Hybrid Aircraft - Daimler-Benz Hawker (Zmaj) Hurricane

Little is known of the Royal Yugoslav Air Force (JKRV) and its brief fight with the Luftwaffe and Regia Aeronautica in April 1941. Many Western historians have written it off as small and insignificant. It will surprise many to learn that the JKRV had over 800 aircraft on its strength at the time of the German invasion. By 1941 the JKRV had on its strength over 160 fighters, made up of 73 Messerschmitt Me-109Es, 44 Hawker Hurricane Is and 30 Hawker Fury IIs, as well as 8 Ikarus IK-2s and 12 Rogozarski IK-Zs, both locally designed and built.

Its bomber strength of 175 aircraft comprised 70 Dornier Do-17Ks, 60 Bristol Blenheim Is (both being licence manufactured in Yugoslavia by the State Aircraft Factory and Ikarus respectively) and 45 Savoia Marchetti SM-79s.

The situation whereby Yugoslavia had to acquire or manufacture aircraft from whatever source presented itself meant that by 1941, the JKRV was equipped with 11 different types of operational aircraft, 14 different types of trainers and five types of auxiliary aircraft, with 22 different engine models, four different machine guns and two models of aircraft cannon.

The Yugoslav manufactured Dornier Do-17K, for example, was a German aircraft with French engines, Belgian armament, Czech photo-recon equipment and Yugoslav instrumentation! It was a quartermaster’s nightmare!

During 1938, The Yugoslav government concluded an agreement with Hawker to purchase 12 Hurricane Is for the Royal Yugoslav Air Force and followed this up with an order for 12 more together with a manufacturing licence to allow production of the fighter at the Rogozarski (orders for 60) and Zmaj (orders for 40) factories. These plants, together with the Ikarus concern, had been designing and manufacturing sporting and training aircraft since the 1920s.

Production was expected to reach eight per month from each assembly line by mid-1941. In the event, by the time of the German onslaught of April 1941 which put an end to further production, Zmaj had delivered 20 Hurricanes but Rogorzarski had delivered none.

The design team had been working on improved versions of the IK-Z. It had originally been planed to power later IK-Zs with new 1,100 h.p. Hispano-Suiza 12Y-51 engine. The German occupation of France had frustrated this plan, and it therefore become necessary to consider a British or German engine. The Air Ministry favored the DB 601 A, and as part of IK-Z development program, the Daimler-Benz engine was installed experimentally in a Hurricane airframe in 1940.

JKRV DB601 Hurricane

Engineers Ilic and Sivcev at the Ikarus plant, Zemun, outside Belgrade, made the conversion, by the fitting of new engine bearers, cowlings and cooling system manufactured at the Ikarus factory.

The one Hurricane fitted with a DB601A engine for comparison with the Merlin-engined version was tested early in 1941. The conversion was extremely successful, and experimental aircraft displayed better take-off performance and climb rate than either the standard Hurricane or the Bf 109 E-3 and was only slightly slower than the latter.

At the same time, a 1,030 h.p. Rolls-Royce Merlin III was installed in one of the IK-Z airframes, but this machine had only just been completed at the time of the German attack, and as enemy forces neared Belgrade it was destroyed by the factory workers, together with four other IK-3s undergoing overhaul or modification. JKRV pilots who flew the Hurricane conversion considered it to be superior to the standard model.

Main material contributed by J. Nemcic.

Line drawing from Hawker Hurricane - Defender Of The Empire; note the Hurricane Projects page at this site by Colin Pratt-Hooson, for various modifications to the Hurricane, including engine variations.



Related links:

Hawker Hurricane - Defender Of The Empire
Colin James Pratt-Hooson's site is a source of information about the Hurricane which touches on most areas of interest to researchers, and, in the context of 'Unreal Aircraft', demonstrates the variations which may be applied to a well-known design.