Development of the Jet and Supersonic Flight
The development of the jet engine and that of supersonic flight are related yet separate. Both originated in the CSDS as part of Josip Broz's near-paranoid obsession with national defence. Supersonic flight research with rocket-powered aircraft began in 1959, while research into jet propulsion commenced following that, in 1967, as part of a search for more efficient methods of aircraft propulsion than rockets.
In 1955, the Air Force and Air Defence of the Danubian People's Army established the 1523rd Research Squadron (still extant as part of the Dalmatian Air Force and Air Defence), and leased a 2500 square verst area from the Malian government for 99 years on which to build research facilities (this lease has passed on to Dalmatia, who continue to operate the Malian research area). Since 1956, when the facility was first opened for use, all new aircraft and weapons systems have been tested in Mali.
In 1957, Colonel (dipl. ing.) Kočo Arsovski of the AF-AD/DPA, employed as a scientist with the Sokol aircraft company, formulated an idea for a piloted rocket after observing a test of a surface-to-surface rocket. He envisioned a series of rocket-plane bases around cities and other strategically important installations, where these piloted rockets would be mounted on launchers pointing at the sky, for near-instant acceleration and take-off to altitude to intercept incoming hostile aircraft. He, together with a rocket scientist from the University of Niš, Prof. Nemanja Đorđević, formulated a proposal which they submitted to the Ministry of Defence. The Ministry approved the proposal, and the two were assigned to the 1523rd to develop the technology required.
For two and a half years, the research team of the 1523rd worked together with scientists at the University of Niš and the Physics department of the "Nikola Tesla" Technical University at Smilyan, Dalmatian SR, on the theoretical and practical development of the system, which resulted in the March 1960 unveiling to the Ministry of Defence and Josip Broz (naturally, this was all very secret) of the Sokol Raketoplan, a rocket-powered aeroplane designed to reach Mach 2 speeds. Following this, Josip Broz personally asked Major Karel "Karčo" Jagr, who was Danubia's top fighter ace in GW2 having scored 23 confirmed kills, to be the chief test pilot of the Raketoplan program. Jagr instantly agreed and he, along with the three rocket planes, a small maintenance crew, two backup pilots and a team of scientists headed by Col. Kočo Arsovski and Prof. Nemanja Đorđević, headed to Mali.
Major Jagr had selected as his technical adviser and crew chief his wartime squadronmate Captain (dipl. ing.) Petru Gabresku. Gabresku and Jagr were entrusted with developing a test plan and to conduct the research at the pace they see fit. They developed a plan which entailed three unpowered and five powered flights, gradually building up speed step by step until the sixth powered flight, in which the supersonic attempt would be made.
The Raketoplan was designed to be dropped in mid-flight like a bomb. For this purpose, a Erakles heavy transport helicopter (which was the world's first aeroplane-helicopter hybrid, entering service in 1959) was modified with extended-length landing struts (to allow space for the rocket plane) was built. This would carry the rocket plane, slung under its belly with shackles, to an altitude of 30,000 feet, where, at a speed of 210 versts per hour, the shackles would be released and the Raketoplan would fall away and begin gliding.
Thus were the unpowered flights conducted; they served to familiarise Jagr thoroughly with the Raketoplan, as all landings would have to be unpowered due to the volatility of the fuel used. The powered flights also began the same way.
The first five powered flights were all flown at subsonic speeds, each setting new air speed records; the fifth flight reached Mach 0.97. There were some difficulties along the way which had to be resolved before testing could continue, but in the event the sixth powered flight took place as scheduled on 23 May 1961, and with this flight, Maj Jagr became the first - and only - man to fly faster than sound.
Following the successful flight, two more supersonic flights were made, and plans were made for further rocket planes, and designs were begun for a serviceable rocket-interceptor system as originally devised by Col. Arsovski. However, none of these plans were realised, as Josip Broz had a sudden change of mind, and decided that conventional aircraft are sufficient to defend Danubian airspace. Thus, all experiments with rocket aeroplanes ceased, and rocket technology remained the monopoly of surface-to-surface missile systems. The Jet
Following the cancellation of rocket aeroplane research, aeronautical research in Danubia turned to improvement of the conventional aeroplane. Ever more efficient engines were devised - piston, radial, supercharged, turbocharged, rotary, until 1976, when a young engineer named Fransesk Vitlesku came up with the concept of the jet engine. However, his idea won no favour and was regarded as a curiosity; funds were instead being allotted to the perfection and improvement of the rotary engine. It wasn't until 1985 that Vitlesku's idea was first seriously entertained by the Danubian military, and the green light was given to develop the jet engine and a jet-powered aeroplane. The work began in earnest, and by early 1987 plans were ready for the construction of a prototype jet aeroplane; ground tests and airborne tests (on a modified rotary-engined aeroplane) were carried out in mid and late 1986.
