The Berg DI was the first operational fighter to go into production based on an Austro-Hungarian, rather than German prototype. It was also produced and deployed in higher numbers than any other Austro-Hungarian craft.
The craft was designed by Dipl. Ing. (Diplom-Ingenieur ) Julius von Berg and went into production in 1917.
Von Berg kept the structural details of the design as simple as possible. Using wood and plywood with relatively little complex contours and metalwork, the simplicity suited less skilled labor in the Austro-Hungarian workforce of the time and the Berg was designed to be easily produced in large quantities in relatively small workshops.
The first production machine — 38.01 — was accepted on May 3rd, 1917.
The first Aviatik DI victory was an Italian Nieuport credited to Hauptmann (Captain) Karl Sabeditsch flying 38.01 on August 20, 1917.
Early production DI’s were powered by the 185 h.p. Austro-Daimler engine but later versions were fitted with Austro-Daimlers more powerful 200 h.p. and 210 h.p. engines. In 1918, the engines were upgraded to a more powerful 225 h.p. Austro-Daimler which required that the airframe and wings be strengthened to handle the extra stress.
The standard propeller fitted was the 2-blade Jaray but at least one machine (serial number 138.106) was fitted with a 4-blade Jaray propellor.
Most Berg DI’s had a car-type radiator in front of the engine at the front of the aircraft. One of the radiator types was rounded at the top, the other angular with two cut aways at the top corners. Fitted above the radiator was a very obvious expansion-condensation unit. Some machines were fitted with 2 small block radiators mounted on each side of the forward fuselage — this allowed more streamlining of the nose which may have helped increase speed but the cooling was not as sufficient as the car type radiator.
The car type radiators were reliable during winter but in summer the thin air over the alps would cause overheating so they would often be flown with top panel and sometimes other panels of the engine cowling removed for better air flow. Later models in the series would use a fringe cowl, cut low and open at the top with engine cylinders exposed and a long single block radiator mounted on the leading edge of the upper wing.
The pilot’s seat was set high in the cockpit to improve the field of vision above and below the upper wing — even so, visibility was not considered a strength of the Berg DI.
The Berg employed an unusual and innovative aerofoil design — the upper camber had a pronounced reflex curvature towards the trailing edge and the maximum depth was further aft than standard practice at that time. As a result, the rear portions of the ribs were rather thin and flexible and tended to absorb sudden forces like gusts of wind without unbalancing the flight. It’s also possible that this wing design limited the travel of the centre of pressure. The end result was a very stable flight sacrificing responsiveness and nimbleness.
In 1918, a Berg DI was brought down by the RAF in Italy with very little damage and was shipped to the UK for analysis. In their report, the technical officers of the wartime Ministry of Munitions commented the design was comparable to those produced by other forces. The structure was light, simple and strong. They found the standard of workmanship to be high quality. The pilot position was considered comfortable, spacious with good view. The craft, minus its engine, was later exhibited publicly in London.
The Berg entered active service with a pair of Schwarzlose guns fitted with a synchronising gear in order to fire between the propeller blades. Apparently, Italian technicians found the synchronising gear only worked well between 900 and 1,600 RPM — at lower or higher speeds the guns were likely to damage the propeller.
The guns were mounted either side of the engine block with the port-side gun mounted at a higher level and further from the centre in order to clear the carburettor and induction manifold. They were fired through short fame tubes to less the risk of fire from muzzle flash hitting the engine. The main drawback to this arrangement was that the guns were too far forward and so out of reach of the pilot in the event of a jam.
In January 1918, trials began on a redesigned airframe with guns mounted further back on the fuselage decking with breeches extending into the cockpit. The higher location allowed them to be mounted equally from the centre. The improved arrangement went into production and service from June 1918.
Prototypes of the DI were finished with with dark stain on plywood and had no camouflage applied. Most DI’s in service were finished with a distinctive paint scheme of hexagons in six or seven colours: green, blue, mauve, buff, grey, brown and indigo. The patterns were usually arrangements of four, five or six colours with dark shades grouped together to form bands three or four hexagons wide running across the surface. Colours were flat and dull. Towards the end of the war, a two-tone scheme of buff and olive green was introduced.
For the pilots, the Berg DI was comfortable with excellent flight characteristics. Italian pilots who flight tested the DI, reported it was fully aerobatic, sensitive to control and stable. According to one of the Luftfahrtruppen’s Hungarian Aces, Offizierstellvertreter (Officer Deputy) Friedrich Hefty of Flik 28, the Berg DI had, “Excellent flying characteristics: it could outclimb any enemy plane, needed only a short take-off run and was as fast as any other at the time — in its final form it was the equal of the Spad.”
Even so, it was not popular with Austro-Hungarian pilots — probably because of the overheating issues over the Alps. The layout of the guns and unreliability of the interrupter probably also affected its reputation. That said, it was widely used on all Austro-Hungarian fronts from the autumn of 1917 until the end of the war and was frequently in battle with Italian and British aircraft at that time. It is likely that up to 800 craft were produced and saw active service.
References and further reading for the Aviatik Berg DI
Books about the Aviatik Berg DI
- Haddow, George (1967). The O. Aviatik (Berg) D.I. Aircraft Profile Number 151. Surrey, UK: Profile Publications. ASIN B0007JXD26.
- Grosz, P.M. (1994). Aviatik D.I. Windsock Datafile 45. Hertfordshire, UK: Albatros Publications. ISBN 978-0948414602.
- Holmes, Tony. Jane’s Vintage Aircraft Recognition Guide. London: Harper Collins, 2005. ISBN 0-00-719292-4.
- Munson, Kenneth. Fighters, Attack and Training Aircraft 1914-19 (The Pocket Encyclopedia of World Aircraft in Colour ). London: Bounty Books, 2004. ISBN 0-7537-0916-3.
Websites or Pages featuring the Aviatik Berg DI