The Fokker Dr.I (Dreidecker, "triplane" in German), often known simply as the Fokker Triplane, was a World War Ifighter aircraft built by Fokker-Flugzeugwerke. The Dr.I saw widespread service in the spring of 1918. It became famous as the aircraft in which Manfred von Richthofen gained his last 17 victories (plus two earlier ones in the Fokker F.I prototype in September 1917), and in which he was killed on 21 April 1918.
In February 1917, the Sopwith Triplane began to appear over the Western Front.[2] Despite its single Vickers machine gun armament, the Sopwith swiftly proved itself superior to the more heavily armed Albatros fighters then in use by the Luftstreitkräfte.[3][4] In April 1917, Anthony Fokker viewed a captured Sopwith Triplane while visiting Jasta 11. Upon his return to the Schwerin factory, Fokker instructed Reinhold Platz to build a triplane, but gave him no further information about the Sopwith design.[5] Platz responded with the V.4, a small, rotary-powered triplane with a steel tube fuselage and thick cantilever wings,[6] first developed during Fokker's government-mandated collaboration with Hugo Junkers. Initial tests revealed that the V.4 had unacceptably high control forces resulting from the use of unbalanced ailerons and elevators.[7]
Instead of submitting the V.4 for a type test, Fokker produced a revised prototype designated V.5. The most notable changes were the introduction of horn-balanced ailerons and elevators, as well as longer-span wings. The V.5 also featured interplane struts, which were not necessary from a structural standpoint, but which minimized wing flexing.[8] On 14 July 1917, Idflieg issued an order for 20 pre-production aircraft. The V.5 prototype, serial 101/17, was tested to destruction at Adlershof on 11 August 1917.[9]
The first two pre-production triplanes were designated F.I, in accord with Idflieg'searly class prefix for triplanes. These aircraft, serials 102/17 and 103/17, were the only machines to receive the F.I designation[10] and could be distinguished from subsequent aircraft by a slight convex curve of the tailplane's leading edge. The two aircraft 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.[11] Richthofen recommended that fighter squadrons be reequipped with the new aircraft as soon as possible.[11] The combat evaluation came to an abrupt conclusion when OberleutnantKurt Wolff, Staffelführer of Jasta 11, was shot down in 102/17 on 15 September, and LeutnantWerner 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.[12]Idflieg issued a production order for 100 triplanes in September, followed by an order for 200 in November.[13] Apart from the straight leading edge of the tailplane, these aircraft were almost identical to the F.I. The primary distinguishing feature was the addition of wingtip skids, which proved necessary because the aircraft was tricky to land and prone to ground looping.[14] In October, Fokker began delivering the Dr.I to squadrons within Richthofen's Jagdgeschwader I.
Compared with the Albatros and Pfalz fighters, the Dr.I offered exceptional maneuverability. Though the ailerons were not very effective, the rudder and elevator controls were light and powerful.[15] Rapid turns, especially to the right, were facilitated by the triplane's marked directional instability.[15]Vizefeldwebel Franz Hemer of Jasta 6 said, "The triplane was my favorite 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 maneuverable, it was no longer fast enough."[16]
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.[17] 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.[18]
The Dr.I suffered other deficiencies. The pilot's view was poor during takeoff and landing.[19] The cockpit was cramped and furnished with materials of inferior quality.[20] 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.[21]
Wing failures
Heinrich Gontermann's wrecked Dr.I
On 29 October 1917, Leutnant der ReserveHeinrich Gontermann, Staffelführer of Jasta 15, was performing aerobatics when his triplane broke up.[22] Gontermann was killed in the ensuing crash landing. Leutnant der Reserve Günther Pastor of Jasta 11 was killed two days later when his triplane broke up in level flight.[22] Inspection of the wrecked aircraft showed that the wings had been poorly constructed. Examination of other high-time triplanes confirmed these findings. On 2 November, Idflieg grounded all remaining triplanes pending an inquiry. Idflieg convened a Sturzkommission (crash commission) which concluded that poor construction and lack of waterproofing had allowed moisture to damage the wing structure.[23] This caused the wing ribs to disintegrate and the ailerons to break away in flight.[23]
In response to the crash investigation, Fokker was forced to improve quality control on the production line, particularly varnishing of the wing spars and ribs, to combat moisture. Fokker also strengthened the rib structures and the attachment of the auxiliary spars to the ribs.[24] Existing triplanes were repaired and modified at Fokker's expense.[25] After testing a modified wing at Adlershof, Idflieg authorized the triplane's return to service on 28 November 1917.[26] Production resumed in early December. By January 1918, Jastas 6 and 11 were fully equipped with the triplane. Only 14 squadrons used the Dr.I as their primary equipment. Most of these units were part of Jagdgeschwadern I, II, or III.[27] Frontline inventory peaked in late April 1918, with 171 aircraft in service on the Western Front.[13]
Despite corrective measures, the Dr.I continued to suffer from wing failures. On 3 February 1918, Leutnant Hans Joachim Wolff of Jasta 11 successfully landed after suffering a failure of the upper wing leading edge and ribs.[28] On 18 March 1918, Lothar von Richthofen, Staffelführer of Jasta 11, suffered a failure of the upper wing leading edge during combat with Sopwith Camels of No. 73 Squadron and Bristol F.2Bs of No. 62 Squadron.[29] Richthofen was seriously injured in the ensuing crash landing.
