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The YAK-41: The Soviet Attempt at a VTOL Aircraft

Our story today begins on a sunny July day, the year is 1960 and the location is a small town called Farnborough, England- the home of an internationally renowned Airshow and the site of the first public demonstrations of the West’s newest stride in the field of aviation. A fully functional VTOL jet called the Short SC-1 which, at the time, was serving as a proof of concept for the soon to follow- Hawker Harrier jump jet. On this day a large crowd of spectators is watching, astounded by its apparent ability to take off like a helicopter and fly like a jet. Of all the people to be present in the crowd that day the last person you might expect to see would be a high-ranking Soviet official. However, that is precisely where Mr. Alexander Sergeyevich Yakovlev found himself on that July morning. Watching with the rest of the crowd at this astounding feat of engineering.

Soviet aircraft designer Alexander Sergeyevich Yakovlev

As the founder of the Yakovlev Design Bureau, this spectacle must have meant something significantly different to him, than to the other spectators around him. After all he was a soviet citizen, and this was the height of the cold war. He was fully aware of the military applications of such an aircraft and to him it could represent just another step closer to utter destruction. On the other hand, he was an engineer and where some Soviet leaders saw a threat, he saw a challenge and a significant development in his own field. Whether this moment inspired fear or simply inspired him we don’t know. What we do know is that it would drive Yakovlev for the next two decades in his attempts to develop a soviet VTOL jet and though he didn’t know it, he would end up creating a design that would serve the Americans better than it ever served the Soviets.

The YAK-36

Upon returning to the Soviet Union, Yakovlev would immediately set about designing his new Soviet version of this jet. Though the soviets were aware of the West’s VTOL program, they showed little enthusiasm for creating a comparable jet of their own. However, Yakovlev went ahead with his development and only a year later would end up convincing the Soviet leadership of the serious potential that would come with a fleet of VTOL capable jets. Leading them to issue the Yakovlev Design Bureau with a directive to produce a single-seat fighter/bomber jet. Giving it the provisional, in house designation of YAK-V. And that ‘V’ doesn’t mean 5 it is short for vertikal’nyy (вертикальный). Why am I telling you this? No reason other than I like to leave Simon pronunciations of increasing difficulty with every script I write.

Anyway, this new directive stipulated the following requirements: the jet could be no heavier than 9150 kg, capable of supersonic flight, able to carry a payload of 500kg and fully capable of vertical take-off and landing. This was no small task even for someone like Yakovlev who had taken a natural interest in VTOL flight long before the project had even begun. This job was made all the more difficult owing to the Soviet Union’s distinct lack of any engines capable of thrust vectoring (which simply means having engines that could point both downwards and horizontally) nor the power delivery needed for Vertical take-off and landing.

If you will recall from the first video of this series the development of the Hawker Harrier could only begin once a jet engine powerful and capable enough to produce the necessary thrust was developed, that being the Rolls Royce Pegasus engine. But as the old saying goes, necessity is the mother of all invention and when you live in the USSR you had better believe that you were gonna make your government issued directives, lest you end up in the Gulag. And so, in that spirit, Mr. Yakovlev came up with the tadpole configuration of engines. Simply put this was two R27-300 Tumanskiy engines, set side by side with two adjustable nozzles attached to the exhausts. These engines would be placed on the forward portion of the jet so as to ensure that when the engines were in their downward position any thrust produced would be directly along the jet’s center of mass. Why is it called a tadpole configuration? No idea.

This was about as simple a solution as you could get and it came with its caveats one of which was a serious lack of stability, to understand why this is we will use the Harrier jet as a comparison. First off, the center of mass is a theoretical point within an object that simply notes the point at which an object can balance without tipping or tilting, unless acted upon. With regard to our current topic consider the Harrier which had 4 separate exhaust nozzles, 2 in front of the vehicle’s center of mass and 2 behind it which provides a much larger platform on which to rest. Compared to the YAK-36 which had only 2 supports both which rested directly on the center of mass, it meant any small fluctuations, like say a gust of wind, could greatly destabilize the system. A good way to visualize this is to get something like a ruler and hold it out in front of you with one finger supporting either end. (maybe Simon could demonstrate?) This would represent the Harrier, now try to hold the ruler up with just one finger. You can see how difficult this would be to control in a jet.

