The positional nature of the First World War reinforced the importance of artillery preparation. The artillery fire, in turn, needed accurate target designation and adjustment. Not very successful attempts were made to use airplanes for this, but the speed of action of such spotters left much to be desired: Morans and Fokkers could not carry the radio station, due to which the transfer of target data could be carried out only orally or in writing and exclusively on the ground. More comfortable were tethered balloons. A cylinder with a light gas raised the observer-spotter to the desired height, from which he could observe the positions of the enemy using binoculars. The transfer of information was via a banal wired phone. But still this option was not fully convenient. To lift a man, the balloon had to be large, which made him vulnerable even for enemy rifle weaponsnot to mention machine guns aviation. Another problem with tethered balloons was ground-based flight support equipment. Gas-discharge stations were visible to the enemy, despite all attempts to camouflage. As a result, even before the balloon was lifted and the shelling started, the enemy could have retreated to safe positions or even fired at the scouts before they lifted the balloon. Finally, it took a relatively long time to transfer the aerostat unit to another section of the front.
In 1917, three Austrians - Sh. Petroshi, T. von Karman and V. Zhurovets - suggested replacing a bulky and inconvenient balloon with a compact helicopter. Their idea interested the military, but the project PZK-2, named after the first letters of the names of the creators, was created with the financial support of several commercial firms. Helicopters of that time, if they could make small flights, had big problems with controllability and stability. Petroshi, von Karman and Zhurovets solved this problem by a very original method. They reasoned simply: if it is not possible to provide the aircraft with proper flight qualities for horizontal flight, then let it fly only upwards. The Austrian designers decided to make virtually the same balloon, but based not on the Archimedes law, but on the principles of a propeller. The design was supposed to be a farm with motors, transmissions and screws. In addition, on the truss base was supposed to mount the cabin for the observer.
In the spring of 1918, a prototype PKZ-2 was assembled. The main element of the design was a frame consisting of three identical trapezoidal parts. In the middle part of the frame, where its parts converged, three star-shaped rotary engines from Gnome Rhone, each with 100 horsepower, were mounted. In the center of the whole structure, the engine shafts converged at the same point where they were connected to the gearbox of the original design. That, in turn, distributed power to two coaxial screws with a diameter of six meters. In this case, the axes of both propellers rotated around a fixed central rod. A cylindrical observer pilot cabin was mounted on it. In the lower part of the structure were attached four inflatable absorber balloons, which performed the functions of the chassis. The large cylinder was mounted on the central bar of the frame, the other three - on the lateral parts of the frame. All control of the apparatus was carried out with the help of levers associated with the engines. The only flight parameters that could be changed by the pilot are engine revolutions and, as a result, the lift height. The design is relatively quickly disassembled, it could be transported in several cars or horse-drawn carts. The estimated weight of the PZK-2 with gasoline reserves per hour hovering in the air, the pilot and machine gun was 1200 kg.
2 April 1918, a tethered helicopter took off at an altitude of less than a meter. This was not enough for combat work, but the prospects became clear. Over the next few days it became clear that the installed motors have insufficient power. PZK-2 was temporarily sent back to the assembly shop. New 120 hp engines only came in may month. From 17 to 21, May conducted several more test flights, during which the helicopter reached a height of 50 meters. During the tests, I had to work hard on several unforeseen problems. Thus, the tethered cables unwound with increasing height, which led to an increase in the load on the engines. It was necessary to find the right balance between the length of the cables and the engine power so that the helicopter would hang in the air and not move from its place. In June 1918, the demonstration flights began in front of the military department commission. At the demonstrations, problems immediately began: first with the engines, and then the PZK-2 fell from a height of several meters and received serious damage. 21 June project was suspended. Petroshi, von Karman and Zhurovtsu were instructed to prepare a report on the causes of the crash. The investigation lasted until the fall. The construction of a new prototype could take several months. For this reason, its assembly did not start - the war smoothly approached its completion and the tethered helicopter could no longer change the situation on the fronts.
Helicopter E. Schmidt
As you know, the further development of rotary-wing cars went a completely different way. Aircraft designers preferred full-fledged aircraft with the ability to fully control the direction and parameters of the flight. However, the idea of a tethered helicopter for artillery spotters was not lost. During the second half of the twenties, German engineer Erich Schmidt reflected on the development of the concept proposed by the Austrians. Only in 1933, Schmidt had the opportunity to test his guesses in practice.
Unlike Petroshi, von Karman and Zhurovtsa, Schmidt created not only a helicopter, but also the whole complex of related equipment. In addition to the helicopter itself, its reconnaissance and observation complex included a truck with an airstrip, an auxiliary machine, communications equipment, etc. Another original innovation related to the power plant of the helicopter. Since the development of gasoline changes the balance of the entire aircraft, Schmidt removed the very possibility of this unpleasant phenomenon. For this, a gasoline electric generator was installed on the truck, and the electric motor was the basis of the helicopter's power plant. At the same time, use was also made of cables for the transmission of electricity: three wires of a large cross-section were wound on separate winches and used to limit flight altitude.
