Boeing cites risks in design of newest Airbus jet

[Check Airman]

Boeing cites risks in design of newest Airbus jet (https://www.reuters.com/article/us-airbus-design-boeing-idUSKCN2AU2RJ)

[Chris2303]

What Boeing are saying may or may not be true, but one would suggest that Boeing would be better spending 24 hours a day 7 days a week looking after their own airplanes and trying to get themselves out of the messes that they (Boeing) have created

[lomapaseo]

This a responsibility for anyone with risk knowledge to advise the regulators of a concern. I'm all for new ideas and equivalent or improved safety as I'am sure that Boeing is as well, A black mark against any manufacturer has a tendency to affect all as well. If this latest issue can not be resolved by equivalency and history then maybe it's time for a new rule making to permit similar changes across all manufacturers

The B737 pop open overwing exits turned out to be a safe innovation done the same way

[GlobalNav]

Guess I've heard everything now? Boeing doesn't trust the certification process to determine compliance with safety standards? So Boeing, who thwarted the certification efforts of FAA, EASA, TC, et al., doesn't trust them to evaluate the type design of their chief competitor. Perhaps Boeing, perhaps using all its remarkable ODA resources, wishes to become the chief worldwide regulator of transport airplanes. I am sure they would be impartial. I think I know where to file this.

[Denti]

I wonder, what is the difference between an integral tank and the usual integral center tanks? Boeing has some experience with those exploding, so it should have a valid input based on those experiences...

Of course there is the huge elephant in the room, that B has absolutely nothing to offer in that specific, and very narrow, market segment.

[Three Wire]

If my understanding is correct, Airbus proposes to use the skin of an aircraft has a tank wall. Been tried before with ships and was a huge environmental disaster.
Airbus has previously used ACT (Additional Centre Tank) in cargo bays. They were a feature in the long range versions of the A310.

[clark y]

Any different to a wet wing?

[kenparry]

In principle, no: but rather closer to the passengers

[Less Hair]

So first it will feel too cold and then too hot?

[DaveReidUK]

Even without Boeing's unhelpful intervention, there seems to be a good chance that Airbus will get its fingers burnt (npi) by the additional conditions that EASA said some time ago that it will impose in respect of the RCT.

There will no doubt be a technical solution to the issues, but anything that adds weight and/or reduces RCT capacity will have implications for the XLR capability and not be popular with customers.

[Maninthebar]

and nearer to the ground, which would give rise to the elevation of risk identified by Boeing in the event of off-piste excursions or gear failure

[ATC Watcher]

For the A321XLR, Airbus plans to eke out more space for fuel by moulding one tank directly into the fuselage, meaning its shape would follow the contours of the jet and carry more fuel.
Not the wing but the fuselage .
Some years ago I few an innovative aerobatic aircraft where the fuel tank extended in the space between my legs. This was supposed to be a brilliant engineer idea to keep the aircraft as aerodynamic as possible and the most weight close to the CG . A brilliant idea indeed on paper but having only a few millimeters between your most valuable parts and a plastic fuel tank made sure I did not renew the experience. The aircraft never went beyond experimental.
Sometimes what looks like good ideas fail to succeed in practice. I hope this one does too. ..

[Uplinker]

How is this significantly different to any aircraft with a centre fuselage tank? We rarely used the A330 centre tank, but many long-haul aircraft have them. Some A321s have extra tanks in the cargo holds - under the floor.

It seems that Airbus are proposing to mould the centre tank more closely into the space to create extra room in the tank? A bag tank would be slightly compromised by not fitting exactly snugly around every rib and contour that it rests against, losing space in the tank.

Presumably installing a composite/plastic tank, then heating and pressurising it in situ so the tank walls push out and exactly fit the metalwork surrounding it like a glove, will increase the volume inside the tank slightly for a little more fuel. Once thus fitted, the tank would be allowed to cool and harden off in its new snug profile?

Boeing clutching at straws, trying to divert attention away from their disastrous recent history.

[Less Hair]

Didn't Concorde have quite a few fuselage tanks that were able to recently get recertified with the final modifiation package by Airbus?

[BEagle]

Well, Boeing would know all about fires with the 7-late-7 batteries and the 747 centre tank explosion some years ago.....

Airbus has been using additional tanks for years; the A310MRTT has 4 additional centre tanks shaped to replace pairs of cargo containers. No problems whatsoever!

[TURIN]

Even though I do agree, Boeing doesn't exactly have the high ground here, there are some serious problems with this idea.
Centre wing tanks tend to be made from rather more robust and thicker material than fuselage skins.
I think D.C-10s have aux tanks in lower fuselage area, but not integral to the structure.
Yes, Concorde does have fuselage tanks. There were quite a few elements of the Concorde design that would probably not get regulatory approval today.
Airbus needs to rethink this. Stab/fin tanks perhaps? Doesn't the A300 have a tank in the fin?

[BEagle]

Both the A300 and A310 have 'trim tanks' in the tailplane, not the fin.

[568]

Turin,
The MD-11 also has an AUX tank which is used for ballast fuel purposes.

[esscee]

Also the A330/A340 both have a horizontal stabilizer fuel tank within the Stab front and rear spars.

