777-8 et 777-9

Paul a écrit:Pour info, l'aile du 747-8 est en aluminium.

According to sources familiar with confidential briefings, a new 777X engine should increase fuel efficiency per seat by 10 percent and its outsized carbon-fibre wings - designed to fold upwards at the tip when parked - will contribute 7 percent.

But engineers must pay back 4-5 percent of these savings because the larger jet's basic structure is expected to be at least 12 tonnes heavier. The net gain from the latest technology will be closer to 12-13 percent, according to these sources.

To achieve the 20 percent increase in efficiency needed to complete their case, Boeing's marketers are moving in two steps.

Firstly, a longer fuselage gives space for 2-3 more rows, which automatically lowers unit costs and opens the door to extra revenue if airlines have enough demand on their network.

But to make it a slamdunk, Boeing is assuming airlines will adopt a denser layout by adding an extra seat to each row to make 10 seats across, instead of the standard nine on most 777s.

To fend off any concerns about discomfort, Boeing is proposing to carve out an extra four inches in internal cabin space by "scalloping" the inside of the fuselage. It believes this will corner its opponent and show up the A350's narrower cabin, which will sit nine abreast.

"They (Airbus) are having to chase the 777 with a tube that is almost a foot narrower. Now you are competing with the comfort of the 777," said Ihssane Mounir, head of Boeing Commercial Airplanes sales for Northeast Asia, including China.

Airbus dismisses the plan, saying it found during earlier discarded designs that such ideas don't work. It accuses its rival of packing in seats to flatter the older 777's economics.

"There is some sleight of hand going on here," said Leahy in an interview. "Nobody asked them for these extra seats. They are doing it to print lower seat-mile costs."

Boeing executives say it is Airbus that scores well in the industry's long-established game of toying with configurations.

Airbus's claim of a 25 percent per seat fuel advantage for the A350-1000 assumes a layout of 369 seats, rather than 350, and 360 seats for the 777-300ER, five fewer than advertised.

SWEET SPOT

How all this affects sales depends in part on whether airlines and passengers accept the proposed 10-abreast layout.

Higher-density seating may be less comfortable but gets airlines' vote in economy, Sanford C. Bernstein analysts said.

Indeed, of the 22 current Boeing 777-300ER operators for which data is available, 27 percent are already at 10 abreast.

Ironically, that may make the 777X's improved efficiencies harder not easier to prove. Airlines already operating this way would not get the full boost advertised for the 777X since the efficiency goal depends partly on going from nine to 10 abreast.

They include the largest 777 operator, Emirates, whose support is vital to get the new 777X launched. It anticipates having to replace as many as 175 Boeing 777-300ERs from the end of the decade, some of which have not even been delivered.

Still, its president Tim Clark has forecast significant 777X demand, prompting talk of a launch at November's Dubai Airshow.

Getting the size right is critical. An undersized plane will spill lost demand into the hands of an airline's competitor. Too many seats will force airlines to discount and hurt yields.