Fokker Dr.I

infobox Aircraft
name = Fokker Dr.I
type = Fighter
manufacturer = Fokker-Flugzeugwerke

---

300px
caption =
designer =Reinhold Platz
first flight = 5 July avyear|1917
introduced =
retired =
status =
primary user = "Luftstreitkräfte"
more users =
produced =
number built =320
unit cost =
variants with their own articles =

The Fokker Dr.I "Dreidecker" (triplane) was a World War I fighter aircraft designed by Reinhold Platz and 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 20 victories, and in which he was killed on 21 April 1918.

Design and development

In February 1917, the Sopwith Triplane began to appear over the Western Front. Franks 2004, p. 9.] The Sopwith swiftly proved itself superior to the Albatros fighters then in use by the "Luftstreitkräfte". Franks 2004, p. 21.] Leaman 2003, pp. 30, 32.] Fokker-Flugzeugwerke responded by converting an unfinished biplane prototype into the V.4, a small, rotary-powered triplane with a steel tube fuselage and thick cantilever wings. Leaman 2003, p. 34.] Initial tests revealed that the V.4 had unacceptably high control forces resulting from the use of unbalanced ailerons and elevators. Weyl 1965, p. 226.]

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. Weyl 1965, p. 228.] 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. Weyl 1965, p. 229.]

Operational history

Two pre-production triplanes, designated F.I, were delivered to "Jastas" 10 and 11 for combat evaluation. These aircraft, serials 102/17 and 103/17, were the only machines to receive the F.I designation. Weyl 1965, p. 231.] They arrived 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" ("Kommandierenden General der Luftstreitkräfte") that the F.I was superior to the Sopwith Triplane. Weyl 1965, p. 232.] Richthofen recommended that fighter squadrons be reequipped with the new aircraft as soon as possible. Weyl 1965, p. 232.] 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 "Leutnant" 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. Leaman 2003, p. 53.] "Idflieg" issued a production order for 100 triplanes in September, followed by an order for 200 in November.Franks and VanWyngarden 2001, p. 22.] Delivery of these machines commenced in October. They were identical to the F.I except for the addition of wingtip skids. All initial deliveries were to squadrons within Richthofen's "Jagdgeschwader" I.

Compared to 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. Leaman 2003, p. 95.] Rapid turns, especially to the right, were facilitated by the triplane's marked directional instability. Leaman 2003, p. 95.] "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." VanWyngarden 2004, p. 75.]

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 due to the low-compression Oberursel Ur.II, a clone of the Le Rhône 9J rotary engine. Nowarra 1990, p. 12.] 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.Franks and VanWyngarden 2001, p. 83.]

Furthermore, the Dr.I proved tricky to land and prone to ground looping, as evidenced by the wingtip skids. Leaman 2003, p. 96.] The cockpit was cramped, Weyl 1965, p. 244.] 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. Weyl 1965, p. 410.]

Wing failures

On 29 October 1917, "Leutnant der Reserve" Heinrich Gontermann, "Staffelführer" of "Jasta" 15, was performing aerobatics when his triplane broke up. Weyl 1965, p. 233.] Gontermann was fatally injured 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. Weyl 1965, p. 233.] Inspection of the wrecked aircraft showed that the wings had been poorly constructed. Examination of other high-time Dr.Is 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 destroy the wing. Weyl 1965, pp. 233-234.] This caused the wing ribs to disintegrate and the ailerons to break away in flight. Weyl 1965, pp. 233-234.]

In response to the crash investigation, Fokker improved 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. Existing triplanes were modified at Fokker's expense. Weyl 1965, p. 235.] After testing a modified wing at Adlershof, "Idflieg" authorized the triplane's return to service on 28 November 1917. Weyl 1965, pp. 238-239.] 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.Franks and VanWyngarden 2001, p. 55.] Frontline inventory peaked in late April 1918, with 171 aircraft in service on the Western Front.Franks and VanWyngarden 2001, p. 22.]

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.Franks and VanWyngarden 2001, p. 25.] 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.Franks and VanWyngarden 2001, pp. 26-27.] 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. Weyl 1965, p. 236.] Production eventually ended in May 1918, by which time only 320 had been manufactured. Gray and Thetford 1962, p. 100.] 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. Leaman 2003, p. 69.]

Surviving triplanes were distributed to training and home defense units. Several training aircraft were reengined with the 100 hp Goebel Goe.II. Leaman 2003, p. 222.] At the time of the Armistice, many remaining triplanes were assigned to fighter training schools at Nivelles, Belgium, and Valenciennes, France. Weyl 1965, p. 246.] Allied pilots tested several of these triplanes and found their handling qualities to be impressive. Weyl 1965, p. 246.]

