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

Brandenburg K.D.W.

   During 1916 Ernst Heinkel prepared a design for a single-seat scout for the Austrian Army. Although conventional in most respects, the aircraft featured a novel system of wing bracing in the form of four vee struts joined in the centre of the wing bay by their apices. This arrangement gave a star configuration, and the aircraft was, in fact, dubbed "star strutter". The Brandenburg K.D. (Kampf Doppeldecker), as the type was designated, was license-built by the Austrian factories of Phonix and Ufag as the D I (Hansa Brandenburg D I (Ph) Series 28 and Hansa Brandenburg D I (Ufag) Series 65). Phonix subsequently developed the design on more conventional lines and introduced a more orthodox strut arrangement and empennage. This variant went into further production as their own D II and D III series.
   In view of the demand for seaplane-station fighter defence aircraft and his considerable seaplane design experience, Heinkel decided to convert the K.D. to a seaplane fighter type as a stop gap, to reinforce the supply of Albatros W 4 and Rumpler 6BI seaplanes. In actual fact, the prototype adaptation amounted to little more than a slight increase in wingspan and mounting the K.D. airframe on a twin-float chassis. Later, the inclusion of a certain amount of fin area below the rear fuselage was found necessary to compensate the additional keel surface presented by the floats, and ultimately an upper fin was also added. Despite these modifications the K.D.W., like the landplane version, proved very difficult to fly. Due to the blanketing of the small rudder by the deep fuselage, directional stability was extremely poor, and recovery from a spin was more by luck than by any degree of skill.
   The prototype (Marine No. 748) and early production models were fitted with the 150 h.p. Benz engine and a car-type radiator; likewise an interim production batch (Nos. 1067-1076), which also had additional outsplayed vee struts to brace the wingtips. All remaining aircraft were fitted with the 160 h.p. Maybach engine and flush-type radiator mounted in the centresection of the top wing to starboard of the centre. Exhaust manifolds were of the chimney type in the Benz-powered aircraft, except on the prototype, which had stub pipes. The Maybach K.D.W.s had a collector manifold with only a single ejector pipe showing on the starboard side.
   Engines were neatly faired with hooded metal panels, which curved in from the upper longerons, giving a "head and shoulders" cross-section which afforded the pilot quite good forward vision. The fuselage itself was based on four spruce longerons, with ply formers forward and spruce spacers and transverse diagonal bracing members aft of the cockpit section. There was very little taper in fuselage depth. The curved decking maintained almost the same height as the depth between the longerons and extended right aft to the sternpost. The whole of the fuselage was plywood covered, as were also the vertical fins.
   Tail surfaces were framed from steel tube and fabric covered. The rectangular rudder had a small balance portion atop the fuselage, but when the upper fin was introduced on the later models this was deleted. The large triangular tailplane, to which the unbalanced parallel chord elevators were hinged, was mounted directly on the upper longerons and braced to the underside of the fuselage with two streamlined steel struts.
   The wings were of straightforward rectangular profile, of equal span and fabric covered. Their conventional wooden construction was based on two main spars, with a further auxiliary spar at approximately two-thirds chord, to which were hinged the unbalanced parallel-chord ailerons. The attachment point for the upper outboard vee of the "star-strut" interplane bracing was located almost at the extreme end of the aileron, and it was found in practice that the considerable overhang portion of the upper wing tended to flex as the ailerons were actuated, reducing the sensitivity of these controls. In consequence, a light steel-tube vee was fitted, splaying outward from the lower strut anchorage, to brace the upper wing more rigidly and make the aileron control more positive. The "star-struts" themselves were basically light-gauge circular steel tubes faired with plywood. Centre-section struts were of plain circular steel tube, like the auxiliary tip struts, and of inverted vee form.
   The undercarriage chassis comprised a neat pair of N struts of steel tube faired with ply. The floats themselves, of single-step design, wedge-shaped forward and tapering to a vertical knife-edge at the stern, were wooden and built up on a framework of ply formers and spruce stringers and covered with mahogany ply. They were connected at the strut stations with rigid steel-tube spreaders and the complete chassis braced fore and aft with stranded cables.
   An interesting point about the Heinkel K.D. and K.D.W. fighter prototypes is that they were developed structurally and aerodynamically before any thought seems to have been given to the armament. This was especially noticeable on the land aircraft, with guns mounted on the top wing. On the K.D.W.s a single synchronised Spandau machine-gun was mounted on the starboard side of the extreme nose, far beyond the reach of the pilot to correct any stoppage. Only on the final batch of twenty aircraft, delivered between October 1917 and February 1918, were twin Spandau guns fitted, clamped either side of the cockpit. By then the type was obsolescent and was being replaced by the far more efficient and flexible Brandenburg W 12. Altogether a total of 58 K.D.W.s were supplied.
   Although these production batches of seaplanes may seem small, they must be viewed in comparison with total aircraft supplies, when by the end of the war a total of some 2,500 seaplanes had been produced, as compared with 44,000 aircraft for land warfare.

