Horton: FMA I.Ae. 37 a Prototype Jet Fighter

The I.Ae. 37 project was initiated by Reimar Horton around 1952, following the cancellation of his previous flying wing projects in 1951. This design was a single-engine jet fighter, incorporating a Delta wing flying wing structure, with engine inlets positioned laterally on each side of the nose.

Wind tunnel testing commenced in 1953, along with tests on scale models at speeds of up to 200 km/h (120 mph). A full-scale glider prototype was constructed and took its maiden flight on October 1, 1954. In a unique design feature, the pilot lay prone, viewing through the clear nose of the aircraft.

The glider’s flight performance was assessed as excellent, leading to the commencement of a prototype powered by a Rolls-Royce Derwent V engine in 1955. This engine was chosen for its availability, despite not meeting the desired thrust for the fighter.


In 1956, the glider underwent modifications to include a standard cockpit. Subsequently, the program was divided, with the existing aircraft evolving into a subsonic trainer and the inception of a new, more powerful fighter, designated as the I.Ae. 48.

FMA I.Ae. 37
This was a single-engined jet fighter that used a Delta wing flying wing structure

This fighter, featuring two podded engines under the wings, aimed to achieve speeds of Mach 2.2 (2,700 km/h). However, both projects were terminated in 1960 as part of an economic measure, just a year shy of the I.Ae. 37’s scheduled flight.

The Genesis of the I.Ae. 37

The genesis of the FMA I.Ae. 37 began in Argentina’s quest to establish a strong foothold in the aviation industry. In the post-World War II era, Argentina actively sought to develop its own aerospace capabilities, striving to become independent of foreign technology and influence. This ambition led to the birth of several aviation projects, among which was the I.Ae. 37.

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At the forefront of the I.Ae. 37 project was Reimar Horten, a German engineer renowned for his innovative approach to aircraft design. Horten, along with his brother Walter, had gained prominence for their work on ‘flying wing’ aircraft during World War II.

Their design philosophy focused on reducing drag and improving aerodynamic efficiency, principles that were central to the development of the I.Ae. 37.

The I.Ae. 37 featured a unique design, characteristic of Horten's innovative approach to aircraft engineering. It was a tailless glider, which was a relatively uncommon design choice at the time.
The I.Ae. 37 featured a unique design, characteristic of Horten’s innovative approach to aircraft engineering. It was a tailless glider, which was a relatively uncommon design choice at the time.

Recognizing the potential of Horten’s expertise, Argentine aviation authorities brought him on board to spearhead this ambitious project. The I.Ae. 37 was envisioned as a training glider, a type of aircraft essential for training pilots in basic flying skills before they transitioned to powered aircraft.

Bold and unconventional

Horten embraced this challenge, setting out to design a glider that would not only serve as an effective training tool but also showcase the innovative capabilities of Argentina’s burgeoning aviation industry.

Horten’s design choices for the I.Ae. 37 were both bold and unconventional. Opting for a tailless glider, he deviated from the more common aircraft designs of the time. The flying wing configuration was a distinctive feature of Horten’s design, aiming to provide a seamless blend of efficiency and performance.

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In designing the I.Ae. 37, Horten and his team had to balance several factors. They needed to create an aircraft that was easy to handle for novice pilots yet sophisticated enough to provide a comprehensive training experience. The choice of materials, the aerodynamic shape, and the overall design of the aircraft were all carefully considered to meet these criteria.

Design and Development

The design and development of the I.Ae. 37 under Reimar Horten’s leadership showcased a blend of innovation and practical engineering. Horten, known for his pioneering work on ‘flying wing’ aircraft, applied his unique design philosophy to the I.Ae. 37, creating a glider that was both advanced and functional for its intended training purpose.

Central to the I.Ae. 37’s design was its tailless structure. This unconventional choice set the aircraft apart from its contemporaries. Horten believed that a tailless design, by reducing drag, would enhance the glider’s aerodynamic efficiency.

The flying wing configuration, a hallmark of the Horten brothers’ designs, was evident in the I.Ae. 37, showcasing their commitment to pushing the boundaries of traditional aircraft design.

FMA I.Ae. 37
The project was spearheaded by Reimar Horten, a German engineer who, along with his brother Walter, was known for innovative aircraft designs during WWII.

In constructing the I.Ae. 37, Horten and his team selected wood as the primary material. This decision was influenced by several factors. Firstly, wood was more economical compared to metal, which was an important consideration given the project’s budget constraints.

Single-Seat Cockpit

Secondly, wood offered the necessary strength-to-weight ratio ideal for a glider, ensuring the aircraft was both sturdy and lightweight.

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The single-seat cockpit design was another critical aspect of the I.Ae. 37. Horten designed the cockpit to provide pilots with an expansive, unobstructed view. This feature was crucial for training pilots, as it allowed them to develop a better sense of their surroundings and improve their flying skills.

Additionally, the simplicity and functionality of the cockpit layout were tailored to the needs of novice pilots, facilitating easier control and handling of the aircraft.

