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

Halberstadt CLS I
   Designed to succeed the CL II and CL IV types, the CLS I was even smaller and lighter, and it was also faster. Type tested on 2nd October 1918, it came too late to go into production. But for the absence of curvature in the lower wing roots and the built-up rear cockpit, the CLS I might be confused with the CL IV: construction was almost identical. Further development in the shape of CLS II and CLS X, with 3.5 cm. revolver cannon, remained no more than projects. Engine, 160 h.p. Mercedes D III. Span, 9.7 m. (31 ft. 9 7/8 in.). Length, 6.95 m. (22 ft. 9 5/8 in.). Height, 3.05 m. (10 ft. 0 1/8 in.). Area, 26.4 sq.m. (285 sq.ft.). Weights: Empty, 682 kg. (1,500 lb.). Loaded, 1,102 kg. (2,424 lb.). Speed, 185 km.hr. (115.625 m.p.h.). Climb, 4,500 m. (14,760 ft.) in 36 min. Armament, one Parabellum and two Spandau machine-guns.

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

HALBERSTADT CLS I Germany

   A requirement was formulated in September 1918 for a two-seat fighter optimised for the close air support role. Climb rate was considered of secondary importance, emphasis being placed on speed, manoeuvrability and dive capability. The Halberstadter Flugzeugwerke responded with a design based on the C VIII reconnaissance biplane, but having reduced wing span and a 160 hp Mercedes D IIIa engine, and designated Cls I. The requirement resulting in the Cls I had specified an increase in useful load (by comparison with the CL IV) from 750 lb (340 kg) to 926 lb (420 kg), apparently to cater for a twin fixed-gun armament and a larger load of anti-personnel bombs, but the provision of a 20-mm Becker cannon for the gunner was also proposed. The Cls I was type tested in October 1918, but when the static testing of components terminated on 6 December, some strengthening of the tail surfaces was called for. Only three or four prototype Cls I close air support fighters were completed.

Max speed, 115 mph (185 km/h).
Empty weight, 1,504 lb (682 kg).
Loaded weight, 2,430 lb (1102 kg).
Span, 31ft 9 7/8 in (9,70 m).
Length, 22 ft 9 5/8 in (6,95 m).
Height, 10 ft 0 in (3,05 m).
Wing area, 284.18 sq ft (26,40 m2).

J.Herris Halberstadt Aircraft of WWI. Volume 2: CL.IV-CLS.I & Fighters (A Centennial Perspective on Great War Airplanes 45)

Halberstadt CLS.I

  Both Hannover and Halberstadt produced successful light C-types as two-seat fighters. The CLS.I was Halberstadt's planned successor to the earlier CL.II and CL.IV. In fact, the CLS.I looked like a refined CL.IV with slightly different proportions. The engine was a 180 hp Mercedes D.IIIau, a high-altitude version of the reliable engine that powered so many fighters and the previous CL.II and CL.IV.
  Aircrew of the CL-types carried extra weapons and ammunition to carry out their missions, including hand grenades, small bombs, and extra drums of machine-gun ammunition. This overloaded the CL-types beyond their designed useful load limit and caused structural damage to the airframes. When Kogenluft addressed this issue on a conference on September 6, 1918, both Idflieg and Halberstadt were found blameless.
  Kogenluft decided that the useful load rating of CL-class Schlachtflugzeuge (infantry-support aircraft) would be raised from 346 kg to 420 kg and the CL-class design specification would be revised to meet the strength requirements (maximum G limits) of fighter aircraft.
  Furthermore, CL-type design emphasis was to be focused on speed, maneuverability, and diving ability at the expense of the fast rate of climb. This reflected the fact that the role of the CL-types had expanded and their use as Schlachtflugzeuge was now a critical role.
  Halberstadt CL.IV aircraft revised to withstand the higher load rating began to come off the production line in September 1918. At the same time, Karl Theis, the designer, was working on the CLS.I, an aircraft designed from the beginning for the stress limits of the Schlachtflugzeuge role.
  CLS.I armament was two synchronized Spandau guns for the pilot and one Parabellum for the gunner. A 3.5 cm revolver cannon was said to be planned for the CLS.II and CLS.X but this was a plan only.
  Despite having a shorter wing-span than the CL.IV, the CLS.I had a heavier loaded weight reflecting the more robust structure and heavier weight of weapons and ammunition.
  The CLS.I was type-tested on 2 October 1918, commendably soon after the changed requirements. It was intended to replace the CL.II and CL.IV but the Armistice intervened.
  Serial numbers 1797/18 and 1799/18 are known, and their were probably others. One of these was work number 2105.


Halberstadt CLS.I Specifications
Engine: 180 hp Mercedes D.IIIau
Wing: Span 9.7 m
Chord, upper 1.600 m
Chord, lower 1.400 m
General: Length 6.95 m
Empty Weight 670 kg
Payload 520 kg
Loaded Weight 1190 kg
Maximum Speed: 185 km/h
Climb: 4500m 36 min
Fuel Capacity: Main tank 60 Liters
Secondary tank 48 Liters
Armament: 3 mgs



Afterword: Halberstadts Postwar by Colin Owers

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  No complete Halberstadt CLS survived the war, but a fuselage of this prototype aircraft was in the Strahle collection and is now on display in the Stiftung Deutsches Technikmuseum in Berlin.