Stretched potential for the Boeing 777


ANA 787

Credit: FlightBlogger


Initially thought likely to be a continuation of General Electric’s exclusivity on the 777-300ER, -200LR and Freighter, the emergence of additional proposals for the 777X from Rolls-Royce and Pratt & Whitney kicks off a fierce battle to power the next-generation twinjet family.

Rolls-Royce has revealed details of its RB3025 concept, rated at 99,500lb (440kN) with a 337cm (132in) fan for the baseline 407-seat 777-9X, giving the powerplant a bypass ratio of 12:1, touting a “better than 10%” improvement in fuel burn over the incumbent GE90-115B engine and 15% better than its Trent 800, says Robert Nuttall, Rolls-Royce vice-president strategic marketing.

Similarly, Pratt & Whitney has responded to Boeing’s RFP on the 777X. It says its PW1000G has “validated our analytical prediction that this engine architecture would be suitable for thrusts up to 100,000 pounds”.

777 incumbent GE is offering the GE9X, a 99,500lb-thrust engine contributing a 10% improvement in fuel burn for the -8X/-9X family, say sources. The 325cm diameter GE9X engine is believed to have a 10:1 bypass ratio, with a 60:1 overall pressure ratio and 27:1 high-pressure compressor ratio, compared with the 42:1 and 23:1 respective pressure ratios on the GE90-115B. The eCore-inspired GE9X would also feature a GEnx-style composite fan casing and third-generation Twin Annular Premixing Swirler combustor, say sources. Under development for almost three years, GE is spending $50 million on technology advancement on the GE9X in 2012, says David Joyce, chief executive of GE Aviation.

Rolls-Royce’s RB3025 engine concept provides a low specific thrust and “excellent” propulsive efficiency, says Nuttall, plus a 62:1 overall pressure ratio which would be the highest OPR in a commercial turbofan engine.

Rolls-Royce builds on its Trent 1000 and XWB engines, but Nuttall says the RB3025 derives from its Advanced3 environmentally friendly engine development that includes a Trent 1000-derived core, lean-burn combustor, composite fan and advanced materials in high-pressure elements of the core.

Nuttall and Joyce say any schedule guidance will come directly from Boeing, which says it would have to formally launch a 777 successor before deciding if the aircraft would have two or more engine options.

“Incumbency or not, our job is to prove that we can demonstrate the value of GE9X on the 777, just like we have on the [GE90], and we have a good track record to prove it. So, game on,” Joyce says.