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The Yakovlev VTOL Family


LostCosmonaut
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During the latter part of the Cold War, the Yakovlev design bureau came up with quite a few designs for VTOL combat aircraft. While they weren't the most successful designs, they are pretty interesting, from both a historical and technical standpoint.

 

The first of these is the Yak-36 (Freehand);

 

0681320.jpg

 

While the Soviets had come up with numerous other VTOL designs in the 1960s, most of them used dedicated vertically mounted engines to take off vertically. However, the Yak-36 had a more modern arrangement, with two engines that used vectored thrust for both vertical and horizontal flight. The Yak-36 was powered by a pair of R27-300 jet engines (the same engines that powered the MiG-23 'Faithless' VTOL concept). In addition to providing vertical and horizontal thurst, the engines also provided airflow for 'puffers' at the wingtips, nose, and tail, which provided control in hover and low speeds (where aerodynamic controls would not be effective).

 

The Yak-36 suffered from various difficulties during its development, among them the engines reingesting exhaust gases. At least two of the prototypes crashed at somepoint. Though the Yak-36 was at various points displayed with underwing armaments (such as rocket pods), it was never deployed to operational units; it was solely used as a testbed.

 

Following the Yak-36 was the more widely known Yak-38 (Forger). It entered service in the early 1980s.

 

yakovlev-yak-38-vto.jpg

 

Unlike the Yak-36, the Yak-38 was fitted with lift jets (two RD-36V engines). Though these engines did an adequate job of providing vertical lift, they had the drawback of being dead weight in horizontal flight. Horizontal thrust was provided by  a single R27-300. Though the Yak-38 was capable of VTOL, it had highly limited performance; it was strictly subsonic, and had marginal payload capability.

 

yak38-1.gif

(pictured: unrestrained optimism)

 

The Yak-38 was designed from the outset as a combat aircraft, intended to be deployed from the Soviets' Kiev class carriers. In this role, it was shit (much like your favorite anime). The first issue was reliability; many of the Forger's components proved to be horrendously unreliable, especially the lift jets. I've seen figures stating that the lift jets had an average lifetime of less than 25 hours, which leads me to suspect they were actually rebranded Jumo 004s. Engine failures were especially bad in the Yak-38 - a failure of a lift jet on one side would lead to the jet entering a fast, unrecoverable roll. The lift jets also had poor thrust in hot conditions; in many cases, the Yak-38 had to fly with only two pylons filled, rather than all four. Considering that the Yak-38 had no internal armament, this was not optimal. Interestingly, in addition to using it as a carrier aircraft, the Soviets also trialed the Yak-38 as a close air support in Afghanistan. This was less than successful; the Yak-38 was only capable of carrying a pair of 100kg bombs, markedly inferior to dedicated CAS aircraft such as the Su-25.

 

Rumors of the Yak-38 being deployed to Colorado are false;

 

SUS2INT.jpg

 

Numerous variants of the Yak-38 were developed, most notably the Yak-38M, which despite having improved engines and other components, was still a dog. There was also the Yak-38U, a serious contender for the title of 'Ugliest Airplane'.

 

 

In the late 1970s, development of a successor to the Yak-38 began. This aircraft was the Yak-41 (Freestyle).

 

Yakovlev_Yak-141_at_1992_Farnborough_Air

 

The general configuration of the Yak-41 was similar to the Yak-38, with a pair of lift jets in the fuselage and a single main engine for thrust. However, its capabilities were massively improved. While the Yak-38 was a strictly subsonic aircraft, the Yak-41 was capable of supersonic flight, setting many records for VTOL aircraft (under the fictional designation Yak-141). Additionally, it incorporated far more advanced materials in its structure (including large scale use of composites), as well as improved avionics (such as a radar set which was actually useful). Its payload capacity, in terms of weight, was roughly the same as what the Yak-38 could (theoretically) carry. However, given that the Yak-41 was a dedicated air superiority craft, this was less of a concern than the Yak-38s payload deficiency in the strike role.

 

avredvt_7.jpg

 

Unfortunately for the Yak-41, it began testing in the late 1980s, just as the Soviet Union was falling apart. Though some testing continued through the early 90s, the Yak-41 never entered operational service. The second nail in the Yak-41s coffin was the Soviet Union / Russian Federation's acquisition of larger aircraft carrier(s), capable of operating aircraft such as the Su-27K and MiG-29K.

 

Interestingly, for a few years in the early 1990s, Yakovlev collaborated with Lockheed Martin on the development of the Yak-41. This has given rise to many conspiracies about the F-35B being a clone of the Yak-41. While this is obviously false, it wouldn't be outside the realm of possibility that a few bits on the JSF might have drawn inspiration from Yak's design in some way.

 

There was one final successor to the Yak-41; the Yak-43. An even more advanced evolution, the Yak-43 could have been quite capable (had it been built). From what I can find, it dispensed with the extraneous lift jets. Power would have been provided by a modified NK-32 turbofan, the same engine that powers the Tu-160. This would have given the Yak-43 significantly improved performance and payload capacity compared to its predecessors. Additionally, the Yak-43 would have incorporated low observability features into its design, bringing it closer to being a true competitor to aircraft such as the F-35B. In any case, the aircraft remained unbuilt, and I have not heard of any efforts to revive the design.

 

Yakovlev_Yak-43.png

 

yak43f35.jpg

 

 

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Forger was horrible.

 

Retired Lt. Colonel Anatoliy Artemyev wrote an article about the YAK VTOL family in volume 10 of International Air Power Review.  Some bits and bobs from that:

 

-During the deployment in Afghanistan, due to the high altitude and general uselessness of the forger, mission radius with two 100-kg bombs was 30-50 km with VTOL.  With CTOL (thus defeating the entire point of the forger) and 500kg of ordnance, ROA was still only 190km, compared to 700km or so for MiG-27.

 

-Pilots would try to weasel out of flying the things by discharging themselves on the ground of minor or imagined sickness, and were quite vocal about disliking it.  It some some admiral's pet project though, so they were ignored.

 

-Between 1974 and 1988 the Yak-38s managed 30,000 flight hours.  There were 37 flight incidents, 21 emergencies and 8 breakages. 

 

-At the beginning of the service of the Yak-38, failures occurred an average of once every 1.2 hours.  This was lengthened to once every 23 hours by the end of service.

 

-By the end of the eighties the aircraft were basically unflyable, and 10 out of every 12 was grounded.

 

 

The Yak-43 is interesting.  Between it and the Yak MFI submission, it appears that Yakovlev had the best grasp of stealth principles of the Soviet fighter OKBs by the end of the Cold War.

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The article cited above also mentions a YAK-39; this was essentially an improved -38M.  It was canned in favor of the more ambitious YAK-41.

 

Does anyone have information on the design of the lift engines in the YAK VTOL series birds?  There are somewhat unusual requirements for lift engines.

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  • 2 months later...
Engine failures were especially bad in the Yak-38 - a failure of a lift jet on one side would lead to the jet entering a fast, unrecoverable roll.

 

And as such, they designed the ejection seat to automatically fire if the airplane rotated 60 degrees from vertical while in VTOL mode.

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