TECHNICAL DATA
   Description: Single-seat seaplane fighting scout.
   Manufacturer: Hansa und Brandenburgische Flugzeug-Werke G.m.b.H.
   Power Plant:
   One 150 h.p. Benz Bz III 6 cylinder in-line water-cooled engine.
   One 160 h.p. Maybach Mb III 6 cylinder in-line water-cooled engine.
   Dimensions: Span, 9.25 m. (30 ft. 4 1/4 in.). Length, 8 0 m. (26 ft. 3 in.). Height, 3.35 m. (10 ft. 11 7/8 in.). Area, 20 sq.m. (216 sq.ft.).
   Weights: Empty, 940 kg. (2,068 lb.). Loaded, 1,210 kg (2,662 lb.).
   Performance: Maximum speed, 170 km.hr. (106.25 m.p.h.). Climb, 1,000 m (3,280 ft.) in 5.9 min. 2,000 m. (6,560 ft.) in 14 min.; 3,000 m. (9,840 ft) in 21 mm. Duration 2 1/2 hr. with 160 litres fuel.
   Armament: One fixed Spandau machine-gun forward mounted on starboard of nose. Last twenty aircraft were fitted with twin machine-guns.
   Serial Numbers: Fifty-eight aircraft delivered. Marine Numbers: 748, 783, 784, 912-921, 1067-1076, 1380-1394, 1554-1573.


Brandenburg W 11
   Built during late 1916, the W 11 was a slightly larger and more powerful version of the series-built K.D.W. single-seat fighter seaplane. Only two machines were built - Nos. 988-989. Engine, 200 h.p. Benz Bz IV. Span, 100 m. (32 ft. 9 3/4 in.). Length, 8.2 m. (26 ft. 10 7/8 in.). Height, 3.32 m. (10 ft. 10 5/8 in.). Area, 31.4 sq.m. (339 sq.ft.). Weights: Empty, 935 kg. (2,057 lb.). Loaded, 1,215 kg. (2,673 lb.). Speed, 176 km.hr. (110 m.p.h.). Armament, two Spandau machine-guns.

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

BRANDENBURG KDW Germany

   The KDW twin-float single-seat fighter seaplane was essentially a conversion of the land-based KD (D I) to provide an interim aircraft for floatplane station defence. The only major change introduced on the prototype apart from provision of a twin-float chassis was some slight extension of the wings, but the fin area was later increased to compensate for the increased keel area resulting from the addition of the floats. The prototypes were fitted with the 150 hp Benz Bz III six-cylinder water-cooled engine, but apart from a pre-production batch of 10 similarly-powered aircraft, all subsequent examples of the KDW had the 160 hp Maybach Mb III six-cylinder water-cooled engine. The first production series was armed with a single synchronised 7,92-mm LMG 08/15 machine gun mounted on the starboard side of the nose, but the final batch of 20 delivered between October 1917 and February 1918 had a gun mounted on each side of the cockpit and additional Vee-type interplane bracing struts. A total of 58 KDW float fighters was delivered.

