A casual question that has to be asked!!

[simmie]

Hi there

Happy new year to everybody on this fine site.

A querie occured to me just now while over on secret projects,

Why did the Soviet Union, in the development of their VSTOL fighters, not just rip off the Harrier concept???

Their first aircraft, the Yak 36(?), was close in that all the power went down thru the nozzles/vains to lift the aircraft.  No seperate, heavy, bulk, fuel burning lift engines.

Answers please

P.S
Why not use this thread, if there isn't somehting like it already, for all you casual queries.

[Weaver]

I suspect for the same reason that many other studies like the VAK-191 used a lift-plus-lift/cruise configuration: it allows the cruise engine to be tailored for high-speed flight, instead of being compromised by having a thumping great low-pressure fan on the front. The price you pay for lift engines is complication and cruising dead-weight of course, but the trade-off must be a finely balanced one, given how often lift engines have been considered.

[McGreig]

Why did the Soviet Union, in the development of their VSTOL fighters, not just rip off the Harrier concept???

My understanding is that, while designers such as Yakovlev would have liked to have gone down the Harrier route, they were thwarted partly because of lack of a suitable engine and partly because of differing views on the best method of achieving VTOL.

According to Yefim Gordon's "OKB Yakovlev", Yakovlev himself originally wanted to produce what would have been essentially a Soviet P1127. However, this would have required a 10,000kgp thrust turbofan with four vectoring nozzles and no such engine existed in  the Soviet Union nor was the Ministry of Aircraft Industry prepared to fund its development.

However, they were prepared to fund the cheaper alternative of fitting a vectoring nozzle to an existing engine - the Tumanskiy R27-300 of 6,350kgp -  and this led to the twin engined Yak-36 VTOL experimental which had two vectoring nozzles near the CG and four small reaction control jet nozzles at each wing tip, at the tail and at the tip of the extended nose boom.

When this arrangement proved too complicated in transitional flight modes, a debate arose between Yakovlev who favoured development of a single lift/cruise engine and Mordovin (who was responsible for the OKB's VTOL projects) who advocated a combination of lift/cruise and lift engines. The Ministry supported the composite engine layout and this led to the Yak-36M Forger.

Interestingly, Tupolev also developed a project - the 136 - in 1963/64 for a VTOL tactical fighter which used a similar layout to the P1127 and was designed round a single engine with four vectoring nozzles but this project also failed to progress because of the lack of a suitable engine.

[Chris707]

While lift engines are useless for the majority of a mission, they did permit more ordnance to be carried in VTOL without developing an uprated Pegasus or equivalent engine. As late as 1967, HS had considered the P.1175 stretched Harrier with a Pegasus and an XJ99 lift engine. As Weaver aptly wrote, it's all a trade off - extra thrust for a critical phase of flight vs the extra dead weight.

Chris
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F-4D walk-around

[simmie]

My Oh my


That was both very quick and informative.

Many thanks everybody, excellent stuff.