Boeing 787 (partie 1)

Early indications from sources signal that the problem was first discovered during static testing in April on ZY997.The problem stems from a design fault in the wing-to-body join area between Section 11 (center wing box) and Section 12 (wing box).

Admin a écrit:Bonsoir Cheyenne,

Sans pouvoir répondre de manière formelle, j'apporte quelques éléments complémentaires :

http://www.flightglobal.com/blogs/flightblogger/2009/06/breaking-boeing-postpones-787.html

Early indications from sources signal that the problem was first discovered during static testing in April on ZY997.The problem stems from a design fault in the wing-to-body join area between Section 11 (center wing box) and Section 12 (wing box).

Voilà ce que je peux rajouter...

Bonne soirée

10:46 AM: Shanahan and Fancher confirm that the problem stems from 18 points where the center wing box (11) meets the wingbox (12) on each side of the aircraft. The fix, once identified, will be installed on location. ZA001 and ZA002 will be modified directly on the flight line. Boeing has not determined a final fix or the material it will use to fix the join. Fancher says the company is leaning towards titanium or aluminum and the fabriction division is ready to start manufacturing parts as soon as a final fix is identified.

The area in question is a few square inches in the side of body. The modifications are relatively small without very much weight [penalty] and a negligible impact on performance."
Shanahan says that the area affected is in the upper region of the wing, centre section and body join, where there are multiple structures and materials including aluminium, titanium and composites. Both aluminium and titanium is being evaluated for the modification package

Sur le problème
In a test where the wing was deflected, the strain gauge measurements were not following the predictive modeling that Boeing had developed for certain areas of the side body join. Jon Ostrower had confirmed that the area in question are 18 small areas on each side of the aircraft at section 11 (center wingbox) and section 12 (main wingbox) are joined (upper wing root). There appeared to be some damage during this test that confirmed what the strain gauges had recorded. Unconfirmed report that there was some delamination of the skin at those areas.
In a conference call today Pat Shanahan and Scott Francher said that there are several areas each about 1 to 2 sq. inches that need to be reinforced.
At this point Boeing is understanding the root cause of the problem and and are concurrently working on several different designs to fix the problem. However they still cannot give guidance at this point for first flight and first delivery.

Sur la résoluion
They still have to finalize a design then proceed with detailed design of the fix. Manufacture the parts and install them on ZY997 in order to be tested. If testing verifies the design then Boeing will retrofit all the 787 whether assembled, in final assembly, or within the supply chain with the required parts. Boeing said in the conference call that the parts will add a negligible amount of weight and should not effect aerodynamic performance of the aircraft. At one point Boeing was considering a temporary solution but decided on a permanent fix over a temporary one. Additionally, they said that ZA001 could have flown without any type of fix but did not want to risk it.

Sur les conséquances
Of great concern is how does this new issue effect further testing and production. ZA001 was on the verge of starting final gauntlet testing followed by taxi tests. Boeing stressed that those activities will continue in the coming days though I'm not sure if they would do the rejected take off (RTO) tests until after the reinforcements have been installed.
In terms of production Boeing said that the other 5 test flight airplanes will continue with their final assembly and testing activities as this issues affects none of those activities. ZA002 is out on the flight line and will soon turn on its engines and will continue with it's pre-flight ground tests as will the other test flight aircraft. They will pull them out of the assembly building when they are done to proceed with their test activities on the ground.
Additionally all production activities will continue uninterrupted whether that is at Everett final assembly or at any of the partner production sites. When the fix is finalized and in production, all airplanes will be retrofitted with these parts in the supply chain or on the tarmac.

Key points raised by the conference call this morning are as follows:

Scott Carson

• Results discovered from testing on static airplane
• Reinforcement of side-of-body join
• Disappointed with setback but described as “manageable”
• Fundamental technology is sound
• Integrated systems maturing as normal
• No schedule yet announced – “there will be some impact”
• Customers respect decision to delay and ensure the airplane is right
• No suspension of production
• Parts can be retrofitted

Patrick Shanahan

• Discovery made during wing bending tests
• Identified stresses in excess of modelled expectations
• Concluded that productive flight test program required fix to side-of-body area
• Focussed on reinforcement solution, materials are not an issue
• Limited area of stresses
• Area consists of wing from MHI, side-of-body built/designed by Boeing & FHI