[EI_DVM]

What is the structural difference between this new center tank and the center tank already in all B737, B777, A320, A321 and A330-200 aircraft? Is there something that makes this particularly more vulnerable to failure than previous center tanks? If anything I would have thought an integrated center tank as proposed for the XLR should provide improved safety over the removable ACTs used currently in the LR?

[Pugilistic Animus]

I read about this in Reuters this morning. What a case of the pot calling the kettle black...or maybe corporations in glass hangars shouldn't throw boulders! I'm aware of the requirement to warn but this is ridiculous

[DaveReidUK]

EASA's proposed Special Condition in respect of the RCT:

Passenger Protection from External Fire

In order to protect the cabin occupants from an external pool fire, the lower half of the fuselage in the longitudinal location of the rear centre tank shall be resistant to fire penetration.

[GlobalNav]

I’d prefer Boeing kept their nose to their own drawing board. They have plenty of work there. I’d also avoid adding Boeing to the coordination trail for a competitor’s certification. It’s not uncommon for officials from OEMs to take shots at one another for the sake of gaining competitive advantage. The regulators should focus on the facts, and on compliance to the safety standards.

[Dave Therhino]

The concerns are legitimate, but Boeing doesn’t have much credibility right now.

If they are essentially making a “wet fuselage section” aft of the gear well then resistance to external fire is only one of the issues. The design must prevent rupture of the tank in a wheels up, on-airport landing. The design of the landing gear must prevent penetration of the tank in the event of a gear failure, including due to an overrun into obstacles.

It’s different from a traditional center tank because a center wing tank is constructed by sealing the center wing structural box, which is heavy structure that typically does not break open in otherwise survivable crashes.

It’s different from typical body-mounted aux tanks, which are dual-wall boxes secured to the cargo floor or the underside of the main deck floor, with considerable separation from the outer fuselage structure, providing protection from crash penetrations and from the heat of an external pool fire.

[Busbert]

It’s not Airbus’ first rodeo. The A340-500 RCT is very similar. In fact the A321 should be easier because there is no CLG to worry about. The FAA required a Kevlar liner on the A345 RCT, it wasn’t a requirement for EASA TC.

[Big Pistons Forever]

For sure Boeing is stirring the pot, however the original A320 was never intended to ba 757 replacement. It is a 30 + year old design that has been stretched far beyond what was originally envisioned. To make the 321XLR work is now requiring work arounds that sure look like klutzy grandfathered solutions that would never be allowed on a clean sheet new design. EASA acted all high and mighty about the FAA failings over the MAX debacle, it will be interesting to see how they act now that the shoe is on the other foot...

[TURIN]

More info here.
https://www.airbus.com/newsroom/stories/First-metal-cut-achieved-for-the-A321XLRs-Rear-Centre-Tank-section.html

[Commander Taco]

Dave Therhino,
If they are essentially making a “wet fuselage section” aft of the gear well then resistance to external fire is only one of the issues. The design must prevent rupture of the tank in a wheels up, on-airport landing. The design of the landing gear must prevent penetration of the tank in the event of a gear failure, including due to an overrun into obstacles.

If memory serves, Airbus wanted this setup for the A340-500. The regulators wouldn’t buy it and the Airbus revised design incorporated a Kevlar bladder for this aft lower fuselage fuel tank.

[Pugilistic Animus]

My personal reason that I think Boeing did that was not to conscientiously apply the duty to warn doctrine but trying to take some of the heat off of Boeing for their muppetry.

[Dave Therhino]

Commander Taco

I know the FAA initially resisted approving the design of that tank that was initially accepted by the European authority, and was particularly concerned about the threat posed by a failure of the center landing gear. The FAA eventually approved the airplane model, but I don't know the details of the configuration that was finally approved by the FAA.

[DaveReidUK]

Big Pistons Forever

"EASA acted all high and mighty about the FAA failings over the MAX debacle, it will be interesting to see how they act now that the shoe is on the other foot..."

We already know the answer to that.

As previously mentioned, EASA have said they plan to impose special conditions that the RCT on the A321XLR will have to satisfy.

[krismiler]

The FAA warned about the danger posed by the vulnerability of Concorde’s fuel tanks to lower wing damage. The rest is history, after the disaster extensive modifications were required before the type returned to service.

Hopefully, Airbus won’t push the A321 any further than the XLR and make the same mistake as Boeing did with the MAX. After 30+ years they’ve got their money’s worth and it’s time for a new design if they want more capability.

[Denti]

We will see. Unlike Boeing, Airbus did not stretch the type beyond its three first variants, whereas the evolution from the -100 to the -10 is rather breathtaking. Yes, it adds no range variants of course, and lets see how it will fulfill EASA and possibly FAA requirements for the protection of the wet fuselage tank.

Since the development focus currently seems more on their hydrogen projects, which are all clean sheet designs, it will be interesting to see that play out. However, Airbus could obviously take another leaf out of Boeing's book and develop another new variant with a new and more efficient wing, that hasn't happened yet, they simply bolted new engines to the same unchanged aircraft with the NEO, a rather easy thing to do. But yes, there is of course a case to be made to do a larger and new plane altogether, while growing the A220 line into a -500 variant, the -300 is already competing with the A319 NEO which of course has the advantage of flightdeck and parts commonality with the rest of the series.

