The first two operators of the Boeing 787-8 are seeing better-than-anticipated fuel burn, despite prior expectations of below-par performance as a result of data from predelivery flight tests.

The numbers, though based on early experience with a relatively small fleet on a variety of routes, are surprisingly positive given the early configuration of the airframes and engines. The operators have not yet incorporated all the planned weight and fuel burn improvements of follow-on production versions.

Four of the current active 787 fleet are from an early production block in which each is thought to be around 8,800 lb. over specification weight, while the remainder are lighter aircraft built from the block point change introduced from line No. 34.

Boeing, which is expected to comment officially on the 787’s in-service fuel burn numbers at the Farnborough air show next month, is in the midst of introducing weight reductions and other enhancements to compensate for what was expected to be a relatively significant shortfall in the planned 20% improvement over the 767.

Yet figures from launch airline All Nippon Airways (ANA) show fuel savings are up to 21% on long-range flights, while figures for the General Electric GEnx-1B-powered aircraft at Japan Airlines (JAL) indicate potentially slightly better numbers.

GE says initial performance data show its GEnx-1B engine has a 2% fuel burn advantage over the competing Rolls-Royce Trent 1000, not counting an additional 1% benefit from expected performance retention in terms of sustained exhaust gas temperature margin. The first GEnx-1Bs are in service with JAL, while 787 launch operator ANA uses aircraft powered by the Trent 1000.

ANA earlier this month was the first to reveal that its aircraft were producing around 21% lower fuel burn on international flights compared to the 767-300ER that the 787 is designed to replace.

The airline, which accepted its ninth aircraft on June 24, is believed to have been anticipating a 17-19% improvement, based on the Trent 1000 Package B that Rolls introduced to counter some deficiencies seen in flight testing.

After its first six months of service, ANA says the 787 efficiency levels are slightly up on the 20% savings originally expected at the beginning of the program. On domestic routes, the saving is 15-20%, which meets expectations, say ANA officials. The short-haul sub-fleet includes four early delivery aircraft powered by the interim Trent 1000 Package A standard engine. ANA’s long-haul configured 787s operate between Tokyo Haneda Airport and Frankfurt Airport, with additional transpacific routes from Tokyo Narita International Airport to Seattle-Tacoma International Airport and Norman Y. Mineta San Jose International Airport in California due to be launched by early 2013.

GE’s claimed advantage over the Trent 1000 comes as it monitors the early performance figures from the first eight engines in service with JAL. Meanwhile, the FAA certificated the 75,000-lb.-thrust variant of its GEnx-1B PIP1 (product improvement package) upgrade on June 14. The engines already in service with JAL are also built to the PIP standard certificated in August 2011, but are rated at a lower thrust level.

PIP1 was designed to improve fuel burn by around 1.6% compared to the baseline GEnx-1B, although the latest in-service data suggest this may have been conservative. PIP1 included a new low-pressure turbine, a revised control schedule and hot section upgrades. GE is currently developing a second PIP package which is aimed at an additional 1.1%.

The upgrade builds on PIP1 and adds 0.5-in. to the fan diameter, optimized outlet guide vanes, improved high-pressure compressor aerodynamics, upgrades to the low-pressure compressor and durability enhancements to the combustor and high-pressure turbine. The second PIP will be certificated in the fourth quarter of this year and will enable thrust growth to 78,000 lb.

GE also is ramping up production of both GEnx-1B and -2B engines to support accelerating delivery rates at Boeing of 787s and 747-8s, respectively; Chuck Nugent, the general manager of GEnx programs, says rate increase is two to three times that of previous large engine programs such as the CF6-80C2 and GE90-115B. Approximately 150 GEnx engines will be delivered this year, rising to more than 200 in 2013 and eventually 300 annually in coming years. Roughly 1,300 GEnx powerplants have been sold to-date, and with more than 250 787s yet to be allocated an engine, GE says the competition is intensifying. GE is “still early in the program, so we expect this is just the start,” says Nugent.