Yakovlev Yak-40 STR-40DT

Once SibNIA had shown with the Yak-40MS that the trijet airframe would fly happily on two engines, the Russian Ministry of Industry and Trade turned the private initiative into a research programme. The aircraft was redesignated STR-40DT — samolyot turboreaktivny 40, technology demonstrator — and its purpose shifted from modernising the Yak-40 to flight-validating solutions intended for a future regional airliner.

The wing is the heart of the programme. The original metal surface — straight, thick and generously sized — gave way in 2018 to an all-composite wing of greater span, smaller area and winglets at the tips: precisely the opposite of what a short-field aeroplane wants, and precisely what a fast, economical cruiser needs. The stated aim was to carry over to a fast aircraft the composite technologies developed for the TVS-2DTS biplane.

The STR-40DT lifted off for the first time on 4 December 2018 from the Yeltsovka works airfield at the Chkalov aviation plant in Novosibirsk, flown by a crew led by Igor Moseikin, head of the institute's aviation certification centre. Testing had originally been planned for late 2017 and slipped by a year.

SibNIA declared the work complete in July 2019. With two engines rather than three and a composite wing, cruising speed rose from about 500 km/h to roughly 700 km/h while fuel burn fell from 1,150 kg/h to between 560 and 590. The institute also announced its intention to build a composite fuselage, which would allow an entirely composite prototype in the size and layout of the Yak-40. English-language sources list the project as STR-40DT and note that Yakovlev endorsed but did not support it.