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Yakovlev's Yak-LSh (Yak-25LSh) light "Shturmovik" (1969)

Stargazer2006

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Adapted from a Yakovlev inhouse publication:

Unknown pages in the history of domestic aviation

Close air support of ground troops has been one of the main tasks of military aircraft since its inception. The experience of wars and military conflicts, the development of aviation technology - all of it continuously made battlefield aircraft improve.

After the Second World War, the rapid development of jet aircraft increased the speed and altitude of aircraft. At the same time, the ongoing conflict consistently reaffirmed the need of the Air Force for quite simple and inexpensive specialized combat aircraft, adapted for assault action against ground targets. In the second half of the 1950s, solutions to this problem tried to accommodate existing high-speed jet tactical fighters. Tactical and technical requirements prevailed in specialized attack aircraft. Conducted in the fall of the 1967 in the Soviet Union, the large-scale "Dniepr" exercise showed, for example, that of all the supersonic MiG-21 and Su-7 and subsonic MiG-17 involved in ground troop support, the best results were achieved by the pilots who flew the MiG-17.

In early 1969 Ministerial Defense Marshal A. A. Grechko appealed to the leadership of the MAP for a proposal to hold a design competition for light attack aircraft (lyegkogo samolyeto shturmovika, or LSSh). By mid-March Air Force leadership had formulated the TTT attack aircraft, and in the same month MAP requested that the design bureaus of S. B. Ilyushin, A. I. Mikoyan, P. O. Sukhoi and A. S. Yakovlev start work on a competitive basis to develop preliminary LSSh designs according to the Air Force's TTT specification as of March 19, 1969. The result of this work, of course, was the emergence and adoption of the Su-25. Competitive projects by Ilyushin (Il-42) and Mikoyan (MiG-21LSh) are also known to the interested reader. The following is a description of Yakovlev's LSSH proposal, the Yak-25LSh (or Yak-LSh), which remained virtually unknown until 2009.

The light attack aircraft was designed for the air support of combined arms by land-attack enemy targets in the tactical and immediate operational depth. The main objective of the aircraft was to be the destruction of manpower and equipment, and the destruction of planes and helicopters from small and medium altitudes. Following the TTT specification, the Yakovlev Design Bureau worked on two light tactical attack aircraft variants. The first option was to create an entirely new aircraft and engine for it, which would require at least five years for its construction, testing and start of production. The second option was based on the operational Yak-25 fighter-interceptor and involved the reworking of the fuselage and the installation of equipment and weapons (attachment #1); it could be set up within 5-6 months. The swept-wing Yak-25 interceptor, with its two AM-5 turbojet engines with 2000 kgs of thrust, had proved an extremely reliable and safe aircraft, easy to pilot and available for rapid development. It was optimized to withstand emergency landings, even on unpaved runways and with the engine power down. As a result, the design bureau was asked to put the priority on an in-depth elaboration of this option.

Some of the major changes in the creation of a ground attack based on the Yak-25 were as follows:
  • The nose of the fuselage was revised to ensure 20-degree forward and downward view;
  • A new set of equipment replaced the interceptor's complex attack aircraft equipment;
  • Two GSh-23 machine guns with 400 rounds and rockets fuselage block APS-57 or the KARS 57 for 100 pcs.
  • Under-wing pylons made provision for outer suspension of six various weapons;
  • The ejection seat allowed for rescue in all flight modes, including takeoff and landing.
Warload of the Yak-25LSh was 1500 kg (typical) and 3000 kg (maximum). Range bomb armament consisted of 50, 100, 250 and 500 kg bombs and of all types. On six underwing pylons could be placed up to four pods with GSh-23 guns and ammunition (250 shells). Guided weapons includes up to four Kh-23 and R-3S, and six S-24 / S-25 unguided rockets. An interesting solution was the accommodation in the fuselage of a 100-projectile unit, which was set within the main landing gear niche and could sink down for reloading or replacement. The unit could shoot forward and down at an angle of 45 deg., which means that missiles could be launched on ground targets in level flight, which in turn increased the survival rate of the aircraft at low altitudes.

As the project developed, it underwent some changes: the wing was moved from low to high position, its size was increased, and take-off and landing characteristics of the Yak-25LSh were improved. The installation of more powerful RD-9F and AM-11 engines was also studied (attachment #5). By the end of December 1971 the original form of attack aircraft had strongly changed. The plane, now called the Yak-LSh-2 (attachment #6) had its fuselage lengthened by 5 m, allowing for increased fuel capacity. The tail stabilizer was moved from the middle of the vertical fin down to the fuselage, its shape and size being increased. A completely new high-wing was also developed. Leading edge sweep was smaller, being 35 degrees instead of 45 degrees in the original version. All this greatly improved the aerodynamics of the aircraft, increased its maneuverability, the provided an opportunity to increase the weight of the payload. Installation of more sophisticated sighting equipment, including the FON-1400 laser range, was also planned.

