Fokker Dr.I: Why the Red Baron's Triplane Shed Its Wings in Mid-Air

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In February 1917 the Royal Naval Air Service introduced the Sopwith Triplane, whose three wings gave it a climb and turn that outmaneuvered Germany's better-armed Albatros fighters. In April Anthony Fokker inspected a captured Sopwith at Jasta 11 and simply told his chief designer, Reinhold Platz, to build a triplane, with no drawings or measurements. Platz drew on his work with Hugo Junkers on thick, self-supporting cantilever wings. The V4 prototype was exhausting to roll, so the V5 added horn-balanced ailerons and elevators plus a single interplane strut to stop wing flutter. After destructive sandbag testing in August 1917, Manfred von Richthofen took an early machine up in September and shot down two Allied fighters in two days.

The Dr.I was directionally unstable, which let it snap into turns but left it slow, weak at altitude with its Oberursel rotary engine, blind on landing and dangerous to the face, with the gun butts inches from the pilot. Under the British blockade Germany ran out of castor oil, and substitute lubricants broke down until engines seized in flight. In late October 1917 Heinrich Gontermann died when his triplane broke apart during aerobatics, and two days later Günther Pastor died in level flight. A crash commission blamed poor wing ribs and missing waterproofing, and Fokker paid for fixes. A 1929 NACA wind tunnel study found the real cause: the top wing carried 2.55 times the lift of the bottom wing at high speed.

• Production peaked with 171 triplanes at the front in April 1918 and stopped by May, after only 320 were built.
• Lothar von Richthofen was badly injured in March 1918 when the leading edge of his upper wing shattered in combat.
• Germany built over 3,000 Fokker D.VIIs to replace the Dr.I.
• Manfred von Richthofen scored his final 17 victories in triplanes before his death in April 1918.
• All three surviving originals were lost, including Richthofen's in a Berlin museum and one Fokker assembled in 1932, both destroyed by bombing.