Fokker Dr.I

From Wikipedia, the free encyclopedia

Replica of Fokker Dr.I, serial 433/17, flown by Lt. Arthur Rahn of Jasta 19. This aircraft is currently displayed at the National Museum of the United States Air Force

Fokker Dr.I, serial 160/17, flown by Lt. Joseph Schulte of Jasta 14

Manfred von Richthofen's red triplane, serial 425/17

Replica of Werner Voss's Fokker F.I, serial 103/17. It is fitted with an authentic Le Rhône rotary engine

The Fokker Dr. I Dreidecker (triplane) was a World War I fighter aircraft designed by Reinhold Platz and built by the company led by Anthony Fokker. It became most famous as the plane flown by the Red Baron, Manfred von Richthofen.

In April 1917, the Royal Naval Air Service (RNAS) introduced the Sopwith Triplane. The Sopwith swiftly proved itself superior to the Albatros and Halberstadt scouts then in use by the German Air Service. In response, the Idflieg immediately solicited designs for new triplane scouts. No fewer than 11 German aircraft manufacturers, including Albatros, Pfalz, AEG, DFW, Schütte-Lanz, and Euler, responded with triplane prototypes. Most showed little promise, though limited production of the Pfalz Dr. I was undertaken.

The Fokker works responded with the V.3, a small rotary-powered triplane with a tubular-steel frame fuselage and thick cantilever wings. Initial tests revealed deficiencies in the V.3, particularly regarding control forces. Instead of submitting the V.3 for a type test, Fokker produced a revised prototype designated V.4. The most notable changes were horn-balanced ailerons and elevators, as well as longer-span wings. The V.4 also featured interplane struts, which were not necessary from a structural standpoint, but which minimized wing flexing.

The V.4 proved far superior to the triplane prototypes submitted by other manufacturers. Climb rate and maneuverability were exceptionally good, though overall speed was low and gliding characteristics were poor. The ailerons were light but 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.

After a type test, an immediate production order ensued. The V.4 prototype was intentionally destroyed in static structural tests. Two pre-production examples, designated F.I, were delivered in the middle of August 1917. These were the only machines to receive the F.I designation. These aircraft (serials 103/17 and 102/17) were shipped to Jastas 10 and 11 for combat evaluation. They arrived on 28 August 1917, at Markebeeke in Belgium. Richthofen quickly reported to the Kogenluft (Kommandierenden General der Luftstreitkräfte) that the F.I was highly satisfactory. The combat debut of the triplane was short-lived, however. Kurt Wolff, Staffelführer of Jasta 11, was shot down in 102/17 on 15 September, and Werner Voss, Staffelführer of Jasta 10, was killed in 103/17 on 23 September.

Delivery of production machines, designated Dr.I, commenced in October. These aircraft were identical to the F.I except for the addition of wingtip skids. All aircraft were delivered to squadrons within Richthofen's Jagdgeschwader 1. While the Dr.I proved very successful in combat, it also demonstrated significant drawbacks. It was considerably slower than contemporary Allied fighters in level flight and in a dive. The triplane was substantially slower than even the Albatros and Pfalz scouts it was supposed to replace. Due to the low-compression Oberursel UR.II, a clone of the Le Rhône 9J rotary engine, performance fell off dramatically at high altitudes. As the war continued, the lack of castor oil made rotary operation more difficult. The poor quality of German ersatz lubricant, known as "Voltol," resulted in many engine failures, particularly during the summer of 1918.

Furthermore, the Dr.I proved tricky to land and prone to ground looping, as evidenced by the wooden skids mounted on the lower wingtips. The cockpit was cramped, and the proximity of the gun butts to the cockpit, combined with poor crash padding, left the pilot vulnerable to serious head injury in the event of a crash landing.

In late October 1917, Leutnants Heinrich Gontermann and Günther Pastor were killed when their triplanes broke up in flight. The remaining triplanes were immediately grounded pending an inquiry. Idflieg concluded that poor construction and lack of waterproofing caused the wing ribs to disintegrate and the ailerons to break away.

Improved quality control on the production line, particularly varnishing of the wing spars and ribs to keep out moisture, largely resolved the problem. Existing triplanes were modified at Fokker's expense. Idflieg authorized the triplane's return to service in late November 1917, and production resumed in early December. However, structural failures of the upper wing continued. On March 13, 1918, Lothar von Richthofen was seriously injured in a crash landing after the upper wing of his Dr.I collapsed in flight. Postwar research revealed that poor workmanship was not the only cause of the triplane's structural failures. In 1929, National Advisory Committee for Aeronautics (NACA) investigations found that the upper wing carried a higher lift gradient than the lower wing--at high speeds it could be 2.55 times as much.

The triplane's problems destroyed any prospect of large-scale orders. Production eventually ended in May 1918, by which time only 320 had been manufactured. As the Fokker D.VII entered widespread service in June and July, surviving triplanes were withdrawn from frontline use and distributed to training and home defense units. Many training aircraft were reengined with the 100 hp Goebel Goe.II.

Very few triplanes survived the war. Serial 152/17, in which Manfred von Richthofen scored his 64th kill, became the centerpiece of Germany's new aviation museum in Berlin. During World War II, it was evacuated to Poland for safekeeping. Its subsequent fate is unknown, but it is presumed to have been destroyed near the end of the war. Today, no original example of the triplane survives.

1 Variants
2 Operators
3 Specifications (Dr. I)
4 References
5 Related content

[edit] Variants

V3 - Initial prototype
V4 - First production prototype
V5 - Fitted with a Goebel Goe.III engine
V6 - Larger version, with a Mercedes D.II engine
V7 - Fitted with a Siemens-Halske Sh.III engine
V8 - Five-winged (triplane set near nose, biplane set aft of cockpit) variant of the V6
V10 - Fitted with an Oberursel UR.III engine