Hansa-Brandenburg KDW

Marine-Fliegerabteilung: 58 floatplane fighters manufactured 1916-1918. In service until 1918

The Hansa-Brandenburg KDW was the first single-seat armed scout seaplane (Jagdeinsitzer Wasser) ordered by the Kaiserliches Marine to defend its North Sea seaplane stations against air attack, and first of the brand to be built in significant numbers. It was designed by then a still relatively young Ernst Heinkel and was adapted from the Hansa-Brandenburg D.I fighter in true floatplane fashion. However it also inherited the issues of the land-based model, notably poor lateral control and stability, and poor pilot vision among others. Only 58 were manufactured in five batches at anemic pace until early 1918.

About Hansa-Brandenburg

Hansa und Brandenburgische Flugzeugwerke (Hansa-Brandenburg) was a relatively short-span German aircraft manufacturer made famous during WW1, and created in May 1914: The Brandenburgische Flugzeugwerke from Liebau was purchased by Camillo Castiglioni, and moved to Brandenburg an der Havel. Brandenburg's chief designer was Ernst Heinkel already, and talented as he was, he kept his post, funding postwar Heinkel Flugzeugwerke. By the Autumn of 1915, Hansa-Brandenburg became the largest aircraft manufacturer in Germany with a capital of 1,500,000 Marks. There were three factories with 1,000 employees at Rummelsburg Plant, Berlin, and Wandsbek plant in Hamburg, in addition to Brandenburg an der Havel. Hambug gave the company an immediate access to the sea as seaplanes soon became its speciality.

Castiglioni was Austrian, and also managed a prosperous trade with the Austro-Hungarian aviation corps. The company specialized not only on floatplane fighters but also versatile reconnaissance aircrafts. However it was unable postwar to adapt to the civilian market, and became bankrupt by 1919 although Finland and Norway continued production under licence for a time. Best sellers of the company were land-based models such as the B.I Recce biplane (1914) (c600 made), C.I Recce biplane (1914) (1318 made), the D.I fighter (1916) (122), and G.I Bomber (1917)(50). But it's really with floatplanes or flying boats that the company thrived: In all, not massive quantities (698 total) but many models all with the "W" (for Wasser/recce or floatplane) identification prefix. Like the model W (1914) Recce floatplane (77), the W.12 (1917) Floatplane fighter (181), W.13 (1917) Flying-boat bomber (130), W.19 (1918) Recce floatplane (55), W.29 (1918) Fighter Floatplane (Monoplan) (78), W.33 (1918) Fighter Floatplane (Monoplan) (26). There were exceptions like the CC (1916) Flying-boat fighter (73), GW (1916) Floatplane torpedo-bomber (20) and the present KDW (1916) Floatplane fighter.

Design

Development

The KDW was certainly not the first seaplane in service from the company with the Navy. They were adaptation of the successful Hansa-Brandenburg B.I landplane. The first "W" was a conventional three-bay biplane with unstaggered wings of equal span, pilot and observer in tandem open cockpits and the undercarriage replaced by short twin pontoons. Only 27 were made, followed by the revised NW with a Mercedes D.III engine and GNW with a Mercedes D.III engine. These reconnaissance models, very comparable to the Gotha WD2 were also allegedly used by the Ottoman Air Force.

But the true roots of the KDW came out as a complement to another model proposed almost in parallel, the CC (1916) Flying-boat fighter. Indeed the company tested both configurations, but the latter was more requested by the Austro-Hungarian Navy. The initials meant "Camillo Castiglioni" which was the driving force behind the order. The model was to be a competitor to the Macchi M.3 in the Adriatic. However in the end, the German Navy still obtained half the order. Whereas the KDW was a floatplane fighter for the Kaiserliches Marine, the first from the company.

To achieve this the best possible way, Hansa-Brandenburg in 1916 simply took under the leadership of Ersnt Heinkel, the successful KD (Kampf Doppeldecker), or D.I in German service. This sturdy but not performing model was still licence-made in Austria as the Phönix D1 for the Kaiserliche und Königliche Luftfahrtruppen or K.u.K. Luftfahrtruppen. This single seat, single engine biplane was of wooden construction, with plywood fuselage skin and dopted fabric for the wings and tails, however it was unusual for its "Star-Strutter" arrangement for its interplane struts, yest still four Vee struts in the centre of the wing bay, all profiled steel tubes.

The prototype was ordered on June 8, 1916, was delivered to the Seaplane Testing Command (Seeflugzeug-Versuchskommando) in Warnemünde for evaluation on September 10 (serial number 784), accepted on September 11, 1916. The first batch comprised #914 and #1067 delivered in March 1917. Firther orders were passed on September 12, 1916 (delivered January 29, accepted February 7, 1917), then on November 3, 1916 with a first delivery from March 20, 1917, acceptance 5 days later. Production ended in early 1918.

However the Hansa-Brandenburg KDW was criticized for its too deep fuselage, resulting in a poor forward view for the pilot and the the small rudder resulted in poor lateral stability. It was difficult to fly for rookie pilots. Armament was also criticized for the time with a single Schwarzlose machine gun, unsynchronized, so it was fitted in a fairing on the upper wing and firing over the propeller. Introduced in the Autumn 1916, in all 122 were made of the "Spider" and despite its limitations it was well used by aces such as Godwin Brumowski and Frank Linke-Crawford.

