For one of its last attempts at a viable frontline fighter for the German air service of World War 1 (1914-1918), Kondor Flugzeugwerke put its efforts into the "E.3" - an "Eindecker", or "single-winged", fighting platform - to secure a potentially lucrative production contract heading into, what would become, the final months of the war. While ordered in number, the E.3 arrived too late to make any sort of impact for the Germans and it is believed that only about ten or so were actually built before the end. A select few went on to see extended service lives in the post-war era as aerobatic performers for foreign parties.
Walter Rethel of Kondor headed this endeavor which gained speed around July of 1918. The company missed out on several earlier attempts at fighter designs during the conflict, beginning with the Dreidecker triplane in the summer of 1917 up to the D.7 biplane of late-Spring 1918. With the E.3, the Fokker E.V (D.VIII) was used as the influence and, with that, the E.3 was formed around the single-winged concept of a parasol arrangement. In such an arrangement, the wing mainplane was positioned over the complete fuselage (as opposed to touching it) to exact as much lift as possible and, therefore, improving maneuvering which proved so vital in the turning dogfights of The Great War.
Around this was built a slab-sided fuselage with a single-seat, open-air cockpit fitted under and aft of the mainplane. The engine took its place at the nose in the usual way and the tail unit utilized a conventional single vertical fin configuration. A "tail-dragger" undercarriage was fitted for ground-running which involved two wheeled main members and a tail skid. Armament was to be 2 x 7.92mm LMG 08/15 machine guns synchronized to fire through the spinning propeller blades.
As built, the aircraft exhibited an overall length of 18 feet with a wingspan of 29.5 feet, and a height of 9 feet. Empty weight was 1,015lb against an MTOW of 1,415lb. Power was from a single Oberursel Ur.III series 14-cylinder twin-row rotary engine outputting 160 horsepower and driving a two-bladed wooden propeller at the nose.
The wings of this aircraft were of particular note for they were of a in-house Kondor-patented design incorporating thin veneer-type sheets placed long-ways about the mainplane. The sheets were set between protruding ribs and fastened via L-shaped strips. This reportedly made for a stronger, highly-reinforced wing unit which could be put through its paced in the heat of battle. The company also claimed that it made for better airflow over and under the member - thus improving straightline speeds, handling, and maneuverability.
The E.3 was readied for the official German air service "Third D-type" competition in September of 1918 and showcased itself as having excellent performance and handling as expected by its designers with its new wing proving sound. Indeed, some authorities at the competition regarded the E.3 as one of the best on display with few reservations. From this, the E.3 was given the military designator of "D.I" to ready it for serial production and operational service and about 100 examples were on order before the end of the war arrived through the Armistice of November 1918. However, the end of the war meant that fewer than a dozen (possible eight or ten) examples were completed.
For its time in the air, the E.3 was able to record a maximum speed of 118 miles per hour with a service ceiling reaching 20,280 feet, and a time-to-altitude of 16,405 feet in sixteen minutes.
Another E.3 form, designated internally as "E.3a" (or "E.IIIa"), was equipped with the Goebel Goe.III rotary engine of 160-200 horsepower under a full cowling (as opposed to the original E.3's partial cowling assembly). The variant reportedly made speeds of 124 miles per hour in testing and reached 16,405 feet in eleven minutes. The fate of this aircraft is unknown.
In the post-war years, a few E.3s were taken over by foreign players - namely The Netherlands and Switzerland - who featured it as aerobatic display performers. At least two were claimed by the Dutch-based NAVO anti-communist group and a single example fell to Swiss Comte Mittelholzer. These flew into the 1920s until their time had run out.