O.Thetford, P.Gray German Aircraft of the First World War (Putnam)
Albatros D XI
The D XI was the first of the Albatros D type lineage to use a rotary engine, and was fitted with the powerful geared Siemens-Halske Sh III of 160 h.p. This engine was installed in a horse-shoe cowling with pointed "elephant-ear" extensions to the rear. These acted as venturi and assisted cooling by sucking air through the cowling, which action also reduced drag.
Two prototypes were built, the first with a four-blade airscrew and balanced ailerons of parallel chord, and the second machine with unbalanced ailerons of inverse taper and a two-blade propeller. Hollow wooden I struts braced the wings. Flying and landing loads were taken by two hollow diagonal struts, which dispensed with need for wire bracing. Both aircraft featured plywood box-type fuselage with built-in fin, the remainder of the aircraft being fabric covered.
Initially flown in February 1918, the D XIs participated in the second D type competition. Remarkable climb performances were established, but no production order was given. Span, 8.0 m. (26 ft. 3 in.). Length, 5.58 m. (18 ft. 3 3/4 in.). Height, 2.86 m. (9 ft. 4 5/8 in.). Area, 18.5 sq.m. (199.8 sq.ft.). Weights: Empty, 494 kg. (1,087 lb.). Loaded, 689 kg. (1,516 lb). Speed, 190 km.hr. (118.75 m.p.h.). Climb (D Comp. at loaded weight of 723 kg.), 15,000 m. (16,400 ft.) in 151 min. Duration, 1.5 hr. Armament, twin Spandau machine-guns.
W.Green, G.Swanborough The Complete Book of Fighters
ALBATROS D XI Germany
Flown for the first time in February 1918, the DXI departed from the traditional Albatros formula in certain respects. Like its predecessors, it was of wooden construction with fabric-covered wings and plywood-covered fuselage, but the unequal-span staggered wings had inclined aerofoil-section I-struts braced from their bases by pairs of diagonal struts which eliminated the need for wire bracing. For the first time in an Albatros fighter a rotary engine was employed, this being a 160 hp Siemens-Halske Sh III, and the unusually large propeller necessitated an exceptionally tall undercarriage. Armament comprised the usual twin 7,92-mm machine guns, and two prototypes were built, the first having a four-blade propeller and balanced parallel-chord ailerons, and the second having a two-blade propeller and unbalanced ailerons of inverse taper.
Max speed, 118 mph (190 km/h).
Time to 6,560 ft (2 000 m), 4.65 min.
Endurance, 1.5 hrs.
Empty weight, 1,089 lb (494 kg).
Loaded weight. 1,519 - 1,594 lb (689 - 723 kg).
Span, 26ft 3in (8,00m).
Length, 18ft 3 1/2 in (5,58m).
Wing area, 199.13 sqft (18,5 m2).
Jane's All The World Aircraft 1919
The single streamlined and outwards inclined strut idea has been carried out with the clear object of minimising the interplane connection head resistance, and in conjunction the inclined struts from the interplane strut bottom joint to the upper fuselage longitudinals doing althogether away with wiring. The Albatros strut form was first seen in the fashion of the 1916-17 L.F.G. Roland Whale effort, while the two inwards inclined struts appear to be of usual streamline shape.
The body nose and the fairly forward position of the Albatros gives the impression of a rotary engine installation.
One fails to see immediately the object of advancing the fin and balanced rudder on the Albatros.
The tail fin and undivided balanced elevator is similar to the one of the biplane scout of the same firm.