First flight for the Mitsubishi Regional Jet (MRJ) on November 11 came almost 20 years after a Mitsubishi Heavy Industries (MHI) proposal for a 100-seat jetliner to be developed jointly with Bombardier. No agreement was reached, the Canadian manufacturer instead exploring a design dubbed BRJ-X before proceeding much more lately with its recently certificated C Series program.
MHI was subsequently a partner with Fuji and Kawasaki in Japanese Aircraft Development Corporation, which considered a regional-jet dubbed JSX. Later still, it developed the MRJ, which it launched in 2008.
The new model has crept slowly into the limelight, with Mitsubishi treading a cautious path – albeit one that included being the launch customer for Pratt & Whitney’s PW1200G-JM geared turbofan engine. As the MRJ has progressed slowly, the powerplant has been adopted for other platforms – not least the C Series – and recently entered service on the re-engined Airbus A320neo.
Mitsubishi Aircraft Corporation (MITAC), established by MHI to manage the project, has been careful to seek outside advice. Last year it opened the Seattle Engineering Center with development partner Aerospace Testing Engineering & Certification (AeroTEC) as a precursor to US flight testing, which could begin later this year. The first flight-test aircraft (FTA-1, manufacturer’s serial number [MSN] 10001) and three of the remaining four such machines are scheduled to cross the Pacific as part of a 2,500 flight-hour certification program aimed at achieving service entry with Japan’s All Nippon Airways (ANA) by mid-2018, five years later than the original target date.
More than half a century after Japan’s previous commercial-aircraft program, the country’s aerospace industry is unfamiliar with such engineering developments (although it does produce very large sub-assemblies for other manufacturers). Nevertheless, in having suffered several delays, MITAC sits alongside some illustrious names, among them both Boeing and Airbus, which have had to adjust schedules; aerospace systems integration has become an increasing challenge to even the largest, most-experienced companies.
A thorough MITAC/AeroTEC program review in mid-2015 recognized the need for structural modifications and systems upgrades, which the partners agreed to introduce after initial flights as part of a rescheduled development program. Now, with that work complete on the first aircraft and underway on the remaining test airframes, the resumption of flight testing has given the project momentum that the partners will want to maintain.
Since unveiling the aircraft at an unusual ‘roll-in’ ceremony at the MHI Nagoya Aerospace Systems assembly plant in October 2014, MITAC has worked with AeroTEC to manage development more conservatively. “Reviews brought to light necessary additional tests and test-confirmation items needed through ground tests, which we carried out prior to first flight,” says MITAC director and strategic-marketing head Hideyuki Kamiya. “We also reviewed future work and this increased the scale of ground tests, such as operational tests to attain more-advanced completion before first flight.”
With static-strength testing and manufacture of remaining flight test articles (FTAs) (all now under construction) “proceeding smoothly”, about a year ago the manufacturer elected to delay first flight to incorporate various ground-test results. MHI and MITAC hoped to “implement intensive flight testing and accelerate manufacture” to deliver the first example during the second quarter of 2017 – a target that has since slipped by a further 12 months.
Wing and a prayer
They also decided to schedule strengthening work, needed where the wing joined the fuselage, to follow the maiden flight. Bending tests on the static-strength test airframe in January 2015 had confirmed that the MRJ wing met limit-load requirements (by accommodating the maximum forces expected in normal operating conditions). However, further work about four months later revealed that the wing did not pass the ultimate-load test, which applies 50% greater loading. “Analysis enabled us to forecast that some components, such as those that join the wing and the fuselage, and those of the fuselage frame, would have insufficient strength,” reported MITAC in late December when announcing a further program delay, the fourth in all. (Three months earlier, senior executive vice president and executive chief engineer Nobuo Kishi had said that following initial flights, modifications were planned “to expand the flight envelope” – a tacit admission of the airframe’s weakness that went unnoticed by most commentators.) Kamiya declined to tell Aerospace Testing International how close the MRJ’s wing came to meeting ultimate-load requirements. Other static-strength testing includes fuselage pressurization to check complete atmospheric sealing of the airframe and the rate at which cabin pressure is reduced during the climb and raised as the aircraft descends.
After manufacture of five flying FTAs and the static-strength airframe (MSN 90001), the seventh airframe to be built is for fatigue testing to verify airframe durability by simulating repeated stresses expected in normal operations. Major assembly of this airframe (MSN 90002) was complete before February this year, with the airframe standing on its landing gear for installation of measuring equipment ahead of tests scheduled to begin later in 2016. “MRJ fatigue-strength testing will assume that the MRJ will make 80,000 flights over a period of more than 27 years, or eight flights per day for 10,000 days,” says MITAC.
Other requirements before flight included ground-vibration (GV) tests performed in mid-2015 with FTA-2 (the second flight-test aircraft). This work plays a key role in the development of aircraft equipped with highly computerized flight-control systems, says MITAC. The GV tests confirm “whether the aircraft will achieve harmonious functioning of the structure and the fly-by-wire system to ensure flight safety”.
Also in mid-2015, MITAC was scrutinizing technical data from the various test programs to assess feedback and consider possible modifications. It opened the Seattle Engineering Center and continued construction of its US flight-test hangar at Grant County Airport at Moses Lake in Washington state and another for the final-assembly line in Nagoya. (MITAC’s headquarters in Japan, Seattle Engineering Center, and Moses Lake comprise the program’s three engineering bases.)
