By Bjorn Fehrm
January 03, 2018, ©. Leeham Co: Both United Aircraft Corporation (UAC) and COMAC got their single-aisle airliner projects into flight test during 2017. The MC-21 and C919 had their first flights within less than a month of each other, with the Chinese C919 first at 5th of May, followed by the Irkut MC-21 on the 28th of May.
Superficially the aircraft and projects are similar. Both are 150-220 seat single aisle projects in the mold of Airbus’ A320neo and Boeing’s 737 MAX programs. Looking a bit closer, they are different. One is extending the state of the art in several areas; the other is playing safe.
The less experienced crew behind the C919 flew first, but then the MC-21 team took the lead with continued test flights in August.
The C919 stayed on the ground until September 28th and then after one flight had another hiatus until November 3rd. The long delays between first flight and following flights for both projects show the immaturity of the programs by first flights. Similar Western projects fly again within a couple of weeks.
One can conclude both first flights were “Monkey off your back” events, more so for the Chinese project than the Russian. Aircraft ground testing and instrumentation for the C919 and MC-21 were not at the level where continued flight-testing was safe or meaningful after a first cautious hop.
It’s possible to fly a test aircraft safely early in the design cycle, as long as speed and altitude are low. The critical danger for a flight test campaign is aerodynamic flutter, an aerodynamic/structural resonance that can break wings and stabilators in seconds. Such resonances only occur when the speed is raised.
The pace of the projects flight-testing shows the necessary ground vibration testing and aircraft instrumentation for these and other tests were not ready in May. Irkut continued the flight-testing in August and kicked it into high gear from October. COMAC is still cautious with flying. Mid-November the C919 had completed five test flights.
The C919 is developed by a country who’s only developed the regional ARJ21 airliner before. The state AVIC organization, from which COMAC was spun off, has developed a few indigenous fighter aircraft after license-producing Russian designs, but no operational airliners except for ARJ21.
The ARJ21 was modelled closely after the license produced McDonnell Douglas MD80. It was developed by a consortium of AVIC companies, called ACAC. After COMAC was created to handle civilian airliners, the ACAC and its ARJ21 were 2009 assimilated into COMAC.
The C919 is a prudent design. It’s closely modelled after Airbus A320 with similar technology. The avionics side has Ethernet-based IMA architecture instead of the older point-to-point design on the A320 and the Fly-By-Wire is all digital, but otherwise, the C919 is similar to the 30 years older base design of the A320neo.
The MC-21 is not a copy of a Western design. It advances the state of art in cabin standards and structures. The fuselage has a circular cross-section which is 0.11m wider than the A320/C919 and 0.27m wider than the 737. It allows a 24-inch-wide aisle where passengers can pass each other or a flight attendant with a serving trolley.
The MC-21 is also the only civil airliner with a Carbon Fiber Reinforced Polymer (CFRP) wing-box which has been produced with Resin infused dry fibre and then cured in an oven instead of an autoclave. The CFRP wing-box broke shortly before reaching Ultimate load (150% of the highest in-service load) in the spring but passed the test in November, after a 25kg reinforcement.
The MC-21 avionics and Fly-By-Wire use the same technology as the C919, now made by Russian vendors (the C919 technology has Western origin).
The projects use the same modern Western engines as the A320neo and 737 MAX. The C919 is standardized on the A320neo’s LEAP-1A engine, now called LEAP-1C. The MC-21 uses the Pratt & Whitney PW1100G engine from the A320neo, now called PW1400G.
Russia is developing an alternative for the PW1400G, the Aviadvidgatel PD14. We have analyzed this engine here.
To avoid a dual development for a limited widebody market, UAC and COMAC have decided to jointly develop a 290 passenger widebody aircraft, competing with Airbus A330/A350 and Boeing’s 787. A separate company has been established for the project, China-Russia Commercial Aircraft International Corporation (CRAIC).
CRAIC, which is based in Shanghai, was formed on 22 May 2017. Development will predominately be done in Russia and assembly in China. Entry into service is projected for 2027.
The aircraft, called CR929, has its closest Western equivalent in the Boeing 787 project, with the base variant modeled closely after the 787-9.
Like for the C919 and MC-21 projects, the aircraft will have Western base engines in the 75klbf class. Russian and China are discussing the joint development of an alternative engine. It could be based on a scaled-up version of the PD14 engine, called PD35.
The MC-21 program is managed by Irkut, a company in Russia’s United Aircraft Corporation. Similar to its Chinese equivalents, the Russian civil aircraft industry developed a regional airliner, the Sukhoi SSJ100, as first modern airliner after the fall of the Soviet Union.
With the sale of the SSJ100 on the world market in cooperation with Italy’s Leonardo, Sukhoi learned how to work with Western airlines and the requirements for Sales and Support of a Worldwide airliner project. Irkut has no such experience.
UAC has therefore decided to create a group-wide Commercial aircraft division where Sukhoi’s sales, service and support structure will be used for all the group’s civil airliners. The Irkut organization will focus on development and production for the MC-21.
For COMAC, which was formed 2008, Sales and Support of civil airliners is new territory. The ARJ21 project gives the organization some experience, but only the for captive customers in the domestic market. It will use the C919 to learn the trade of civil aircraft development, sales, production and support.