Horten’s approach to the aerodynamics of the I.Ae. 37 also demonstrated his expertise. He meticulously shaped the wings and the body of the glider to maximize lift and minimize drag. #This attention to aerodynamic detail ensured that the glider could achieve optimal performance, particularly in terms of glide ratio and maneuverability – key characteristics for a training aircraft.

During the development phase, Horten and his team faced the challenge of balancing performance with simplicity. The I.Ae. 37 needed to be sophisticated enough to provide a comprehensive training platform yet simple enough to be maintained and operated by the relatively less advanced Argentine aviation industry of the time.

Flight Testing and Performance

The flight testing and performance evaluation of the I.Ae. 37 highlighted the glider’s capabilities and validated Reimar Horten’s innovative design choices. Once the development phase culminated, the I.Ae. 37 underwent a series of rigorous flight tests to assess its aerodynamics, handling, and overall performance.

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Pilots at the helm of the I.Ae. 37 during these tests experienced first-hand the glider’s exceptional flight characteristics. The tailless design and flying wing configuration, hallmarks of Horten’s vision, contributed to a smooth and stable flight experience.

This stability was particularly beneficial for training purposes, as it provided novice pilots with a forgiving platform to hone their skills.

One of the key performance metrics for the I.Ae. 37 was its glide ratio. This measure, crucial for any glider, indicates how efficiently the aircraft can maintain altitude without power.

Horten’s Design

Test flights revealed that the I.Ae. 37 had an impressive glide ratio, a testament to its aerodynamic efficiency. This efficiency not only made the glider a valuable training tool but also demonstrated the practical application of Horten’s design principles.

Maneuverability was another critical aspect tested. The I.Ae. 37, with its responsive controls and well-designed aerodynamic structure, exhibited excellent maneuverability. This trait allowed pilots to execute a range of flight maneuvers with precision, an essential feature for an aircraft intended to teach the fundamentals of flying.

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The flight tests also focused on evaluating the I.Ae. 37’s performance under various conditions. Pilots tested the glider in different weather scenarios and altitudes to ensure its reliability and safety. These tests were crucial in affirming the I.Ae. 37’s suitability for the diverse environments in which it would operate.

Moreover, the tests served to refine and optimize the I.Ae. 37’s design. Feedback from pilots and observations made during the flights were used to make adjustments and improvements. This iterative process was instrumental in fine-tuning the glider’s performance, ensuring it met the high standards required for a training aircraft.

Challenges and Limitations

The I.Ae. 37, despite its innovative design and successful performance in test flights, encountered several challenges and limitations. These issues were reflective of the broader context of aircraft development during that era and specific to the design choices made for the I.Ae. 37.

One significant challenge was the aircraft’s wooden construction. While wood offered cost-effectiveness and favorable weight-to-strength ratio, it also posed limitations in terms of durability and longevity compared to metal constructions.

The wooden structure of the I.Ae. 37 was more susceptible to wear and tear, and environmental factors like humidity and temperature variations could affect its performance and lifespan. This material choice necessitated more frequent maintenance and inspections to ensure the aircraft’s structural integrity and safety.

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Another limitation stemmed from the rapidly evolving landscape of aviation technology during that period. The world of aviation was swiftly moving towards jet engines and metal airframes. In this context, the I.Ae. 37, with its traditional propeller-driven, wooden design, risked becoming outdated.


Although perfectly suited for training purposes, its design and technology did not align with the emerging trends in faster, more advanced jet-powered aircraft.

The I.Ae. 37’s tailless design, while innovative and beneficial in terms of aerodynamics, also presented challenges. Tailless aircraft can have ‘flying wing’characteristics, especially in terms of pitch control and stability.

Training pilots on such an unconventional platform, although advantageous in certain aspects, required specialized training techniques and adaptation by the pilots. This uniqueness in handling was a double-edged sword, offering a unique training experience but also necessitating a steeper learning curve for both instructors and trainees.

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Moreover, the I.Ae. 37 faced constraints in terms of its operational scope. As a glider designed primarily for training, its utility was confined to this role. Unlike more versatile aircraft that could be adapted for various purposes, the I.Ae. 37’s design and capabilities limited its use to the specific context of pilot training.

Impact on Argentine Aviation

The I.Ae. 37 had a notable impact on Argentine aviation, marking a significant stride in the country’s aerospace development. This project exemplified Argentina’s ability to innovate and produce indigenous aircraft, contributing to the nation’s growing stature in the global aviation community.

Firstly, the I.Ae. 37 project showcased Argentina’s capability in aircraft design and manufacturing. By successfully developing a unique tailless glider, Argentina demonstrated its technical prowess and independence in the aerospace sector.

This achievement was particularly significant in an era when many countries heavily relied on foreign technology for aviation advancements.

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The project also served as a training ground for Argentine engineers and technicians. Working on the I.Ae. 37 allowed them to gain valuable experience in various aspects of aircraft design and production. This experience was crucial in building a skilled workforce, capable of contributing to future aerospace projects within the country.