A major milestone was reached in January 2015 with the running of the MRJ’s first PW1200G-JM engine. Operation of the starboard powerplant verified various systems including air conditioning, electrics, fuel and hydraulics. Sister company MHI Aero Engines performs final assembly of the engines.
When asked about the importance of the engine-delivery schedule and any flexibility MITAC hoped to agree with Pratt & Whitney – given the MRJ’s extended development schedule – Kamiya responds, “We are moving forward with P&W in developing a safe, reliable engine. We will keep tabs on the status and remain in close contact.”
Testament to the MITAC/AeroTEC partnership’s careful approach and emphasis on thoroughness is that almost five months elapsed before MRJ taxi trials began with low-speed (10 knots) tests in June to confirm braking and nosewheel steering behavior. Mid-speed taxiing followed, with 13 runs that included emergency-braking and rejected-take off performance. Speeds were increased to 120 knots before Japan Civil Aviation Bureau approval for test flights (without an airworthiness certificate or installation of some required equipment) was granted on October 29.
With, in Kamiya’s words, “a better-integrated aircraft” following the mid-year review and additional ground testing, the MRJ made its first flight from Nagoya on November 11, followed quickly by two more. “We were able to obtain valid, reliable results through these flight tests,” says Kamiya, before MITAC paused to introduce the wing/fuselage modifications and system upgrades.
In these initial operations, the MRJ achieved a “maximum altitude of 15,000ft and maximum speed of 200 knots,” continues Kamiya. “Approximately 4.5 hours was logged. We are expecting certification to require around 2,500 flight-hours for all five FTAs.” Mitsubishi is seeking type certification in Japan, Europe and the USA.
The MRJ’s 87-minute first flight, during which the landing gear was locked down and the trailing-edge flaps set at 30° throughout, confirmed basic operating characteristics in maneuvers including ascent, descent and circling left and right. All that Mitsubishi will say regarding initial results is that the flight-tests have all gone “as planned”, with basic characteristics “satisfactory” and landing gear and flap functional performances “according to specification”.
Following the post-flight modifications and upgrades to the avionics, and the engine- and flight-control systems software, test flights resumed on February 10. To strengthen the wing/fuselage attachment, MITAC says that additional reinforcement plates were placed on the original parts. Kamiya says, “It was not necessary to implement the upgrades at this stage, but we decided to implement the upgrades that are required for type certification if the MRJ is to satisfy ultimate-load requirements.” The modification increases aircraft weight by “only a few kilograms” and the MRJ90’s maximum take-off weight remains unchanged at “about 87,000 lb”, according to Kamiya.
Under the most recent program review, MRJ development and certification partners have extended the initial flight-testing period (but not the number of flight-hours) in Japan to increase the scale of ground tests and the time for test feedback. Flight testing in the USA, also over an extended period (again, with no increase in flying volume), is scheduled to begin between the fourth quarter of 2016 and the first quarter of 2017.
Kamiya is keen to emphasize that MITAC will continue to review all flight tests thoroughly, with results being taken account of in subsequent development work and the schedule adjusted as necessary. “We have conducted scheduling revisions as specific content has come more precisely into view. We will be managing our milestones and increasing the precision of our schedule as we progress,” he says. MITAC will begin its US flight-test campaign “as soon as feasible” and will assign the roles and responsibilities of the three engineering bases “for prompt execution in all fields”.
In addition, MRJ certification work will take place at other US sites, very often tied to specific tests. These tests include rejected take off, water ingestion, and high-intensity radiated fields (HIRF). Specifically, Kamiya cites three locations: Roswell International Air Center (New Mexico) – special runway testing; McKinley Climatic Laboratory (Florida) – extreme environment test; and Gunnison-Crested Butte Regional Airport (Colorado) – high-altitude take-off and landing.
As flight testing resumed, MITAC president Hiromichi Morimoto was quoted in Japan as saying that US flying could begin as early as September, since a later date would make mid-2018 delivery to ANA difficult. “But we’ll be prepared for unforeseen circumstances if we tighten the schedule and aim to obtain type certification near the end of 2017.”
According to the report in Nikkei Asian Review on February 13, Morimoto suggests an intensive US flight-test program involving MRJs FTA-1, -2, -3 and -4 each flying four times a day. Inevitably such a rate would generate an enormous volume of flight-test data, but the MITAC president is clear: “If we log about 50 hours a week, assuming that things go well, we’ll be done with trials by the fall of 2017,” Morimoto reportedly said.
Kamiya says that MITAC has factored in “all the risk we are aware of. We will do our utmost to advance the scheduling of each operation to create a scheduling buffer, just in case.” But he cautions that program reviews may necessitate additional tests and test-confirmation items. “The upgrades will be carried out concurrently with flight testing in a timely and appropriate manner.”
Meanwhile, more than five years after MRJ manufacture began with machining of a horizontal-stabilizer component, last October MITAC began assembly of the first delivery aircraft for ANA with the riveting of a port-wing structural component. Earlier this year, ANA inspected and approved work underway on what in 2018 should be the first new Japanese airliner to enter service for more than two generations. \
Ian Goold is a UK-based aviation journalist, specializing in the civil sector