The Yak-15Db, or don't let politics and aviation mix....

[PR19_Kit]

The Yak-15Db

An aeronautical and political history

During the mid-40s the Russian aviation industry was delving into jet powered flight, helped by transfusions of hardware and staff  from the recently defeated German Reich and later by the controversial sale of British centrifugal jet technology in the shape of the R-R Nene and Derwent engines. One of the many Russian Design Bureaux working in this area was that of A.S Yakovlev, a well respected  aircraft designer of the period who's piston engined Yak-3 and Yak-9 were some of the mainstays of the Soviet fighter regiments during the dark days of WWII. Indicative of the respect these aircraft gained is the fact that modern versions of the Yak-3 are still being built in the Yakovlev plant today, using the original drawings and jigs, albeit powered by the Allison V-1710 engine rather than the original Klimov M-105P.

In 1945 the Yakovlev Design Bureau designed and built the first Soviet jet fighter to enter service, the Yak-15 (NATO reporting name 'Feather'). The Yak-15 was also the world's lightest ever jet fighter, as Yakovlev followed 'simplicate and add lightness' techniques. The Yak-15 used the rear fuselage and most of the wing structure from the previous Yak-3, and had a Klimov RD-10 axial jet engine installed in the nose, pointing downwards and exhausting via a duct under the cockpit, giving the short jet-pipe length that was required for the rather basic engines of the period. The RD-10 was developed from the Junkers Jumo 004B, which powered both the Me-262 and Ar-234 Luftwaffe jets, and in its Russian built version developed just 2000 lbs thrust. The design development and the construction of the first prototype of the new aircraft went quite quickly considering that new ground was being broken, helped along by the use of the Yak-3 components. The first aircraft was completed early in 1946 and first flew on the 24th April of that year.

After solutions to the expected teething troubles were found, the aircraft was accepted into service and production versions started to reach the Voyska PVO in early 1947. Generally the Yak-15 was well received at unit level, even though only 280 were built, and these only served with the VVS, unlike later Yak jets which were exported throughout the Eastern Bloc. All participants in the programme were only too aware that the Yak-15 was only a first step on the road to properly developed jet fighters however, and even before the prototype had flown the Design Bureau was working on its replacement, which was to become known as the Yak-17. The major difference between the two types was the adoption of tricycle landing gear, primarily to avoid the heavy ground erosion that had been experienced during take-off with the tailwheel Yak-15. There were also visibility advantages as the cockpit had to be located quite far aft due to the engine's nose mounted position. This configuration was tested on a single Yak-15U but the production Yak-17s were also fitted with the uprated Klimov RD-10a engine with 10% added thrust over the Yak-15.

However, at this point politics entered the field, with bizarre results. A.S Yakovlev was an original student of the MAI, Moscow Aviation Institute, and along with his contemporaries Tupolev and Mikoyan, became Professors there later in their lives. While primarily an academic institute, the MAI held great sway throughout the Soviet aviation industry, although it had no official influence on research programmes or funding. These factors were handled by the TsAGI, the Central Aerodynamics Institute, a fully Government run and funded organisation located in Zhukovsky, the Aviation City of the Soviet Union. Naturally the remit of the TsAGI covered the introduction of jet power to the VVS, and indeed to Russian civil aviation as well, although this took a lot longer to come to fruition, as it did in the West. Although outwardly both part of the Soviet aviation research effort, there was no love lost between the MAI and the TsAGI at this time, each believing the other was not taking the tasks seriously. The TsAGI of the time thought the industry, in the shape of the various Design Bureaux, was guilty of personality cults, whilst the ex-MAI Design Bureaux chiefs thought that the TsAGI hierarchy were far too influenced by Party doctrine to have a clear picture of the work required.

Reports of the Yak-15's service introduction were passed through to the TsAGI Jet Power Office, then headed by Academician Alexii Karsparkov, a man of great belief in his own talents, but who had very little time for anyone else, let alone heads of external Design Bureaux. Karsparkov had written numerous papers, both before and during WWII, all of which modified history to a greater or lesser extent, by inserting his own name over developments that were plainly those of others, or of his rivals as he saw it. At ground level these papers were largely ignored as the output of an ignorant and arrogant political figurehead, but at a political level Karsparkov had considerable influence as a Head of Department at TsAGI.

The limited performance of the Yak-15 was only too obvious with its maximum speed of 438 mph, and maximum altitude of 44000 ft. While the Yakovlev Design Bureau wanted to follow a slow and steady approach to improving these figures, an attitude fully
supported at regiment level of the VPVO, Karsparkov produced a radical and wholly untried 'solution' to the Yak-15's lack of performance by proposing twinning the aircraft!

