney to Perth at MTOW.

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We're not sure if you read the entire article since nowhere did it argue they'd use the entire remainder of 14t for cargo. The conclusions refers to a "meaningful cargo load". In fact, the article specifically focused on the volumetric space rather than weight, since the cargo constraint on these missions will be volumetric rather than weight.

The purpose of the "volumetrically" framing was to compare and contrast the volumetric trade-off between the LR and XLR, since that was the binary choice. It's clear why Qantas didn't choose the standard A321neo. It would struggle to carry the required fuel (volumetrically) and when it could it might also suffer from payload restrictions.

So the choice was between the LR and XLR. The conclusion isn't that they'll carry 14t, but that the XLR ALLOWS THEM TO CARRY MORE CARGO THAN THE LR. This isn't limited by the payload parameters, but by the volumetric space. The LR would be able to carry about 1 LD-56 container. Given the container has a maximum gross weight of about 1.5t, that would only allow 1.5t of containerised cargo anyway! The XLR has about 3 container positions available, so a maximum of 4.5t containerised cargo anyway. These are well within the 5.6t that you suggest is the true cargo!

So yes, we understand MZFW. The purpose of the blog isn't to over complicate but to contextualise Qantas's choice between the LR (an aircraft the know well since they operate them over at Jetstar) and the XLR. If you think the payload and volumetric cargo hypothesis is incorrect, then we're happy to hear an alternative hypothesis why they've ordered the A321XLR to replace the B737-800s!

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FWIW, the example in the article has landing weight at 79t, which is exactly MLW. Didn't show it since it wasn't particularly neccessary, but if you ran the numbers then it should have been an obvious hint how we got there! You estimated true cargo potentially as 5.6t but as you'll see our estimates were slightly conservative on fuel, OEW, etc. Using your parameters, we'd come slightly lower actually, probably 78t.

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Not saying that you're focused on weight in your calculation.

But you're making mention that the A321XLR will have a possible cargo weight of 14t for the specified route. "Assuming the same passenger configuration and load (200 passengers), crew, baggage, fuel load and reserve, the baseline neo, LR and XLR could have up to 7t, 10t, and 14t available for cargo (Table 4)."

"nowhere did it argue they'd use the entire remainder of 14t for cargo. The conclusions refers to a "meaningful cargo load"."

7t or 10t or 14t is purely not "meaningful" with full passenger load.

I used your numbers here, MLW= OEW + PAX + RESERVE + CARGO

51 + 19 + 5 + 14 =89t. 9.8t higher.

MZFW = OEW + PAX + CARGO

51 + 19 + 14 =84t. 8.4t higher.

"In fact, the article specifically focused on the volumetric space rather than weight, since the cargo constraint on these missions will be volumetric rather than weight."

Yes, the article focuses on volumetric cargo, but you should know that ACT are like cargo pallets, it can and are easily removable just like a standard LD3-45, but RCT is a permanent fixture.

There's just a lot of variables to determine that it's volumetric cargo space that's the reasoning behind the decision over the LR.

But they could have done a combination of the NEO and XLR instead.

"It's clear why Qantas didn't choose the standard A321neo. It would struggle to carry the required fuel (volumetrically) and when it could it might also suffer from payload restrictions."

The A321NEO can fly any current B737 missions at Qantas without restrictions. If volumetric cargo was it for them, they could possibly have gone for a mix of the two (A321NEO and A321XLR).

Running the fuel burn calculations here,

The baseline have a range of 4,610km

With 1 ACT 5410km

2 ACT 6,245km

3 ACT 7,045km

The baseline XLR will go 7,975km with only RCT.

8,775km with RCT plus 1 ACT.

(Typical in service operational scenarios considered, wind and temperature). Qantas longest B737 route is Sydney to Denpasar (might be wrong) it's 4,620km Long, the baseline A321NEO should be able to hit it with its 4,610km range. (All weight calculations are done with the numbers you provided, fuel reserve given by the software used is 4.5t, fuel burn averages 2.6t).

