Yakovlev Yak-40 variant
Yakovlev Yak-40 Yak-40MS
Experimental re-engining by the SibNIA institute in Novosibirsk: two Garrett/Honeywell TFE731 turbofans on the side pylons and, in place of the centre engine, an auxiliary power unit with fairings over the former intake and nozzle. It first flew in November 2016. The Yakovlev bureau declined to take part.
History
An initiative without the manufacturer
In 2012 the SibNIA aeronautical research institute in Novosibirsk began, on its own initiative, to re-engine a Yak-40. Approached about the work, the Yakovlev bureau said it had no interest in it. The institute went ahead anyway: airframes were cheap, its own airfield made a natural test bed, and the argument was simple — Russia needed a regional aircraft and did not have one.
From three engines to two
The work proceeded in stages. One AI-25 was replaced by a Garrett TFE731, then the second. Once the pair of Western engines had proved sufficient, the third engine buried in the fuselage was removed and an auxiliary power unit installed in its place, with fairings closing off the dorsal intake and the tail nozzle. The resulting aircraft, far cleaner aft and with the Yak-40's familiar silhouette noticeably altered, was designated Yak-40MS and flew in November 2016.
What it proved
Two modern engines instead of three old ones transform the economics of the aeroplane: lower fuel burn, less noise, less maintenance and more thrust available. SibNIA's interest was not in modernising the surviving fleet but in having a cheap flying demonstrator on which to test the configuration of a future Russian regional airliner.
The starting point for another programme
The twinjet was the first leg of the journey rather than its end. On the same airframe the institute later fitted an all-composite wing and turned it into the STR-40DT technology demonstrator, commissioned by the Ministry of Industry and Trade. In that sense the Yak-40MS is the link between a 1960s aeroplane and a twenty-first-century research programme.