If it didn’t become immediately apparent when Boeing began alluding to time frames that implied a replacement of the 737 might not materialize until 2020, the company’s recent revelations of new set of
design enhancements certainly erased any doubts that a direct replacement will have to wait until designers and engineers squeeze all the efficiency and comfort available from the existing narrowbody family.
Boeing estimates the improvements, unveiled in late April during a day of media briefings that included a tour of Boeing’s 737 assembly plant in Renton, Wash., will result in a 2-percent decrease in fuel burn, thanks to aerodynamic refinements and modifications to the CFM56-7B engines. Separately, a new interior called the Boeing Sky will include new LCD lighting, redesigned sidewalls and window reveals and pivoting overhead bins shaped to add to the openness of the cabin and allow for more roller-bag capacity.

“We think the 737 has a lot of life left in it,” said Boeing 737 chief engineer John Hamilton. “We’re going to continue to look at how we improve this airplane, but for right now we think we’ve got a dynamite partnership with CFM…and we’re going to stick with them.” Boeing plans to use one of Continental Airlines’ 737-800s to flight test engine and airframe drag improvements starting at the end of 2010.

Called the CFM56-7B Evolution, the engine program will deliver a 1-percent improvement in fuel burn over today’s CFM56 Tech Insertion powerplant. The modification includes changes to the outlet guide vanes, the number and shape of the blades in the high-pressure turbine and the disc. All told, CFM expects to reduce the number of airfoils in the high- and low-pressure turbines by 9 percent. 

The company plans to start ground testing the engine in September and begin flight testing at GE Aviation facilities in Victorville, Calif., early next year, in time for expected engine certification in July 2010. Flight testing on a Boeing 737 would start in October 2010, ahead of expected certification for that airplane in the second quarter of 2011. Once certified, the Evolution engine will carry the nameplate CFM56-7BE.