1. Erich Schmidt helicopter undocked and laid on a truck for transportation. 2. The first prototype of a helicopter with an engine power 50 HP and lower arrangement of screws. 3. Final version
Like the PZK-2, the Schmidt helicopter consisted of several main parts that were mounted on a single frame. To remove the cable attachment points from the center of gravity of the frame, the frame consisted of three triangular units. The center housed the electric motor power 50 hp and cockpit. Two coaxial propellers were fastened on the axles that were removed at the bottom of the frame. Tests of the first version of the helicopter confirmed the reality of using an electric motor as a power plant for a tethered aircraft. However, the cable attachment points were higher than the screws, because of which the lift of the device was not stable. In addition, the fifty horsepower engine was not enough. By the beginning of 1940, the design of the helicopter was revised and significantly changed. The main construction farm remained the same, but instead of the old low-power electromotor, a new one was delivered, producing up to 200 hp. The two screws are now located above and below the frame. The observer cabin was not installed on the updated helicopter. Instead, the aircraft on test raised the load equivalent to the mass of the pilot and useful equipment. The design characteristics of the new power plant looked promising. So, on the winches it was placed only on 300 meters of cable, but according to the calculations, the motor had enough power to lift for a whole kilometer. Apparatus weight 1250 kg had a folding structure; It took only a few minutes to transfer from transport to flight and back.
In the winter and spring of 1940, the second Schmidt helicopter made several flights, during which it showed all its capabilities. However, it was not adopted. The reason for this was the excessive novelty of not only the design, but also the very concept of application. In addition, now, unlike in the times of the First World War, aviation could correct artillery fire or reconnaissance. Schmidt’s projects were closed as unnecessary and no longer resumed.
Nevertheless, the idea of a tethered rotary-wing apparatus was not completely forgotten and abandoned. By 1942, the German navy men had a serious problem. Submarines could not independently search for potential targets at relatively long distances. In the coastal zone, aircraft helped them in this matter, but they could not fly far into the Atlantic. The solution to this problem could be its own submarine aircraft.
In 42, Kriegsmarine’s command appealed to Fokke-Achgelis to create a lightweight collapsible gyroplane that could be transported on a submarine and launched from it. The project, called the FA-330 Bachstelze (“Wagtail”) took only a few months. The design of the autogyro was extremely simple. From several pipes and metal profiles a light frame was welded, on which the tail assembly, the propeller column, the pilot's seat and the control system were installed. The lifting of the 68-kilogram structure (weight without pilot) was carried out using a three-blade screw with a diameter of 7,32 meter, rotating under the pressure of the incident flow. In the lower part of the gyroplane there were attachments for the towing cable. The design of the FA-330 autogyro was collapsible. Moreover, all the details could be brought inside the submarine through standard hatches. The safety of the pilot was ensured at once in several ways. First, if necessary, the device could come down in autorotation mode. The second mechanism, designed for more serious situations, meant dropping the propeller and opening the parachute. The pilot safely descended by parachute, the aircraft fell separately. At the beginning of 1943, the first flight of the Automaw "Wagtail" took place. The vehicle towed by car quietly took off, made a small flight and sat down. The minimum speed at which the FA-330 could take to the air was equal to the entire 25 kilometers per hour, which made it possible to use it on submarines without any problems. Soon after the start of testing, the gyroplane was recommended for mass production. The first carrier of Bachstelze was the U-177 submarine (project IXD2). The surface speed of the boat allowed easy take-off, towing and landing.
Regarding the practical application of FA-330 autogyros, little is known. These devices left a double impression on the submariners. The autogyro was conveniently assembled and disassembled, and did not take up much space inside the boat. On the other hand, if necessary, he did not allow for an emergency dive. True, the last minus of the "Wagtail" was somewhat compensated by the range of view from its side. Rising to a height of 120 meters, the pilot was able to observe the surroundings within a radius of forty kilometers. From the deck, the range of vision in good conditions was limited to 7-8 kilometers. From the middle of 43, the FA-330 autogyros were regularly used to patrol the waters of the Atlantic and Indian Ocean. Due to the peculiarities of the war at sea, in these regions submarine pilots did not achieve much success. In any case, only one case of detection of an enemy vessel by the autogyro was widely known. In early August, the X-NUMX-th pilot of the U-43 boat saw the Greek steamer Efthalia Mari. A few minutes after this, the ship was attacked. In the future, there were several more cases of such attacks. Over time, boats equipped with FA-177, began to send on duty in the Indian Ocean. However, this patrol lasted a relatively short time. Soon, Germany agreed with Japan on the organization of bases for submarines. Among other things, the agreement involved the purchase of several Japanese folding aircraft.
The total number of FA-330 autogyros released was barely over two hundred. Some of them were lost as a result of flight accidents, or they died together with the carrier submarines. A larger number of “Wagtails” was disposed of after the end of the Second World War. Until our time lived about a dozen autogyroes, which are stored in museums.
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