This proposal mounted two Yak-15 fuselages on a short common wing centre section and using the outer wing panels from the standard aircraft. A new tailplane was to bridge the gap between the fins, and the standard landing gear was to be used on the outer wings, but only one main wheel, retracting to starboard, for the extra fuselage. This resulted in three main-wheels and two tail wheels, albeit located slightly asymmetrically. Apparently Karsparkov's 'calculations' showed that such a configuration would achieve '......a considerable increase in the speed of the aircraft with very little added cost'. Seemingly the added drag of a second fuselage did not have a high priority in his 'calculations'.

Needless to say this idea was greeted with scorn by Yakovlev, who continued guiding his Bureau on the path to their next step, the Yak-17. When he realised that his proposal was not going to be acted upon Karsparkov went into one of his infamous rages, apparently virtually destroying his outer office in the process, and he went directly to Moscow to request an audience with Stalin! Such was his reputation, and due to his earlier associations with Stalin in the '30s, that he got this without delay and he put the situation if front of the General Secretary, soliciting his support for what he saw as a great loss of face in the aviation field.

Stalin, not normally well known for his support of industrial theorists, came out on the side of his old comrade and issued an edict that the twinned aircraft be built forthwith! Karsparkov returned in triumph to Zhukovsky and promptly started issuing a barrage of memos to Yakovlev demanding action. With the sword of Stalin's edict hanging over him, Yakovlev had little choice but to comply and appointed a small body of men to carry out the design and construction of what became to be known as the Yak-15Db, 'twin' in Russian being 'dbojhoj' using an Anglicised spelling, thus the 'Db' suffix.

One extra 'inducement' supplied by Karsparkov was his proposed use of the 'Db' as a two seat trainer for the embryo Soviet jet fighter force, ignoring the large disparity in power/weight ratio and expected flight characteristics between the 'Db' and the standard Yak-15. In any case the Yakovlev Design Bureau was already involved in the development of what was eventually to become the singleton Yak-21 for this purpose.

In a small corner of the Bureau experimental hanger two previously flown Yak-15s were arranged side by side and jigged to the dimensions supplied by the TsAGI Office. The new build wing centre section and tailplane were rapidly produced and assembled, with the control runs of the two aircraft inter-connected by a system of bell cranks and sprung links. Yakovlev wanted all the flying control surfaces rigidly interconnected in such a complicated airframe but the TsAGI proposal included provision for one set of controls to still function if the other half had been disabled! This of course ignored the fact that resulting airframe would only have one aileron and one rudder connected to the controls. This was to prove a decisive factor in the aircraft's fate, as will be seen later.

The 'rival' airframe, the Yak-17, had its first flight in  June 1947, with the expected small increase in performance, and was greeted with satisfaction by most parties. When the report of this flight was delivered to Karsparkov, as the system demanded, he apparently set fire to it and flung it out of his office window! By this time the Yak-15Db was approaching its own first flight, and ground runs of the two engines caused some concern at the amount of erosion caused by the twin exhausts in close proximity to each other, and to the ground. However any and all objections were overruled by Karsparkov and the first flight duly took place from the grass field, flown by Yakovlev's Chief Test Pilot Piotr Stevanofskij, on August 18th 1947.

Stevanofskij's report on that flight has never been published, but it would seem that the TsAGI's sprung links, installed as part of the control redundancy proposal, meant the aircraft was extremely difficult to fly with any accuracy, and it was cut short after only some 10 mins. in the air. The aircraft remained on the ground for some weeks after that flight while the controls were firmed up, and other modifications made. Karsparkov grew impatient at what he saw as Yakovlev's slowness in moving the flight test programme along, and sent one of his own staff, Engineer Josef Privalov, to the flight test centre to act as a direct link back to TsAGI. For the first flight only the pilot's seat had been installed, in the port fuselage, but Privalov insisted that a second seat be fitted to the starboard cockpit so that he could monitor the flights himself. Yakovlev's thoughts on that idea have not been recorded but they can be imagined.

The modifications duly took place and flight tests resumed late in September, with Privalov acting as flight test observer. It was at this point that the flight test staff learned that Privalov had not flown at all previously, not even as a passenger, and as a result he suffered chronic air sickness during the flight and took very little part in the proceedings. Stevanofskij explored the flight envelope of the Yak-15Db over a series of 15-20 flights, but TsAGI's expected '..considerable increase...' in the maximum speed of the aircraft over the single fuselage Yak-15 was not observed. The 'Db' did exhibit a much better initial climb rate, and accelerated considerably faster, but the maximum speed was found to be only some 35 mph faster than the single engined version.

