O.Thetford, P.Gray German Aircraft of the First World War (Putnam)
Kondor D 7
Appearing late in 1917, the single-seat lighter D 7 bore unmistakable signs of Albatros influence, although design of the machine is credited to Westphal. Bracing of the wing cellule was novel, as was also the slinging of the ply-skinned fuselage between the wings. The extremely robust undercarriage chassis was attached to the main longerons, which were in the vertical and horizontal centre-line planes. The fuselage, with underslung lower wing, evolved from an earlier triplane design which was a failure. The D 7 also failed to come up to expectation. Engine, 160 h.p. Mercedes D III. Span, 8.5 m. (27 ft. 10 3/4 in.). Length. 6.2 m. (20 ft. 4 1/8 in.). Height, 2.3 m. (7 ft. 6 1/2 in.). Area, 15.7 sq.m. (169.5 sq.ft.). Weights: Empty, 590 kg. (1,298 lb.). Loaded, 785 kg. (1,727 lb.).
W.Green, G.Swanborough The Complete Book of Fighters
KONDOR D 7 Germany
The D 7 single-seat fighter was essentially a re-work of the original Kondor triplane fighter as a biplane, retaining the plywood-covered steel tube fuselage, tail and lower wing. The bracing of the wing cellule was novel, the interplane struts taking the form of inverted tripods, and the fuselage was mounted between the wings, the lower wing being braced to the robust undercarriage rather than directly to the fuselage. The initial flight tests of the D 7 are unrecorded, but an Idflieg report stated that the D 7 had now been fitted with a standard 160 hp Mercedes D III engine with which it was expected to resume flight testing in early May 1918. The D 7 did not make an appearance at the second D-type contest in June 1918, development having apparently been discontinued meanwhile.
Max speed, 112 mph (180 km/h).
Endurance, 1.45 hrs.
Empty weight, 1,300 lb (590 kg).
Loaded weight, 1,731 lb (785 kg).
Span, 27 ft 10 2/3 in (8,50 m).
Length, 20 ft 4 in (6,20 m).
Height, 7 ft 6 1/2 in (2,30 m).
Wing area, 169 sq ft (15,70 m2).
J. Herris German Aircraft of Minor Manufacturers in WW1. Vol I (A Centennial Perspective on Great War Airplanes 49)
As far as is known, the Kondor D.III-D.V designs were not built. The Kondor D.VII was thus the next Kondor fighter built. The D.VII represented a complete departure from the previous D.I, D.II, and D.VI family.
The D.VII eliminated the low-powered rotary engine in favor of a more powerful 160 hp Mercedes D.III water-cooled 6-cylinder engine. This was the same engine used in the Albatros fighter series, Pfalz D.III/IIIa, and the initial production Fokker D.VII. The Mercedes and its cooling system were heavier than rotary engines but offered more power and better high-altitude performance.
The fuselage of the D.VII closely resembled that of Albatros fighters, which had undoubtedly influenced its design. A triplane variant of the D.VII was also built but was unsuccessful, - unfortunately, no photos or data on the Kondor triplane fighter have survived.
One influence of the triplane design was that the lower wing of the D.VII was mounted under the fuselage. This gave the D.VII sufficient gap between the upper and lower wings to avoid aerodynamic interference. The landing gear appears to be very robust and does not follow the typical design of the period. The wing bracing was also different than typical practice. It also appears robust but the lower wing apparently had a single spar, a design flaw that made the lower wings of fighters with the Nieuport wing cellule subject to failure from aerodynamic flutter.
No performance data has survived, but the Kondor D.VII remained a single prototype. Significant performance advances over contemporary Albatros fighters could not be expected because the fighters shared the same engine, construction, and technology. The innovative thick airfoil wing used by the Fokker D.VII was the secret to its success, and the Kondor D.VII did not have this great technical advantage.
Kondor D.VII Specifications
Engine: 160 hp Mercedes D.III
Wing: Span 8.5 m
Wing Area 15.7 m2
General: Length 6.2 m
Height 2.3 m
Empty Weight 590 kg
Loaded Weight 785 kg