The solution to this instability problem was to use something very similar to what we have already seen on the Harrier jet. And this was to set a reaction valve on both wings, the tail and the nose of the jet and use this as a means to control and direct the jet while in vertical flight. However, with the jet engines being so far forward the engineers had to rely on a bit of mechanical advantage to ensure the valve on the nose was strong enough. You will see what I mean in a moment.

After only 2 years of development the Yakovlev Design Bureau released something resembling a finished product in the form of the YAK-36. Unfortunately, this jet would meet a premature end during the testing phases. With only 4 jets ultimately being produced.

The final product of this development process was a pretty strange looking vehicle with 2 enormous, circular air intakes beneath the body and a conspicuous pipe protruding from the nose (this is what we meant by mechanical advantage). It also came with a particularly unusual feature, due to the instability of the vehicle when in vertical flight and the uncertainty as to whether or not it would even be able to consistently transition from one flight mode to another, the engineers made the decision to incorporate a proprietary automatic ejection system into the jet. If the jets onboard systems detected a sharp change in pitch during VTOL mode, the automatic ejection sequence would be activated, in which the pilots’ hands would be yanked from the throttle and stick and forcibly restrained, after which the jet would automatically eject the pilot regardless of whether they wanted that.

After several months of testing and 2 significant crashes, the program for this jet was cancelled. However, this was not the end of the line for Yakovlev or his jets, as we will soon find out.

The YAK-38 and Yak-41

With the program meeting a premature end it would be easy to think that this jet had been a complete failure for Yakovlev, however the Soviet Navy, who had originally resisted the idea of a VTOL jet, were impressed by the YAK-36 (who knows why?) and now saw it as a potentially feasible concept, given another round of development.

And so, on the 27th of September 1967 The Yakovlev Design Bureau was given a second directive to develop a new VTOL aircraft but this time it would be solely an attack aircraft. Now with a little more time available for development, Yakovlev could devote a lot more time and thought into the mechanism upon which this new jet operated. At first development focused on perfecting the tadpole design, however after much discussion it was eventually decided to use a different power plant configuration, electing, this time, to go for a mixed power plant design.

What that means is that instead of having two engines with variable thrust vectoring, as we have seen in the likes of the Harrier and the original YAK-36, they would have a set of secondary engines installed specifically for vertical lift and one large primary engine at the back, that would have a variable thrust vector. These secondary engines would be detached from the rest of the system in regular flight and would only become activated when carrying out a VTOL maneuver.

Now that might seem a little familiar to those of you who have already seen our previous video on the F-35 lighting. Which, if you haven’t, I would suggest you give it a watch as it is truly an amazing video and contains some of the best writing available on YouTube, possibly anywhere and whoever wrote that script deserves a raise.

Anyway… yeah, that engine configuration had a large resemblance to a certain US jet, but we will get into that a bit later. For now, development was going ahead on this new configuration and by early 1970 the first prototypes were in production, with the first completed test flight being carried out in 1971. After several more years of testing and tweaking the final designation YAK-38 was applied and the jet went into production.

Yak-32 Take off
Yak-38 by Vladimir Rodionov is licensed under CC-BY-SA

Seeing this new jet, it is difficult not to notice the similarities it shares with the Harrier; however, those really were only skin deep, in fact the previous generation, the YAK-36, shared far more in common with the Harrier with regard to engine design and operation. This new jet may have looked similar to the harrier, but its engine operations were, in some ways, many decades ahead of the Harrier and in other ways were many decades behind, more on that later. Suffice it to say that this jet was capable of supersonic flight, a feat the Harrier was originally supposed to accomplish but never did. This jet was also far more dangerous than the Harrier… Dangerous to the pilot that is, there was a reason why the British elected against using the mixed power plant design.