[Uplinker]

I don't think it is quite the same as the 737; The A320 started out as a fully integrated electronic FBW computer jet. The 737 is an essentially mechanical design from the 50's that has had various electronic gizmos added on in recent years, but never fully integrated. Even now, its systems do not have the full capability of the A320 family.

If Airbus can find more fuel capacity with closer fitting tank liners then why not go for it? That's refinement of a good design.

[Lord Bracken]

For sure Boeing is stirring the pot, however the original A320 was never intended to ba 757 replacement. It is a 30 + year old design that has been stretched far beyond what was originally envisioned.

Huh? A 321XLR is the same length as the first 321 that rolled out of the hangar in 1989. The wing is almost identical apart from returning to a single-slotted flap (similar to the 320, amusingly). MTOW is around 20% higher than the prototype. It's a very considered, stable, almost natural evolution of the product.

[lomapaseo]

I'm still wondering what form of communication did Boeing choose that led to all the speculations in this thread about their motives.

I don't at all trust the news that prints headlines suggesting nefarious reasons

[Momoe]

"It is a 30 + year old design that has been stretched far beyond what was originally envisioned. To make the 321XLR work is now requiring work arounds that sure look like klutzy grandfathered solutions that would never be allowed on a clean sheet new design."

OK, I'll bite, apart from the number of years, the same could be said about the 737 in the light of the Max debacle.

1960's era 737's evolution (sic) against the organic evolution of the A320 series into the mature product it is today does not bear comparison, Boeing had the choice of bringing a clean sheet design to the table or take the cheap option and tart up grandma (again).

None of the changes to the 320 series affected the aerodynamics unduly, if they did Airbus compensated accordingly (larger tail area A318).

I'd like to think I've missed the irony but I'm not sure it was ever intended.

[toratoratora]

Momoe, you beat me to it!

[Commander Taco]

Dave Therhino,

Did some deeper digging and it looks like the tank was redesigned to accept a Kevlar liner/bladder. From Flightglobal August 2003:


Although the -500 shares much commonality with the larger A340-600, it is unique in having a 19,930 litre (5,260USgal) rear centre tank (RCT). ... The Kevlar-lined tanks willbe certificated as a major modification by the JAA on behalf of the FAA.Aug. 11, 2003


Very prescient of the FAA as evidenced by the severe lower aft fuselage damage on an Emirates A340-500.
Emirates 407 A340-500 Tail Strike (https://en.wikipedia.org/wiki/Emirates_Flight_407#Aircraft_damage_and_repair)

[lomapaseo]

A klutzy design could be said of every 30 yo basic design. But that issue is only important to the ability to sell to its customers, something more attractive in their fleet plans

It appears that most of the recent news is about the safety of the intended modifications and for that the FAA does look at applicable history of the original design against all aircraft. This base history is now matched up against any obvious questions concerning what is proposed.

That is a public process and comments from experts in these comparisons are welcome within the regulatory process not withstanding all the hyperbole started in the press

[Big Pistons Forever]

When originally designed the A320 series was never intended to have a full body conformal internal fuel tank, just like the MAX was never intended to have its engines hung out in front of the wing. Sadly the "so what" of the engine decision ultimately led to catastrophe. New engine vs new fuel tank may seem to be an apples to orange comparisons but I think not as in In both cases the mod was central to the appeal of the airplane. In the MAX case no new engines meant no competitor to the A320NEO series. In the case of the 321XLR no internal conformal fuel tank means no ability to own the medium range single aisle market. Therefore the pressures to make it work are going to high.

The true test of whether the MAX debacle has really fundamentally changed aircraft certification is, IMO, how this design change is certified. Personally I have great difficulty in seeing how a comparable level of crashworthiness to an aircraft without the tank can be maintained with the current design. It will be interesting to see how this plays out as ultimately the stakes are much higher than the success of one 320 family model variant......

[lomapaseo]

I guess you need to define what crashworthiness is in a regulation. With g-loads if you exceed the spec it's gonna break..be it wings or fuselage, overhead bins seat tracks, etc.. All they have to do is to design the tank to be the last to break after crap happens elsewhere in the plane.

[Big Pistons Forever]

No you need a process that ensures that the inevitable compromises to make the tank work don’t reduce the safety of the aircraft. For that to happen business and political pressures have to be designed out of the safety determination process. If you think EASA is not as vulnerable to regulatory capture as was the FAA, then you are deluding yourself.

[Chris2303]

It is deplorable that an industry that supposedly prides itself on "safety first" should have allowed the safety determination process to have been hijacked in this way

[Momoe]

This isn't about whether EASA is better or worse than the FAA, it's about Boeing taking the phrase "People in glass houses....." and OWNING it.

However, just because you can, doesn't mean you should.
The time to do this would have been after EASA certification, not before, it's not as if Airbus hasn't already run this by EASA.
Granted it might be a tactical move to make Airbus/EASA consider their options and gain some time but either way it doesn't sit well coming from Boeing at this juncture.

Any publicity is good publicity isn't necessarily a truism, the Boeing brand is tainted at present and this has not helped.

[DaveReidUK]

Has anybody actually read the article linked in post #1 ?

The U.S. plane giant's intervention is not without precedent in a global system that regularly allows manufacturers to chime in whenever safety rules are being interpreted in a way that might affect the rest of the industry.

