Boeing’s Transonic Truss-Based Wing concept.
PARIS–Boeing is closely monitoring CFM International’s RISE future engine technology program, but the airframer will be balancing potential efficiency gains with the relative risk associated with new technologies.
“Our focus is to have capabilities that will spell a double-digit improvement, in the 20% range plus,” Boeing Commercial Airplanes CEO Stan Deal told journalists June 18 just ahead of the Paris Air Show.
When asked specifically about the CFM RISE open-fan project, Deal said, “It's got some promising opportunities, with some technical risk that has to be collapsed.” This will be weighed against the lower technological risk of scaling existing technologies.
However, Deal said that RISE’s 20% efficiency gains are unlikely to correlate to installed performance. “Every engine runs better uninstalled. Installed, there is always a knock-down effect,” he said. He noted that the true efficiency gains will only be known once the airframe and engine are combined.
“The good news is CFM, collectively, started early. You want to address technical risk as early as you can and try to collapse it. And so we encourage them to continue to do those things, as well as Rolls[-Royce] on their technology suite, which they have, and then Pratt [& Whitney] as they work theirs.”
Engine choice is a priority for Boeing’s airline customers and the US airframer said it will continue to review all engine options for its future platforms. However, Deal did say that he was happy with Boeing’s decision to select CFM as the sole engine option for the 737 MAX program. He added that GE, the sole supplier for 777 engines and the US partner with Safran in the US-French CFM 50-50 joint venture, has “technologically superior engines” and he is confident that they will continue to invest in their platforms.
Boeing’s Transonic Truss-Based Wing (TTBW) concept was mentioned several times during the briefing. The TTBW is a long and highly flexible slender wing, braced by trusses that also generate lift.
The TTBW is being developed in partnership with NASA. In January, Boeing said this technology could be used to create a two-aircraft family, comprising the VS-1 and VS-2, which would hold 130-160 and 180-210 passengers, respectively. The TTBW is expected to cut fuel burn and emissions by up to 10%, growing to 30% when combined with other technologies.
“We’ve done a lot of wind tunnel tests. We are not at day one; we are actually many years in,” Deal said. “This is that step from wind tunnel model results to actual flight results.”
The question is whether those wind tunnel models will translate into real life, on a full-scale model, he said.
“The nice thing about the configuration of the Transonic Truss-Based Wing is the high wing gives more geometry to deal with those engine choices,” Deal said, referring to the fact that it offers more ground clearance to accommodate larger fans.
Deal also acknowledged that there have been lessons from the 787 program, which means that design and production capabilities must be aligned.
“That’s one of our key takeaways,” Deal said. “We’re not going to deliver an airplane unless it’s precisely conforming.”
Boeing continues to harvest technology ideas from its ecoDemonstrator program, which has been running for over 10 years, delivering over 250 technologies to Boeing programs. This year, 19 projects will be evaluated.
“About a third of our projects tend to yield out of that ecoDemonstrator program,” Deal said.
