Friends,
I had a bit of free time. On the link, i translated it into English so that it would be an education for the average forum user.
Although I am not much familiar with aviation technical terms, I try to use the correct terms as much as possible. If I have been mistaken, my apologies and any corrections are welcome.
What are the engine options at Hürjet?
Supersonic training aircrafts are necessary to train pilots in military aviation and are an integral part of the air force. They have a very important role in completing the trainings required for pilots' high-speed flights and sighting tactics. For this purpose, Turkish Aerospace Industries (TAI), on 14 August 2017 in accordance with the needs of the Turkish Air Force and to take the place of the currently used T-38 fleet, is aiming to develop jet training and light aircraft, and therefore "Training Jet and Light attack aircraft (Hürjet) Project "has been started.
Although we don't have much information about the project because it is at the consept phase at the moment, we had the opportunity to see Hürjet's mock-up in the live broadcast of President Recep Tayyip Erdoğan's at the Kahramankazan facility of TAI on Monday, June 19th. It was remarkable that the model aircraft was single-engine one. Hürjet came out as a twin-engine training plane in the pictures published on TAI's website and the plane that we had the opportunity to see for the first time on the evening of 19th June was a single engine model.
WHAT ARE THE ENGINE PREFERENCES?
In this short article we will examine some of the engine preferences of some supersonic training aircrafts and carry out ideas about the Hürjet engine. It is useful to be aware that we are looking for an answer to a rather complex question, and that the answer needs to be searched in the light of various factors.
Some questions are not easy to answer and this is one of them!
Jet Training Aircraft and Engine Preferences
It would be useful to review some of the jet training aircrafts before interpreting single or dual engine options for Hürjet. We can start by reviewing the turbofan engines used in the T-50 / -50A, Hawk T2 (Hawk 128) Hongdu L-15 and Alenia Aermacchi M-346 Master training aircrafts. The engines used in the airplanes are given comparatively on the table.
While T-50 / -50A and Hawk T2 training aircrafts are single-engine, the L-15 Falcon training aircraft used by the Chinese Air Force and the Italian M-346 are dual-engine.
Jet training aircrafts
Turbofan engines used in jet training aircrafts
If we go back to the main topic of our writing, is the selection of single / dual engine selection; being a single or dual engine is a question that needs to be answered for every platform rather than just a question asked for training aircraft. For example, by examining F-22 and F-35:
A dual motor was needed to get the F-22 to work in accordance with the design goals / requirements and to achieve the necessary propulsion for the platform. The F-35 is designed with a single engine and can provide the necessary thrust. Although both aircraft were designed by Lockheed Martin and the engines by Pratt & Whitney, the F-22 is a dual-engine, while the F-35 is a single-engine. The choice of a single / dual engine should be at the center of the decision making of the platform to be fitted.
Single-engine airplanes can not achieve as high an altitude or cruising speed as dual-engine versions, and must operate safely with a single engine for a long period of time. If we look at the progress of security in an example:
The F135 engines used in the F-35 were built based on the F119 engine which is used in the F-22 and were never wrecked during the 50,000-hour flight. It takes into account the fact that several decades have provided significant improvements in reliability. Especially, with dual engine, air combat ability of aircraft is more effective. Besides, dual-engine designs are heavier, more expensive, but offer a clear advantage in terms of safety and sometimes performance.
Summarizing our single / dual engine comparison:
1) Advantages of single engine:
A lighter aircraft
Higher thrust / weight ratio and higher performance
Lower running cost
Less spare parts and maintenance cost
2) Advantages of dual engine:
Safety (the fact that the second engine is available, but the reliability issue needs to be credited with significant improvements over the last few decades) is often better with the dual-engine and platform air combat capability
The biggest disadvantage of single engine arises when the total thrust provided by the dual engine is required from only one - existing- engine is required. The engine may require warmer operation, or a larger engine may be needed. As a result, mechanical difficulties in design will increase. When single / dual engine selection is made, the platform should be tailored around the engine in accordance with design-performance criteria and existing engine technology. I will briefly mention what these criteria are:
Design - Performance Measures: Expected task parameters, service ceiling (altitude), acceleration time / climb rate, range, useful load capacity and maximum take-off weight etc. Performance criteria are largely limited to existing engine technology.
Let's go back to the single / twin engine spec for Hürjet. In the 62nd issue of C4Defence defense magazine, an interwiev with Dr. Mahmut F. Akşit, General Manager of TAI Motor Sanayii A.Ş. (TEI), contains very important clues about Hürjet's engine. Based on this interwiev, I will go out of the details and start guessing what kind of engine is being considered for Hürjet. I want to convey the details that I see as important from the interview of Mr. Mahmut Akşit Bey:
"Hürjet's engine, half of the National Combat Aircraft engine, and twice the size of the National Helicopter motor. They consider the ready purchase in the first place; because we will be busy with both the national helicopter engine and the national combat aircraft engine. So we do not have the capacity to take the time right now. In Hürjet, it is likely that the first engine will be purchased as ready to use parts; However, as TEI, we'll be producing more than 150 of these engines in Turkey. That's our goal. We want Hürjet's engines to come out with the TEI serial numbers. Licensed production is also spoken in this framework. In licensed production, we produce 50-60 percent of the engine here, but we use what we do not get into our mass production, such as pipes, cables, from the OEM supply chain. After all, it is our production. "
A Power Pack around 60 kN of thrust is considered to be produced under licence in Turkey. If we take into account the desired thrust value, there are 2 different alternatives:
In the case of using an engine with thrust of 30 kN, similar to Rolls-Royce / Turbomeca Adour, Honeywell / ITEC F124-GA-200 or Ivchenko AI-222-25F, a twin engine version would be available,
In the case of a General Electric F404 or similar engine providing 60 kN thrust, it will be a single-engine aircraft.
During this selection, the most decisive detail will be the under license production permission in Turkey. Under similar conditions, we can give the T50 training plane as an example of licensed production. T-50 is powered by F404-GE-102 engine which is manufactured by Samsung Techwin under license. The General Purpose Helicopter project, in which TEI is working as a subcontractor responsible for licensed engine production, is also ongoing. Within the scope of this project; more than 50% of 236 pieces of T-700-TEI 701D turboshaft engines, including Engine Installation and Tests (AIT) processes, is manufacturing with TEI serial umbers in Turkey. It is contemplated that a similar business model will be applied for Hürjet's engine.
The selection of the engine, which will be procured from a ready to use supplier in the first stage and which is thought to be produced under the license will be very important. As a matter of fact, the platform will be shaped according to the engine and we have a goal to develop it with a motor of our own design. If an engine choice that is relatively easier to design is made, it will be shorter to develop the engine that will take its place. The point I want to emphasize is that if our current technology is to develop a 30 kN thrust engine, we would have to choose a 30 kN thrust twin engine design for Hürjet if it would be less risky with our human power. The opposite is also true. If our ultimate goal is to develop a domestic engine of the 60 kN class, the engine we produce under license for Hürjet must be in the 60 kN thrust class. We can list the decisive factors in motor selection as follows:
Which engines can be produced in Turkey under licence.
According to our technological competence, in which propulsion class we can develop the engine,
According to the roadmap of the engine design, which propulsion class of the engines improvement would be more suitable,
The cost, the financial strength and operational service lifetime,
Platform and accordingly, engine selection considering the potential market.
Wishing this article i prepared would be helpful, with the hope of finding an answer to a question that is not easy to answer.