Paris Air Show

Mitsubishi keeps MRJ on course; critical design review under way

 - June 17, 2009, 10:08 AM

Development of Mitsubishi Aircraft Corporation’s MRJ regional jet continues on schedule, as some 800 engineers, designers and subcontractors in Nagoya, Japan, work to complete the project’s critical design review by year-end. The engineering team finished with the project’s preliminary design review in April and aims to ready the first of four MRJ90 prototypes for first flight near the end of 2011. Development of the 70- to 80-seat MRJ70 lags behind its larger MRJ90 sibling by roughly a year, according to Mitsubishi Aircraft executive vice president Junichi Miyakawa.

Holding firm orders for 25 MRJ90s from Japan’s All Nippon Airways, Mitsibushi plans to deliver the first of the batch in 2013. Judging by the company’s ability to quietly meet the financial, technical and organizational milestones it had set for itself early in the program, it appears unlikely that Mitsubishi has left much to chance in its choice of a target date for service entry.

The company’s market forecast projects a requirement for regional jets with a 70- to 100-seating capacity of more than 3,000 in the 2014-2027 period, of which it aims for a one-third share. Target price of the MRJ90 is $40 million (in 2009 dollars).
Financing of 85 percent of the purchase price will be available from Japanese export credit agencies.

Miyakawa reported that engineers have frozen the design of the outer mold line and decided on the sizing of the major structural elements of the MRJ, based on aerodynamic loads taken from wind-tunnel testing. He explained that Mitsubishi has completed its evaluation of the structure and systems interface in one of the most complicated parts of the airplane–the nose section–to define maintainability, accessibility and manufacturing processes. The company has also completed the definition of the engine-pylon interface, another particularly complex part of the aircraft in terms of parts integration and loads, according to Miyakawa.

Mitsubishi Aircraft counts as minority partners Toyota, Mitsubishi Corp., Mitsui & Company, Sumitomo Corp., Tokio Marine Nichido, JGC Corp., Mitsubishi Electric, Mitsubishi Rayon and the Development Bank of Japan. Majority shareholder Mitsubishi Heavy Industries controls 64 percent of the company. A major partner with Boeing on the 787’s all-composite wing box, MHI brings considerable experience with the technology to the MRJ, whose design includes composite wings and virtually the entire empennage, together accounting for about 30 percent of the aircraft by weight.

However, for the MRJ, Mitsubishi plans to break with traditional autoclave methods to make composite parts for the tail unit (and possibly for the wings) with a process called advanced vacuum-assisted resin transfer molding (A-VARTM). While conventional RTM uses pressure to push resin into a mold held together with rigid, typically metal upper and lower sections, the VARTM method uses a vacuum to draw resin into the mold, allowing for the use of cheaper materials such as nylon tape for one side of the tool. Mitsubishi’s advanced VARTM also involves the treatment of the preform with a spray of thermoplastic particles, which allow for the use of less viscous and cheaper epoxy resins.  Miyakawa said Mitsubishi will perform the first layup of an MRJ composite structure “toward the end of this year.”

Powered by a pair of Pratt & Whitney 17,000-pound-thrust PW1000G “geared” turbofans mounted under the wings, the standard MRJ90 will fly a “typical” range of 1,200 nm with 92 passengers at a cruise speed of Mach 0.78 and a takeoff field length of 4,790 feet. While carrying 76 passengers, the MRJ70 would fly as far as 1,080 nm and require a takeoff field length of 4,560 feet. Mitsubishi lists three maximum takeoff weights for each airplane, ranging from 81,200 pounds in the standard MRJ70 to 94,400 pounds in the MRJ90LR.

“It was a very tough decision for us to make,” said Miyakawa, referring to the choice of the still largely unproven geared turbofan design. “We had a very good proposal from every engine company. The reason we chose the Pratt & Whitney engine was simply because of its game-changing performance and fuel burn, which perfectly fits with our product concept.” According to Mitsubishi, both the MRJ70 and MRJ90 will use 21 percent less fuel per seat on a 400-nm trip than the comparably sized jets now produced by Embraer. At least half of that benefit would come from the engines.

Notwithstanding its purely regional airline pedigree, the MRJ would use Rockwell Collins avionics “equivalent to the ones used on the 787,” said Miyakawa. Other suppliers include risk-sharing partner Sumimoto Precision (landing gear), Parker Aerospace (hydraulic systems), Spirit Aerosystems (engine pylons), Hamilton Sundstrand (APU, electrical power and air management systems) and Nabtesco (flight control actuator). This past January Taiwan’s AIDC agreed to design and build the airplane’s slats, flaps, belly fairings, rudders and elevators.

Mitsubishi Aircraft Corp. is responsible for design, procurement, sales and support, while parent company Mitsubishi Heavy Industries (MHI) will take care of manufacture and final assembly, as well as flight testing.