| Fokker Dr.I | |
|---|---|
 Fokker Dr.I | |
| General information | |
| Type | Fighter |
| Manufacturer | Fokker-Flugzeugwerke |
| Designer | Reinhold Platz |
| Primary user |  Luftstreitkräfte |
| Number built | 320[1] |
| History | |
| First flight | July 5, 1917 (1917-07-05) |
| Developed from | Fokker V.4 Fokker F.I |
| Variant | Fokker V.7 |
TheFokker Dr.I (Dreidecker, 'triplane' inGerman), often known simply as theFokker Triplane, was aWorld War Ifighter aircraft built byFokker-Flugzeugwerke. The Dr.I saw widespread service in the spring of 1918. It became famous as the aircraft in whichManfred von Richthofen gained his last 17 victories (plus two earlier ones in theFokker F.I prototype in September 1917), and in which he was killed on 21 April 1918. The Fokker Dr.I was flown with great success by many other German aces, most notablyJosef Jacobs with 30 confirmed kills in the type.[2]
In February 1917, theSopwith Triplane began to appear over theWestern Front.[3] Despite its singleVickers machine gun armament, the Sopwith swiftly proved itself superior to the more heavily armedAlbatros fighters then in use by theLuftstreitkräfte.[4][5] In April 1917,Anthony Fokker viewed a captured Sopwith Triplane while visitingJasta 11. Upon his return to the Schwerin factory, Fokker instructedReinhold Platz to build a triplane, but gave him no further information about the Sopwith design.[6] Platz responded with theV.4, a small, rotary-powered triplane with a steel tube fuselage and thick cantilever wings,[7] first developed during Fokker's government-mandated collaboration withHugo Junkers. Initial tests revealed that the V.4 had unacceptably high control forces resulting from the use of unbalancedailerons andelevators.[8]
Instead of submitting the V.4 for a type test, Fokker produced a revised prototype designatedV.5. The most notable changes were the introduction of horn-balanced ailerons and elevators, as well as longer-span wings. The V.5 also featuredinterplane struts, which were not necessary from a structural standpoint, but which minimized wing flexing.[9] 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.[10]
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The first two pre-production triplanes were designatedF.I, in accord withIdflieg'searly class prefix for triplanes. These aircraft, serials 102/17 and 103/17, were the only machines to receive the F.I designation[11] and could be distinguished from subsequent aircraft bya slight convex curve.Archived 2010-11-03 at theWayback Machine The two aircraft were sent toJastas 10 and11 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 theKogenluft (Kommandierender General der Luftstreitkräfte) that the F.I was superior to the Sopwith Triplane.[12] Richthofen recommended that fighter squadrons be reequipped with the new aircraft as soon as possible.[12] The combat evaluation came to an abrupt conclusion whenOberleutnantKurt Wolff,Staffelführer ofJasta 11, was shot down in 102/17 on 15 September, andLeutnantWerner Voss,Staffelführer ofJasta 10, was killed in 103/17 on 23 September.