"Public consultation is part-and-parcel of an aircraft development programme," an Airbus spokesman said, adding any issues raised would be tackled together with regulators.

[Denti]

Thanks for that, you are of course correct. Consultation is not only normal for safety stuff, but for regulations as well. I do get invited to a lot of EASA regulations consultation processes whenever they update regulations, everyone can comment on that, and of course the relevant working group will weigh that input and, sometimes, act on it. The same is true for pretty much all EU secondary law.

[Uplinker]

@ Dave Reid, yes, but I think the issue is that Boeing have rather spoiled their once great reputation with regard to safety !

PS: There is nothing 'klutzy' about the Airbus FBW family. Whereas one only has to sit in a B737 to see how klutzy it is. The 737 F/O still has a series of flows to perform, to switch various things on or off, that even our cars can manage to do automatically. F/Os shoulder straps can knock out CBs behind. The tractor-like controls which impede the view of the instruments. The wire ropes and pulleys to operate the flight controls. No A/P rudder control. Do 737 cabin crew still have to bend down to physically pick up and place the girt bar into the floor brackets every time they arm or disarm a door? (Airbus doors engage the slide by simply closing the arming handle).

I have much more respect and trust in Airbus for their design processes and innovation.

[Denti]

To be fair, that is actually available. Just one of the many options (like the AoA display) that nearly nobody buys. However, even if it is bought, it works only during approach below roughly 1500 ft AGL until rollout or go around until another lateral mode is selected. And then it simply disconnects, which, in a OEI scenario gives a huge kick if one is not prepared for it, well, even then to be fair, as it only controls the rudder, but not the trim.

[FlyingStone]

The wire ropes and pulleys to operate the flight controls.

Those things keep you in control when you lose all hydraulics and/or electrics.

[NWA SLF]

And those pulley and ropes are there when someone decides to pull a breaker to reset the computer in response to a rudder fault like AirAsia 8501.

[568]

Uplinker

"No A/P rudder control"
Not entirely true as the AP takes up rudder control when the APP mode is selected and the self test initiates at approximately 1400 feet. Runway alignment occurs at 500 feet RA if there is a crosswind.

[krismiler]

Hopefully, the company culture at Airbus is different to Boeing, and solution found to the fuel tank issue will be one that prioritises safety rather than cost cutting and bonuses.

Oversight from EASA will likely be a lot better than FAA’s hands off approach with Boeing.

Airbus have done well with the basic A320 design but at 30+ years old, it’s getting a bit dated, particularly in the flight deck. Time to start thinking about a new clean sheet design which integrates all the technological advances made since the 1980s. The current design can easily see out this decade, but by then Boeing will be coming out with a long overdue B737 replacement which will likely be superior to the NEO.

[procede]

I do not think that they could improve much on the basic A320 design which they haven't already done on the NEO. Carbon fibre will not do much for a short to medium range aircraft and any advances in electronics and avionics do not require a new basic design. Maybe for the A321XLR you would want a slightly larger wingspan, to fit the extra fuel in the wing, but the benefits do not outweigh the costs.
The 737 design has two basic flaws compared to the A320: No space for a longer landing gear and no fly by wire.

[Denti]

krismiler

"Airbus have done well with the basic A320 design but at 30+ years old, it’s getting a bit dated, particularly in the flight deck. Time to start thinking about a new clean sheet design which integrates all the technological advances made since the 1980s. The current design can easily see out this decade, but by then Boeing will be coming out with a long overdue B737 replacement which will likely be superior to the NEO."

I guess the new hydrogen models are slated as a replacement in about 9 years. That said, Airbus was actually in development for an A320NEO enhanced version, with a new flightdeck close to the A350 layout. Not identical of course, space constraints make that impossible. But apparently customer demand was not very high, while development costs were, so that was scrapped around two years ago. In essence, airlines were not willing to pay for not much additional use, heck, most do not pay for stuff that has been available for 10 years now, like autopilot TCAS and FLS.

[krismiler]

I’m looking at it from a pilot’s point of view but those who make the decisions are looking at it from a monetary point of view, no prizes for guessing which will prevail.

Competition is fierce and every cost saving measure counts, particularly with LCCs driving hard deals.

I guess I’ll have retired before the next generation of narrow bodies comes to market.

[Uplinker]

@ 568 Thank you for the correction.

@ NWA SLF, Pulling CBs in flight is not generally permitted, unless expressly ordered by a QRH or ECAM action. To "illegally" pull a flight control CB in flight without understanding what you are doing has nothing whatsoever to do with the design of the aircraft.

My point was that the A320 family is not even remotely 'klutzy'. One only has to do a walk around of a B737 and an A320 and do a cockpit set up, to see that the A320 is an order of magnitude further on from the B737. Systems and cockpit design, layout - even cockpit size - are all on the next level. This is not to say the Boeing is necessarily bad per se; it is just basic, and the wire rope flight controls and pulleys etc, were the level of technology in the 1950's.

The Airbus FBW stands tall as an extremely well thought out, well integrated and well developed design. The A320 family has three independent hydraulic systems. Five sources of AC power. Seven fly by wire computers, and all seven can be easily (and "legally") reset in flight via push button switches on the overhead panel.

