The Junkers J.2 was the first all-metal aircraft intended as a dedicated military aircraft design; the first all-metal aircraft meant to be a fighter aircraft and was the direct descendant of the pioneering J.1 all-metal aircraft technology demonstrator design of 1915.
The J 2 differed from the J 1 in having a cowling that almost entirely enclosed the engine, a rounded upper and lower fuselage section instead of the rectangular section of the J 1., and a narrower and deeper ventral radiator enclosure, and had a horizontal stabilizer planform shape that would become familiar on later, all-duralumin Junkers monoplane designs to be built during 1917-18.
The “all-moving” rudder still possessed no fixed fin, like the J 1.
A faired-in headrest was provided for, as well as the possibly pioneering appearance of a “roll bar” for an open-cockpit aircraft, placed above the headrest for additional pilot protection in case of the aircraft overturning during landing.
The landing gear was of the usual vee-type, but taller than that of the J 1’s and having the upper ends of the legs anchored not onto the lower longerons as on the J 1, but to the first wing rib bay beyond the wing root, with a long tailskid that emerged from the lower rear fuselage directly below the stabilizer’s leading-edge root.
The wings had at least three different airfoil changes between root and tip and had sections of them electrically roll-welded for stronger, more continuous bonding for greater strength.
The resulting aircraft was intended to be smaller than the J 1 demonstrator, but with its steel structure, it almost equalled the J 1’s completed weight.
One feature pioneered in the J 2 that would also be used in later all-metal monoplanes designed and built by Junkers in World War I, was a “unitized” forward fuselage structure, combining the engine mount, wing roots and cockpit framing into a single structure.
The first production example of the J.2, (serial number E.250/16) was delivered to Adlershof on 2 July 1916 and started its IdFlieg-mandated static load testing.
Otto Mader, one of the J 2’s designers, then promised IdFlieg that the following example, E.251/16, would have even greater structural strength than that of the E.250’s airframe.
Leutnant Theodor Mallinckrodt, the pilot who had first “hopped” the J 1 some seven months previously, flew E.251/16 for the type’s maiden flight on 11 July 1916.
Mallinckrodt gave the aircraft a good overall evaluation, judging it as “very manoeuvrable”, with good turning qualities and safe aerodynamic behaviour.
A short time later, IdFlieg test pilots Unteroffiziers Wendeler and Max Schade, began performing full flight evaluation tests on the six examples of the J 2 as they arrived at Adlershof .
Schade would eventually take one of the test aircraft on a flight from Berlin to Dessau later in the summer of 1916, achieving a speed of 180 kilometres per hour (110 mph) with the aircraft, which was some 16 kilometres per hour (9.9 mph) faster than the contemporary French Nieuport 11, but, as the J 2 test aircraft still seemed to come up short in climbing performance tests when evaluated against wood structure designs like the then new Albatros D.I, the steel structure of the J 2 made it just too heavy to be able to compete in air combat over the Front.
At least one example (E.253/16) of the J 2 was fitted with slightly longer wings and matching longer ailerons, possibly in an effort to decrease the wing loading of the initial J 2 design, and at least one of the aircraft was fitted with the then-new 119-kilowatt (160 hp) Mercedes D.III engine, achieving 200 kilometres per hour (120 mph) at full throttle.
