The Zmaj R-1 was a prototype twin-engine bomber manufactured by Zmaj aircraft of the former Yugoslavia in the 1930s.
However, due to a number of difficulties encountered during testing, the aircraft remained a prototype.
In 1936, Dušan Stankov, the technical manager at the Zmaj factory, initiated the design and construction of a reconnaissance-bomber.
After undergoing wind tunnel tests in Warsaw and being accepted by the Yugoslavian Air Force, the project was designated as the Zmaj R-1.
Engineer Djordje Ducić and a team of designers, along with a few young engineers, completed the prototype before a large aerospace workers strike began in April 1940.
The final assembly took place at the military part of the airport in Zemun.
The first flight was on 24 April 1940, piloted by reserve Lieutenant Đura E. Đaković, a transport pilot with Aeroput.
The initial testing proved that the aircraft had excellent aerodynamic characteristics and performance.
Unfortunately, during the third flight, the pilot was unable to lower the landing gear and had to land with the undercarriage extended, damaging the propellers and engines.
Replacement parts for the propeller and landing gear had to be imported from Germany and France, which caused significant delays in repairs.
The aircraft was rebuilt so that testing could be resumed at the end of March 1941, but in early April, the bombing of Zemun airport damaged the prototype Zmaj R-1 again.
In late June 1941, the Germans scrapped the aircraft.
This twin-engine mid-winged aircraft was powered by two 750 PS (552 kW; 740 hp) Hispano-Suiza 14AB engines and was of mixed construction.
It was well-armed, with two 20 mm (0.787 in) Oerlikon cannon and four 7.9 mm (0.311 in) machine guns and had a fuselage bomb-bay capable of carrying 1,600 kg (3,500 lb) of bombs.
The reconnaissance variant carried cameras, extra fuel tanks, and three crew members in lieu of guns and bombs.
3 – 4
12.78 m (41 ft 11 in)
14.40 m (47 ft 3 in)
2.50 m (8 ft 2 in)
33.80 m2 (363.8 sq ft)
2,600 kg (5,732 lb)
5,094 kg (11,230 lb)
Max take-off weight
5,664 kg (12,487 lb)
2 × Hispano-Suiza 14AB,
14-cyl air-cooled radial piston engine,
552 kW (740 hp) each
450 km/h (280 mph, 240 kn)
320 km/h (200 mph, 170 kn)
1,000 km (620 mi, 540 nmi)
10,000 m (33,000 ft)
Rate of climb
5.55 m/s (1,093 ft/min)
2x 20 mm (0.787 in) Oerlikon cannon
4x 7.9 mm (0.311 in) machine guns
1,600 kg (3,500 lb) of bombs carried internally.
Sources One Hundred Years of the Serbian Air Force, 1912-2012-Miroslav Jandrić. Short History of Aviation in Serbia-Čedomir Janić & Ognjan Petrović. Yugoslav Fighter Colours, 1918-1941, Vol 1-Ognjan Petrovic & Djordie Nikolic. Yugoslav Fighter Colours, 1918-1941, Vol 2-Ognjan Petrovic & Djordie Nikolic. Serbian Aviation, 1912 – 1918 – Srpska Avijatika.