Fokker Dr.I
From Wikipedia, the free encyclopedia
| Fokker Dr.I | |
|---|---|
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| Type | Fighter |
| Manufacturer | Fokker-Flugzeugwerke |
| Designed by | Reinhold Platz |
| Maiden flight | July 1917 |
| Primary user | Luftstreitkräfte |
| Number built | 320 |
The Fokker Dr. I Dreidecker (triplane) was a World War I fighter aircraft designed by Reinhold Platz and built by Fokker-Flugzeugwerke. It became most famous as the plane flown by the Red Baron, Manfred von Richthofen.
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[edit] Development
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 superior to the triplane prototypes submitted by other manufacturers. After a type test, Idflieg issued an immediate production order.
[edit] Combat Debut
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. 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 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. Compared to the Albatros and Pfalz fighters it replaced, the Dr.I offered remarkable maneuverability and initial rate of climb rate. 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.
The Dr.I also demonstrated significant drawbacks. The triplane's instability made it a poor gun platform. More importantly, it was considerably slower than contemporary Allied fighters in level flight and in a dive. 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.
[edit] Wing failures
On October 30, 1917, Leutnant Heinrich Gontermann, commander of Jasta 15 and a 39 victory ace, was killed when his triplane broke up in flight. Leutnant Günther Pastor was killed on the following day under similar circumstances. The remaining triplanes were immediately grounded pending an inquiry. Idflieg convened a Sturzkommission (crash commission) which concluded that poor construction and lack of waterproofing caused the wing ribs to disintegrate and the ailerons to break away.
In response to the crash investigation, Fokker improved quality control on the production line, particularly varnishing of the wing spars and ribs, to keep moisture from destroying the wing. Fokker also strengthened the rib structures and the attachment of the auxiliary spars to the ribs. 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. Despite corrective measures, the triplane continued to suffer from wing failures. On 18 March 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.
[edit] 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 1930's. Serial 152/17, in which Manfred von Richthofen scored three kills, 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 152/17 is presumed to have been destroyed near the end of the war. Today, no original example of the Dr.I survives.
[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
[edit] Operators
[edit] Specifications (Dr. I)
Data from Quest for Performance[1]
General characteristics
- Crew: One
- Length: 18 ft 11 in (5.77 m)
- Wingspan: 23 ft 7 in (7.20 m)
- Height: 9 ft 8 in (2.95 m)
- Wing area: 201 ft² (18.70 m²)
- Empty weight: 895 lb (406 kg)
- Loaded weight: 1,292 lb (586 kg)
- Powerplant: 1× Oberursel UR.II 9-cylinder rotary engine, 110 hp (82 kW)
- Zero-lift drag coefficient: 0.0323
- Drag area: 6.69 ft² (0.62 m)
- Aspect ratio: 4.04
Performance
- Maximum speed: 115 mph (185 km/h)
- Stall speed: 45 mph (72 km/h)
- Range: 185 mi (300 km)
- Service ceiling: 20,000 ft (6,095 m)
- Rate of climb: 1,130 ft/min (5.7 m/s)
- Lift-to-drag ratio: 8.0
Armament
- 2x 7.92 mm "Spandau" LMG 08/15 machine guns.
[edit] Notes
- ^ Loftin, LK, Jr. Quest for performance: The evolution of modern aircraft. NASA SP-468. Retrieved on April 22, 2006.
[edit] References
- Leaman, Paul. Fokker Dr.I Triplane: A World War One Legend. Classic Publications, 2003. ISBN 1-90322-328-8.
- Green, William and Swanborough, Gordon. The Great Book Of Fighters. MBI Publishing 1994. ISBN 0-83173-939-8.
- Weyl, A.R. (1988) Fokker: The Creative Years. Putnam, 1988. ISBN 0-85177-817-8.
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