The remaining pre-production aircraft, designatedDr.I, were delivered toJasta 11.[13]Idflieg issued a production order for 100 triplanes in September, followed by an order for 200 in November.[14] 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 toground looping.[15] In October, Fokker began delivering the Dr.I to squadrons within Richthofen'sJagdgeschwader 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.[16] Rapid turns, especially to the right, were facilitated by the triplane's marked directional instability.[16]Vizefeldwebel Franz Hemer ofJasta 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."[17]
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 theOberursel Ur.II, a clone of theLe Rhône 9J rotary engine.[18] As the war continued, chronic shortages ofcastor oil made rotary operation increasingly difficult. The poor quality of Germanersatz lubricant resulted in many engine failures, particularly during the summer of 1918.[19]
The Dr.I suffered other deficiencies. The pilot's view was poor during takeoff and landing.[20] The cockpit was cramped and furnished with materials of inferior quality.[21] 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.[22]
On 29 October 1917,Leutnant der ReserveHeinrich Gontermann,Staffelführer ofJasta 15, was performing aerobatics when his triplane broke up.[23] Gontermann was killed in the ensuing crash landing.Leutnant der Reserve Günther Pastor ofJasta 11 was killed two days later when his triplane broke up in level flight.[23] 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 aSturzkommission (crash commission) which concluded that poor construction and lack of waterproofing had allowed moisture to damage the wing structure.[24] This caused thewing ribs to disintegrate and the ailerons to break away in flight.[24]
In response to the crash investigation, Fokker was forced to improve quality control on the production line, particularly varnishing of thewing spars and ribs, to combat moisture. Fokker also strengthened the rib structures and the attachment of the auxiliary spars to the ribs.[25] Existing triplanes were repaired and modified at Fokker's expense.[26] After testing a modified wing at Adlershof,Idflieg authorized the triplane's return to service on 28 November 1917.[27] 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 ofJagdgeschwadern I, II, or III.[28] Frontline inventory peaked in late April 1918, with 171 aircraft in service on the Western Front.[14]
Despite corrective measures, the Dr.I continued to suffer from wing failures. On 3 February 1918,Leutnant Hans Joachim Wolff ofJasta 11 successfully landed after suffering a failure of the upper wing leading edge and ribs.[29] On 18 March 1918,Lothar von Richthofen,Staffelführer ofJasta 11, suffered a failure of the upper wing leading edge during combat withSopwith Camels of No. 73 Squadron andBristol F.2Bs of No. 62 Squadron.[30] 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.[31]
The triplane's chronic structural problems destroyed any prospect of large-scale orders.[32] Production eventually ended in May 1918, by which time only 320 had been manufactured.[33] The Dr.I was withdrawn from frontline service as theFokker D.VII entered widespread service in June and July.Jasta 19 was the last squadron to be fully equipped with the Dr.I.[34]
Surviving triplanes were distributed to training and home defense units. Several training aircraft were reengined with the 75 kW (100 hp) Goebel Goe.II.[35] At the time of theArmistice, many remaining triplanes were assigned to fighter training schools atNivelles, Belgium, andValenciennes, France.[36] Allied pilots tested several of these triplanes and found their handling qualities to be impressive.[36]
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Several Dr.Is were used as testbeds for experimental engines. One aircraft, designated V.7, was fitted with theSiemens-Halske Sh.III bi-rotary engine.[37] The V.7 exhibited exceptional rate of climb and ceiling, but it proved difficult to handle.[37] Serial 108/17 was used to test the 118 kW (160 hp) Goebel Goe. III, while serial 469/17 was used to test the 108 kW (145 hp) Oberursel Ur. III.[38] None of these engines were used on production aircraft. One triplane was used as a testbed for an experimental Schwade gear-driven supercharger.
Three triplanes are known to have survived the Armistice. Serial 528/17 was retained as a testbed by theDeutschen 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.[39] Serial 152/17, in whichManfred von Richthofen obtained three victories, was displayed at theZeughaus museum in Berlin.[39] This aircraft was destroyed in an Allied bombing raid duringWorld War II.
In 1932, Fokker assembled a Dr.I from existing components. It was displayed in theDeutsche 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 inTwentieth Century Fox’s 1966 filmThe Blue Max. Replica 001 EI-APW is the oldest surviving example of the Dr.1. Because of the expense and scarcity of authenticrotary engines, most airworthy replicas are powered by aWarner Scarab orContinental R-670 radial engine.[40] A few, however, feature vintageLe Rhône 9J[41] or reproduction Oberursel Ur.II rotary engines.[42]
In 2014,Iron Maiden lead singerBruce Dickinson purchased replica G-CDXR.[43]
Data fromQuest for Performance.[44]
General characteristics
Performance
Armament
Aircraft of comparable role, configuration, and era
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