Why the F-35 Engines (F135), which can transform the MMU Kaan into a Fifth Generation Aircraft from the Scratch, Should be Used in New Prototypes and Mass Production Aircraft?

Is the First Flight of the MMU Kaan Something to Underestimate or Overestimate?

The National Combat Aircraft (MMU) Kaan is a promising, albeit prototype, platform that will take Turkey into the league of countries producing modern fighter jets. There is no doubt that the development and subsequent production of a fifth-generation aircraft is inherently costly. Turkey sees this gigantic project as a 'state project'. Despite the high cost and technical complexity it entails, at the Defence Industry Executive Committee (SSİK) meeting on January 8, 2015, the current political authority took ownership of the project and decided to proceed with the option that offers the highest range of capabilities of the options, but at a higher cost than the other two options: the twin-engine Lockheed Martin 'airframe structure' option. I believe that this decision is vitally important as it shows that Turkey has the will to finally realize the slogan of "build your own aircraft".

The operational requirements and concept of operations for the MMU Kaan are in line with the internationally defined criteria for fifth generation fighter aircraft. At the end of the day, the Air Force expects and should have a fifth generation MMU Kaan. The aerodynamic structure of the aircraft, the wing planform (the silhouette of the wing when viewed from above or below) were designed using 'digital design' tools and calculations performed on super-fast/powerful computers. When necessary, three-dimensional prototypes were produced. At the same time, each of the resulting fuselage options was tested in wind tunnels rented abroad on an hourly basis, giving the final shape to the aircraft we saw flying on February 21. I therefore believe that the radar cross-sectional area of the aircraft will be low enough to meet the fifth generation stealth requirements. 

Nevertheless, I do not think it is right to claim that Turkey has produced the world's best fighter jet, or vice versa, to downplay this achievement by referring to the fact that a platform that is still in the prototype (development) stage has successfully made its first flight. I would like it to be known that I am especially concerned that this issue is being reduced to the banality of 'chewing gum' that is chewed daily in the political arena. 

There is indeed an important achievement that cannot and should not be underestimated. However, the road ahead is long and arduous. The key is patience, perseverance and hard work. Each of us should see this great project as a state project, and we should be able to discuss everything as much as possible on a supra-political ground, without denying our own realities, and with an 'impartiality' that is free from ideological and political concerns and expectations, in order to serve the purpose of developing a better platform. If we can do this sincerely, as Namık Kemal so eloquently put it, I have the conviction and belief that we will be able to develop the best fighter aircraft we need for our national defense as a result of the clash of our ideas.

MMU Kaan's Flight Test Process Just Begins 

Of course, design verifications will be made through flight tests to be carried out with the prototype aircraft, which will be 8 in total, and design deficiencies will also be revealed, but these deficiencies will definitely be eliminated with revised designs and the road will continue.

In 2028, TAI will produce 20 MMU Kaans in the 'F-16+' scale and deliver them to the Turkish Air Force. At least this is the stated goal. However, the main problem here is that not even prototype aircraft have been produced yet, and even the flying platform was not actually produced to fly, but is known to be 'flying' as per the decision taken on January 7, 2023. TAI has somehow set aside its original plans and 'strengthened' the platform that will not fly and made it fly. In my opinion, flight tests will not be continued with the prototype named "P0 Star", which flew on February 21, and perhaps it will remain within the envelope in which it first flew, and will make 'demonstration' flights from time to time. Beyond this, I would like to express that I find it risky to conduct a real flight test activity with this prototype. 

When should the MMU Kaan Serial Production Decision be taken?

TAI management will definitely show the necessary will to produce new prototypes and start flight tests as soon as possible. However, this is a process, and it has its own defined schedule and time management. Moreover, even the production of 8 prototypes means mass production in a way. If 20 aircraft are to be delivered in 2028, flight tests must be completed by 2026, and at least the flight envelopes must be opened to the envisaged altitude of 55,000 feet and a speed of 1.8 mach. I would like to share with you that I have read between the lines of the news about MMU Kaan and official statements that a decision on 'mass production' will probably be taken before the flight tests are completed.

I find the decision of 'mass production' to be taken before the flight tests are fully completed risky. The mistake made in Hürkuş in this regard is obvious. In 2018, we should act with the awareness of why 15 Hürkuş aircraft were (not) taken into inventory by the Air Force. Aircraft development and production processes have a 'playbook' that must follow its own course. The rules are clear. As long as these rules are followed, we may be a little delayed in time, but we will definitely produce a 'proper' aircraft. The Hürkuş, whose deliveries should have started in 2018, is not even on the serial production line as of 2024, despite the fact that six years have passed since then. Moreover, Hürkuş is a relatively low-cost project. If every step is not taken according to the book in an $8 billion project like MMU Kaan, we may have to bear a few billion dollars of extra costs at the end of the day.

In this respect, at least South Korea's KF-21 flight test process can be taken as an example. The KF-21, which made its first flight in 2022, and whose flight tests have been largely completed with a total of six prototypes, has now reached the stage where a mass production decision is being taken, according to South Korean defense authorities. Based on this example, I believe that Turkey will be able to make a decision on serial production in 2026 at the earliest. I hope that this serial production issue will not be rushed, and that the devil will not be involved.

Are the two 35,000-pound engines envisaged for MMU Kaan sufficient?