[Diavel]

Boeing has nothing that can compete with Airbus A321 LR/ XLR, and in the light of the recent scandals regarding Boeings commercial aircraft division, it seems like pure envy from the beancounters at Boeing.
Boeing should focus on repairing their tarnished reputation,instead of trying to smear their competitors.
When it comes to the narrow isle airplane market, Boeing needs to develop a replacement for the antique B737. Max was one stretch too much for this 1960s design.
On top of that Boeing has until recently done everything to hide the quality problems with the B787.

Boeing used to be a proud manufacturer of quality aircraft, those days are unfortunately long gone.

[hoistop]

Boeing should keep quiet on this and sort the mess-up in their house first. What they did tarnished entire aviation industry. And someone should go to jail for that, instead of taking outrageous searing money and benefits.
And hope Airbus will be very careful with extending the A-320 design again. The wing is more or less still the same, as I understand..?

[568]

Uplinker.
All valid points considering how technology has advanced since the first 737 flew.
Airbus were very clever from the start in being able to keep a common cockpit theme from type to type.

[TURIN]

Those things keep you in control when you lose all hydraulics and/or electrics.

To be fair, hydraulic loss on the 737 is/was worse than the 320 has ever been.

[Momoe]

BigPistonsForever,

Your post about hanging the engines out the front to keep the aircraft appeal is half true, it was the only way they keep the 737 competitive without resorting to a clean sheet design; airlines like the 737 and trusted that Boeing would produce a better 737.

IMO, wet fuselage fuel tank versus aerodynamically compromised airframe are not comparable.

This won't be decided by this thread or forum, it'll be the airlines and their customers. (And perhaps Boeing if they continue to aim at their feet instead of the sky)

[Big Pistons Forever]

I disagree. The A321XLR does not work without the conformal fuel tank because the number of conventional approved belly hold aux tanks required would mean there would not be enough belly hold space left. There is obvious pressure on the regulatory bodies to approve this mod.

Conformal fuselage fuel tanks by definition are not approved. To get around the regulatory requirements will require “special” approvals. This is the exact road that ended up with 2 crashed MAX jets. Yes Boeing is obviously trying to change the channel, but that does not change the fact that this is significant post MAX test for all regulators when dealing with grandfathering legacy aircraft design changes

I hope the lessons from the MAX have truly been learned.....

[Less Hair]

Could this be meant to become some sort of deal? The MAX will not need the tricky third sensor and the XLR can get it's tank?

[Momoe]

Whatever we disagree on, learning lessons from the Max is something hopefully everyone agrees with.

No deals, it's either safe or it's not, NO compromises.

[DaveReidUK]

Big Pistons Forever

"Conformal fuselage fuel tanks by definition are not approved. To get around the regulatory requirements will require “special” approvals. This is the exact road that ended up with 2 crashed MAX jets."

Are you suggesting that Airbus are planning not to tell EASA the whole truth about what the conformal tank does, and how it does it?

[Big Pistons Forever]

DaveReidUK

I am not suggesting that EASA wasn’t being transparent about the conformal tank design. What I am suggesting is there is a lot riding on getting it approved, as the XLR variant is not viable without it. Since this tank does not meet the certification requirements, other means will be required to mitigate the risks.

Again my point is the PROCESS to evaluate those risks and ascertain what are appropriate mitigation strategies using a apolitical transparent process, is the test to see if the lessons from the MAX tragedy has been learned.

The abject failure by Boeing and the FAA in dealing with a legacy aircraft regulatory non compliance, the inability to meet stick force gradients in some flight configurations, is fundamentally that of a process that should have worked but did not.

Sunlight is the best disinfectant. If Airbus and EASA can go on the record and prove they have used a transparent and thorough process untainted by commercial pressures or regulatory capture, then they can blow off Boeing. If substantial structural changes are now determined to be required to get the tank approved, which IMO is going to be the case then, like it or not Boeing was right.

[8029848s]

Boeing are becoming an embarrassment......the 321XLR is an excellent piece of kit and its timing is amazing. Boeing have nothing to offer...a 737 Max with no credibility and a 777x that is a white elephant. They are clueless at the highest level from what I hear from inside.

[osborne]

The A321XLR is great too

[WillowRun 6-3]

I've tried even serious reinterpretation, but none of the available icons quite fit a "shoot the messenger" quip.

In one of the several 737 MAX threads or Boeing-focused threads - or more than one of these - a good number of comments were made about how professional engineers have an obligation, as a matter of professional ethics, to call out safety concerns, design flaws, and other similar serious concerns. Even if it means putting career at risk - and of course these comments prompted others to note the realities of the working world.

Presumably Boeing's comments to EASA weren't the imaginings of some idle lawyer or SLF with a latent "aviation enthusiast" trait to expunge. Presumably the comments on the safety of the tank design, or its adherence and conformance to certification standards (I'm not sure which is the proper context here), were originated by an engineer whose professional obligations meant something to that person.

How does Boeing's awful recent failures and its longer-term decline obviate the obligation of an engineer who spotted this safety issue or certification concern? -- how does Boeing's bad repute at this time require the engineer to find someone else to deliver the comment? Double standards, it seems to this SLF/atty, are in play here.