When submitted this request for a Nordsee naval station point-based seaplane fighter, Ernst Heinkel just borrowed this design just swapping the undercarriage for a pair of floats and was able to submit a design at the same time as the land-based model. Based on prospective performances, the Jagdeinsitzer Wasser was approved for production, a first prototype flew in September 1916 with a few changes. It was approved and a serie of 58 were produced until the end of the war, albeit delivery rate was lethargic, to the level of a workshop.

From mid-1916 onwards, the KDW operated between the North Sea and Adriatic until 1918. By 1917, however, it was largely already obsolete, inferior to the Albatros W.4 and Hansa-Brandenburg W.12.

Specifics and Changes

Borrowing the D.I meant most its characteristics remained the same: It kept the trademark "star strutter" wing bracing with four vee struts, two facing up, two facing down, joined by their vertices at a point midway between the upper and lower wings making for a unique eight-arm star. The model was thus nickname "Wasser Spinne" (water spider). The greatest change however was a small increase in wingspan due to the drag of the twin-float chassis. To counteract the keel effect resulting from these floats, a vertical tailfin area was added below, and later above, the fuselage.

However it still inherited the poor lateral stability of the D.I and deep fuselage, so handling was not great, and the pilots lacked visibility, which for a fighter/scout was not ideal. It was difficult to control, for example returning from a bank to vertical flight and the fuselage still blanketed the small tailfin and rudder. Stability and control remained very poor, more so with the floats and it was very difficult to recover from a spin. Like the previous model also, the first an a unsynchornized single machine gun. However the model was improved during its two-year production span.

The KDW measured 8 m (26 ft 3 in) overall for a wingspan of 9.22 m (30 ft 4 in) (versus 8.5 m/27 ft 11 in on the D.I). Having no floats, the D.I was also shorter at 6.35 m (20 ft 10 in). It was also taller at 3.30 m (11 ft 0 in) versus 2.79 m (9 ft 2 in) and its wing area augmented to 29.15 m² compared to 23.95 m2 (257.8 sq ft). The ailerons was 1.85 m² in surface, and the elevators from 1.08 to 1.10 m², the rudder from 0.52–0.65 m² so pretty small. Without surprise, the KDW was also heavier, at 760 kg empty and 1040-1045 kg (2,293 lb) at take-off (versus 672 kg/1,482 lb and 920 kg/2,028 lb)).

It could be equiped by a water-cooled 6-cylinder inline engine—Benz Bz III in standard, but Mercedes D III or Maybach Mb III initially for a take-off power of 150 hp (approx. 110 kW) up to 160 hp (approx. 120 kW) in latter batches making for a top speed at 172–175 km/h (107 mph, 93 kn) at sea level. The climb rate to 1000m was 4:30 min versus 3 minutes on the D.I. It went down to an anemic 11–14 min to 2000 m and 21:30 min to 3000 m, certanly not interceptor matter. Service ceiling was anyway tested slightly above 4000 m (13,000 ft), 1,000m less than the D.I. Range was 500–540 km however or 3h versus a bit less on the D.I. thanks to a fel tank ranging from 169l and later 174l. It had a wooden 2-bladed propeller of 2.75 m diameter with a pitch of 1.8. All versions but the last had a single had MG 08/15 Schwarzlose machine gun 7.92 mm (.315 in).

Variants

First production Batch

The first production model, reaching units in early 1917, saw the added, unbraced part of the upper wing flexing when the ailerons were actuated, countering the effet. The engine was the same as the D.I, 150 hp (110 kW) Benz Bz.III. One fixed Spandau machine gun mounted on the starboard side of the nose.

Second production Batch

To address this issue, these had light steel-tube vee braces added outboard of the star struts to stiffen the outer upper wing. First with Daimler’s Mercedes D IIIa.

Third production Batch

Same as above, it seems there were no changes compared to the 2nd batch. In total these three batches represented only 23 seaplane. Also Daimler’s Mercedes D IIIa engine.

4th production Batch

Summoned to do better, the rate was augmented for the last two batches for 35 total, including 15 for this one. The 4th batch differed by having the 160 hp (120 kW) Maybach Mb.III engine. However it still had the same unsynchronized machine gun. It had the same issue as the others, positioned out of their reach of the pilot, and thus impossible to clear stoppages.

5th production Batch

This last batch was the best production wise with 20 machines delivered from October 1917 to February 1918, completely obsolete at the time. However for the first time, they received two synchronized Spandau machine guns on either side of the cockpit. The final serie also was fitted with the 160 hp Maybach Mb III engine.

As for numbers, #748 was the prototype. 783/784 were the first two of the pre-production batch (1st batch) with #912–921 (10 aircraft) for the second batch, #1067–1076 (also 10) for the third, #1380–1394 for the 4th batch (15) and #1554–1573 for the 5th batch (20).

Evolution

-W 11 variant was constructed powered by a 200 hp Benz Bz IV engine (3 made).
-W 16 variant prototype powered by a 160 hp U III rotary engine
-W 25 variant featuring conventionally braced wings, also prototype.

⚙ specifications
Length:	8 m (26 ft 3 in)
Height:	3.35 m (11 ft)
Wingspan:	9.25 m (30 ft 4 in)
Empty weight:	760 kgs
Gross weight:	1040-1045 kgs
Powerplant:	Benz Bz.III 6-cyl. water-cooled inline piston engine 112 kW (150 hp)
Maximum speed:	172 km/h (107 mph, 93 knots)
Range:	500-540 km (335 miles, 291 nm.)
Endurance:	2 hrs 30 mins
Ceiling:	4,000 m (13,000 ft)
Crew	1 pilot
Armament	Early batches: 1x Schwarzlöze 8mm, see notes.