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24-519: Design work was conducted in 1934, the designer was aeronautical engineer Milenko Mitrović - Spirta, whose initials are on the plane as the MMS label (such was then the custom among constructors of Yugoslav aircraft). The number on the label represents a 3-seater passenger plane. Mr Milenko Mitrović - Spirta was then technical director of Aeroput and suggested that the Board of Directors on the basis of his project, which

48-644: A 2 d p ρ = − 1 a 2 − ρ V d V ρ = V a 2 d V {\displaystyle -{\frac {d\rho }{\rho }}=-{\frac {1}{a^{2}}}{\frac {dp}{\rho }}=-{\frac {1}{a^{2}}}{\frac {-\rho VdV}{\rho }}={\frac {V}{a^{2}}}dV} The 1-D area-velocity is known as: d A A = ( M 2 − 1 ) d V V {\displaystyle {\frac {dA}{A}}=(M^{2}-1){\frac {dV}{V}}} The minimal area A where M=1, also known as

72-767: A l = P s t a t i c + P d y n a m i c = P s + 1 2 ρ V 2 {\displaystyle P_{total}=P_{static}+P_{dynamic}=P_{s}+{\frac {1}{2}}\rho V^{2}} Putting Bernoulli into the continuity equation gives: V m 2 = 2 C 2 C 2 − 1 P s e t t l − p m ρ ≈ 2 Δ p ρ {\displaystyle V_{m}^{2}=2{\frac {C^{2}}{C^{2}-1}}{\frac {P_{settl}-p_{m}}{\rho }}\approx 2{\frac {\Delta p}{\rho }}} The contraction ratio of

96-454: A conventional type, with the tail wheel located at the rear of the fuselage and the main wheels mounted on one side of the gondola fuselage and on the other side to engine mount. The main wheels had aerodynamic fenders. In 1940 year, the MMS-3 was used to test tricycle undercarriage , i.e. with a nose wheel. During this time the engineer Mitrović and Prof. Dr. Ing. Miroslav Nenadović collaborated on

120-552: A propulsion system usually consisting of large axial fans that increase the dynamic pressure to overcome the viscous losses. The working principle is based on the continuity and Bernoulli's equation : The continuity equation is given by: A V = c o n s t a n t ⇒ d A A = − d V V {\displaystyle AV=constant\Rightarrow {\frac {dA}{A}}=-{\frac {dV}{V}}} The Bernoulli equation states:- P t o t

144-548: A twin engine light bomber project called Nemi, and that was supposed to have a similar arrangement as used on the MMS-3, but with a tricycle undercarriage. The project Nemi was never realised. The appearance of plane Aeroput MMS-3, because of its outstanding aerodynamic characteristics, caused a great interest in France, United Kingdom, Germany and Czechoslovakia. Negotiations for the sale of the license were started, but were not concluded, and no series production did ever take place. In

168-518: A windtunnel can now be calculated by: C = A s e t t l A m {\displaystyle C={\frac {A_{settl}}{A_{m}}}} In a return-flow wind tunnel the return duct must be properly designed to reduce the pressure losses and to ensure smooth flow in the test section. The compressible flow regime: Again with the continuity law, but now for isentropic flow gives: − d ρ ρ = − 1

192-561: Is a recreational aerodrome in Divci near the City of Valjevo , Serbia and mountain resort Divčibare . The field has a single grass runway that is 1,250 metres long and 50 metres wide. The idea of the construction of a cargo-transportation centre in Valjevo, 25 years ago, is again in the focus of interest . The backbone of all plans are Bar's railway, i.e. Valjevo - Loznica railway, future highway to

216-434: Is required, a convergent-divergent nozzle is required. Otherwise: Conclusion: The Mach number is controlled by the expansion ratio A A t h r o a t {\displaystyle {\frac {A}{A_{throat}}}} Valjevo Airport Valjevo Airfield ( Serbian : Аеродром Ваљево / Aerodrom Valjevo ), also known as Divci Airfield ( Serbian : Аеродром Дивци / Aerodrom Divci ),

240-785: The MMS-3 aircraft was taken over by the JKRV and placed in the 603rd Auxiliary Squadron where it was to be used as a liaison aircraft for deployment and courier needs. According to eyewitness reports, after the German invasion of Yugoslavia in April 1941, the aircraft was destroyed by the crew at the airport near the village of Divci in Valjevo region so that it would not fall into enemy hands. The Plane constructor Milenko Mitrović Spirta (15 February 1905 Novi Sad , Serbia - 23 August 1986 Peterborough , NH, USA) photographed

264-544: The Prandtl type). These tunnels use large axial fans to move air and increase dynamic pressure, overcoming viscous losses. The design principles of subsonic wind tunnels are based on the continuity equation and Bernoulli's principle , which allow for the calculation of important parameters such as the tunnel's contraction ratio. Transonic wind tunnels (0.75 < M < 1.2) are designed on similar principles as subsonic tunnels but present additional challenges, primarily due to

