Boeing 787 (partie 2)

Paul a écrit:Je crois que nous verrons si Boeing a fait les bon choix pour le 787 lors du prochain clean-sheet, probablement le remplaçant du 737/757, entre 2025 et 2030. Si ce dernier n'a pas un fuselage composites full barrel et autres technos développées sur le 787, cela voudra dire que ce n'était pas nécessairement de bonnes "innovations".

The key issues driving delays also are a moving target for each airline.

In Addis Ababa, a critical problem for Ethiopian Airlines is a persistent glitch with the 787’s four cabin air compressors (CACs).

“It’s still an issue where every time you fly, there’s one compressor not working,” says Hailemariam.

Other carriers, however, had few complaints about the compressors. Hama says the CACs on JAL’s 787s have had “little, minor troubles”. At ANA, Nishiwaki says the reliability of the CACs is “very, very good”.

Indeed, the part number of the CACs in the ANA 787 fleet has remained the same since entry into service more than three years ago. Other parts in the electrical system have been redesigned several times over the same period, he says, so that the part numbers are augmented with a “-2”, “-3” or even “-4”, but not the CACs.

Boeing is addressing some “reliability issues that we have” on the CACs, a source at the company says.

Ethiopian expects the CAC issue to continue, says Zemene Nega, managing director for maintenance, repair and overhaul. “It is just a fundamental design issue,” he says. “It’s not going to be fixed with software.”

One of the universally problematic parts for airlines has been the variable frequency starter/generators (VFSGs). There are two on each engine, and they represent one of the major innovations introduced by the 787. In all other commercial aircraft, functions such as cabin pressurisation and wing de-icing are powered by bleeding compressed air from the engine. To improve fuel efficiency, Boeing converted those systems to electric power. That required significantly more powerful engine-mounted generators, so Boeing introduced VFSGs on the 787 that each produce up to 250kVA of electricity.

“We have experienced a lot of troubles with the VFSG,” Hama says.

It is an issue that Boeing acknowledges has been a long-term problem, and one that may still not be completely solved. So far, Boeing has rolled out three improved versions of the VFSG, with each upgrade requiring a reinstallation.

“We expect that the latest configuration of the VFSG is the one that we will have for quite a while,” Fleming says. “While we know that further issues may arise, so far the data says that the VFSG reliability is improving.”

As each new version of the VFSG becomes available, airlines face another headache. The VFSGs deliver significantly more power than integrated drive generators on bleed-air systems, but they are also heavier.

“Each component is getting bigger and bigger,” one 787 airline customer says. “The weight of the VFSG is 200lb. It is so difficult to replace.”

Boeing provides tooling, such as slings, to help airline maintenance workers remove heavy equipment. Airlines also have taken more elaborate steps, such as pulling a 787 out of service for 10 days to fix various reliability issues, such as the VSFG, all at the same time. Air India reported to parliament that each aircraft in its fleet was grounded sequentially for a 10-day period between December 2013 and March 2014

The Rolls-Royce Trent 1000 engine has powered the latest phase of Boeing ecoDemonstrator aircraft flights, on a 787 Dreamliner.
The aircraft will, over several weeks, assess more than 25 technologies designed to improve aircraft fuel efficiency and reduce noise.

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Obviously, the composite design and more electric system architecture will benefit the airlines from in-service rate and maintenance cost standpoints. Likewise, the improved comfort inherent in the Dreamliner’s larger, quieter and cleaner cabin will cause passengers to select it over legacy aircraft when given a choice.
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A new APU design has recently entered service that prevents the shaft from “bowing” under certain conditions and needing a replacement, Boeing says.
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"While our customers understand and are comfortable with the changes that we’ve made on the airplane,” Fleming says, “there are some that would still like to see a battery that doesn’t vent.”