[tdracer]

.the 321XLR is an excellent piece of kit and its timing is amazing.
Quite a statement for what is effectively a paper airplane at this point.

How does Boeing's awful recent failures and its longer-term decline obviate the obligation of an engineer who spotted this safety issue or certification concern? -- how does Boeing's bad repute at this time require the engineer to find someone else to deliver the comment? Double standards, it seems to this SLF/atty, are in play here.
Bingo!
New rules and the like routinely go out for public comment - I used to see those on a semi-regular basis. There would be a focal that we'd direct any comments to that would incorporate those comments into an input to the relevant authority. It's call 'doing your job' and 'due diligence'.
"Wet fuselage" fuel tanks have not been previously used on commercial airliners. Perhaps there is a good reason for that...

[Lord Bracken]

Quite a statement for what is effectively a paper airplane at this point.


Meh. It's a 321LR with a bit of extra range.

[llagonne66]

It seems from what is written here https://www.airbus.com/newsroom/news/en/2021/02/airbus-sites-gear-up-for-a321xlr-s-major-component-assembly-phase.html, that the XLR is well beyond the paper phase.

[tdracer]

So, you can pronounce an aircraft "an excellent piece of kit" more than a year before it's scheduled first flight, and "its timing is amazing" more than two years before it's scheduled to certify?
Based on that, the 787 is the greatest aircraft ever built...

[lomapaseo]

WillowRun 6-3

In both cases there is a process by which concerns can be vetted. The vetting includes regulatory agencies or their designates. Presumably there was not enough validate concern with the B737 to overturn the certification of the Max.
Yet there is a concern for the possible application of rules to the A321.

It is not clear whether your arguments are against, the process or the judgements offered or in the application of the judgements to the process.

Did Airbus file any concerns over the Max and what specifically were or how were they disposed of in the certification process?

This board might consider if there are any flaws regarding either the max or A321 regulatory function and how they should be addressed

[WillowRun 6-3]

lomapaseo

On the 737 MAX certification, indeed there were not enough concerns properly communicated, within Boeing and then to the FAA, to change the course of the FAA decision. I mean, Boeing has admitted criminal responsibility regarding its role in the process (with regard to actions and omissions by two individuals in part of the process). And there are as you know reams of reports by qualified industry professionals (start with JATR and the list isn't a short one) about the failures.

But my post was not intended to suggest a comparison, and did not actually suggest a comparison, between the 737 MAX certification debacle on one hand, and the pending EASA decision on an Airbus aircraft on the other hand. I'm sorry if it is the case that I wrote it sloppy enough to be misunderstood like that.

The point was made, in some prior thread or threads, that professional engineers have an obligation to call something out, if it implicates safety or otherwise impacts their profession's standards. There were pretty strident assertions that this professionalism has lapsed in some places, with the MAX being a case in point. That being said, then when engineers -- and yes I've presumed that the comments by Boeing about the fuel tank design originated in whole or in part from engineers -- when engineers COMPLY with their obligation, what do some posters retort here? Oh, their company is tainted, never mind their concerns. Or if these comments don't overtly assert a "never mind' attitude, to my reading they surely imply it and leave it to readers to put into words.

So that's why I said, where's the icon for "don't shoot the messenger." If the engineering point is valid, and some knowledgeable posters here have suggested it is valid or probably is valid, then Boeing's departure from an engineering focus in the MAX and in general -- while deplorable and tragic and part of a pattern of corporate decadence -- also is irrelevant to the merits, to the design adequacy question.

[tcasblue]

How does Boeing's awful recent failures and its longer-term decline obviate the obligation of an engineer who spotted this safety issue or certification concern? -- how does Boeing's bad repute at this time require the engineer to find someone else to deliver the comment? Double standards, it seems to this SLF/atty, are in play here.

Exactly. All these same posters saying that Boeing should mind their own business would be the first ones to demand, after a tragedy, why Boeing didn't speak up if they knew something was not safe.

Perhaps these posters should try a career in politics, as their hypocrisy qualifications seem to meet the required standard.

[GlobalNav]

I don’t know. We see Boeing discounting and hiding details of their own designs in spite of their responsibilities, and yet finding time to raise doubt about another manufacturer’s design. Not for safety but for throwing darts and trying ( not successfully) to gain some advantage. Sure, like any member of the public, they are free to comment and we are free to comment in response. I wouldn’t call it hypocrisy. We aren’t hiding anything.

[Momoe]

tcasblue,

Airbus are being (more than) transparent about the conformal fuel tank, maybe if Boeing were as transparent about the changes to make the Max 'work', specifically MCAS then perhaps there would have been reciprocity.

Anyway, good to know that Boeing are focused on safety.

[lomapaseo]

Well if Boeing leaves the field who else is going to call the kettle black?

I might have an opinion on this but I trust Boeings experience in this a lot more.

[Old Carthusian]

Boeing is literally caught between a rock and a hard place. Their failure to adhere to quality standards in pursuit of financial gain has lowered their authoritativeness. However, they are experts and who should know whether a proposal is a wise option but the experts working on designing, building and developing aircraft? The concerns they raise are certainly valid and not inconsequential.