I'm guessing it's more about price (good price from Airbus) and fleet utilisation/maintenance commonality that drove the XLR decision over a mix. It's definitely not Volumetric cargo.

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You're intentionally misinterpreting the quotes from the article out of context.

"Assuming the same passenger configuration and load (200 passengers), crew, baggage, fuel load and reserve, the baseline neo, LR and XLR could have up to 7t, 10t, and 14t available for cargo (Table 4)."

Yes, it may have, but it doesn't. The remainder of the paragraph and the next paragraph explains why it doesn't. When you ignore that as you intentionally do it looks out of place. But it's a clear paralipsis by proposing it using "may" when in fact it can't. That the remainder of the paragraph and the next paragraph explain a more relevant reason exposing the use of a (somewhat provocative) literary device.

7t, 10t, and 14t is not what meaningful refers to and nobody would view it as that. Meaningful is an abstract relative term, so how could one draw any inference in absolute terms? Meaningful refers to 4.5t become more meaningful than 1.5t since the conclusion is explicitly referring to the difference in the XLR and LR. It seems as though you're so intent of finding a hole that you're digging your own one by intentionally isolating context.

"The A321NEO can fly any current B737 missions at Qantas without restrictions. If volumetric cargo was it for them, they could possibly have gone for a mix of the two (A321NEO and A321XLR)."

For someone going on about MZFW you should know that this is patently false. The standard 321neo simply doesn't have the fuel capacity. Like it's 19t is simply not enough space!

Firstly, you're only calculating trip fuel, not hold fuel, reserves, contingencies, EDTO, ATC, weather, etc. Secondly, who the hell measures fuel and range in km rather than time?!?! A westbound SYD-PER are taking anywhere up to 5:20 at the moment compared to eastbound at well under 4 hours - km are not relevant. The difference in fuel burb on 5 to 4:20 is massive! The whole reason for using the westbound was - as the article stated - using the longer leg to show the example!

Taking SYD-DPS is even worse, it'll take anywhere from just below to more than 6 hours. So we're looking at 16t to 17t block fuel. Then let's add at hold fuel (much needed for DPS just due to congestion, nevermind weather), then an alternate (shit, what are you going to do if you can't land), then contingencies and reserves. Trip fuel is now 25t or thereabout. This isn't event getting to TEMPO fuel which is often needed in the tropics, yet your standard A321neo is only going to hold 18 or 19t (actually the article may have overstated mistakenly with 18.9t). So how the hell is your standard neo going to make it? You don't even need to get as far as payload restrictions since it literally can't even load the fuel!

Reassessing you own example, your software may be right, but your inputs are bizarre. Even at the very generous fuel burn of 2.6t, 6 hours is 15.6t. How about hold fuel? (let's call it an hour). How about alternate? (Qantas are probably going to want CGK, so call that 90 minutes). Then only can talk about contingencies and reserves. But easily, that's an additional 9t. And 2.6t is very generous FWIW. So again, you're making stuff up!

SYD-PER could barely do it under optimal conditions (barely), add in some of the joys like EDTO and hold fuel, nevermind unavailable alternates and once again the trip fuel is going to be well above 19t. The challenge is that you can't simply trade away payload, it just can't do it! You can't focus on fuel burn, but rather trip fuel - that is the relevant constraint. You don't need to worry about MLW since you flights to DPS are ending up in the water! So yes, I'm calling your estimates utter garbage.

So no, the standard neo isn't doing SYD/BNE/MEL-PER and even SYD-DPS. Hence the argument about cargo and the choice between the LR and XLR. Commonality isn't a big deal since there is no difference in operations. Jetstar have no problem operating both LR and XLR (they have the former, and the latter is on order).

Also, yes, ACTs can be removed and added, but it's not something that is as quick as you say. It's generally something that requires an overnight trip to the hanger. It's not something that can get done during turnaround.

FWIW, JQ have the LRs with 2 ACT. Never used a third. You might want to read up on the procedure for removing and usability of the space. You might be surpised!

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