The Fokker Dr.I Dreidecker 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.
Design and development In February 1917, the Sopwith Triplane
began to appear over the Western Front. 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.
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, 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. 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. 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. Operational history
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 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 that the F.I was superior to the Sopwith Triplane.
Richthofen recommended that fighter squadrons be reequipped 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 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. Idflieg issued a production order
for 100 triplanes in September, followed by an order for 200 in November. 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. 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
maneuverability. 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
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."
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 takeoff
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. = Wing failures=
On 29 October 1917, Leutnant der Reserve Heinrich Gontermann, Staffelführer of
Jasta 15, was performing aerobatics when his triplane broke up. 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. 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 which concluded that
poor construction and lack of waterproofing had allowed moisture to
damage the wing structure. This caused the wing ribs to disintegrate and the
ailerons to break away in flight. 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 repaired and modified at Fokker's expense. After testing a
modified wing at Adlershof, Idflieg authorized the triplane's return to
service on 28 November 1917. 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. Frontline inventory peaked in late April
1918, with 171 aircraft in service on the Western Front.
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. 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. 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 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. Production eventually ended in May 1918, by which
time only 320 had been manufactured. 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.
Surviving triplanes were distributed to training and home defense units. Several
training aircraft were reengined with the 75 kW Goebel Goe.II. At the time of
the Armistice, many remaining triplanes were assigned to fighter training
schools at Nivelles, Belgium, and Valenciennes, France. Allied pilots
tested several of these triplanes and found their handling qualities to be
impressive. = 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.
The V.7 exhibited exceptional rate of climb and ceiling, but it proved
difficult to handle. Serial 108/17 was used to test the 118 kW Goebel Goe. III,
while serial 469/17 was used to test the 108 kW Oberursal Ur. III. None of these
engines were used on production aircraft. One triplane was used as a
test bed for an experimental Schwade gear driven supercharger. Had the war
progressed into 1919, Fokker D.VIIIs might have been equipped with them.
Postwar Three triplanes are known to have
survived the Armistice. Serial 528/17 was retained as a testbed by the
Deutschen Versuchsanstalt für Luftfahrt at Adlershof. After being used in the
filming of two movies, 528/17 is believed to have crashed sometime in the
late 1930s. Serial 152/17, in which Manfred von Richthofen obtained three
victories, was displayed at the Zeughaus museum in Berlin. 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. Replica and reproduction aircraft
Large numbers of replica and reproduction aircraft have been built
for both individuals and museums. Bitz Flugzeugbau GmbH built two Dr.I replicas
for use in Twentieth Century Fox’s 1966 film The Blue Max. 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. A few,
however, feature vintage Le Rhône 9J or reproduction Oberursel Ur.II rotary
engines. Variants
V.4 - Initial prototype V.5 - First production prototype
V.6 - Enlarged prototype with Mercedes D.II engine
V.7 - Prototype with Siemens-Halske Sh.III engine
Operators German Empire
Luftstreitkräfte Specifications
Data from Quest for Performance General characteristics
Crew: One Length: 5.77 m
Wingspan: 7.20 m Height: 2.95 m
Wing area: 18.70 m2 Empty weight: 406 kg
Loaded weight: 586 kg Powerplant: 1 × Oberursel Ur.II
9-cylinder rotary engine, 82 kW Zero-lift drag coefficient: 0.0323
Drag area: 0.62 m2 Aspect ratio: 4.04
Performance Maximum speed: 185 km/h at sea level
Stall speed: 72 km/h Range: 300 km
Service ceiling: 6,095 m Rate of climb: 5.7 m/s
Lift-to-drag ratio: 8.0 Armament
2 × 7.92 mm "Spandau" lMG 08 machine guns.
See also Sands Fokker Dr.1 Triplane, homebuilt
replica Aircraft of comparable role,
configuration and era Sopwith Triplane
Sopwith Camel References
= Notes= = Bibliography=
External links Fokker DR1.com - Research on the Fokker
Dr.I Fokker Dr.I Triplane: Germany
Fokker DR.I - The Aerodrome Fokker DR1 Fact Sheet – National Museum
of the US Air Force Cole Palen's rotary powered Dr.I
reproduction at Old Rhinebeck Aerodrome