Russia's Central Aerohydrodynamics Institute (TsAGI) has turned to a second Irkut MS-21 wing-box to continue tests after the first example developed cracks under loading earlier this year.
TsAGI is contracted to do the wing testing and approval work by AeroComposite, which is itself contracted by Irkut and its parent company United Aircraft. AeroComposite will be supplying wings and other large composite structures for the MS-21 and Superjet 130 New Generation.
"The wing cracked in an expected zone when excessive loading was applied," said TsAGI. This initial specimen had been intended for technology mastering, checking design solutions and conducting tests for structural integrity and strength.
Testing began last summer, after the first wing box was manufactured by AeroComposite in cooperation with FACC of Austria.
Initial MS-21 specimens measure 10.2m x 2.9m x 2.05m and are manufactured from carbonfibre reinforced plastic, by means of vacuum infusion. Irkut chose this untried technology in 2010, gambling on lower manufacturing expenses by not using large autoclaves.
Tests and measurements conducted on the first wing-box helped determine the wing's ultimate strengths. TsAGI also carried out frequency and stiffness tests on the cracked wing-box specimen, and researched possible effects from typical airline operations.
TsAGI said the first round of wing-box testing helped collect necessary data on modern composite structures for next generation commercial airliners as part of TsAGI's multi-tiered effort on creation of "a comprehensive data base on composite [airframe] parts".