Postwar

Very few triplanes 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. Leaman 2003, p. 181.] Serial 152/17, in which Manfred von Richthofen obtained three victories, was displayed at the "Zeughaus" museum in Berlin. Leaman 2003, p. 181.] The triplane was destroyed by an Allied bombing raid during World War II. Today, only a few original Dr.I artifacts survive in museums.

Reproductions

While no Dr.I airframes survive, large numbers of flying and static reproductions have been built. The Omaka Aviation Heritage Centre in Blenheim, New Zealand, maintains four flyable aircraft. Two examples are displayed at Old Rhinebeck Aerodrome in Rhinebeck, New York. Two others fly with the Great War Flying Museum from Brampton, Ontario. Due to the expense and scarcity of authentic rotary engines, most airworthy reproductions are powered by a Warner Scarab, Continental R-670, or a similar radial engine. Nowarra 1990, p. 47.] A few reproductions, however, feature vintage Le Rhône 9 engines.

Variants

*V.3 - Initial prototype
*V.4 - First production prototype
*V.5 - Prototype with Goebel Goe.III engine
*V.6 - Enlarged prototype with Mercedes D.II engine
*V.7 - Prototype with Siemens-Halske Sh.III engine
*V.10 - Prototype with Oberursel Ur.III engine

Operators

;flag|German Empire
*"Luftstreitkräfte"

pecifications (Dr.I)

aircraft specifications
plane or copter?=plane
jet or prop?=prop
ref= Quest for Performance Loftin 2004, Table I.]
crew=One
length main=18 ft 11 in
length alt=5.77 m
span main=23 ft 7 in
span alt=7.20 m
height main=9 ft 8 in
height alt=2.95 m
area main=201 ft²
area alt=18.70 m²
empty weight main=895 lb
empty weight alt=406 kg
loaded weight main=1,292 lb
loaded weight alt=586 kg
max takeoff weight main=
max takeoff weight alt=
more general=Zero-lift drag coefficient: 0.0323
*Drag area: 6.69 ft² (0.62 m)
*Aspect ratio: 4.04
engine (prop)= Oberursel Ur.II
type of prop=9-cylinder rotary engine
number of props=1
power main=110 hp
power alt=82 kW
max speed main=115 mph
max speed alt=185 km/h
stall speed main=45 mph
stall speed alt=72 km/h
range main=185 mi
range alt=300 km
ceiling main=20,000 ft
ceiling alt=6,095 m
climb rate main=1,130 ft/min
climb rate alt=5.7 m/s
loading main=
loading alt=
power/mass main=
power/mass alt=
more performance=

Lift-to-drag ratio: 8.0
armament=
*2 × 7.92 mm "Spandau" LMG 08/15 machine guns.

ee also

aircontent
related=
similar aircraft=
*Sopwith Triplane
*Sopwith Camel
sequence=
see also=

References

Notes

Bibliography

* Franks, Norman. "Sopwith Triplane Aces of World War I (Aircraft of the Aces No. 62)". Oxford: Osprey Publishing, 2004. ISBN 1-84176-728-X.
* Franks, Norman and Greg VanWyngarden. "Fokker Dr.I Aces of World War I (Aircraft of The Aces No. 40)." Oxford: Osprey Publishing, 2001. ISBN 1-84176-223-7.
* Gray, Peter and Owen Thetford. "German Aircraft of the First World War". London: Putnam, 1962. ISBN 0-93385-271-1
* Leaman, Paul. "Fokker Dr.I Triplane: A World War One Legend". Hersham, Surrey, UK: Classic Publications, 2003. ISBN 1-90322-328-8.
* Loftin Jr., Laurence K. "Quest for Performance: The Evolution of Modern Aircraft." NASA Scientific and Technical Information Branch, 2004. [http://www.hq.nasa.gov/pao/History/SP-468/cover.htm] Retrived on 22 April 2006.
* Nowarra, Heinz J. "Fokker Dr.I In Action (Aircraft No. 98)". Carrollton, TX: Squadron/Signal Publications, Inc., 1990. ISBN 0-89747-229-2.
* Vanwyngarden, Greg. "Richthofen's Flying Circus: Jagdgeschwader Nr I (Aviation Elite Units No. 16)." Oxford: Osprey Publishing, 2004. ISBN 1-84176-726-3.
* Weyl, A.R. "Fokker: The Creative Years". London: Putnam, 1965. ISBN 0-85177-817-8.

External links

* [http://www.fokkerdr1.com/ Fokker DR1.com - Research on the Fokker Dr.I]
* [http://www.aviation-history.com/fokker/dr1.html Fokker Dr.I Triplane: Germany]
* [http://www.theaerodrome.com/aircraft/germany/fokker_dri.php Fokker DR.I - The Aerodrome]