It is inevitable that these concerns will be seen as a spoiler and there is almost certainly an element of that in Boeing's comments. This has to be accepted as part of the environment Boeing and Airbus operate in - it is highly competitive and if one can legitimately delay or even scuttle a threat to one's market share then one should. One would certainly expect Airbus to do exactly the same if the boot were on the other foot.

This is not a good PR move for Boeing but it is one that needs to be made - even though their motives might be suspect they are still raising what is a valid safety issue and doing aviation in general an important service.

[CCA]

Anyone seen the design for the conformal tanks?

I assume like others have said they will be part of the wing to body fairing.

Similar to the F15/16 & 18

https://en.m.wikipedia.org/wiki/Conformal_fuel_tank

[DaveReidUK]

CCA;11006266]

"Anyone seen the design for the conformal tanks? I assume like others have said they will be part of the wing to body fairing. Similar to the F15/16 & 18"

No, that's not the case (and I don't think anyone here has said that it is).

"Conformal" here is being used in the sense that the RCT occupies the entire cross-section of the fuselage below the floor beams and so differs from a conventional rectangular-section centre wing tank.

Might not have been the best choice of adjective, feel free to suggest an alternative. :O

[CCA]

CCA;11006266]

"Anyone seen the design for the conformal tanks? I assume like others have said they will be part of the wing to body fairing. Similar to the F15/16 & 18"

No, that's not the case (and I don't think anyone here has said that it is).

"Conformal" here is being used in the sense that the RCT occupies the entire cross-section of the fuselage below the floor beams and so differs from a conventional rectangular-section centre wing tank.

Might not have been the best choice of adjective, feel free to suggest an alternative. :O

Just wanted to be clear as others had said that it’s not a tank that’s installed in the cargo areas.

The 747-400ER has a option for one or two additional tanks in the forward cargo and there’s very little dead space outside the cargo area. The water tanks used to be installed on the front of the CWT but were relocated to aft of aft cargo. How much space is available on a A321 outside the cargo area?

Boeing complaining means it must be fairly radical or something they can’t benefit from.

Quote from the article. “Into the fuselage” is a little generic not much space that isn’t already occupied by design.

To meet demand for longer routes, Airbus has already added optional extra fuel tanks inside the cargo bay of some A321s.

For the A321XLR, Airbus plans to eke out more space for fuel by moulding one tank directly into the fuselage, meaning its shape would follow the contours of the jet and carry more fuel.


The only other option is empty space that isn’t part of the cargo section forward of the CWT? Top of the CWT under the floor usually has space but has also historically been filled with air conditioning filters. (747)

pictures would be good 😃

Pictures and description from Boeing’s own magazine re cargo tanks for what it’s worth.

http://www.boeing.com/commercial/aeromagazine/aero_21/747E.pdf (http://www.boeing.com/commercial/aeromagazine/aero_21/747ER.pdf)

[DaveReidUK]

CCA

"Just wanted to be clear as others had said that it’s not a tank that’s installed in the cargo areas."

Well yes and no. :O

The RCT does indeed occupy part of the space that in the non-XLR A321 is used for cargo or, optionally, for the removable ACT(s) in the A321LR.

The difference is that, while the ACTs are able to be removed, the RCT is permanently built in to the aircraft, and thanks to its shape the single RCT holds more fuel than 3 ACTs combined while sacrificing less cargo space.

[CCA]

Got it, a permanent structure built aft of the wheel well from the lower skin filling the lower bilge area up to the main cabin floor beams. Elegant.

[Less Hair]

Capacity is more like 2 ACTs. Another optional ACT can be installed in the forward hold.

[DaveReidUK]

Less Hair

"Capacity is more like 2 ACTs. Another optional ACT can be installed in the forward hold."

An ACT holds just on 3,000 litres. The RCT holds 12,900 litres.

My calculator reckons that's more than 4 times as much.

[Momoe]

Boeing are within their rights to flag a potential risk from anywhere in the aerospace industry, however, whilst aimed at Airbus, it's more likely the real intent was to make EASA aware that the rest of the industry is watching.

321XLR is an excellent piece of kit, it's a (well) proven and respected design, with some relatively uneventful upgrades it's still a top tier performer and giving it the extra range makes it very desirable with longer, thinner routes becoming the new norm..

I have no doubts that it will gain EASA approval, whether in the proposed format or in an EASA specified format.

[Less Hair]

It is substituting the two ACTs in the back leaving more cargo space there while the front ACT can still be installed. Total fuel, range and MTOW will be above the LR obviously.

[DaveReidUK]

Less Hair

"It is substituting the two ACTs in the back leaving more cargo space there while the front ACT can still be installed."

Indeed it can, if the A321XLR's projected 4,700 nm range isn't enough for customers.

[Ian W]

It is a rather obvious point. But Boeing is a large complex global business with 3 major subdivisions loaded with Engineers with various levels of experience in aircraft systems and aircraft design.
An aircraft design is published for comment and is circulated around the engineers in Boeing. Somewhere in a lonely cube an engineer reads the design from Airbus and think that it doesn't look 'safe'. So that engineer raises the concern through the channels of Boeing. After a suitable length of time the comment percolates to the group who deal with Boeing <-> Airbus and FAA<->EASA comments. the group puts the response into the agreed format for comments and publishes the comment.

