Aeroput MMS-3

Work on the design of aircraft Aeroput MMS-3 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 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 stellar engines, without guards and shields, placed at different distances from the gondola hull. Finally, selected system characterized by aerodynamic perfection of Class 12, in those years achieved only by a very good gliders. During 1935 the prototype is made, which take-off for the first time in January 1936. The first flight and test of aircraft conducted by pilot Vladimir Striževski, head of Aeroput transport pilots. As the plane showed good performance, in the same season in 1936 year is included in the traffic.

The MMS-3 was a twin-engine high-wing monoplane of wooden construction with the fuselage covered with plywood, and the wings with fabric, intended primarily for avio taxiing. It was powered by two 88 hp (66 kW; 90 PS) Pobjoy Niagara III 7-cylinder piston radial engines. These engines were characterized by low fuel consumption and very quiet operation, allowing greater passenger comfort. Airplane was launched by two bifurcated wooden propellers with fixed steps. For that time the plane had unusual concept, instead of conventional fuselage, in 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. Cabin had a large window area that provided excellent visibility to the pilot and passengers. This made it an extraordinary airplane for panorama flights. He had a fixed landing gear of a conventional type, tail wheel was located at the rear of the gondola fuselage and the main gondola wheels were mounted on one side of the gondola fuselage and on the other side to engine mount. The main wheels have aerodynamic fenders.[1] In 1940 year, the MMS-3 was used to test the tricycle undercarriage with the front wheel.[2] During this time the engineer Mitrović and Prof. Dr. Ing. Miroslav Nenadović worked together on the project of twin engine light bomber who work called Nemi, and that was supposed to have a similar arrangement which is used in aerodynamics of the MMS-3, but with a tricycle undercarriage. The project Nemi was never realized.

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 unfortunately were not concluded, and production did not take place.

In 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 the flight on line 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 the aircraft by the end of 1937 year had 65 hours of flight time, 1938 year – 79 hours, 1939 year – 102 hours. In addition, it was used for Aeroput's pilots training. It was also used for publicity purposes, taking the visitors of aero-meetings at the minimum prices which contributed to the popularization of aviation and air transport in Yugoslavia. The plane had another advantage: passenger seats could be easily removed from 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, ahead of the tense of international situation around Yugoslavia, MMS-3 aircraft took over the Royal Yugoslav Air Force (JKRV) and placed him in the 603rd Auxiliary Squadron, where it was to be used as a liaison aircraft, deployment and courier needs.

Milenko Mitrović Spirta with MMS-3, before he set it on fire, to prevent Germans taking it (1941).

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 that would not fall into enemy hands. The Plane constructor Milenko Mitrović Spirta (15 February 1905 Novi Sad, Serbia - 23 August 1986 Peterborough, NH, USA) in April 1941 photographed the plane before it was destroyed.

Data from all-aero.com - Aeroput MMS-3[3]

General characteristics

• Crew: 1
• Capacity: 3 passengers
• Length: 7.42 m (24 ft 4 in)
• Wingspan: 11.56 m (37 ft 11 in)
• Height: 2.25 m (7 ft 5 in)
• Wing area: 16 m² (170 sq ft)
• Empty weight: 630 kg (1,389 lb)
• Gross weight: 1,030 kg (2,271 lb)
• Powerplant: 2 × Pobjoy Niagara III 7-cylinder air-cooled geared radial piston engines 66 kW (90 PS; 89 hp)
• Propellers: 2-bladed wooden fixed-pitch propellers

Performance

• Maximum speed: 235 km/h (146 mph, 127 kn)
• Cruise speed: 215 km/h (134 mph, 116 kn)
  
• Landing speed: 75 km/h (47 mph; 40 kn)
• Range: 600 km (370 mi, 320 nmi)
• Endurance: 3 hours (2pax) ; 5 hours (1 pax)
• Service ceiling: 6,000 m (20,000 ft)
  

1,800 m (5,906 ft) (single engine)

• Rate of climb: 6.5 m/s (1,280 ft/min)
• Time to altitude: 5,000 m (16,404 ft) in 22 minutes
• Wing loading: 64.38 kg/m² (13.19 lb/sq ft)
• Power/mass: 0.128 kW/kg (0.078 hp/lb)

• Jat Tehnika
• Yugoslav Royal Air Force

• The Aeroput MMS-3 three view drawing