Richard von Mises (1883-1953), who greatly contributed to various branches of applied mathematics and engineering, worked in many academic institutions throughout his career, and produced several well-known publications. Von Mises, who received his engineering training in Vienna and later became a professor at the University of Berlin, made a name for himself with his studies in applied mathematics. The regime-change in Germany also affected von Mises, and he served as a faculty member at the Mathematics Institute of Istanbul University between 1933 and 1939. Like some foreign scientists who fled Türkiye as World War II drew near, von Mises accepted an offer from the United States and resumed his studies at Harvard University up until his passing.1

Having published 32 scientific papers during his stay in Türkiye, von Mises wrote an important article for the book Beiträge zur Flugtechnik (Contributions to Flight Technology) published in 1937 in honor of the 25th anniversary of the Vienna Technical University Aeromechanics Laboratory: "Ein 600 PS - Grossflugzeug vom Jahre 1916" (600-Horsepower Aircraft of 1916)2

During World War I, von Mises, who served as a reserve officer in the Austro-Hungarian Aviation Troops, started this project in November 1915 upon an order from Major Ludwig Leidl. On July 4, 1916, the first flight test was conducted at Aspern Airport. Although the aircraft had been designed and built for almost 20 years, no papers about the project were made available until 1937. In the first paragraph, von Mises stated that he created this article by gathering his own recollections with the drawings and technical details he acquired from various sources.

The article consists of the following subsections:

1.Project

a)Engine Layout

b)Weapons

2.Outline of the Design

a)Aerodynamic Fundamentals

b) Mass Distribution

c) Static Calculations

d) Propeller

e) Tail Assembly

3.Designing and Prototyping

4.Tests

In April 1915, the Land Forces Command ordered two V-type 300 horsepower engines from Austro-Daimler. The engine was planned to be positioned vertically rather than horizontally on the chassis, and the power transmission was planned to be positioned on the propeller axle at 90 degrees to the shaft with the help of a bevel gear. The engines would be located at the front and rear of the pilot cabin. The front engine would drive the tractor propellers and the rear engine would drive the pusher propellers. The wingspan of the aircraft was calculated as 22.6 m, fuselage length as 15.4 m, wing area as 118 m2, empty weight as 3080 kg, and loaded weight as 4720 kg.

This concept was intended to be a bomber and weapon bays were designed in the nose and center fuselage. Since it was quite large, two machine gun compartments were placed in front of and behind the pilot's cabin in order to reinforce it in air-to-air combat. In addition, it was also discussed to place a horizontal machine gunner underneath the fuselage.

It was decided to use airfoil profile number 32, one of the models tested by Gustave Eiffel in his own wind tunnel in Paris. However, as it would be tested on a very large aircraft, von Mises aimed to lessen the center of pressure movement of this profile and modified it to a slightly S-shaped design.

All aerodynamic data tests of the selected airfoil were performed at the Aeromechanics Laboratory in Vienna under the leadership of Prof. Richard Knoller. Within the framework of the theoretical calculations, a power loss of 5 percent due to the gearbox was anticipated at an effective engine power of 640 horsepower, and the maximum cruise speed was determined as 41.5 m/s (≈150 km/h). Altitude to 1000 meters was calculated as 7 minutes 40 seconds at a speed of 29 m/s.

The weight of fuel, oil, and water to be used in the aircraft is 820 kg. With a cruising speed of 150 km/h and a climbing time of 30 minutes, the operational radius is 300 km. The engines supplied by Austro-Daimler weigh a total of 1448 kg together with the gearbox, cooler, and propellers. The 118 m2 load-bearing surfaces are made of materials weighing 4.9 kg/m2. The fuselage weighs 435 kg, the tail assembly 165 kg, and the landing gear, which is highly complicated to design, 370 kg. For the second prototype, it was planned to integrate 3 machine guns and 7 bombs of 50 kg each into the design. With a crew of four, a payload of 820 kg was considered, and thus a total maximum weight of 4720 kg was obtained when the payload (including fuel) was added to the specific weight of 3080 kg.

As of 1915, there was no sufficient and trustworthy mathematical basis for calculating static forces as well as aerodynamic forces. Karl Josef Saliger, a young engineer, should be mentioned here. He carried out in-depth studies on aircraft statics at the outbreak of the war. He published two significant papers in the Österreichische Flugzeitschrift, issues 5/6 and 13/14 of 1916, both under the pseudonym "Rethingg", Unfortunately, he was killed in the summer of 1917 in a crash with an airplane of his own design. The static calculations of this aircraft were the work of Saliger.

The most critical feature of this design is the interaction between the front and rear thrust power due to the back-to-back positioning of the propellers The propellers at the rear should have a greater camber at equal rpm, as they will be operating in the wake of the front propellers.In Prof. Knoller's laboratory, experiments were carried out on a 1:100 scale model and a suitable design was strived to be achieved. The axial planes of both propellers with a diameter of 2800 mm are located at a distance of 3350 mm.

