Guy Norris/LOS ANGELES
Boeing has firmly decided to offer only new-design engines on the proposed 747X family, rather than presenting a choice including derivatives of 747-400 turbofans.
The decision is a boost to the General Electric-Pratt & Whitney Engine Alliance and to Rolls-Royce. Both are working on designs tailored to the 747X. Until last month, the aircraft was being offered with CF6 and PW4000 derivatives. R-R, which was unable to offer a suitable variant of the RB211-524G/T for the 747X, stands to gain most from the move.
The decision to opt for new engine types will provide more margin for weight growth but, in the near term, was made "mainly because of noise considerations", says Boeing vice-president product strategy and development John Roundhill. The newer technology inlet and fan designs, plus updated exhaust noise treatments, are guaranteed to meet projected Stage IV standards. Boeing says, however, that meeting these higher levels with the CF6 and PW4000 variants was questionable, particularly at heavier maximum take-off weights.
Boeing's move comes as Engine Alliance prepares to make the first core rig tests of the GP7000. These tests will validate performance of advanced high-pressure compressor and three-dimensional aerodynamic design features only recently introduced because of delays to the Airbus A3XX project.
The GP7000 core will power the proposed 747X and competing A3XX. The GP7167 version aimed at the 747 derivatives will have a thrust range of 67,000lb (300kN) to 73,000lb, with a 2.51m (8.2ft)-diameter wide chord hollow fan. The larger GP7275 for the A3XX family will generate up to 75,000lb thrust, using a 2.79m diameter fan. The Alliance plans to offer a 67,000lb thrust derated version for the initial A3XX-100 version.
R-R says its Trent 600, provisionally rated at 68,000lb thrust, can grow to meet the needs of all proposed 747X versions.
Source: Flight International