This increase was nowhere near the figures produced by Karsparkov in his 'calculations' and he immediately accused Yakovlev of not only sabotaging the aircraft's performance but also of drugging Privalov, and thus causing his airsickness! As Privalov had only flown in the RH seat for 4-5 of the test flights, Yakovlev the proposed removal of the starboard cockpit interior and its canopy to use the remaining space for an extra fuel tank. One of the problems exhibited by the 'Db' was its lack of range/endurance, due to the fact that it had twice the fuel burn rate of the Yak-15, but only some 27% more fuel tankage. The large starboard cockpit fuel tank would go a long way to solve that problem, but was also to prove a decisive factor later on.

During the winter of 1947 very little work was done on the 'Db', Yakovlev managing to fend off Karsparkov's threats of dire action by pointing to his urgent work on the Yak-23, then seen as the Soviet Union's main export fighter for its satellite states, which had flown in mid-1947 for the first time. But in the spring of 1948 TsAGI's power came to the fore again and a number of their engineers descended on the Yakovlev test centre to monitor the work programme that Karsparkov had deemed necessary. These tests included the functionality of the redundant control system idea, and despite Stevanofkij's misgivings these tests remained part of the programme. The test itself involved a remote link to the starboard aileron,elevator and rudder bell-cranks, which was supposed to be removed by the pilot while in flight. This left the starboard side controls free-floating while control of the aircraft was meant to be maintained by those on the port side. Yakovlev insisted that some means of re-connecting the controls be installed to ensure the survival of the aircraft and pilot and this was done, although the operation could not be guaranteed.

In late March 1948 Stevanofskij took off on the first flight to test this arrangement, and at some 12000 ft pulled the dis-connecting link that removed his control over half the aircraft. At first nothing happened, and pitch movements followed the control movements as intended. This was to be expected as the single elevator had bell-cranks on both ends, only one of which had been disconnected. A gentle left turn was also carried out successfully but on attempting  to level out Stevanofskij found he could not make the aircraft follow his commands. The down-going port aileron produced a large amount of adverse yaw and drag but without any corresponding input from the trailing opposite aileron the 'Db' refused to turn to starboard, although it levelled out.

Stevanofskij managed to produce some semblance of straight and level flight by large applications of rudder and by using differential engine thrust but the reaction time was very slow. The emergency re-connection system did not work as intended and after many lurches and swoops he managed to bring the 'Db' back to the airfield but the starboard landing gear leg failed on touchdown as ground effect induced roll could not be corrected in time, and the 'Db' ended up back in the hanger for repairs once more.

After some time, while Yakovlev tried to get others at TsAGI to stop the maniacal pressure he was being subjected to, the aircraft was readied for other tests, amongst which was maximum range flight to check the usable capacity of the new cockpit tank. Accordingly on April 22nd 1948 Stevanofskij once more climbed aboard the 'Db' and taxied toward the runway. He complained over the radio the aircraft was difficult to turn and that he was using the wheel brakes more than the rudder, but he did not seem too concerned, and started his take-off run. The Control Tower observed the 'Db' slewing across the grass much more than usual, but then it became airborne and the gear was observed to retract as normal.

However the expected turn downwind for a check run across the airfield did not occur and the aircraft climbed away to the North and vanished into the cloud. After some time Stevanofskij came up on the radio and reported he could neither bank nor turn the aircraft by any significant amount using the normal flight controls although he could climb and dive as expected. The engineering staff were summoned to the Tower and after some suggestions and questions diagnosed that the over-complex control linkages had been connected wrongly during the repair, and the rudders were acting in opposition to each other, while the ailerons, working as forward elevators, just acted as enhanced pitch controls.

The situation was reported to Yakovlev himself, who was providentially present at the test centre at the time. He talked to Stevanofskij for a while, and then told him to bail out as there was no chance of making a good landing, let alone returning to the centre. Stevanofskij descended to around 8000 ft, jettisoned the canopy and stepped over the side, leaving the 'Db' to its fate. However the aircraft then entered a gentle climb and the last the pilot saw of it was a twin smoke trail vanishing into the cloud as he prepared for landing.

The Yak-15Db's wreckage has never been found to this day.



Profile by ElectricBlue from original data from the Oranleed Collection at
http://oranleed.hp.infoseek.co.jp/collection.html

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In reality of course, Yakovlev was himself the 'political animal' of the Soviet aviation industry, having been a compatriot of Stalin prior to the 'Great Patriotic War' and he was made Vice Minister of the Aviation Industry between 1940 and 1946. He was well known for pouring scorn on the designs of other OKBs, and his political clout was almost certainly responsible for the cancellation of the superior Polikarpov I-180 which was in competition with his own Yak-1 at the time. As a result Polikarpov himself became a 'non-person' in the USSR and never designed another airframe from then onwards.