The rudder and ailerons were developed by considering the moment of inertia of a fully loaded airplane, based on the experience gained from earlier aircraft. The horizontal and vertical stabilizers were designed in pairs. As a result, the rear end of the fuselage was tapered horizontally unlike conventional airplanes. The ailerons were placed at the tips of the upper wing to maximize their efficiency in strong air flow. The elevator and rudder were balanced in such a way that the pilot would fly an airplane of this size as if he were controlling a regular airplane.

When the manufacturing process for the aircraft, which was intended to be flown in a short period of time, started, it was discovered that there were no available staff. This was due to the fact that all equivalent institutions were busy with the current projects assigned to them by the army, and there was no chance that they would discontinue their ongoing tasks. Engineers Karl Josef Saliger and Hugo Gutmann (who had worked for the Deutz factory in Cologne before the war) and Engineer R. Gabriel were involved during the design process. The M.A.G. Engine Factory (Magyar Általános Gépgyár) undertook the engine assembly and related works. In this factory, Engineer Stanislaus, a younger and capable designer, took over the project after Engineer Okanyi. These engineers and numerous others did their best throughout the entire process.

The project's unlimited financial resources and von Mises' freedom to exercise his power were the two most critical advantages. Colonel Uzelac, the commander of the Imperial Army Air Force, was personally involved in the project and was always supportive. All demands for the manufacturing of components and for experiments were welcomed. The current condition of the industry, which was very active due to the war, was taken into consideration when planning all actions. 

The aircraft was built by Österr.-Ungar. Flugzeugfabrik Aviatik GmbH, which set up a special plant in Essling, near the airport in Aspern. Raw materials and staff were supplied by the company and all parts were manufactured according to the technical drawings. Von Mises' assistant, Engineer Plattl was personally involved in the entire process.

In January 1916, the technical drawings of all components were completed, and the manufacturing process started. First, the construction of the main fuselage began. In mid-March 1916, the initial engine and transmission tests were conducted. On May 7, 1916, the engine and gearbox were mounted on the fuselage and on May 19, 1916, steady-state propeller tests were performed. On June 1, 1916, the aircraft was rolled out of its hangar but due to a design error, the landing gear was damaged and had to be replaced. On June 23, the error was fixed, and the aircraft was ready for flight tests. On the other hand, the manufacturing of the second prototype, which differed slightly from the first, was started immediately.

The first test flight was piloted by Engineer Sattler, with von Mises himself in the cabin as an observer. On July 2, 1916, about six months after the first drawings were made, the Mises aircraft took to the skies for the first time. Von Mises noted down his findings during the test flights, and some improvements were made to certain mechanical components.

Throughout this process, von Mises voiced his concern that interest in giant-sized aircraft would wane. Such concepts were more complex, heavy, and laboriously built than the aircraft actively used in operations. Von Mises claimed that at the time, such an aircraft had never been employed in combat by any country. Smaller combat aircraft were more efficiently used in operations. 

By the end of October 1916, the manufacturing of the second prototype was completed and First Lieutenant Lányi was assigned to conduct the test flight. Von Mises was unable to participate in the test flights of this prototype as he was on another assignment. On November 23, 1916, the technical report prepared by pilot Lányi drew the following conclusions:

1.The aircraft can taxi on the ground at 900 rpm. 

2.The landing gear’s springs are strong. Pneumatics needs to be improved. 

3.Maneuverability during taxi is excellent.

4.The maximum power of a single engine is sufficient to lift the aircraft off the ground. It can fly horizontally with a single engine. 

5.The aircraft can be controlled easily. Once it pulled to the left due to a strong wind, but it could be corrected with a counteract.

6.The rudder stability is excellent.

7.The elevator is more responsive compared to those on large Brandenburg type airplanes.

8.All rudder surfaces can be easily controlled without much force.

9.The airplane can land easily. The landing gear appears to be strong enough.

10.Flaw: The engines are overoiled and shutting down is difficult.

The second prototype was delivered to the army around January-February 1917. However, by 1917, the state of the air combat, the challenges in the R&D and manufacturing process of large-sized aircraft, and the overburden of industrial institutions led to a gradual decline in interest in such designs. In July 1917, Von Mises emphasized that the manufacturing of such large aircraft should definitely be abandoned when he considered the technical issues he was confronted with in terms of aircraft supply.

It is important to draw attention to a small detail that Von Mises did not mention in his article. The two prototypes produced were given an official code: Aviatik 30.07 Gr.I and Aviatik 30.17 Gr.II. Some sources state that a third model coded 30.18 Gr.III was also manufactured. However, there is no available information that this model has ever flown. When the second prototype 30.17 Gr.II crashed in April 1918, the 600-horsepower aircraft program was cancelled. Since von Mises was working on another project at the time, he was unable to intervene, even though he was the chief designer.3  

20 years later, while he was a professor at Istanbul University, von Mises penned the aforementioned article, remembering those days, and concluding it as follows:

"...Thus, the timeless endeavor that began in 1916 came to nothing. However, this experience can take its humble place in Austrian aviation history, which is rich in indigenous work and has had a significant impact.”