Russian airframer Irkut plans soon to transfer the first MC-21-300 narrowbody to its flight-test station in the Siberian city of Irkutsk as preparations for the maiden flight progress into their advanced stages. The company, which is part of the United Aircraft Corporation group, staged a rollout ceremony in June 2016 for Aircraft 0001, and during the second half of last year tested its fuselage for airtightness, installed on-board equipment and calibrated measurement systems.

“The first operable airplane has been switched to electric power at the Irkut Aviation plant; its frequency response testing has commenced,” according to Irkut president Oleg Demchenko. “All tests at the factory shall be complete by the end of the first quarter.”

In addition to the frequency response testing on Aircraft 0001, he named as the “second largest task” for the near term assembly of Airframe 0002 for static testing at TsAGI, the Central Aerohydrodynamic Institute in Zhukovsky, just outside Moscow. “These are the two major points on the way to collect proving documentation for certification authorities to get permission for first flight,” he explained during a press briefing.

In late December officials showed a group of local journalists Aircraft 0002 in a TsAGI workshop, where mechanics had attached wing consoles to the fuselage. The airframe was still missing leading and trailing edges, engine pylons and other items necessary for bona fide static testing, however. After they complete final assembly as planned next month, TsAGI specialists will attach weights and sensors on the static airframe before subjecting it to loading. Afterward, “the work at TsAGI will start in earnest,” promised Demchenko.

In March the manufacturer plans to submit “the whole package of documentation” to the aviation authorities to win their permission for first flight. Plans then call for inspectors at TsAGI, Gromov’s Flight Test and Research Institute and Baranov’s Central Institute of Aviation Motors to study the documents and issue their conclusions on readiness of the first operable prototype for flight trials for final consideration at the Methodical Council, a branch of the national civil aviation authorities assigned to new aircraft types.

Meanwhile, plans call for Aircraft 0002 to conduct static and endurance tests. Its wing box arrived at TsAGI in July. Engineers completed mating the main force-bearing members of the wing and fuselage in mid-November, after which it underwent a series of preliminary tests to assess their airworthiness. By the end of that month, they subjected the assembly to 67 percent, then to more than 80 percent of the maximum permitted loading on the wing-box. The assembly went through a series of local testing involving forces on landing gear struts and engine pylons. Following completion of tests in preparation for first flight, Aircraft 0002 will undergo more vigorous tests for endurance and ultimate loading.

Separately, the manufacturer reported completing tests on “hundreds” of individual airframe components and subassemblies to assess their strength. They include tailfin and stabilizer force-bearing structures, as well as landing gear struts, elevators, air brakes, rudder, trailing and forward wing edges, interceptors, flaps, ailerons and the forward fuselage.

During endurance testing, the fuselage section surpassed 47,000 load cycles and the fuselage tail section endured 240,000 load cycles, each corresponding to a real flight, according to Irkut.

Irkut reports that 40 percent of the MC-21 airframe consists of composites, mostly in the central fuselage, wing boxes and forward and trailing edges. As part of the initial testing effort, the company built four wing box “prototypes.” Testing on final version of the wing box—a specimen for mass production—continues, as does onboard systems being tested using a so-called Iron Bird and Copper Bird.

Irkut has not specified an exact date for MC-21’s first flight, although it promises to reach the milestone in the first half of 2017.