Max speed, 106 mph (170 km/h).
Time to 3,280 ft (1000 m), 5.9 min, to 6,560 ft (2 000 m), 14 min.
Range, 310 mis (500 km).
Empty weight, 1,673 lb (759 kg).
Loaded weight, 2,290 lb (1 039 kg).
Span, 30 ft 6 1/8 in (9,30 m).
Length, 25 ft 9 1/2 in (7,86m).
Height, 10 ft 11 7/8 in (3,35m).
Wing area, 313.77 sq ft (29,15 m2).

J.Herris German Seaplane Fighters of WWI (A Centennial Perspective on Great War Airplanes 2)

Brandenburg KDW

   The Brandenburg KDW [Kampf Doppeldecker Wasser - literally 'combat biplane water') was developed from the earlier Brandenburg KD (Kampf Doppeldecker) landplane fighter. The Brandenburg KD was designed in Germany in 1916 and went into production for the Luftfahrtruppe, the Austro-Hungarian air service, as the Brandenburg D.I fighter.
   The Brandenburg KD, or D.I, was basically a conventional, wire-braced wooden design of the time except for one notably different feature, the interplane struts. The metal interplane struts, streamlined by laminated wood fairings, were designed as a set of four triangles that met at their apex, giving a unique star appearance. The star-strut design was very strong and eliminated the need for the drag-producing bracing wires featured by contemporary designs. The resulting Brandenburg KD was a strong, fast fighter. Unfortunately, its single machine gun was mounted in a streamlined housing above the wing, making it impossible for the pilot to clear jams during flight. Worse, the KD lacked both maneuverability and stability, and was prone to stalling and spinning with little provocation.
   The German Navy's need for a seaplane station defense fighter led to development of the Brandenburg KDW, a straight-forward conversion of the KD to a floatplane fighter. Floats replaced the wheels and both the wing span and area were increased to provide additional lift to compensate for the extra weight of the floats. Fortunately, a synchronized machine gun was mounted on the starboard side of the fuselage instead of the clumsy, over-wing mounting used by the KD. Initially the gun was mounted too far forward to be reached by the pilot in case of a jam during flight, but this was rectified with the first production series. The final production series was intended to mount two guns adjacent to the cockpit where the pilot could reach them in flight, but some machines carried only one gun.
   The three prototype aircraft had the 150 hp Benz Bz.III engine with car-type, frontal radiator. Aircraft of the second production series had the 150 hp Benz Bz.III (if intended for the Baltic) or the 160 hp Mercedes D.III engine with radiator in the starboard side of the upper wing (if intended for Flanders or the North Sea). All aircraft of the first, third, and fourth production series had the 160 hp Maybach Mb.III engine with radiator in the starboard side of the upper wing. In the summer of 1917 early production aircraft were refitted with additional small interplane struts bracing the upper wing to increase torsional stiffness of the longer span wing, thereby improving aileron response. From the third production batch these struts were installed during production.
   Based so closely on the KD, the KDW inherited its performance and flying qualities. These included structural strength and good speed for a floatplane fighter, although the additional weight and drag of the floats and longer wings necessarily reduced speed and climb given that engine power was essentially the same. Less happily, the KDW also inherited the poor stability and flying qualities of the KD. A number of changes to the vertical tail surfaces were made during production in an attempt to improve these, but without notable success. As a result, the KDW was able to engage reconnaissance seaplanes and similar targets with a reasonable chance of success, but was at a distinct disadvantage in combat with contemporary landplane fighters. The KDW's most significant operational success was when the first example, Marine Number 748, downed Russian Ilya Mouromets IM-6, a four-engine reconnaissance-bomber, one of only three downed in air-to-air combat during the war.
   The KDW was delivered in small batches from September 1916 to February 1918. Only about 2,365 aircraft were produced for the German navy during the war, so the 58 KDW aircraft produced represented a reasonable success. However, the competing Albatros W4, the floatplane conversion of the successful Albatros D.I fighter, was produced in twice the numbers of the KDW, 118 being delivered from September 1916 to December 1917. Although the KDW with 160 hp Mercedes D.III had a slight speed advantage over the Albatros W.4, the KDW with the 150 hp Benz was slower. Furthermore, the W.4 had better climb rate and maneuverability, better visibility from the cockpit, and, perhaps most important, much better flying characteristics. Both types served on the Flanders front, the North Sea, and in the Baltic. Eventually the KDW succumbed to the same poor flying qualities and cockpit vision problems as its landplane predecessor, the D.I.


