Mitsubishi, Triumph Progressing On M100 Design Changes

Credit: Mitsubishi Aircraft Corp.

PARIS—Mitsubishi Aircraft Corp. (MITAC) and engineering partner Triumph Group have identified design changes that should allow them to exceed weight-savings targets established to morph the MRJ70 into a fully U.S. scope clause-compliant, 76-seat-dual-class regional jet (RJ).

Triumph’s structural optimization efforts focus on three areas of the recently renamed M100 SpaceJet: the wing, aft fuselage, and empennage. The company’s assignment: remove 15% of the combined structural weight. After just a few months on the job, Triumph is confident it will deliver. 

“We’ve already identified a path to get that weight out of the structure,” Triumph Aerospace Structures EVP Pete Wick tells Aviation Week. “We actually believe that we may well be able to get more.”

Transforming the MRJ70 into the 76-seat, two-class, scope-compliant RJ requires adding six seats but no weight. MITAC’s changes include adding 2 ft. to the fuselage—its new, single-class capacity will be 88 seats—and redesigning the entire main deck area. Space was taken from the rear cargo hold, while a Safran-designed cabin interior with a pivoting, concave overhead bin panel allows each passenger to place a roller bag overhead.

The result will be what MITAC chief development officer Alex Bellamy calls an “optimized” version of the MRJ70, the original family member that targeted the U.S. RJ market. That aircraft was designed under the assumption that U.S. pilot contract scope clauses would be relaxed. The most restrictive clauses limit 76-seat flying and put a maximum takeoff weight of 86,000 lb. Early insight from talks at United Airlines—the next of the U.S. majors to have an amendable pilot contract—suggest that current scope limits are here to stay.

“We have no choice but to be nimble,” Bellamy says. “We have no choice but to adjust our strategy.”

U.S. airlines want their RJ cabins to be as close as possible to mainline interiors while maximizing capacity. This means 76 seats with space for both first class and a few rows for more spacious economy seating are de facto musts for large RJs. Bombardier’s CRJ700 is scope complaint but is ending its production life in 2020. Among Embraer’s offerings, only the legacy E170 series meets scope clauses. MITAC sees an opportunity to offer a newer design as a replacement for older CRJs and an alternative to Embraer’s offering.

Morphing the MRJ70 design into the M100 also includes changing the canted wing tip design, shortening the span by about 4 ft., to just more than 91 ft. Much of the resulting performance reduction will be made up through other changes, such as reducing drag, Bellamy said, leaving the M100 capable of flying “99.5%” of today’s regional routes. More importantly, the modified winglet will reduce wing load, creating opportunity for Triumph to remove stiffeners that the MRJ70’s wing required.

Triumph is no stranger to aircraft structural design, having purchased long-time structures supplier Vought Aircraft in 2010 and folded it into Triumph’s Aerostructures business. More recently, it manufactured wings for the Bombardier Global 7500 (G7500) business jet before selling the operation to the Canadian manufacturer.

Wick points to G7500 wing certification testing as an example of his company’s capability. Triumph’s finite element model pinpointed where the wing would break, and how far above limit load—the maximum load expected during its service life—the failure would take place. The model was correct—right down to the exact percentage beyond limit load that the wing broke.

“What that tells you is, our modeling methods produce optimized structures,” Wick says. “We’re able to identify all of the opportunities to remove unnecessary weight to ensure that you don’t have an over-engineered structure.”

The wing area has the most potential. Besides removing unneeded stiffeners, plans call for modifying the engine pylons and wing box.

The altered wing brings more than weight-reduction opportunities. Bellamy said the new dimensions make the M100 more compatible with current RJ gate facilities, as well as compliant with a 95-ft. wingspan maximum in place at Colorado’s Aspen-Pitkin County Airport, a popular tourist destination. The airport’s configuration, including the separation between its single runway and taxiway, requires special, FAA-approved restrictions. The only other in-production RJ that can meet the restrictions is the CRJ700.

The M100 will be the smallest SpaceJet family member. Plans call for it to enter service in 2024. The larger M90—the former MRJ90—is on pace to be certified by Japanese regulators and enter service with launch customer All Nippon Airways in 2020.

CORRECTION: The dateline on this article was corrected.

Sean Broderick

Senior Air Transport & Safety Editor Sean Broderick covers aviation safety, MRO, and the airline business from Aviation Week Network's Washington, D.C. office.


 

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