Saying the merits of using composite materials could not be harnessed as well as anticipated for a jet the size of the MRJ70, Mitsubishi Aircraft Corporation (MJET) announced it is reducing composite use from about 50% to 15%, making it a much more conventional, and thus, less risky, aircraft.

Composites, it seems could not deliver the weight targets and a return to more conventional structures gives it the flexibility to offer a newly announced 100- to 110-seat version as a concept while maximizing range performance for the proposed larger jet. MJET said the change to an aluminum wing box will ease the manufacture of the optimal wing structure and increase competitiveness for the 78-seat MRJ 70 and MRJ 90 as well as a newly offered stretch 100 seater. The stretched MRJ awaits sufficient market demand to trigger a formal program launch.

When initially launched, the MRJ targeted composites for the wings and fuselage barrels but restricting composites to the empennage and tail reduces composite structures, long used in other aircraft programs, to 10-15% of the aircraft by weight.

Spokesperson Mick Corliss told Aviation Today’s Daily Brief that the fortification needed for certain parts of a composite solution would not allow for the weight reduction the company is seeking. He also said it is as much a scale issue as anything, adding that returning to an aluminum wing box will facilitate the optimization of wing boxes across the family.

The first Japanese aircraft program since the 1960s and Japan’s first entry into the regional jet marketplace has slipped its schedule with first flight for the 92-seat MRJ90 delayed from the fourth quarter of 2011 to the second quarter of 2012. It is also adding a fifth flight test aircraft to shorten the testing certification period. Delivery to launch customer, All Nippon Airlines, is set for the first quarter of 2014, rather than at the end of 2013. ANA placed a 25-aircraft order for the 92-seat MRJ 90.

The aircraft is powered by Pratt & Whitney’s new geared turbofan. With the MRJ 70 and 90 already in competition with older generation regional jets such as Embraer’s ERJ 170/190, the stretch puts it in competition with Embraer’s larger ERJ 195 as will as Bombardiers larger aircraft, the developing CRJ 1000. It will be pitted against the Russian/Italian Sukhoi/Alenia Superjet program. This morning Sukhoi annouced the start of high altitude tests assessing takeoff and landing performance as well as climb-rate characteristics. These tests shall demonstrate the capability of the aircraft to sustain safe take off and landing, including missed approach in such complicated natural conditions. Besides, this test series is aimed at evaluation of main aircraft systems performance, while main focus will be on engine and auxiliary power unit operation. The tests are being done at high altitude airport Shirak in Armenia, a challenging facility surrounded by mountains which limit takeoffs to the south.

“The aluminum wing box will allow for a shorter lead-time to make structural changes, and with an aluminum wing box, the wings can be optimized to match the attributes of each member of the MRJ airplane family,” said the company. “This will maximize the performance of all MRJ models, including the possible stretch version. We remain more committed than ever to our mission of revolutionizing the regional jet market through the application of mainline jet technology and mainline customer support.”

The company also announced the final MRJ configuration and said this placed “the aircraft on a path to completing critical design review and design freeze in the coming months.” Improvements promise greater value to customers, said MJET at the Asian Aerospace Expo, and results from customer feedback.

Among the improvements, the cabin has been modified to offer a wider cabin as well as more head room, already a premium above its competitors, according to displays at last Spring’s Regional Airline Association meeting. Cabin height was raised an additional 1.5 inches to 80.5 inches, translating into an additional 12% volume of space in the overhead bins.

MJET is also improving the cargo compartment by combining the forward and aft cargo compartments into a single after compartment. Total cargo volume remains the same at 644 cubic feet. However, the company indicated the change will make baggage handling easier and stacking more efficient.