The Aero L-29 Delfín | Slow, Simple and Remarkably Successful

[00:00:12]Today we're taking a brief look at one of the most important training aircraft ever made. For decades, it was the pride of the Czechoslovakian aircraft industry. And no, I'm not talking about the L39 Albatross. I'm talking about its predecessor. You see, at the height of the Cold War, the pilots of the Soviet Air Force and many other Eastern block nations owed much of their training and sometimes the preservation of their lives to one machine, and that was the Aero Vahi L29.

[00:00:46]Hello and welcome back. My name is Christopher Rex Elen. I like to talk about planes a lot and today is the first video where I'm actually talking about a jet aircraft that entered production and was actually useful. It's only taken me nearly 5 years to get this far, but you know, your patience is finally being rewarded. Okay. And I'm sorry to disappoint a lot of you.

[00:01:06]Today's video is not on something like the F86 Saber, the P80 Shooting Star, the MiG 15, what have you. It is on a training aircraft. And that is because I firmly believe the L29 is wholly underappreciated for what it contributed to the training of pilots in Eastern block nations in the Cold War. It is basically responsible for the pilot training of most of the major frontline pilots that you would see in the '60s, '7s, and even to a degree going into the 1980s. This video also marks the first time where I'm testing out a new audio setup using a lav mic instead of my high sensitivity studio mic just to see if I can get a better balance between audio quality and also not keeping a giant microphone in shot. So, we'll we'll see how this sounds. You know, let me know in the comments if you think this audio is okay or if you want me to go back to the higher quality studio mic. Anyway, let's actually talk about the L29, shall we? The L29 was developed during a time when a lot of the world's air forces needed to upgrade their training fleets.

[00:02:08]Chief among them being the Soviet Union.

[00:02:10]By the mid1 1950s, a critical gap had emerged in pilot training. Student pilots were often learning on low-erformance piston engine aircraft like the Yak 18. But they were then required to transition directly onto higherformance training versions of frontline fighters like the MiG 15 UTI.

[00:02:30]This was understandably very dangerous.

[00:02:32]The performance and handling characteristics of the two types were simply far too different for it to be a safe progression and fatal training accidents were not uncommon. There was a desperate need for a dedicated jet trainer that could handle something known as all through training. This would take pilots from their first flights all the way through to intermediate levels of training which include weapons familiarization. They would then be able to more safely transition into final training into whichever aircraft that they would be operating in their frontline combat units. The Soviet Air Force eventually wrote up such a requirement for this training aircraft in the mid to late 1950s. Over time, this requirement was progressively expanded towards the goal of developing a jet trainer that could be easily adopted across the various national air forces that made up the Eastern Block. Now during this time the Czechoslovakian air force had also been developing their own requirements for an all through jet trainer. This led to a private venture with engineers working with the Czechoslovak Aviation Research Testing Institute VZLU and the manufacturer Eero Vodi. Zeny Grublich and Carol Tomsh were the original designers behind what would become the L29, but they would retire before its completion, and the design and development of the L29 would be finalized by another engineer by the name of Yanville. Their design philosophy prioritized simplicity, ruggedness, and ease of control. Their goal wasn't just to produce a safe aircraft that was easy to fly, but also one that would be easy to manufacture in large numbers economically. The result of their efforts was the prototype XL29 completed in the spring of 1959. It immediately showed all of the hallmarks of a promising jet trainer. The mid-mounted main wings were unswept.

[00:04:21]This was to improve stability, but also to make them easier to massproduce. It also had the added benefits of allowing the air intakes to be installed in the wing roots that would feed the centrally mounted engine in the rear of the fuselage. Ease of control was a major priority as loss of control accidents was often the number one cause of fatalities among young pilots training up in various air forces. Slotted flaps were used for both takeoff and landing.

[00:04:47]The ailerons used aerodynamic compensation to reduce roll forces and the landing gear was reinforced to absorb the hard, unsteady and sometimes panicked landings of various inexperienced pilots. But the standout aerodynamic feature of the L29 is its T-shaped tail, which and correct me if I'm wrong here, is unique among mass-produced and dedicated jet training aircraft. By keeping the horizontal tail surfaces in clean air high above the wake generated by the wings, it makes the elevator far more effective during a spin. It also prevents the elevator from shadowing or blocking the air flow going over the rudder, which makes spin recovery far easier. Tata of course have their own drawbacks over a more conventional tail layout. They can be a bit more difficult to maintain and service, but more importantly than that, they do have a major aerodynamic drawback. At high angles of attack at high speed, the main wings can block the air flow going over the tail, which can lead to a deep and dangerous stall. This is something you don't really encounter with conventional tail layouts, which is why you'll see a lot of very highly maneuverable aircraft not featuring this particular layout of tail design.