What would the 'get back in your box you broke the 737 commenters' have Boeing do? Sit on the comment from an engineer nothing to do with the 737 and who had spotted a real problem? So what happens if that problem turns into a loss of life crash and the get back in your box you broke the 737 commenters hear that Boeing sat on one of their engineers comments for 'political' reasons that could have helped prevent an Airbus loss of life crash? They would go after Boeing again questioning their lack of an open and non-commercial approach to flight safety.

Seems like Boeing had no option but to pass the comment on - and do not think for a moment that the thought processes above were not considered prior to release of the comment. I would not be surprised at all to hear that informal comments were shared prior to the official comment. Teams from Boeing work with Airbus and vice versa. There is a LOT of coopertition.

[retired guy]

Even without Boeing's unhelpful intervention, there seems to be a good chance that Airbus will get its fingers burnt (npi) by the additional conditions that EASA said some time ago that it will impose in respect of the RCT.

There will no doubt be a technical solution to the issues, but anything that adds weight and/or reduces RCT capacity will have implications for the XLR capability and not be popular with customers.
Agree Dave Think of all the crashes which were catastrophic but no fire in particular BD at Kegworth. The slightest rupture of the aircraft skin which is inevitable in a crash would presumably release a great deal of fuel? Sometimes I wonder if the human race has forgotten that we got where we were by learning from mistakes of the past!

[Less Hair]

At least the A340-500 had a wet wingbox, with a center gear strut below pointing at it, and even this could get certified.
https://images.app.goo.gl/rw71hjpaa1A5Qe9a6

[peterinmadrid]

Maybe Boeing should check the safety of Airbus jets and Airbus can inspect Boeings, rather than each company inspecting their own planes. It seems they're highly motivated to find problems in their rival's aircraft, whilst no so much so when looking at their own.

[Commander Taco]

Love it Peter! A contrarian’s approach to a problem.

[Hugo1980]

Chris2303

You'd wonder how Boeing have the time to do Safety Audits on other manufacturers. In order to do a correct assessment Boeing would need all the production drawings and tech specs. Now if the FAA made the comment I'd probably listen more carefully!

[Big Pistons Forever]

You don’t need to see records to say “hey that doesn’t look right” when you see a fuel tank design that goes right to the fuselage skin around the bottom of the airplane......

Like I said in an earlier post if the original conformal tank design goes in unchanged then Airbus can tell Boeing to piss off. But if there are significant changes before it is approved, a situation I think is highly likely, then Airbus’s attempt to smoke this pass the regulator was properly called out.

This in no way absolves Boeing of their culpability in the MAX fiasco, it instead shows how deep the
rot is in aircraft certification goes for both the FAA and EASA

[Big Pistons Forever]

Looks like Airbus's attempt to smoke through the extended range fuselage center aux tank design has been stopped by the FAA. The traditional extra baggage bay tanks won't work because they would use up too much room, so Airbus designed a new center section tank that goes right to the fuselage skin on the center belly in order to be big enough to hold the required fuel.:=

Airbus tried to skate over the obvious issue of what would protect the tank in the event of a belly landing and got EASA to approve it anyway. Now looks like FAA will require major structural changes to provide tank protection. I think the MAX fiasco has forced the FAA to start being more authoritative when asking skill testing questions and this new unwillingness to just rubber stamp the manufacturer's data will become standard for all regulators

It will be interesting to see what EASA does about the MAX dash 7 ands10 certifcation.....

[Less Hair]

It looks like everything got settled already before the FAA green light. The XLR problem "suddenly" surfaced and might now be done with a little liner or similar while the MAX gets rubber stamped, no EICAS needed.

[nicolai]

Boeing complaining about another airplane when they're trying to use the finest 1960s safety design in the alerting systems in the most recent 737 Max designs is more than a little dishonest and ungraceful.

Cobbler, stand by your last!

[DaveReidUK]

Boeing complaining about another airplane when they're trying to use the finest 1960s safety design in the alerting systems in the most recent 737 Max designs is more than a little dishonest and ungraceful.

Manufacturers comment on their competitors' certification programmes as a matter of course, as they are perfectly entitled to do.

And Boeing's comments about protection for the RCT are both perfectly legitimate and, it would appear, are shared by the FAA (if not by EASA).

[Fly3]

I agree that Boeing have every right to comment on other companies designs but the fact that they are trying to force through a 60 year old design of a less safe system for the Max 700 and 100 is disingenuous to say the least.

[ATC Watcher]

Airbus tried to skate over the obvious issue of what would protect the tank in the event of a belly landing ..
Indeed an issue , but frankly when was the last time an A320 family aircraft did a belly landing ?

On an anecdotal remark, I flew (and still do) some single engine aircraft where the fuel tank is located between the engine and the cockpit , and even one where part of the tank was between my legs.
All certified by EASA and we alll wonder how it can be determined a "safe" design . ., Agreed they do not carry 200 pax but as the old saying goes, ,when there is a will, there always is a way.:E

[Less Hair]

The certified A340-500 has a center tank and a center gear strut that can get pushed right into the center tank on a very hard landing.

[DaveReidUK]

See the quote (much) earlier in the now-merged thread about EASA's concerns, which are primarily to do with resistance to penetration of the fuselage and tank by an external pool fire, rather than impact from a hard or belly landing.