Early in 1918, it was suggested to Ernst Heinkel that a successor to the W.12 two-seat fighter would soon be required if the German Navy was to maintain its superiority over Allied types being encountered over the North Sea. To conserve valuable time, Heinkel installed the new 195hp Benz Bz IIIbo eight-cylinder Vee engine in a modified W.12 airframe and a 160hp Mercedes D IIIa in a second W.12. Wing span and gap were reduced, stagger was increased to improve visibility, and aerofoil- section I-type interplane struts were adopted. Armament comprised two synchronised 7.92mm LMG 08/15 machine guns and one 7.92mm Parabellum on a flexible mount in the rear cockpit. The Benz-engined prototype received the designation W.27 while that powered by the Mercedes engine became the W.32, but both were found inferior to the W.29 monoplane and no further development was undertaken.

W 27
Max take-off weight: 1619 kg / 3569 lb
Empty weight: 1109 kg / 2445 lb
Wingspan: 11.20 m / 37 ft 9 in
Length: 9.23 m / 30 ft 3 in
Height: 3.06 m / 10 ft 0 in
Wing area: 36.06 sq.m / 388.15 sq ft
Max. speed: 170 km/h / 106 mph

The last of the Heinkel-designed single-seat fighter float seaplanes built by the Hansa- und Brandenburgische Flugzeug-Werke, the W.25, produced as a single prototype late in 1917, was the final development of the KDW. Reverting to the 150hp Benz Bz III engine used by the prototype and pre-production KDWs, the W.25 possessed an essentially similar fuselage, but discarded the “star” interplane strut arrangement in favour of normal strut bracing. Initially the prototype flew with ailerons on the upper wing only, but these were subsequently added to the lower wing, each pair being joined at the wingtip.by link struts. Armament comprised two synchronised 7.92mm LMG 08/15 machine guns. Having by this time lost interest in single-seat fighter floatplanes, the German Navy did not foster further development of the W.25.

Max take-off weight: 1182 kg / 2606 lb
Empty weight: 918 kg / 2024 lb
Wingspan: 10.40 m / 34 ft 1 in
Length: 8.80 m / 29 ft 10 in
Height: 3.45 m / 11 ft 4 in
Wing area: 36.53 sq.m / 393.21 sq ft
Max. speed: 160 km/h / 99 mph

The W.18 single-seat fighter flying boat was, like the CC that it supplanted, intended primarily for the Austro- Hungarian Navy. The prototype was flown early in 1917 with a 150hp Benz Bz III six-cylinder water-cooled engine, and production with a 200hp Hiero engine was undertaken on behalf of the Austro-Hungarian Navy, a total of 47 being delivered between September 1917 and May 1918. Armament normally comprised two fixed forward-firing 8mm Schwarzlose machine guns, and the W.18 was employed for both station defence and fighter patrol tasks. One Benz-engined example was delivered to the German Navy in December 1917.

Max take-off weight: 1145 kg / 2524 lb
Empty weight: 875 kg / 1929 lb
Wingspan: 10.70 m / 35 ft 1 in
Length: 8.15 m / 27 ft 9 in
Height: 3.45 m / 11 ft 4 in
Wing area: 34.38 sq.m / 370.06 sq ft
Max. speed: 170 km/h / 106 mph

A single-seat fighter flying boat developed for the Austro- Hungarian Navy, the prototype of the W.17 (also designated A 49/I) was a biplane with a cantilever lower wing and was tested at Pola in July 1917. K.u.k. Linienschiffsleutnant Gottfried Banfield, responsible for the evaluation of the W.17, felt that the cantilever lower wing was unsuited for marine use and that the flying boat possessed inadequate manoeuvrability. Armament of the W.17 comprised two 8mm Schwarzlose machine guns and the initial aircraft was allegedly lost when the upper wing broke away in flight. A second aircraft (the A 49/II) was completed as an equispan triplane with interplane bracing struts. This is believed to have been submitted to the Austro-Hungarian Navy for evaluation in July 1917.

Intended primarily as a successor to the KDW in the station defence fighter role, but also to investigate the potentialities of the application of rotary engines to seaplanes, the W.16 was designed by Ernst Heinkel in 1916, and was a conventional twin-float single-seat fighter floatplane of wood and fabric construction with ply-skinned fuselage and floats. Like Heinkel’s earlier “star strutter” fighters, the W.16 lacked bracing wires, these being rendered unnecessary by single struts extending from the base of the inclined Vee-type interplane struts to the top of the forward fuselage mainframe. Power was provided by a 160hp Oberursel U III rotary engine and armament comprised two synchronised LMG 08/15 machine guns. Three prototypes were ordered, the first of these being tested in February 1917, and the third example was sent to Adlershof for static tests. No further development was undertaken as the German Navy had lost interest in single-seat fighter floatplanes.

Max take-off weight: 896 kg / 1975 lb
Empty weight: 636 kg / 1402 lb
Wingspan: 9.25 m / 30 ft 4 in
Length: 7.35 m / 24 ft 1 in
Height: 2.92 m / 10 ft 7 in
Wing area: 21.35 sq.m / 229.81 sq ft
Max. speed: 170 km/h / 106 mph

A heavier and more powerful derivative of the KDW, the 1917 W.11 single-seat twin-float fighter biplane was powered by a 220hp Benz Bz IVa water-cooled engine and retained the “star” interplane bracing arrangement of its predecessor. Armament consisted of two synchronised LMG 08/15 machine guns, and two prototypes were completed during February-March 1917. No series production was undertaken.

Max take-off weight: 1233 kg / 2718 lb
Empty weight: 935 kg / 2061 lb
Wingspan: 10.10 m / 33 ft 2 in
Length: 8.10 m / 27 ft 7 in
Height: 3.32 m / 11 ft 11 in
Wing area: 31.42 sq.m / 338.20 sq ft
Max. speed: 176 km/h / 109 mph
Range: 350 km / 217 miles