The issue was that, on a fundamental level, jet aerodynamics do not suit three-dimensional travel. In other words, you can travel efficiently in one direction or the other but not both. The best way to understand this is to think about an engineer designing a conventional jet. They will know what direction the air will be coming from and they will make the jet as aerodynamic as possible in that direction. That process unavoidably makes the aerodynamics in every other direction awful. Think about looking at a jet from nose point on and then from a top-down point of view, two very different silhouettes. In a conventional jet that isn’t an issue but, in a VTOL; you start to see the problem.

Now pretty much all vertical maneuvers don’t need to be made at speed, so the efficiency here is not the issue, the real issue is that the jet, which needs to be very narrow in order to reduce resistance in forward flight, does not provide a lot of space for installing a jet engine that would be pointing at the ground. Any engine that you could fit in that area would have to be tiny and would produce a minuscule amount of thrust relative to the amount needed to lift the jet off the ground. The Harrier avoided this issue with the use of one huge engine with adjustable nozzles, this way it could take advantage of the lateral space available to it.

Only now are we even coming close to the kind of technology that would allow a powerful enough jet to be packed into that small a space and Soviet Russia way back the 1970’s they most definitely did not have that available to them. The solution, it seemed, was to use two jet engines for lift and make the main jet engine able to adjust its angle to assist with the remainder of the lift. This engine gimbal feature would be no small feat either and would require a very precise and complex bit of engineering, but it was achievable, and they did achieve it, however even though they now had the main engine adding to the lift, those smaller engines would still have to be pushed to their absolute limit in order to meet the lift requirements.

So, tying this whole tangent back together- those over strained engines had an unfortunate habit of simply cutting out when under significant stress. It just so happens that these moments of significant stress also occurred at times when you needed the engines to work most, like when you were coming into a landing at a faster speed than usual. Owing to the fact that this would be happening at high speed these accidents would occur too fast for the pilot to react. Thankfully Mr. Yakovlev had a solution to this, remember that trusty automatic ejection system? Well after several years of development they weren’t as temperamental as they had been in earlier models and they were probably put to better use as well.

You may also be surprised to hear that this was not even the biggest issue with the jet, that prize goes to its inability to perform in certain weather conditions. It’s a simple fact of jet engine design that cooler air increases engine efficiency and warmer air decreases it. As with most jet engines, the goal is to push that threshold up as high as possible to make the engine as efficient as possible in all conditions. However, with those overworked lift engines there wasn’t much room to improve the efficiency. In fact, that threshold was so low that, during the summer months the jet would frequently be incapable of carrying out a vertical take-off unless completely stripped of its weaponry. And when the Soviets went to war in Afghanistan the jet was completely incapable of taking off at all.

Despite this, the Soviet Navy ordered a total of 200 of these jets during the entire production run of the aircraft and throughout this time the jet served its purpose well… As long as the sun wasn’t out. In one of the more memorable incidents regarding the YAK-38, a pilot was carrying out a routine vertical take off when the jet malfunctioned and automatically ejected the pilot, there was, however, nothing wrong with the jet and it simply continued to rise, without the presence of the pilot, eventually crashing into a farm building. It is unclear if anyone was killed in the crash but this being Soviet Russia, we can be pretty certain that if the owner did survive, they were probably sent to the Gulag for building their farmyard in the way of a government crash site, or perhaps he was just breathing too loudly.

Despite these minor issues, the jet was kept in regular use by the Navy for 15 years, and seemingly happy with the jet’s performance, they put in another request for the Yakovlev Design Bureau to create a second more modern version of the YAK-38. Shortly after the request was accepted however Alexander Yakovlev died in 1989, never seeing the end of this final development. But the show must go on, as they say, and by 1991 this new jet, given the designation of YAK-41 was nearing completion.

