The aircraft was of mixed construction, with wooden wings and tail, an Alclad monocoque fuselage, and Alclad rudders covered with fabric. The flaps and landing gear were hydraulically operated. The R-1 was powered by two Hispano-Suiza 14AB fourteen-cylinder two-row air-cooled radial engines each rated at 690 hp. The crew of three was accommodated in separate cockpits.
Armament consisted of two Oerlikon 0.787 in (20 mm) cannons in the wing roots, while two 0.311 in (7.9 mm) machine guns were mounted in the upper nose. Bombs could be carried internally but for dive bombing missions a bomb rack was mounted too. Aiming and firing of the armament was made from the upper cockpit while bomb aiming was performed from the front cockpit. For defense a flexible 0.311 in (7.9 mm) machine gun was mounted in the rear cockpit.
The prototype was first flown in the spring of 1940. However, due to landing gear failure, the aircraft made a belly landing after its third test flight, causing damage to the engine, propellers and landing gear. Due to the very critical situation in Europe and the impossibility to obtain spare parts from France or Germany, the aircraft was grounded for a long period of time, test flying was not resumed until February 1941.
It is not certain the test flying was completed, as on April 6, 1941, Yugoslavia came under attack and after the eleven days of severe fighting, it surrendered. The R-1 was captured by Germans and stripped from engines, armament and instruments and later scraped. Some sources state that the aircraft was destroyed in sabotage by workers who cut it with an axe, but this story could not be confirmed."
Span: 47 ft 2.9 in (14.40 m)
Length: 41 ft 11.1 in (12.78 m)
Height: 8 ft 2.4 in (2.50 m)
Wing area: 363.82 sq.ft (33.80 sq.m)
Loaded weight: 12,487 lb (5,664 kg)
Max speed: 280 mph (450 kmh) at 13,123 ft (4,000 m)
Service ceiling: 32,808 ft (10,000 m)