Landing Results: Test Milestones of the Mitsubishi Regional Jet

June 2017
Mitsubishi Regional Jet performing the hot and cold soak test at Eglin Air Force Base.

by Alex Bellamy

Our goal with the MRJ is to set a new benchmark in regional aviation, drawing on 130 years of experience at Mitsubishi Heavy Industries building transportation systems, defense aircraft, advanced rocketry and components for commercial aviation. Before being approved to enter into revenue service, though, every new commercial aircraft must go through a complex series of rigorous testing and analysis known as type certification.

To ensure progress toward certification, Mitsubishi Aircraft Corp. has restructured the MRJ development program and built one of the best teams in the industry, hiring many global engineers with experience in innovative commercial aviation programs to work alongside the Japanese experts in design and manufacturing. Six months ago, we formed a new Program Management Office that overarches our engineering groups to make sure decisions are integrated and linked back to the overall product strategy. And we’ve tweaked our work processes to enhance accountability so obstacles are now surfaced earlier and addressed through a more collaborative effort.

We are already seeing significant progress under this new approach, positioning the MRJ to successfully enter the market with type certification in 2019 and first delivery of the MRJ90 in mid-2020. Here is a list of some of our recent flight and ground test accomplishments that are vital towards achieving certification.

Static Strength Test

Required for all new clean-sheet design aircraft, the Full-Scale Static Strength Test ensures the aircraft’s ability to meet structural strength safety standards and comprises testing of the wings, vertical stabilizer and fuselage. The test rig, a system of hydraulic actuators positioned to distribute force across the airframe simulating operating loads, was designed and manufactured by Mitsubishi Heavy Industries at a facility near the Nagoya Airfield in the Aichi Prefecture, Japan.

We successfully completed all limit and ultimate load assessments in November 2016. At both levels the MRJ met requirements, successfully reaching limit load and ultimate load (150% limit load), indicating that the airframe had no deformation that might inhibit flight safety, confirming the strength required for certification.

Company Lightning Test

As a prerequisite to the type certification lightning test later this year, we completed an internal simulated lightning strike assessment on Flight Test Aircraft 5 (FTA-5) in December 2016 in Nagoya, Japan. To simulate lightning strikes, we applied a low electrical current to the aircraft that produces a magnetic field around certain areas of the aircraft such as the ports, engines and the edges of the empennage on the tail.

From there, we tested to ensure that the transient levels of electrical current passing through the sensors and electrical components across the aircraft meet the design requirement, which includes adequate shielding of the aircraft’s wiring bundles. FTA-5 performed well under these conditions and revealed areas in which we’ve already determined design improvements to be made before the forthcoming type certificate test. 

Natural Icing Test

In February and March 2017, Flight Test Aircraft 4 (FTA-4) performed initial natural icing tests based out of the Rockford International Airport in Illinois, the first off-site test campaign to collect data in these conditions. Tests performed by a team of global specialists using dedicated flight test instrumentation obtained valuable data to analyze the airframe ice accretion and Ice Protection Systems performance. Guided by a meteorologist on the ground, FTA-4 flew through clouds with specific moisture content, water droplet size and temperature resulting in varied icing conditions to understand how the aircraft would perform and eliminate ice on the leading edge of the wings and engines during flight.

These test cases featured scenarios involving delayed system activation and simulated system failures to understand how ice accumulates and sheds on the aircraft surfaces. This test milestone, proving that the plane is capable of handling ice, builds on the prior completion of an initial Artificial Ice Shape test campaign at Moses Lake Flight Test Center.

Hot and Cold Soak Test

At Eglin Air Force Base in Florida, FTA-4 underwent extreme temperature tests between February 28 and March 17, 2017. After initial set up, temperatures sunk down to -40° C for five full days of extreme cold testing. Following which, the testing team removed their winter coats, swapped in their t-shirts, and ratcheted the heat up to 50° C for several more test days.

Among other systems, the test and data gathered is used to validate the performance of the Environmental Control System (ECS). “Pull-Up” and “Pull-Down” tests, which begin in a cold or hot soaked condition, measured the ability of the system to control the cabin and flight deck to a comfortable temperature within a specified time. The results from this test have allowed our engineering teams to validate the thermal models and improve the design. Once ECS design improvements are implemented the next steps are FTA-4 deployments to natural hot and cold locations to continue the testing and validation.

High Speed Flutter and Flight Load Survey Tests

Two vital tests that dictate the maturity of the aerodynamic design and confirm an aircraft can safely operate throughout its flight envelope at the highest speeds and perform the most challenging maneuvers, both High Speed Flutter and Flight Load Survey tests were completed in February 2017 and April 2017 respectively at Nagoya Airfield in the Aichi Prefecture, Japan and Moses Lake Flight Test Center.

Flying at varying altitudes and speeds beyond maximum operation limits, the high-speed flutter test demonstrated sufficient margin on the normal operating envelope of the MRJ. Testing for flutter – a phenomenon that occurs when aerodynamic forces cause rapid self-excited destructive vibration – required a heavily instrumented aircraft operated by well-trained crew that was monitored by engineering specialists on the ground. Supported by a chase plane, the flight crew tested a wide range of speeds up to Mach 0.85.

Flutter testing marks another important MRJ milestone as it’s the first type certification flight test witnessed by the Japanese Civil Aviation Bureau and builds on the momentum towards type certification.

During the flight load survey tests, more than 250 pressure sensors and strain gauges affixed to the aircraft measured the maximum loads on its external surfaces and components. Throughout the test flights, the crew maneuvered the aircraft to reach specified G-loads, maximum rudder deflection, and roll and side slip thresholds as our engineers monitored the data and Japanese aviation authorities witnessed and approved the test via the telemetry room.

Results from the flight load survey test were as expected and aerodynamic loads for each component fell firmly within the design limit loads. Completion of both tests clears the aircraft to fly through its entire envelope, allowing pilots to fully exercise all control inputs.

Bellamy is senior director, program management office, MRJ at Mitsubishi Aircraft Corporation.

To track the ongoing progress of the MRJ, please visit progress.flythemrj.com.