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 coefficient than the lower wing – at high speeds it could be 2.55 times as much.
The triplane's chronic structural problems destroyed any prospect of large-scale orders.[30] Production eventually ended in May 1918, by which time only 320 had been manufactured.[31] The Dr.I was withdrawn from frontline service as the Fokker D.VII entered widespread service in June and July. Jasta 19 was the last squadron to be fully equipped with the Dr.I.[32]
Surviving triplanes were distributed to training and home defense units. Several training aircraft were reengined with the 75kW (100hp) Goebel Goe.II.[33] At the time of the Armistice, many remaining triplanes were assigned to fighter training schools at Nivelles, Belgium, and Valenciennes, France.[34] Allied pilots tested several of these triplanes and found their handling qualities to be impressive.[34]
One of Richthofen's Fokker Dr.Is, on display at the Zeughaus
Experimental engines
Several Dr.Is were used as testbeds for experimental engines. One aircraft, designated V.7, was fitted with the Siemens-Halske Sh.III bi-rotary engine.[35] The V.7 exhibited exceptional rate of climb and ceiling, but it proved difficult to handle.[35] Serial 108/17 was used to test the 118kW (160hp) Goebel Goe. III, while serial 469/17 was used to test the 108kW (145hp) Oberursel Ur. III.[36] None of these engines were used on production aircraft. One triplane was used as a testbed for an experimental Schwade gear-driven supercharger.
Postwar
Three triplanes are known to have survived the Armistice. Serial 528/17 was retained as a testbed by the Deutschen Versuchsanstalt für Luftfahrt (German Aviation Research Institute) at Adlershof. After being used in the filming of two movies, 528/17 is believed to have crashed sometime in the late 1930s.[37] Serial 152/17, in which Manfred von Richthofen obtained three victories, was displayed at the Zeughaus museum in Berlin.[37] This aircraft was destroyed in an Allied bombing raid during World War II.
In 1932, Fokker assembled a Dr.I from existing components. It was displayed in the Deutsche Luftfahrt-Sammlung in Berlin. In 1943, the aircraft was destroyed in an Allied bombing raid. Today, only a few original Dr.I artifacts survive in museums.
Large numbers of replica and reproduction aircraft have been built for both individuals and museums. Bitz Flugzeugbau GmbH built two Dr.I replicas, serial numbers 001 and 002, for use in Twentieth Century Fox’s 1966 film The Blue Max. Replica 001 EI-APW is the oldest surviving example of the Dr.1. Because of the expense and scarcity of authentic rotary engines, most airworthy replicas are powered by a Warner Scarab or Continental R-670 radial engine.[38] A few, however, feature vintage Le Rhône 9J[39] or reproduction Oberursel Ur.II rotary engines.[40]
The Sopwith Camel is a British First World War-era single-seat biplane fighter aircraft that was introduced on the Western Front in 1917. It was developed by the Sopwith Aviation Company as a successor to the Sopwith Pup and became one of the best known fighter aircraft of the Great War.
The Fokker E.V was a German parasol-monoplane fighter aircraft designed by Reinhold Platz and built by Fokker-Flugzeugwerke. The E.V was the last Fokker design to become operational with the Luftstreitkräfte, entering service in the last months of World War I. After several fatal accidents due to wing failures, the aircraft was modified and redesignated Fokker D.VIII. Dubbed the Flying Razor by post-war pulp-fiction writers, the D.VIII had the distinction of scoring the last aerial victory of the war.
The Sopwith Triplane is a British single seat fighter aircraft designed and manufactured by the Sopwith Aviation Company during the First World War. It has the distinction of being the first military triplane to see operational service.
The Idflieg designation system was used to classify German heavier-than-air military aircraft from the early days of the Fliegertruppe/Luftstreitkräfte to the end of World War I. The system evolved during this period as new classes of aircraft came into use.
