O.Thetford, P.Gray German Aircraft of the First World War (Putnam)

Euler Quadruplane
   The designation of quadruplane (vierdecker) was something of a misnomer, for the top surfaces were, in fact, full-span ailerons, although the machine was later modified and normal ailerons fitted. Engine, 100 h.p. Oberursel U I. Area, 46.175 sq.m. (498.7 sq.ft.). Weights: Empty, 883.5 kg. (1,844 lb.). Loaded, 1,383.5 kg. (3,044 lb.).

W.Green, G.Swanborough The Complete Book of Fighters

EULER VIERDECKER Germany

   Although referred to as a vierdecker (quadruplane), this Euler fighter powered by a 100 hp Oberursel U I seven-cylinder rotary, which commenced its flight test programme in December 1917, was technically a triplane in that the top surfaces were, in fact, full-span ailerons acting as a controllable fourth wing surface. The poor performance demonstrated during evaluation at Adlershof, which was continuing in May 1918, precluded further military interest in the design, although a second prototype was completed with a 110 hp Goebel Goe II seven-cylinder rotary. Both prototypes were transported out of the Allied zone of occupation in December 1918.

Empty weight, 1,948 lb (883,5 kg).
Loaded weight, 3,054 lb (1385,5 kg).
Wing area, 497 sq ft (46,17 m2).