They had done away with the large ovular air intakes and opted instead for the classic square intakes, similar to that of the Russian MIGs. Everything seemed to be going smoothly, they were almost ready to begin testing when a small hiccup occurred in the form of the Soviet Union collapsing. Overnight all demand for weapons manufacturing and development disappeared and that was the end of Russian VTOL program. But not the end of the YAK-41.

A second life

Ok, so you know the old saying, “the enemy of my enemy is my friend”? Well, that has nothing to do with this. However, we are going to explain all of those hints about the American’s finding use from the YAK-41. Because once that Iron Curtain fell on the 26th of December 1991, a certain US based jet manufacturer got word of a certain Russia based Design Burau that just so happened to have a great deal of research and knowledge on a certain VTOL jet engine configuration. It also just so happened that this Russian company recently lost their entire revenue stream and was trying to find a way of not going bankrupt.

We are of course talking about Lockheed-Martin, specifically a small development team in the world-renowned Lockheed Skunk Works, who were working on a jet called the X-35, which if you saw our previous video, would later become the F-35 Lightning, America’s flagship jet. In a deal of around $300-$400 million the Yakovlev Design bureau agreed to provide Lockheed-Martin with 3 jets and vital research in the design and operation of that kind of an engine layout.

The YAK-41 was just another evolution on the previous YAK-38, better tuned, with more efficient and most importantly, more reliable lift engines. This new iteration also had a radar system which was a feature the previous generation lacked and most significant of all, its design criteria had been altered. Originally an attack aircraft the jet had become solely focused on air superiority and defending the Soviet naval fleet.We don’t really know how well the YAK-41 actually fulfilled these requirements and it didn’t really matter because that was not what Lockheed-Martin was interested in, no, Lockheed Martin was interested in the how the Yakovlev Design Bureau had managed to engineer their lift fan and vectoring engine configuration.

And you can see just how much of an influence this jet has had on the F-35 today, with that weird moving engine exhaust being one of the jet’s most recognizable features. Depending how you look at it, this jet was either a partial success or a complete failure. It was inefficient, unsafe, and incapable of even taking off in certain conditions, however despite all of that it was still the first jet capable of surpassing the speed of sound and then carrying out a vertical landing all in the same journey, no small feat and whether Yakovlev would like it or not, his jets engine design would become a crucial mechanism in America’s premier military jet.

It’s difficult to know whether Yakovlev would’ve been happy with the fate of his life’s work, he undoubtedly had a love for engineering and the development of jet aircraft in general but he was also a soviet citizen and a profiteer of the cold war. Over his many years of service, he distinguished himself and was the recipient of a great many awards from the Soviet state, so he was clearly at the very least, supportive of the Soviet regime.

When you look at it like that, it’s pretty easy to conclude that Yakovlev would not have been happy with his life’s work in the hands of his enemies, however, that’s maybe not looking at the whole picture.

Consider this: would you say the YAK-36 was a success or a failure? Perhaps it was a failure, it certainly lacked in some crucial aspects, like safety and simple operational effectiveness. But perhaps it was a success, not in the ways that would matter to military personnel but would matter to someone who took value in advancements in engineering, such as Yakovlev. Few jets from that era still have their technology in the machines of today, let alone being a fundamental part of the most advanced jet of our time. In the same way, concluding that Yakovlev would have been unhappy with the fate of his work perhaps does not take the whole situation into account and overlooks one of his most significant traits. That being the fact that above all else he did not want the world to end in a nuclear holocaust.

Despite how the media might depict the Soviet Union and its inhabitants, they were just as opposed to a nuclear war as any average western citizen. From this we could conclude that Yakovlev would just be glad that the world of the future was not a baron nuclear wasteland, a fact that I think we can all be pleased about.

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