Werner Voss was a World War I German flying ace credited with 48 aerial victories. A dyer's son from Krefeld, he was a patriotic young man while still in school. He began his military career in November 1914 as a 17‑year‑old Hussar. After turning to aviation, he proved to be a natural pilot. After flight school and six months in a bomber unit, he joined a newly formed fighter squadron, Jagdstaffel 2 on 21 November 1916. There he befriended Manfred von Richthofen.
The Deutsche Luftstreitkräfte —known before October 1916 as Die Fliegertruppen des deutschen Kaiserreiches —was the air arm of the Imperial German Army. In English-language sources it is usually referred to as the Imperial German Air Service, although that is not a literal translation of either name. German naval aviators of the Marine-Fliegerabteilung were an integral part of the Imperial German Navy. Both military branches operated aeroplanes, observation balloons and airships.
Royal Prussian Jagdstaffel 11 was founded on 28 September 1916 from elements of 4 Armee's Kampfeinsitzerkommandos 1, 2 and 3 and mobilized on 11 October as part of the German Air Service's expansion program, forming permanent specialised fighter squadrons, or "Jastas". It became the most successful fighter squadron in the Luftstreitkräfte.
The Albatros D.V is a fighter aircraft of the German aircraft manufacturer Albatros Flugzeugwerke. It was the final development of the Albatros D.I family and the last Albatros fighter to see operational service with the Luftstreitkräfte during the First World War.
The Fokker D.VI was a German fighter aircraft built in limited numbers at the end of World War I. The D.VI served in the German and Austro-Hungarian air services.
The Fokker D.III was a German single-seat fighter aircraft of World War I. It saw limited frontline service before being withdrawn from combat in December 1916.
The Fokker D.V was a German biplane fighter of World War I.
LeutnantHans Weiss was a German World War I flying ace credited with 16 aerial victories.
Royal Prussian Jagdstaffel 18 was a "hunting squadron" of the Luftstreitkräfte, the air arm of the Imperial German Army during World War I.
Royal Prussian Jagdstaffel 15, commonly abbreviated to Jasta 15, was a "hunting group" of the Luftstreitkräfte, the air arm of the Imperial German Army during World War I. The unit would score over 150 aerial victories during the war, at the expense of seven killed in action, two killed in flying accidents, three wounded in action, one injured in a flying accident, and two taken prisoner of war.
Royal Prussian Jagdstaffel 6 was one of the original units of the Luftstreitkräfte, the air arm of the Imperial German Army during World War I.
Royal Prussian Jagdstaffel 12 was a World War I "hunting group" of the Luftstreitkräfte, the air arm of the Imperial German Army during World War I. As one of the original German fighter squadrons, the unit would score 155 aerial victories during the war, at the expense of seventeen killed in action, eight wounded in action, and one taken prisoner of war.
Royal Prussian Jagdstaffel 26 was a "hunting group" of the Luftstreitkräfte, the air arm of the Imperial German Army during World War I. As one of the original German fighter squadrons, the unit would score 177 verified aerial victories, including four observation balloons destroyed. The Jasta would pay a bloody price for its success: five pilots killed in action, nine wounded in action, and one prisoner of war.
Royal Prussian Jagdstaffel 27, commonly abbreviated to Jasta 27, was a "hunting group" of the Luftstreitkräfte, the air arm of the Imperial German Army during World War I.
Jagdgeschwader II was the Imperial German Air Service's second fighter wing. Established because of the great success of Manfred von Richthofen's preceding Jagdgeschwader I wing, Jagdgeschwader II and Jagdgeschwader III were founded on 2 February 1918. JG II was assigned four squadrons nominally equipped with 14 aircraft each. The new wing was supposed to be fully operational in time for an offensive slated for 21 March 1918. Named to raise and lead it was 23-victory flying ace Hauptmann Adolf von Tutschek. However, he was killed in action on 15 March 1918.
Jagdgeschwader III was a fighter wing of the Imperial German Air Service during World War I. It was founded on 2 February 1918, as a permanent consolidation of four established jagdstaffeln —2, 26, 27, and 36. JG III was formed as a follow-on of Manfred von Richthofen's highly successful Jagdgeschwader I. With a nominal strength of 56 aircraft, JG III would be under direct orders of an Armee headquarters. The German General Staff was planning a German spring offensive to begin on 21 March 1918, and wanted to assign a fighter wing to each of the three Armees involved in the assault. An experienced flying ace with 22 victories, Oberleutnant Bruno Loerzer, was appointed to command JG III.
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