Construction of the prototype jet plane began in February of 1988, but due to political events and the outbreak of civil war in Danubia, all work on the jet aircraft was suspended. Fortunately for the jet program, the work was taking place at the research facility in Mali, thus it survived the war intact, though the base was cordoned off by Malian authorities, the CSDS citizens there all removed from the facility except for a handful of ethnic Dalmatian caretakers (the Malians, being Dalmatophones, supported the Dalmatian cause during the civil war). After the Dalmatian declaration of independence, Mali viewed that facility as Dalmatian.
In 1997, after the war was more or less concluded as far as Dalmatia was concerned, work could resume. However, Dalmatia first had to rebuild herself, so it wasn't until 2000 that work with the jets resumed, as the number one priority of the defence industry. This test aeroplane was the flying prototype of the Spretu jet fighter, which had been transferred to the Mali base in 1988 after the beginning of the civil war in an incomplete state. The prototype was then finished and tests commenced, while back in Dalmatia the Sokol works resumed development of the actual combat-capable Spretu. The first combat capable Spretu prototype was finished in January 2001, and testing in simulated real-world situations of this prototype was concluded in July of the same year; the 1523rd recommended adoption of the Spretu into front-line service, and series manufacture of the aeroplane commenced in October.
The first ten two-seat trainer units arriving to the 172nd Fighter (Training) Sqn at the Military Aviation Academy on 22 December 2001; the first combat-capable (single seat) Spretu fighters were delivered to the 127th Fighter Sqn (204th Fighter Regiment, 1st Corps) on 7 April 2002. Operational conversion of the pilots of the 127th Sqn from Urakana-I interceptors to the new jets was completed on 27 March 2002, and the 127th became the first all-jet squadron on 23 May 2002, with twelve Spretu Mk I aircraft (ten less than the nominal aircraft strength of a Dalmatian fighter squadron). The squadron as a whole then commenced training as a squadron, and on 16 November was transferred to the front lines of the then-raging Dalmato-Sanjak war. That war ended six days later, and the 127th saw very limited combat, but one kill was claimed by a pilot of the 127th.
Since the successful introduction into service of the Spretu Mk I, it has already been superseded by the Mk II, which is an improvement of the Mk I with more powerful engines, wing hardpoints for air-to-air heat-tracking rockets (presently under development by the Vimpel firm) and air torpedoes, a catapult seat for the pilot and an air search radar capable of detecting and tracking targets up to a range of 5.5 miles. The twelve Mk Is that were built and assigned to the 127th have since been sold to Louisianne and the 127th has converted to the Mk II with a full 22-aeroplane complement; the 124th Fighter Sqn (117th Fighter Regt, 5th Corps) is the second squadron to begin conversion to jets, presently their complement is 10 Spretu Mk II and 12 Taifun-I fighters (the Taifun-Is are being retired and sold to Mali).
Further, a naval variant is entering production as a replacement for the Navy's Falkoana fighters serving on board the aircraft carrier Aurial Vlaiku. This Spretu-N model is a variant of the Mk II with all the same features, but replacing the air search radar with a surface search radar and adding an infrared seeker-tracker system, as well as arrester hook to allow landing on the carrier deck.
Development of new jet aeroplanes is going apace. The Sokol company had developed and proposed the Sterszlyen ("Hornet") ground-attack jet fighter prototype. The prototype is currently undergoing evaluation by the 1523rd, but was not be taken up, as the plane was underpowered, underarmed and underarmoured for the role, and was unstable at the low speeds necessary for attacking ground targets with precision.
Sokol is not the only concern developing jet aircraft either. The recently-established Ikarus Aerospace Company is also working hard in the field. Ikarus has three projects currently in advanced stages.
The Biantayla ("Windwing") heavy transport helicopter-aeroplane hybrid, designed to be a replacement for the aging Erakles and Xhigant (both Vertoplan products) heavy transport hybrids, is in comparative testing against the Vertoplan XGE-2; the Biantayla, unlike the XGE-2, has jet engines in place of the four heavy piston engines of the XGE-2.
The other two Ikarus projects are both pure-jet fighters. The Biaspa ("Wasp") is designed to be a short-range base-defence fighter in the final stages of testing, and will be adopted into frontline service in the near future. Armed with six .50-cal machine guns and two underwing hardpoints for air-to-air rockets, the Biaspa's role as a base-defence fighter will complement the Spretu's main role as a medium-range interceptor. The second of the two Ikarus jet fighter projects is the Vukilak ground-attack fighter. Following some delays, the type entered service in 2007; however, only one squadron has yet been equipped with the type.
Many other projects are in the works. According to the plans of the AF&AD, by 2025 all combat roles currently performed by propeller aircraft will be performed by jets - an all-jet air force.