KDW Production
Marine Number Qty Notes
748, 783, 784 3 Prototypes. 1 gun, 150 hp Benz Bz.III engine. Completed September 1916.
912-921 10 1 gun, 160 hp Maybach Mb.III engine. Series completed February 1917.
1067-1076 10 1 gun, either 160 hp Mercedes D.III engine (aircraft destined for the Western Front) or 150 hp Benz Bz.III engine (aircraft destined for the Baltic). Series completed in March and April 1917.
1380-1394 15 1 gun, 160 hp Maybach Mb.III engine. Series completed in summer 1917.
1554-1573 20 1 or 2 guns, 160 hp Maybach Mb.III engine. Series delivered between October 1917 and February 1918.

C.Owers Hansa-Brandenburg Aircraft of WWI Vol.2: Biplane Seaplanes (A Centennial Perspective on Great War Airplanes 18)

Type KDW

   The Brandenburg KD (D.I) land based fighter was the basis of the KDW single seat fighting floatplane. The floatplane retained the "star struts" of the KD; in fact the prototype was virtually a KD fuselage mounted on floats with wings of slightly increased area. The KDW was designed due to a requirement for a naval air station defence fighter.
   The fuselage followed the construction of the KD with four spruce longerons, ply formers forward, spruce spacers and transverse diagonal bracing members aft the cockpit and ply covering, eliminating the need for internal wire bracing. Metal panels enclosed the engine. The fuselage was deep and tapered to a vertical knife edge. A synchronised Maxim 08/15 machine gun was mounted on the starboard side. Initially this was mounted too far forward for the pilot to be able to rectify a jam while in flight. On later machines it was mounted within reach of the pilot. The fin was ply covered, while the tail surfaces were of metal tube with fabric covering.
   The horizontal tailplane was mounted on the longerons and braced by steel tubes to the lower longeron. The parallel chord elevators were of steel tube and fabric covered.
   The KDW proved as difficult to fly as its landplane counterpart. It was necessary to increase the fin area below the fuselage, and an upper fin had to be added as well. The machine had poor directional stability due to the deep fuselage blanketing the rudder and spin recovery was marginal, "more by luck than by any degree of skill."(38)
   The prototype received the MN 748, and five batches were constructed as noted in the table, for a total of 58 aircraft. The prototype and early production aircraft up to MN 1076 were fitted with the 150-hp Benz and a nose mounted radiator. On 27 June 1917, flying on all Brandenburg KDW and CC fighters was forbidden until an additional pair of light tubular struts supporting the wing overhang were fitted, thereby obviating the benefit of the star-strut arrangement. This modification was standard on the last two batches. The aircraft from the first, third and fourth batches were fitted with the 160-hp Maybach Mb.III engine and an aerofoil radiator mounted in the wing to starboard of the centre line. The Maybach powered examples can be identified by their single exhaust manifold on the starboard side. Aircraft of the second production batch had either the 150-hp Benz Bz.III if intended to serve in the Baltic, or, if intended for the North Sea and Flanders, the 160-hp Mercedes D.III. The selection of engine provides a statement as to what area was considered the greater threat to the seaplanes.
   The German Navy found the "star-strutters," both the KDW and CC, heavy, tricky and unsafe to fly. The view from the cockpit of the KDW was poor, making it unsuitable for air fighting as the risk of a collision was constant. The type was known as the "Spider" in service due to the unusual strut arrangement. The survivors of the 58 KDW fighters were stored at the Navy Depot at Hage.
   KDW fighters MNs 1571 - 1573 were to go to Turkey but were instead sent to the Seddin depot. One KDW is reported by Turkish sources to have been used by the Ottoman air force as a maritime reconnaissance machine. When it arrived it had no armament and was powered by a Mercedes engine. KDW MN 1557 was sent to Japan post-war. The Japanese showed more interest in the Brandenburg floatplanes than any of the Allied powers, even receiving Austro-Hungarian Brandenburg C.I biplanes.


