May 21, 2013
Credit: General Electric
Boeing has begun flight tests of a 747-8 passenger model powered by upgraded General Electric GEnx-2B engines, which are expected to improve fuel burn by a further 1.8%.
The flight tests, using RC021, an aircraft formerly destined for Lufthansa, began on May 20 with a four-hour flight from Everett, Wash. The flight evaluated the initial performance of the GEnx-2B Performance Improvement Package (PIP), as well as upgrades to the flight management computer (FMC) software. These latter changes—incorporated as FMC 3.0—will add improved required navigation performance and “quiet climb” functionality.
The FMC changes also are related to the activation of the aircraft’s horizontal tail fuel tank, the design and operation of which will also be validated in the test program. The 3,300-gal. tailplane fuel tank, which is a feature only in the passenger version, was de-activated before the first aircraft entered service when analysis indicated that, under certain fuel load circumstances, the tail tank could induce flutter.
Re-activation of the tail fuel tank will provide added range and improve the aircraft’s performance says Lufthansa, the launch customer of the 747-8. The extra weight of the fuel in the aft of the aircraft can be used to assist in trimming the 747-8 to lower cruise drag. As a result, the airline asked Boeing to make minor software changes to the fuel transfer system which would extend the length of time the fuel remains in the aft tank, thereby increasing the trim benefit.
Boeing says that as a result of the latest batch of enhancements—plus other upgrades introduced since the aircraft entered service in 2011—it will have produced a combined 3.3% improvement in efficiency. Eric Lindblad, vice president and general manager of the 747 program, says the 1.8% fuel-burn improvement from the package now under test will save airlines “approximately $1 million per year in fuel per airplane and reduces the carbon footprint.”
To combat the original GEnx-2B’s fuel-burn shortfall of more than 2%, GE designed an all-new low-pressure turbine, and added compressor, combustor and turbine improvements derived from the second batch of upgrades devised for the GEnx-1B engine on the 787.
Flight tests of the -2B PIP were conducted on GE’s 747 flying testbed earlier this year, and a final round of ground tests are nearing completion with FAR Part 33 certification expected by mid-year.
Boeing says the new configuration will first be delivered in early 2014 and be available for retrofit. Entry into service of the new engines and FMC software will take place in late 2013. The test aircraft, originally destined to be Lufthansa’s fifth 747-8, will be used for flight testing throughout 2013 and refurbished for onward sale in 2014, either as a standard airliner or for a possible business jet modification.