O.Thetford, P.Gray German Aircraft of the First World War (Putnam)
Euler Dr 1
The first Euler triplane, powered with 160 h.p. Oberursel U III. No data. The designation was not official, neither is it completely certain.
Euler Dr 2
Another experimental triplane powered with 160 h.p. Mercedes D III engine. No data. The designation was not official.
Euler Dr 3
Further experimental triplane, a development of Dr 2 fitted with 100 h.p. Oberursel U I engine. No data. The designation was not official.
Euler Dr 4
This triplane emerged from the Euler-Werke in 1916 and was an extremely ungainly aircraft intended for training duties and featuring side-by-side seating arrangement. Engine, 220 h.p. Mercedes D IV with reduction gears. Span, 10.0 m. (32 ft. 9 3/4 in.). Length, 8.0 m. (26 ft. 3 in.). Height, 3.1 m. (10 ft. 2 in.). Area, 37.5 sq.m. (405 sq.ft.). The designation was not official.
W.Green, G.Swanborough The Complete Book of Fighters
EULER DREIDECKER (TYPE 2) Germany
In 1917, the Austro-Hungarian engineer Julius Hromadnik joined forces with August Euler, the result of this partnership being a series of private venture biplane, triplane and quadruplane fighters comprising approximately half of the 22 experimental aircraft produced by the Euler-Werke during World War I. The first-known Euler experimental fighter triplane developed in collaboration with Hromadnik was first reported in July 1917, this being Euler’s second wartime triplane as, in August of the previous year, the company had flown a side-by-side two-seat training triplane powered by a 220 hp eight-cylinder Mercedes DIV engine. The fighter triplane was powered by a 14-cylinder two-row Oberursel U III engine of 160 hp and featured I-type struts between the centre and lower wing, and V-type struts between the centre and upper wing. Disappointing performance led to the modification of this experimental fighter to biplane configuration and in this form it was still under test in April 1918. No specification is available.
EULER DREIDECKER (TYPE 3) Germany
An entirely new single-seat fighter triplane produced by the Euler-Werke with the assistance of Julius Hromadnik was flown for the first time in November 1917. Built, like its predecessor, as a private venture, it had parallel-chord equi-span wings with I-type interplane struts and a 160 hp Mercedes D III engine. This type evidently fell short of requirements as, like the earlier fighter triplane, it was rebuilt in biplane form (see Doppeldecker Type 1) for further trials. No specification is available.
EULER DREIDECKER (TYPE 4) Germany
The most successful of the Euler-Hromadnik fighter triplanes was powered by the newly-perfected Goebel Goe III nine-cylinder rotary engine of 180 hp. By virtue of having achieved an altitude of 16,405 ft (5 000 m) in 13.5 min, the Goe III-powered triplane was demonstrated during the second D-type contest at Adlershof in May 1918. However, service pilots were unimpressed by the fighter, the tailplane of which was severely damaged during taxying, and the aircraft was returned to the Euler-Werke in consequence, remaining there until removed from the factory in December 1918. No specification is available.
EULER DREIDECKER (TYPE 5) Germany
Some doubts concerning the efficacy of the full-span ailerons acting as a controllable wing, as utilised by the Euler-Vierdecker (which see), resulted in the development of a more orthodox triplane version of the same basic design with normal ailerons fitted. Initially powered by a similar 100 hp Oberursel U I seven-cylinder rotary, it was reportedly later re-engined with the more efficient 110 hp nine-cylinder Siemens und Halske Sh I counter-rotating power plant. At the same time, equal wing gap replaced the unequal gap with which initial flight testing was conducted, the centre wing being raised on the fuselage and the cabane struts being lengthened. No specification is available.