The Fokker DR.I Dreidecker (triplane) was a World War I fighter aircraft built by Fokker-Flugzeugwerke. The DR.I saw widespread service in the spring of 1918. It became renowned as the aircraft in which Manfred von Richthofen gained his last 19 victories, and in which he was killed on 21 April 1918.
The first two pre-production triplanes were designated F.I, in accord with Idflieg’s early class prefix for triplanes. These aircraft, serials 102/17 and 103/17, were the only machines to receive the F.I designation and could be distinguished from subsequent aircraft by a slight curve to the tailplane leading edge. They were sent to Jastas 10 and 11 for combat evaluation, arriving at Markebeeke, Belgium on 28 August 1917.
Richthofen first flew 102/17 on 1 September 1917 and shot down two enemy aircraft in the next two days. He reported to the Kogenluft (Kommandierender General der Luftstreitkräfte) that the F.I was superior to the Sopwith Triplane. Richthofen recommended that fighter squadrons be re-equipped with the new aircraft as soon as possible. The combat evaluation came to an abrupt conclusion when Oberleutnant Kurt Wolff, Staffelführer of Jasta 11, was shot down in 102/17 on 15 September, and Lieutenant Werner Voss, Staffelführer of Jasta 10, was killed in 103/17 on 23 September.
The remaining pre-production aircraft, designated DR.I, were delivered to Jasta 11. Idflieg issued a production order for 100 triplanes in September, followed by an order for 200 in November. Apart from minor modifications, these aircraft were almost identical to the F.I. The primary distinguishing feature was the addition of wing-tip skids, which proved necessary because the aircraft was tricky to land and prone to ground looping. In October, Fokker began delivering the DR.I to squadrons within Richthofen’s Jagdgeschwader I.
Compared to the Albatros and Pfalz fighters, the DR.I offered exceptional manoeuvrability. Though the ailerons were not very effective, the rudder and elevator controls were light and powerful. Rapid turns, especially to the right, were facilitated by the triplane’s marked directional instability. Vizefeldwebel Franz Hemer of Jasta 6 said, “The triplane was my favourite fighting machine because it had such wonderful flying qualities. I could let myself stunt — looping and rolling — and could avoid an enemy by diving with perfect safety. The triplane had to be given up because although it was very manoeuvrable, it was no longer fast enough.”
As Hemer noted, the DR.I was considerably slower than contemporary Allied fighters in level flight and in a dive. While initial rate of climb was excellent, performance fell off dramatically at higher altitudes because of the low compression of the Oberursel Ur.II, a clone of the Le Rhône 9J rotary engine. As the war continued, chronic shortages of castor oil made rotary operation increasingly difficult. The poor quality of German ersatz lubricant resulted in many engine failures, particularly during the summer of 1918.
The DR.I suffered other deficiencies. The pilot’s view was poor during take-off and landing. The cockpit was cramped and furnished with materials of inferior quality. Furthermore, the proximity of the gun butts to the cockpit, combined with inadequate crash padding, left the pilot vulnerable to serious head injury in the event of a crash landing.