[00:06:04]However, the L29 would need to be pushed far beyond its intended performance envelope for this to be a risk. And because of that, the TTL was kept. Ease of maintenance was of course another major priority when they were designing the L29. And because of that, the airframe was covered with panels that could be easily removed to access critical internal components. On top of this, the fuselage was designed to split in half behind the wing, allowing the rear section to be rolled away on a special trolley for the engine to be able to be easily accessed. This was a feature that was inspired and borrowed by the training version of the Mig 15 then in Soviet service. Now speaking of the engine, the Czechoslovak air force was reluctant, shall we say, to rely on Soviet licensed-built turbo jets for a number of reasons, and they had invited the engine manufacturer Motolet to produce a domestic alternative. This resulted in the Multilelet M701, which was designed specifically with this new jet training aircraft in mind. This was a single stage centrifugal flow turbo jet generating a maximum thrust of approximately 1,900 lb. It ran successfully for the first time in 1958, but it was still expected to be in testing when the first prototype aircraft was due to be completed. To avoid delays, therefore, the XL29 was completed with a different turbo jet, the Bristol Sidley Viper, and it made its first flight with this engine on the 5th of April 1959. The next prototype, not counting a static test airframe that was built as the second, also carried the Viper engine. But in July of 1960, the Multilelet engine powered the third flying prototype successfully. With this, Jacos Slovakia had finally freed itself from relying on foreignbuilt turbo jets. And from that point on, it became the exclusive power plant for the Aero L29. It was also around this time that the L29 finally received its nickname of Delphin or Dolphin, which soon became its official moniker. And when you look at it from certain photographic angles, it's really easy to see why they picked this name. The front end of it really does look like the head of a dolphin. With its intended engine now installed, the L29 would go through a period of accelerated testing. This was because the Soviet Union had announced a competition that would select the next generation of military training aircraft for the entire Eastern block and Arrow had been invited to submit their promising prototype for consideration. On the whole, the flight tests went smoothly, but they did result in some minor changes. Perforation holes were added to the air brakes, which had a nasty habit of causing severe vibrations when deployed, which was not ideal. and the PTO tube was relocated from the tail to the wing. This was because it was giving incorrect readings during sharp aerial maneuvers. In 1961, after completion of its initial testing, the third flying prototype was flown over to Moscow. There it would enter into a grueling two-month evaluation against two other competing prototypes for the new Eastern Block jet trainer.

[00:09:18]These were the Soviet built Yakavev Yak 30 and the Polishbuilt PZL TS11 Iscra.

[00:09:25]These trials were sophisticated and exhaustive, overseen by a commission with representatives from all three of the participating nations and headed by Soviet Lieutenant General Mattv. The aircraft were evaluated for their performance, handling qualities, technical complexity, ease of tactical readiness, ergonomics, ease of maintenance, the time required for engine replacement, ruggedness, rough field operations capacity. The list went on and on. The whole thing was treated very seriously. Indeed, the competition put the prototypes under more scrutiny than the evaluations of the supersonic MIG 21 fighter. This was after all going to determine the future of aerial training for most of the Eastern Blocks fighter pilots. It was a big deal. At the conclusion of the trials, the Yak 30 was quickly eliminated from consideration. It was built more like a racer rather than a trainer and it didn't offer the balanced or forgiving handling qualities that were required.

[00:10:28]That left the Aero L29 and the PZL TS11.

[00:10:32]Now depending on what sources you read, each aircraft is claimed to have outperformed the other, which of course is impossible. In truth, both had their merits, and both met all the requirements to which they had been built. But after due consideration, it was the L29 that was selected as the overall winner. This was on the grounds that it was considered to be more reliable, durable, and easier to maintain along with having superior handling on rough and unpaved runways.

[00:11:06]In terms of performance, it also had lower stall and landing speeds, and it required a shorter length of runway for takeoff, all of which were very valuable qualities for a trainer to have. But all of that being said though, the true reason for its selection was most likely political. The decision was heavily influenced by the goal of integrating the various aviation industries of member nations of the Council for Mutual Economic Assistance, also known as Comic-Con. To prevent the Czechoslovakian aircraft industry from stagnating, it had already been decided that Czech factories would be given the responsibility of producing the new training aircraft regardless of who won.

[00:11:46]Thus, selecting the L29 not only ensured that production lines in Czechoslovakia would remain active for years to come, but it also meant that production could start pretty much immediately, as the Aerofactory had already toled up for the purpose of building this airframe. The Poles did not take this decision well.