MMU Kaan will be the world's largest fighter aircraft in terms of size. The fifth-generation fighters closest in size to the Kaan are the Su-57 and the F-22. The J-20 is also close in scale. When we look at these four aircraft, the maximum take-off weight of all but the Kaan is in the 77,000-80,001 pounds range. According to open source information, the maximum take-off weight for the Kaan is 70,000 pounds. The twin-engine Kaan is expected to perform at the level of the single-engine F-35A. Because the maximum take-off weight of the F-35A is 69,999 pounds. I do not think it is right to take the F-35A, which has a 43,500-pound (191 kN) Pratt Whitney F135 engine, as a reference for the Kaan. It can be said that "For now, each of the engines we have can produce 29,400 pounds of thrust. For this reason, we are limiting the Kaan's take-off weight to 70,000 pounds for the near term. However, in the future, when we produce 35,000-pound engines with TR Motor, our maximum take-off weight will increase to an F-22-like weight, 80,000 pounds..." While I understand this approach, I would like to express that I do not find it very correct.

The Kaan has a profile that is very similar to the F-22A Raptor in terms of its external appearance. The Kaan has an aluminum nose and titanium mid-fuselage, and its surfaces are apparently covered with lightweight, low radar reflective composite carbon thermoplastics, using the capabilities gained during the F-35 production partnership. Although it is not ready yet, I believe that the internal weapons bay under the fuselage will be able to carry air-to-air missiles, SOM-J and similar modern ammunition. I foresee no major problems in the production of modern sensors, including the AESA radar and EOTS (electro-optical targeting system), over time. This is because TAI's leading subcontractors, including ASELSAN, have been involved in the F-35 production process in one way or another, partly as part of the sensors and/or systems they are currently working on. Therefore, we can say that they have had the chance to 'learn' something, albeit to a limited extent beforehand. Therefore, I believe that there will not be any major problems in terms of sensors, and even if there are, I believe that possible problems that may arise can be easily overcome over time with a 'learning organization' culture, as in the case of ASELSAN CATS.

However, I fear that the engine issue will not be easily overcome. I am one of those who consider the selection of F110-GE-129 turbofan engines (also used in F-16 fighter jets), an engine known to the Turkish defense industry, for the MMU Kaan as a necessity at the prototype stage. However, it is understood that these engines will continue to be used in the serial production phase, and that a 'decision' has been taken in this direction. The fact that the F110 engine is a fifth generation engine that is not optimized for low visibility is the biggest handicap for the MMU Kaan. It is the biggest obstacle to the transformation of the aircraft into a fifth generation aircraft. I find it inconvenient and problematic to start with this 'handicap' at the very beginning.

Why Don't We Consider Using the F-35 Engine Instead of the F-16 Engine in the MMU Kaan?

The second problem with the engine is that the engine power targeted with the TR Engine is 35,000 pounds. The aircraft type taken as a reference for MMU Kaan seems to be the twin-engine F-22 Raptor in general terms. F-22s also use engines of 35,000 lbs each, but optimized for low visibility. On the other hand, the F-22 was originally developed in an air defense role, claiming air superiority. Later, a limited number of air-to-ground munitions (2 GBU-32s of 1,000 pounds and 2 GBU-39s of 250 pounds) were integrated into the F-22. In this respect, the F-22 is still far from being a multi-role aircraft. It has a relatively low maximum take-off weight for a multi-role aircraft. Therefore, its two 35,000-pound engines may be sufficient for a maximum take-off weight of 80,000 pounds.

On the other hand, Kaan is a multi-role aircraft by design. There is no other option other than multi-role under current conditions. After our exclusion from the F-35 program, the Kaan was supposed to evolve into a multi-role aircraft rather than an air superiority fighter, and it has done so. In the foreseeable future, the Kaan will constitute the fighter backbone of the Turkish Air Force. From this point of view, I foresee the maximum take-off weight of the multi-role MMU Kaan to be approximately 100,000 pounds, together with the capabilities to be acquired in the future. The engine, which is envisaged to be developed with the TR Engine, will be based on China's fifth-generation fighter J-20 engines, instead of the 35,000-pound P&W-made F119-PW-100 used by the F-22, and the 40. An engine of this size would not only allow the aircraft to reach a maximum take-off weight of 100,000 pounds, but also to easily reach super cruise speeds of up to 1.8 mach without the need for afterburners, and even 2.2 mach if the airframe aerodynamics are revised. In addition, the operational radius of the aircraft could be longer than currently envisaged.

Conclusion

Currently, apart from the 10 F110 engines declared to have been procured for MMU Kaan in 2022, no road map has yet been drawn for the procurement of new engines and/or the production of these engines under license in Turkey. I believe that the fifth-generation national jet engine to be developed for the MMU Kaan may only be ready in the early 2040s. We should all recognize that the development of high-performance fifth-generation turbofans is extremely difficult. Even China, which has considerable resources in this field and has been struggling for years, has yet to fully overcome its dependence on Russian engines. 

Without prejudice to this situation, it is clear that the decision to use F-110 engines, which will obviously delay the Turkish Air Force's fifth-generation MMU Kaans, needs to be re-evaluated, and that until our own indigenous engine is ready in every aspect, it may be more appropriate to put the procurement of F-135 engines used in F-35 aircraft on the agenda instead of the F-110 engine, so that the Turkish Air Force can start flying fifth-generation aircraft from the first mass-produced MMU Kaan, and that the Turkish Air Force can start flying fifth-generation aircraft with a total of two 43. 500-pound engines, the high-power MMU Kaan could become a technological marvel envied by the whole world.

It is not too late yet. It is worth thinking about with the seriousness of a state!