Yakovlev was made 'General-Colonel of Aviation' in 1946 after the award of two 'Hero of Socialist Labour' medals and no less than ten 'Orders of Lenin', as well the French 'Legion d'Honour' amongst many other awards. While he was indeed a member of the MAI his colleagues there hardly held him in high esteem as the result of all his political mischief making, and he was thoroughly despised at all levels. I didn't have to invent Karsparkov, I just transferred Yakovlev's attributes across to him.

As for the Yak-15Db, of course it happened for real, it's just that no-one's been able to find it yet............

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Model build is here :-

http://www.whatifmodelers.com/index.php/topic,23822.msg347150.html#msg347150

[The Rat]

As for the Yak-15Db, of course it happened for real, it's just that no-one's been able to find it yet............

Two words - Groom Lake. 

[PR19_Kit]

Two words - Groom Lake. 

Hehehe, I don't think even that cockpit fuel tank would be THAT big! 

[redstar72]

Greetings!
I found this old topic just now, thanks to Tophe's link: http://www.whatifmodelers.com/index.php/topic,20326.msg416494.html#msg416494. I like your twinned Yak-15, it is a nice-looking aircraft. It's sad that in your backstory, it was such a failure   .

But I must reply on this:

In reality of course, Yakovlev was himself the 'political animal' of the Soviet aviation industry, having been a compatriot of Stalin prior to the 'Great Patriotic War' and he was made Vice Minister of the Aviation Industry between 1940 and 1946. He was well known for pouring scorn on the designs of other OKBs, and his political clout was almost certainly responsible for the cancellation of the superior Polikarpov I-180 which was in competition with his own Yak-1 at the time.

This is no more than a myth, created in Perestroika years by some "historians" searching for dark mysteries and sensational exposures. Regarding I-180 - it was just an aircraft which killed two experienced test pilots during its tests, including legendary hero of thanspolar long-range record flight - Valeriy Chkalov who crashed during first I-180 flight at December 15, 1938. The other was Thomas Suzi, crashed with second prototype (I-180-2) at Seprember 5, 1939.

Also, I-180 completely wasn't superior comparing to Yak-1: they were absolutely equal. But I-180 was powered by M-88 engine, well-known for its lack of reliability: finally it was developed to reasonable conditions and was used on Il-4 bomber, but this task took a lot of time and was accompanied by many accidents. Also Yak-1 was armed with 20-mm motor cannon, while radial-engined I-180 had only machine guns - two 12.7-mm and two 7.62-mm. And finally, I-180 is usually reported to be "very similar to I-16" in handling qualities - but I-16 was very difficult in handling, only well-experienced and high-quality pilots could fly with it. Opposite to this, Yak-1 was simple and pleasant for handling. Almost all pilots liked it and its successors.

So... if You would choose between these two - what would be Your choice? Did Yakovlev need any "political clout", any intrigues, to beat this I-180?

To be correct - Yak-1 wasn't direct competitor to I-180. Enjoying absolute trust as a "King of fighters", Polikarpov obtained an order for I-180 design without any other contenders. Yakovlev's team and other, mostly new-established design teams got their orders for fighter designs much later - in middle 1939, when it became clear that I-180 - if isn't a complete failure - needs a lot of time to be developed into something reasonable.

As a result Polikarpov himself became a 'non-person' in the USSR and never designed another airframe from then onwards.

After I-180, Polikarpov designed: I-190 biplane fighter, I-185 fighter, TIS heavy escort fighter, ITP cannon fighter, NB night bomber (aka Aircraft "T"), BDP assault glider and its motorized version called MP. I mentioned only the aircrafts which were actually flown - there was also plenty of unrealized projects.

To my mind, just the work on so much and so different projects at the same time mostly involved Polikarpov's unsuccesses in his late years. Another cause was a chain of disasters. Two mentioned I-180 crashes were quickly followed with similar accidents with another Polikarpov design - SPB dive bomber; the first (April 27, 1940) killed 3 crew members, the next (July 30, 1940) another two. In this last accident, the aircraft fell to pieces in the air!.. I think, after all this, the designer's reputation would be spoilt inevitably - without any intrigues of any "evil" rivals.

And, of course, the Russian word for "twinned" is Dvojnoj (Двойной), vith second letter V - not Dbojnoj.

[PR19_Kit]

Redstar72,

Thanks for the clarification, but you have the advantage over me of living in the right part of the world to know these things.  

We in the 'decadent west' have obviously suffered from a 'dis-information campaign' put about to discredit Yakovlev for some reason.  

As for the Russian word for 'twinned', I couldn't find ANY translation for it anywhere, so I just did the best I could under my limited circumstances.