Boeing 787 Dreamliner - Mark Wagner [59]
Just a few weeks later, in the United States on March 19, a new sound filtered through the cedar, oak, and maple trees on the rolling tops of the Allegheny plateau in southern Ohio. Barely audible at idle thrust beyond the immediate area of Stand 6A on General Electric’s remote seven-thousand-acre engine test site in Peebles, this was the first run of the GEnx turbofan for the 787.
The two engines were the most technologically advanced commercial powerplants since the first generation of high-bypass turbofans of the 1960s, and their first runs marked pivotal moments for the emerging strategy of both companies. Coming just under two years after GE had been selected by Boeing as the second engine for the 787, the GEnx was emerging as a popular option and had won its way on to both the recently announced Boeing 747-8 and Airbus A350. For Rolls-Royce, its selection as the launch engine on the 787 marked the first time a non-U.S. engine maker had won pole position on a new Boeing twin-aisle and crowned its decades-long battle to beat Pratt & Whitney into the number-two slot in the big-engine world.
Rolls-Royce’s Trent 1000 was the first major mechanical piece of the 787 to run in February 2006. Fourteen months later a Trent 1000 is pictured being readied for critical blade-off tests toward final certification. Note the high-speed camera systems mounted on the gantry facing the front of the engine and the sacrificial multicolored blade. Rolls-Royce
But this outcome was far from clear in 2000, when Boeing asked all three engine makers for Sonic Cruiser propulsion proposals as part of its wide-ranging “20XX” future airliner project. At first these tended toward 777-based derivative engines, as the requirements were a good match in terms of thrust and compressor efficiency, and also because Boeing hoped the derivative route would help keep it more affordable.
However, through the fall of 2001, continuing analysis of the Sonic Cruiser’s performance profile, wind tunnel tests, and customer studies began to show that derivative engines would not work. Sonic Cruiser Marketing Vice President John Roundhill said the studies argued “for a major change, if not a brand-new engine.” The main reason was the higher thrust needs of the Sonic Cruiser at higher altitudes, plus emissions and noise targets that pushed the edges of the envelope beyond the 777.
“This aircraft has a different relationship of climb thrust to takeoff thrust, and we found the optimal core size was smaller than the 777,” said Roundhill. GE, Pratt, and Rolls immediately responded with hybrid solutions that combined the takeoff performance of the 100,000-pound-thrust class 777 engines with the cruise performance of the standard 777-200ER/300 engines. However, Roundhill reported that “we gave them some explicit criteria in terms of inlet diameter because of drag, and exhaust velocity because of noise. The results showed us we required a new engine.”
By early November 2001 the revised requirements called for a 90,000-pound takeoff thrust-class engine giving a 10,500-foot runway roll at a maximum weight, coupled with a high subsonic cruise capability. Here was a key difference between the Sonic Cruiser and anything that went before it. A propulsion engineer seeing these first two figures would have punched the numbers into a calculator and come up with a 100,000-pound-plus-thrust engine, not one with around 10,000 pounds less thrust. The Sonic Cruiser, however, had to be a good neighbor on the ground yet cruise close to the sound barrier for most of its mission.
Boeing’s late 2001 course correction to seek all-new engines for the Sonic Cruiser dovetailed well with GE’s developing next-generation-engine plan, which the company originally called GEN X. This was aimed at prospective power demands in the lower-thrust CF6-size bracket for a range of new studies under way by Airbus and Boeing. In 1999/2000 these were focused on a 67,000-to-70,000-pound-thrust growth version of the CF6-80 dubbed the CF6-80G2,