Scott Fancher

• Developing right solution
• Several planned modifications, yet to select which is best method
• Could be titanium or aluminium solution
• Components to be fabricated and undergo full scale tests
• Will not compromise for overall schedule
• New schedule due in several weeks time
• Final gauntlet tests still due in the days ahead
• ZA001 in flight ready condition
• 36 locations of required localised strengthening identified
• Require on handful of parts
• Don’t see any increase in weight, negligible impact on performance
• 1 or 2 square inches of each affected area at upper wing root section
• No external body fairing/aerodynamic adjustments/changes
• Problem does not extend elsewhere
• Gauges didn’t meet modelled expectations
• Nothing prevents final gauntlet test from starting
• ZA001 will proceed with taxi tests
• One fix to be incorporated into production stream
• Fixes can be done in situ, no factory work required
• Likely nothing would have happened if ZA001 flew
• Nothing compromises certification
• Production airplanes have lower weight, incorporated weight reduction already

Jeannot a écrit:Il est certain que si Boeing a pris la seule décision valablement possible et même s'il est certain que Boeing résoudra le problème il est aussi normal que d'aucuns se posent des questions sur la bonne conception de cet avion.

Une compagnie aérienne cliente est en droit de se poser des questions comme :
. Sommes nous au bout de nos peines en terme de retard ?
. Quelle sera la prochaine mauvaise surprise ?
. Quel crédibilité puis-je accorder au informations distillées par le constructeur ?
. Quel impact sur sur les planning de livraison ?
. Quel sera le vrai MTOW du 787-8 ?
. Quel sera la vraie distance franchissable de l'oiseau de rêve ?
. L'avion va-t-il répondre au business case pour le quel il m'a été vendu ?

En dehors des clients Boeing devra apporter des réponses aux fournisseurs qui inévitablement devront apporter des modifications à leur planning de livraison et ainsi en supporter les conséquences sur la trésoerie ou alors demander au constructeur de constituer des stocks.

militent en faveur d'un retard supplémentaire d'au moins six mois, comme l'avait indiqué BERNSTEIN !

La deuxième compagnie aérienne japonaise All Nippon Airways (ANA) s'est déclarée "déçue" mardi soir par le report surprise du premier vol d'essai du Boeing 787 "Dreamliner", un avion de ligne de nouvelle génération qu'elle doit être la première à exploiter.

2009 AFP

Boeing has been forced to postpone the first flight of its troubled 787 Dreamliner, its flagship new aircraft development programme, after discovering a weakness in the flagship structure of the jet.

Shares in the US aircraft maker fell by 6.5 per cent by the close of trading in New York after news of the embarrassing setbackon Tuesday, which came only a week after Boeing said at the Paris Air Show that the start of the flight test programme was on track.The US aircraft maker, which was already running nearly two years behind schedule, had been due to make the maiden flight by June 30.
Boeing said it would be “several weeks” before it could come up with a fresh schedule.

.....service, two years late, in the first quarter next year with All Nippon Airways.
The Japanese carrier said on Tuesday it was “disappointed” the first flight had been postponed again and urged Boeing “to specify the schedule for the programme as a whole as quickly as possible”.

The problems at Boeing are a stark reminder of the daunting complexity of developing new generation large commercial aircraft and follow more than two years of delays suffered previously by Airbusin bringing its A380 superjumbo into commercial service.
Boeing is greatly increasing the use of lighter materials in the 787, including the first all-composite airframe, and has tried to streamline manufacturing and assembly processes and to outsource much more of the engineering and manufacturing to suppliers around the globe.

For the first time the wings of a Boeing aircraft are being made in Japan, which is accounting for 35 per cent of the airframe in total, with other key outside suppliers in Italy and the US. Boeing said it was engaged with both Mitsubishi and Fuji Heavy Industries in engineering the necessary reinforcement parts.

The ticking clock has once again got the better of Boeing. The company announced on Tuesday that, for the fifth time, its flagship new aircraft will not be taking to the air on schedule. The discovery of an area of structural weakness means that it will be several weeks before a new plan for flight tests can be set. There is now a significant chance that the entire Dreamliner programme becomes a commercial disaster.

The previous delay was related to fastners, compounded by last year’s machinists strike. With perhaps 4m parts on the modern airliner, even small problems in one area can then impact on other parts. For instance, earlier this decade BAE Systems discovered a initially small problem in the Nimrod military aircraft, which ultimately resulted in great delays and catastrophic cost overruns. The latest postponement at least suggests that Boeing’s very short timetable for testing and certification is too aggressive.

Even brief delays are expensive, both for Boeing and members of its long supply chain. For instance, thanks to delays to its Airbus A380 programme, analysts estimate the break even point has risen from 250 deliveries to about 400. As staffing makes up the vast bulk of expenses, time equates to higher costs that must then be spread over eventual sales.
Meanwhile, delivering late allows customers to impose a financial penalty. The worst scenario for Boeing would be a failure to get production up to speed in time – a rate of 10 aircraft a month is targeted by 2012 – and then not catch up with the delivery schedule for the 860 on order. In such a case, there would little hope of making a profit on the programme for several years. The clock ticks ever louder.