The Phonix D.I was a single-seat fighter platform developed and produced by the Phonix Flugzeug-Werke firm in Germany. The aircraft was produced in over 200 (sources vary on the total) examples covering the D.I , D.II and the D.III variants. The prototype D.I first flew in 1917 and was unveiled shortly after Phonix had delivered its armed C.I reconnaissance fighter.
Phonix had already garnered some much-needed experience in the production of fighter aircraft for the Austro-Hungarian Empire during World War 1, ultimately producing some 22 different aircraft types during the course of the war. Its early forays were in manufacturing aircraft for other companies (including Albatros and Hansa-Brandenburg) while, in its later ventures, the firm broke free and produced their own wartime designs. By the beginning of 1917, Phonix Flugzeug-Werke jumped at the chance to replace the outclassed Hansa-Brandenburg D.I. The result was the Phonix D.I, an aircraft not too dissimilar from the Hansa-Brandenburg product it looked to replace.
The D.I was of a conventional biplane wing configuration featuring single bays with parallel struts angled forward. The front of the fuselage was dominated by the engine and cooling system, consisting of a Hiero liquid-cooled, 6-cylinder inline engine developing 200 horsepower (D.I). The cockpit, with seating for one, was situated directly aft of the powerplant compartment. The fuselage featured slab facings with some curvature under the engine to help promote aerodynamic qualities. The fuselage ended rather abruptly into the empennage which itself sported a unique collection of angular tail fins. The undercarriage was made up of two main landing wheels braced to the underside of the fuselage while a simple tail skid was fitted under the empennage. In all, the D.I was a stout and small design and, like other Phonix designs - was not going to win any beauty contests. Armament revolved around two forward-firing fixed 8mm Schwarlose machine guns. The D.I showcased a wingspan was 29 feet, 6.5 inches with the aircrafts top speed listed at 112 miles per hour. Endurance was rated at about 2 hours of flight time while a ceiling of 19,685 feet was possible.
In practice, the early form version of the D.I proved something of a disappointment. Though well-armed, relatively fast and offering good vision, the aircraft exhibited poor climbing capabilities, was difficult to maneuver and had some structural weaknesses. These limitations allowed the D.I to be used somewhat effectively as a photo-reconnaissance platform early in her service life.
Maneuverability was addressed through the introduction of the improved D.II variant fitting balanced elevators and ailerons. The D.II was itself further improved in the D.III. The D.III featured balanced ailerons on both wing assemblies as well as a Hiero inline engine of 230 horsepower. The D.III initially appeared on March 15th, 1918 with the final product delivered on November 4th, 1918. Ultimately, the D.-series, as a whole, proved serviceable and ended up a reliable and resilient mount. Pilots were quick to make use of her above-average diving capabilities in a fight.
The Phonix D-series was utilized by the Imperial and Royal Aviation Troops (KuKLFT) of Austria-Hungary as well as their naval branch. The air force and naval versions both entered service at the same time. Sweden became the only other operator of the aircraft, this in a post-war role and of the D.III variety.