Service use of the KDW(39)

   Prototype MN 748 was flown to Angernsee where it was to be tested under actual service conditions. Here the Germans were facing the Russians. Sikorsky bombers that, together with other aircraft, carried out attacks against the German base. MN 748 commenced its first mission on 12 September 1916, as escort to torpedo bombers. On 23 September MN 748 was in the hands of Ltn.d.R. Fritz Hammer when he intercepted one of the giant Sikorsky bombers and after making four runs at the bomber, Hammer succeeded in forcing it down near a forest near Dunamunde. During the combat Hammer had been caught up in the turbulence from the Sikorsky's engines and had nearly lost control of his small floatplane, a type not known for its stability.
   On 12 February 1917, Zeebrugge had the following Brandenburg aircraft out of a total of 53 aircraft on strength:
   KDW: MNs 912 - 916, and 1067 - 1068
   W.11: MNs 988 - 990
   CC: MNs 1137, 1139, 1141, 1143, and 1145
   W.12: MNs 1014 - 1015
   The superlative W.12 would replace the obsolescent KDW in the fighter role.
   The 28 March 1918, was not a good day for the KDW fighter-trainers of the floatplane school at Putzig. KDW fighters MNs 1385 and 1072 were part of a group of three when they collided. The KDW had been criticized for the lack of visibility from the cockpit, particularly when trying to fly in formation. MN 1385 cut off the tail of MN 1072 that crashed, killing the pilot. MN 1385 also crashed but the pilot survived. The third KDW, MN 917, also crashed trying to avoid the other two and although destroyed, the pilot survived. This was not the end of the saga as MN 915 took off to assist the machine side-slipping out of a turn at 100 metres and crashing, again destroying the aircraft but the pilot managing to survive. The pilots owed their survival to being picked up by local fishing boats. The school did not have a fast motor launch and the unit's diary recorded this fact.
   As a result all KDW training was cancelled, the machines being grounded. As the current course could not be completed without these machines the ban was soon lifted and the KDW floatplanes were soon flying, and crashing, again. However, not all the blame could be levelled at the Brandenburg as Albatros W.4 and Rumpler 6B2 biplanes also contributed to the statistics. In the period of one month eight single-seat floatplanes had been destroyed or seriously damaged, five of them being KDW fighters with three deaths on the Brandenburg machines. It appears that the school continued to use the Brandenburgs till at least July, with one, 1387, being shipped from there to Hage in early November.
   Given the small number of marine aircraft built for the German Navy, the KDW was a reasonable success. The competing Albatros W.4 floatplane based on the D.I biplane fighter was built in double the numbers of the KDW, had a better performance, and was a better fighting machine due to its speed and the view from the cockpit.
   The British confidential Types of German Seaplanes and Flying Boats of July 1918, contains photographs and silhouettes of the KDW wherein it is described as "Brandenburg Seaplane 1917." Apart from stating that the machine was powered by a 150-hp Benz or 160-hp Maybach, no other technical information is described. A second entry repeats the description but states the motor is a 200-hp Benz and it is apparent that the aircraft is the W.11; however, it is illustrated with photographs of a machine bearing MN 508. This Marine Number was assigned to a Friedrichshafen FF33E. This error was repeated for the Type NW. As the photographs have been copied from a German publication the question arises if they were designed to mislead the Allies, yet the photograph of the Type GW show MN 700 and correctly identifies the engines as 160-hp Mercedes.

