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Boeing cites risks in design of newest Airbus jet

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Boeing cites risks in design of newest Airbus jet

Old 3rd Mar 2021, 15:34
  #21 (permalink)  
 
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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
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Old 3rd Mar 2021, 16:17
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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.
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Old 3rd Mar 2021, 16:33
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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.
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Old 3rd Mar 2021, 19:54
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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.
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Old 3rd Mar 2021, 21:09
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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.
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Old 4th Mar 2021, 00:05
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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...
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Old 4th Mar 2021, 00:16
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More info here.
https://www.airbus.com/newsroom/stor...k-section.html
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Old 4th Mar 2021, 03:16
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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.

Last edited by Commander Taco; 4th Mar 2021 at 03:41.
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Old 4th Mar 2021, 03:51
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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.
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Old 4th Mar 2021, 05:03
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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.
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Old 4th Mar 2021, 07:21
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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.
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Old 4th Mar 2021, 09:22
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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.
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Old 4th Mar 2021, 09:42
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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.
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Old 4th Mar 2021, 09:56
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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.

Last edited by Uplinker; 4th Mar 2021 at 10:20.
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Old 4th Mar 2021, 13:14
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Originally Posted by Big Pistons Forever View Post
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.
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Old 4th Mar 2021, 14:40
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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
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Old 4th Mar 2021, 14:43
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"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.


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Old 4th Mar 2021, 17:31
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Momoe, you beat me to it!
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Old 4th Mar 2021, 18:59
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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
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Old 4th Mar 2021, 19:00
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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
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