‘Flying Wing’

Moreover, the I.Ae. 37 played a role in fostering innovation within the Argentine aviation industry. Reimar Horten’s unconventional design approach, particularly the tailless ‘flying wing’ concept, inspired local engineers and designers to think creatively and explore novel solutions in aircraft design. This culture of innovation would be instrumental in future Argentine aviation projects.

In terms of pilot training, the I.Ae. 37 provided a unique platform for training Argentine pilots. Its distinct flying characteristics and the challenges associated with piloting a tailless glider offered valuable learning experiences.

Pilots trained on the I.Ae. 37 gained a deeper understanding of aerodynamics and aircraft control, skills that were transferable to other types of aircraft.

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Additionally, the I.Ae. 37 project contributed to the establishment of a more self-reliant Argentine aviation industry. The experience gained through this project reduced dependence on foreign technology and expertise, paving the way for Argentina to develop and produce more of its own aircraft in the future.

Finally, the I.Ae. 37 symbolized Argentina’s ambition and potential in the field of aerospace. Its development was a matter of national pride and an indication of the country’s commitment to advancing its aviation capabilities. The success of this project served as an inspiration for future endeavors in the aerospace sector.

The Legacy of Horten Brothers in Argentina

The legacy of the Horten brothers, particularly through their involvement in the I.Ae. 37 project, significantly influenced Argentina’s aviation landscape. Reimar and Walter Horten, renowned for their pioneering work in aviation, brought a wealth of knowledge and innovative design principles to Argentina, which resonated well beyond the I.Ae. 37 project.

Their ‘flying wing’ design concept, a defining feature of the I.Ae. 37, left a lasting impression on Argentine aircraft design.

This innovative approach, focusing on aerodynamic efficiency and reduced drag, inspired a new generation of Argentine engineers and designers. The Hortens’ philosophy encouraged thinking outside conventional design norms, leading to more creative and efficient aircraft designs in Argentina’s future projects.

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The Horten brothers also played a crucial role in transferring valuable technical knowledge and skills to the Argentine aviation industry.

Argentine Engineers

Their expertise in advanced aerodynamics and aircraft construction techniques was a boon for the local aerospace community. Working alongside the Hortens, Argentine engineers and technicians gained firsthand experience in implementing cutting-edge design concepts and construction methods.

Furthermore, the Hortens’ presence in Argentina helped to elevate the country’s status in the global aviation community. Their involvement in the I.Ae. 37 project brought international attention to Argentina’s aerospace endeavors, showcasing the country’s ability to undertake sophisticated aviation projects.

The Hortens also contributed to fostering a culture of innovation within the Argentine aviation industry. Their willingness to explore unconventional ideas and push the boundaries of existing technology instilled a spirit of exploration and experimentation in Argentine aerospace projects.

Moreover, the Hortens’ work in Argentina, exemplified by the I.Ae. 37, served as a catalyst for future aerospace developments in the country. The success of this project proved that Argentina had the capability to develop unique and efficient aircraft, setting the stage for more ambitious aerospace endeavors in the years to come.

The I.Ae. 37 in Aviation History

While not as famous as other gliders or military aircraft, the I.Ae. 37 does hold a unique place in aviation history. It stands as a symbol of Argentina’s post-war ambition to establish a self-reliant aviation industry. The aircraft is remembered for its innovative design, its role in training pilots, and its contribution to the development of Argentine aviation.

The End of the I.Ae. 37 Program

The conclusion of the I.Ae. 37 program marked a turning point in Argentina’s aviation journey. As the project came to a close, it reflected the evolving nature of aerospace technology and the shifting focus of Argentina’s aviation industry.

The decision to end the I.Ae. 37 program was influenced by several factors. Primarily, the rapid advancement in aviation technology, particularly the shift towards jet engines and metal airframes, made the I.Ae. 37’s design increasingly outdated.

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The wooden construction and propeller-driven design of the I.Ae. 37, while innovative at the time of its conception, could not keep pace with the emerging trends in faster, more advanced aircraft technologies.

Moreover, Argentina’s strategic priorities in aviation began to shift. The focus moved towards developing and acquiring more advanced, versatile aircraft, capable of fulfilling a broader range of roles beyond basic pilot training.

This shift in focus was a natural progression for a growing aviation industry seeking to expand its capabilities and assert itself more prominently on the global stage.


The end of the I.Ae. 37 program also reflected the changing needs of the Argentine Air Force. As the demands of pilot training evolved, there was a growing need for training aircraft that could better simulate the performance and handling of the more modern aircraft entering service.

The unique characteristics of the I.Ae. 37, while valuable, were less aligned with these new training requirements.

Despite its conclusion, the I.Ae. 37 program left a significant legacy. It served as an important stepping stone in Argentina’s aerospace development, demonstrating the country’s ability to undertake complex aviation projects and contributing to the growth of its indigenous aviation technology and expertise.

The lessons learned from the I.Ae. 37 program, particularly in terms of design innovation and project execution, provided valuable insights for future Argentine aircraft projects. The experience gained by the engineers and technicians who worked on the I.Ae. 37 was instrumental in enhancing Argentina’s overall aviation capabilities.