(38) Gray, P. & Thetford, O. German Aircraft of the First Word War, Putnam, UK, 1962.
(39) This section is based on the pioneering work of Ron Kinter. See "The Brandenburg KDW Operational History," Over the Front Journal, Vol.24, No.3, P.217.


Brandenburg KDW Production
Marine Numbers Class Engine Delivered Notes
748 ED 150 Bz.III Sept. 1916 Prototype. Completed Sept. 1916
783 - 784 ED 150 Bz.III Sept. 1916 Prototypes. Completed Sept. 1916
912 - 921 ED 160 Mb.III Jan. - Feb. 1917 Completed Feb. 1917
1067 - 1076 ED 160 D.III/ 150 Bz.III Oct. 1917 - Apr. 1918 Completed in Mar. & Apr 1917. Aircraft for North Sea had Mercedes. Aircraft for Baltic had Benz.
1380 - 1394 ED 160 Mb.III Mar. - Aug. 1917 Additional interplane struts as standard.
1554 - 1573 E2MG 160 Mb.III One or two machine guns. Completed between Oct. 1917 &. Feb. 1918. Additional interplane struts.


Brandenburg KDW Specifications
Source Typenschau (see note) Gray & Thetford SVK MN 784 SVK MN 914 SVK MN 1067 SVK MN 1554 Brandenburg 3-View
Dimensions in m
Span, Upper 9.30 9.25 9.300 9.300 9.300 9.250 9.300
Span, Lower 9.30 - 9.300 9.300 9.300 9.250 9.300
Chord, Upper 1.655 - 1.650 1.650 1.650 1.650 1.650
Chord, Lower 1.655 - 1.650 1.650 1.650 1.650 1.650
Length 7.86 8.0 8.000 7.900 7.900 8.000 7.860
Height - 3.35 3.150 3.370 3.370 3.350
Areas in m2
Wings 29.15 20 - - - - -
Ailerons 1.85 - 1.85 1.85 1.85 1.74 -
Elevators 1.10 - 1.08 1.10 1.10 1.10 -
Rudder 0.64 - 0.65 0.64 0.62 0.53 -
Weights in kg
Empty 759 940 768 759 775 940 768
Loaded 1,039 1,210 1.048 1,059 1,065 1,210 1,048
Performance
Speed in km/hr 172 170 - - - - -
Time to 800 m 3 min. - 4 min. 3 min. 3 min. 4.5 min. -
Time to 1000 m 4 min. 5.9 min. 4.5 min. 4 min. 4 min. 5.9 min. 4.5 min.
Time to 1500 m 6 min. - 7.5 min. 6 min. 7 min. 9.5 min. -
Time to 2000 m 9 min. 14 min. 11 min. 9 min. 11 min. 14.9 min. 11 min.
Time to 3000 m 16 min. 21 min. 21.5 min. 16 min. 22.5 min. 21 min. 21.5 min.
Endurance - 2.5 hour - - - - -
Motor 160-hp Maybach/150-hp Benz 150-hp Benz Bz.III/160-hp Maybach Mb .III 150-hp Benz 160-hp Maybach 150-hp Benz 160 Maybach 150-hp Benz
Note: The Typenschau specifications are for a machine with a single machine gun.

M.Dusing German Aviation Industry in WWI. Volume 1 (A Centennial Perspective on Great War Airplanes 84)

Hansa und Brandenburgische Flugzeugwerke AG (Brand)

Aircraft Development:

<...>
  Just after mid 1916 Heinkel’s team of marine aircraft designers had their greatest success thus far when the Brandenburg Type “KDW” was ordered in quantity for the German Navy. 58 examples were constructed, utilizing the Benz Bz.III engine of 150 hp and 10 aircraft were delivered with the more powerful Maybach Mb.III of 160 hp. One further Maybach powered example with increased wingspan may also have been built.
<...>