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

Friedrichshafen D I
   This clean little single-seat fighter was built during 1916, but as it offered no improvement over the Albatros lighters, which had obviously influenced its design, it did not go into production. Engine, 160 h.p. Mercedes D III. Armament, twin Spandau machine-guns forward.

J.Herris Friedrichshafen Aircraft of WWI (A Centennial Perspective on Great War Airplanes 21)

Friedrichshafen FF46 (D.I)

   In September 1916 Friedrichshafen presented a proposal for a single-seat land fighter to Idflieg. Developed from the FF43 floatplane fighter, but with no common assemblies, Idflieg ordered three prototypes. Power was from the 160 hp Mercedes D.III, the same engine powering the Albatros fighters then arriving at the front, and armament was the two synchronized guns carried by the Albatros, then becoming standard on German fighters. At least two of the three prototypes ordered were built; these differed in their cabane strut design.
   Idflieg testing of the Friedrichshafen D.I was prolonged, lasting until April 28, 1917. Idflieg’s conclusion was that the aircraft's performance and flight characteristics were inferior to the Albatros and series production was not undertaken. Unfortunately, the performance figures that Idflieg considered uncompetitive are not available.

Friedrichshafen FF46 (D.I) Specifications
Engine: 160 hp Mercedes D.III
Wing: Span 9.00 m
Area 25.80 m:
General: Length 7.10 m
Height 2.70 m
Empty Weight 686 kg
Loaded Weight 901 kg

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

FRIEDRICHSHAFEN FF 43 Germany

   In September 1916, the Flugzeugbau Friedrichshafen presented the Idflieg (Inspektion der Fliegertruppen - Inspectorate of Flying Troops) with a proposal for a single-seat, land-based fighter based on the FF 43 floatplane. This, the FF 46, received an order for three prototypes, which, like the FF 43, were to be powered by the 160 hp Mercedes D III, but were to be armed with twin synchronised 7,92-mm MG 08/15 machine guns. The FF 46, or D I, was a single-bay staggered biplane, the first prototype having vertical cabane strutting, but the second having splayed struts to improve forward vision. The Idflieg testing of the FF 46 was not completed until 28 April 1917, when it was concluded that the type was not acceptable for series production as its flight characteristics and performance were inferior to those of its contemporaries. There is no record of the third prototype being completed.

Empty weight, 1,512 lb (686 kg).
Loaded weight, 1,986 lb (901 kg).
Span, 29 ft 6 1/3 in (9,00 m).
Length, 23 ft 3 1/2 in (7,10 m).
Height, 8 ft 10 1/3 in (2,70m).
Wing area, 277.72 sqft (25,80 m2).