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288-728: The sonic throat area is than given for a perfect gas: ( A A t h r o a t ) 2 = 1 M 2 ( 2 γ + 1 ( 1 + γ − 1 2 M 2 ) ) γ + 1 γ − 1 {\displaystyle \left({\frac {A}{A_{throat}}}\right)^{2}={\frac {1}{M^{2}}}\left({\frac {2}{\gamma +1}}\left(1+{\frac {\gamma -1}{2}}M^{2}\right)\right)^{\frac {\gamma +1}{\gamma -1}}} High subsonic wind tunnels (0.4 < M < 0.75) and transonic wind tunnels (0.75 < M < 1.2) are designed on

312-467: The speed of sound , such as high-speed aircraft and spacecraft during critical phases of flight. Low-speed wind tunnels are used for operations at very low Mach number , with speeds in the test section up to 480 km/h (~ 134 m/s , M = 0.4). They may be of open-return type (also known as the Eiffel type, see figure ), or closed-return flow (also known as the Prandtl type, see figure ) with air moved by

336-493: The aircraft, by the end of 1937, had completed 65 hours of flight time, 1938 – 79 hours, 1939 – 102 hours. In addition, it was used by Aeroput for pilot training. It was also used for publicity purposes, taking the visitors of aero-meetings for joy-rides at minimum prices which contributed to the popularisation of aviation and air transport in Yugoslavia . The plane had another advantage: passenger seats could be easily removed from

360-600: The cabin and the plane turned into a cargo airplane (the first Yugoslav cargo plane). Just before the April War in 1941 the aircraft was used by the 603rd training squadron of the Royal Yugoslav Air Force (JKRV) which was located at Grab Airport near Trebinje and it was destroyed during withdrawal from the airport. According to other sources, in March 1941, in light of the tense international situation around Yugoslavia,

384-490: The extension of the engine carrier had two tail fins (bi-fuselage). Fuel tanks were located in the wing between the two engines with fuel capacity of 265 L (70 US gal). Cabins of pilots and passengers represent one unit, which like gondola is located below the airplane wings. The cabin had a large window area that provided excellent visibility to the pilot and passengers. This made it an extraordinary airplane for panorama flights. The plane had fixed landing gear of

408-419: The plane before it was destroyed. Data from all-aero.com - Aeroput MMS-3 General characteristics Performance Subsonic and transonic wind tunnel Subsonic wind tunnels are used for operations at low Mach numbers , with speeds in the test section up to 480 km/h (~ 134 m/s, M = 0.4). They may be of open-return type (also known as the Eiffel type) or closed-return flow (also known as

432-452: The prototype was built, the maiden flight occurring in January 1936. The first flight and test of the aircraft were conducted by pilot Vladimir Striževski , head of Aeroput transport pilots. As the plane showed good performance, in the same season in 1936 it entered operational use. The MMS-3 was a twin-engine high-wing monoplane of wooden construction with the fuselage covered with plywood, and

456-476: The reflection of shock waves from the walls of the test section. To mitigate this, perforated or slotted walls are used to reduce shock reflection. In transonic testing, both Mach number and Reynolds number are critical and must be properly simulated. This often necessitates the use of large-scale facilities and/or pressurized or cryogenic wind tunnels . These tunnels are crucial for studying aerodynamic properties of objects at speeds approaching and surpassing

480-473: The same principles as the subsonic wind tunnels. The highest speed is reached in the test section. The Mach number is approximately 1 with combined subsonic and supersonic flow regions. Testing at transonic speeds presents additional problems, mainly due to the reflection of the shock waves from the walls of the test section (see figure below or enlarge the thumb picture at the right). Therefore, perforated or slotted walls are required to reduce shock reflection from

504-413: The summer of 1936 year the MMS-3 received a certificate and was registered as YU-SAR. It was used on passenger routes from Belgrade to Sarajevo , Podgorica and Skoplje , also carrying mail and newspapers. During a flight on the route Belgrade – Podujevo – Skoplje on 15 September 1936 it made a forced landing due to an engine failure and was damaged slightly. The damage was quickly repaired so that

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528-444: The walls. Since important viscous or inviscid interactions occur (such as shock waves or boundary layer interaction) both Mach and Reynolds number are important and must be properly simulated. Large-scale facilities and/or pressurized or cryogenic wind tunnels are used. [REDACTED] With a sonic throat, the flow can be accelerated or slowed down. This follows from the 1D area–velocity equation. If an acceleration to supersonic flow

552-421: The wings with fabric, intended primarily for aerial taxi operations. It was powered by two 88 hp (66 kW; 90 PS) Pobjoy Niagara III 7-cylinder piston radial engines, driving two-bladed fixed-pitch propellers. These engines were characterized by low fuel consumption and very quiet operation, allowing greater passenger comfort. For that time the plane had unusual concept, instead of conventional fuselage, in

576-554: Was in March 1934 tested in the Eiffel wind tunnel in Paris, made for Aeroput in his workshop for repairing aircraft an airplane which would be used as aviotaxi, for whom he felt a great need. The constructor then tried several configurations, including inline and radial engines, without guards and shields, placed at different distances from the fuselage. The final configuration was characterised by an aerodynamic perfection of Class 12, in those years achieved only by very good gliders. During 1935

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