[00:12:07]Despite the commission's clear recommendation for the L29, the Polish government rejected the results and chose to proceed with the TS11 ISCRA for its own air force, both to save costs and to continue developing its domestic aviation industry. However, all the other Warsaw packed nations would follow the recommendation and they would soon adopt the L29 as their primary trainer.

[00:12:30]The result would be the largest aircraft production plan to take place in any Comic-Con nation outside the Soviet Union. During its 11-year production run, a total of over 3,660 L29 trainers would eventually be produced. It also resulted in a major production program for the Motolet 701 Turbo Jet. Over 9,000 would eventually be produced with at least 5,000 being delivered purely in support of L29 production and servicing. To this day, the L29 is still the most produced dedicated military jet trainer in the world. The only other trainer that was built in more numbers was the Locked T33, but that was a conversion of the F80 Shooting Star and not designed as a dedicated trainer from the outset. The L29 was produced across 42 production batches or series, eventually incorporating over 45 modifications and changes. Beyond serving the Warsaw Pact, the Delphin was exported widely, serving with countries including Egypt, Syria, Iraq, Afghanistan, Indonesia, Nigeria, and Uganda. In terms of overall production, the majority of the aircrafts built would be of the standard L29 configuration, but there were a few exceptions. The L29A, standing for Acrobat, was a pet project by some of the more enthusiastic engineers at Arrow who wanted to see just how far the airframe could be pushed. Only two of these would be built, one converted from the third prototype and then one dedicated airframe. They would spend their time participating in various international engineering fairs and wowing western audiences at the 1969 Paris Air Show. The only true subvariant of the L29 would be the L29R.

[00:14:24]It was developed as a tactical reconnaissance aircraft intended for operations near front lines. Its primary modification involved the installation of a container which would hold photo reconnaissance equipment and multiple downward-facing cameras. And this would be installed in the location where the rear cockpit usually was. Now, while some records indicate that the project to develop this was terminated in 1965, other sources state that it was produced in a small series, specifically within the 18th production batch of the L29.

[00:14:58]This is supported by Czech documentation and there is strong evidence as well that a batch was exported to Egypt. In general, the L29 saw an incredibly long and active service life. The Soviet Air Force was the largest operator, receiving approximately 2,000 units to replace their aging fleet of trainers, as well as the training variants of the MiG 15. The perception of the aircraft by those who flew it was overwhelmingly positive. Soviet pilots and instructors famously used car analogies to describe its quality. They compared the smooth handling of the Delphin to a vulgar automobile, while older planes like the Yak 18 were likened to a primitive Mosvich and the MiG 15 to something called a Porba. I think that's how I pronounce it anyway. Soviet instructors especially praised the aircraft for its handling. It was described as being both forgiving and dosile and it was capable of tolerating many student errors that would have been fatal in less stable airframes. This sentiment is reflected elsewhere as well. In Czechoslovakian service, the aircraft was affectionately known as the flying pram because of the comfort and security that it offered instructors as their babies made their first tentative ventures into the sky.

[00:16:17]According to them, a cadet could be ready for a first solo flight after around 13 hours with an instructor. It was not a machine designed to impress experienced pilots, but it was apparently very good at preventing the inexperienced ones from killing themselves, which was perhaps the most useful quality you would want to find in a trainer. Now, as it often happens, as the type matured, its role was sometimes expanded from training to direct combat operations, and this had mixed results.

[00:16:49]Egyptian L29s were used for strike missions against Israeli ground forces during the Yom Kapur war, and the type saw active service during the Nigerian civil war. However, its combat limitations became clear during the first Nagorno Carabach war, where Azeri forces would lose some 14 out of 18 aircraft to Armenian anti-aircraft fire.

[00:17:12]The trainer's slow speed and lack of any real armor protection made it highly vulnerable in high threat environments, and it was only ever really used successfully in combat in situations where it was able to enjoy the protection of aerial superiority. By the early 1970s, the L29 was already being succeeded by Arrow's more capable L39 Albatross. Nevertheless, the Delphin remained in military service with some operators for decades, often flying alongside its replacement. Some were still registered as active military aircraft at the beginning of the 2020s.

[00:17:48]Following the end of the Cold War, large numbers of surviving L29s would fall into private ownership. there. The same qualities that had made it appealing to military flying schools, simple handling, sturdy construction, and straightforward maintenance made it a popular civilian jet and an air racing aircraft. Today, the L29 is still flying at air shows, the occasional flight school, and even for research purposes.

[00:18:14]In 2007, an unmodified L29 made history by completing the world's first jet flight powered solely by biodiesel. And three other aircraft are still in active use with American universities, mostly for high dynamic flight research. And that is 65 years after the type first entered service. That is a fantastic testament to a well-designed airframe.