When considering the LSSh projects presented by the contestants, Sukhoi's Su-25 was declared the winner but the losing design bureaus were denied access to the general conclusions of the Air Force. Yet the work of the teams at the Yakovlev OKB on the stormtrooper project had not been in vain. Despite the new level of technology involved, it was useful in the development of the Yak-130 combat training aircraft.


NOTE: Translation was approximative. Some bits were left out for lack of understanding. If anyone feels like improving it, the original text is also attached.
 

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hesham

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Great find Stargazer,


I know that aircraft from Mr. Tony Butler's book,but no drawings to it in the
book,can you tell us the source,that's only for knowledge.
 

overscan (PaulMM)

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That is awesome Stephane - to my knowledge this project has never been illustrated before in English. Corrected a few minor typos in your post (e.g. P-ZS should be R-3S, Gs-23 is GSh-23).

Source appears to be online here:

http://www.yak.ru/DOCS/2009_01.pdf
 

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Jemiba

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Thanks for digging this out !
Reminds me much more to the SNCASO SO.405 Vautour (IIA in this case), then the
basic variant.
 

cluttonfred

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This is very interesting, I am always fascinated by aircraft designed to go deliberately into the range of small arms and other ground fire in support of friendly troops. With the Soviet heritage of armored attack aircraft, I am surprised to see no mention of armor protection for the pilot and vital systems in the Yak-25LSh design. Am I missing something? Cheers, Matthew
 

hesham

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PaulMM (Overscan) said:
That is awesome Stephane - to my knowledge this project has never been illustrated before in English. Corrected a few minor typos in your post (e.g. P-ZS should be R-3S, Gs-23 is GSh-23).

Source appears to be online here:

http://www.yak.ru/DOCS/2009_01.pdf


Thank you my dear Paul for the source,


and may be there is anther projects in those Yakovlev documents,I mean anther PDF
reports.
 

Jemiba

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cluttonfred said:
With the Soviet heritage of armored attack aircraft, I am surprised to see no mention of armor protection for the pilot and vital systems in the Yak-25LSh design. Am I missing something?

I thought of the green areas in LSh-03 as armour ?
 

Jemiba

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Two GSh-23 would have meant to hose a target with around 5000 bullets per minute. And the 23mm calibre should
be quite effective even against lightly armoured vehicle, as during WW II it proved often enough effective against
German tanks, when used by Il 2 Shturmoviks. "Tank busting" wasn't the main concern of the Soviets, I think.
 

cluttonfred

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Thanks, all, for the clarification on the armor. On the cannon, there are rounds for the U.S. 20x102mm that can penetrate 15-30mm of RHA, so presumably an AP round in the GSh-23's 23x115mm either existed our could easily have been developed for even better performance. That's certainly not enough to take on an MBT from the frontal arc but it would likely penetrate an MBT engine compartment from above and behind and would certainly ruin the day of anyone in a lighter APC or IFV.
 
C

CostasTT

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Jemiba said:
Two GSh-23 would have meant to hose a target with around 5000 bullets per minute. And the 23mm calibre should
be quite effective even against lightly armoured vehicle, as during WW II it proved often enough effective against
German tanks, when used by Il 2 Shturmoviks. "Tank busting" wasn't the main concern of the Soviets, I think.
There is a crucial difference; the VYa-23 of the Il-2 fired the 23x152B round, while the GSh-23, as mentioned, fires the 23x115 round, the older cannon having correspondingly higher MV and thus armor penetration with the proper projectiles. Other than that, yes, the cannon of the LSh would be effective against a variety of battlefield targets.
 

cluttonfred

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The larger 23mm round remained in use then and now in the ZSU-23 series of AA cannon, so presumably a dedicated anti-tank variant using sub-caliber saboted rounds would not have been hard to put together.
 

riggerrob

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23mm cannons seem a bit light for anti-tank/ground-attack work.

Remember that tanks only have thick armour on their fronts, with progressively thinner armour on their flanks and tops. While a generic Cold War tank might have 100 mm on the front, it may only have 30 mm on its roof. That allows a 23 mm top-attack gun to kill tanks from the top.

As an aside, during the summer of 1944, WALLIED fighter-bombers killed comparatively few Panzers, but they wrecked German supply truck and trains. Hundreds of Panzers were abandoned when they ran out of fuel, ammo or spare parts.
 

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