M.Schmeelke Zeppelin-Lindau Aircraft of WW1 (A Centennial Perspective on Great War Airplanes 42)

Zeppelin (Ja) C.I / C.II

  Due to the imminent reduction in airship orders beginning in 1917, Luftschiffbau Zeppelin management had to search for new products in order to utilize the company's full production capacity. In 1918, the Zeppelin company employed 11,500 workers in Friedrichshafen. The danger was that should these well-educated specialist workers be underemployed, they would he reassigned to the military or other companies, or simply leave. Some of this could be compensated by shifting workers to other operations; for example, the LZ foundry began to cast crankcases for the Maybach Motorenbau Mb IVa engine, or to the Lindau factory. In addition, Colsman planned an expansion of the aircraft business.
  Two subsidiaries of LZ, the ZWL and the aircraft hangar in Staaken, had already successfully established themselves. Now Colsman wanted LZ's Friedrichshafen hangar to take a larger role in producing aircraft for the army and navy.
  In the summer of 1917, Colsman assigned LZ engineer Paul Jaray to design a C-Type for the air force. Jaray, who was born in Vienna, had studied mechanical engineering in Vienna and Prague. He came to Friedrichshafen in 1912 as one of the first specialists in aerodynamics - a topic that would interest him his entire life. In 1914 he moved to LZ, where he participated in the construction of various airships, and could spend time intensely researching aerodynamics.
  On June 30th, 1917, Paul Jaray began development of the Zeppelin C.I, a two-seater high-altitude surveillance aircraft. Within 14 days he had drafted a blueprint of a prototype. This two-seater biplane "showed the most consequential consideration of all new regulations to achieve most economical flight", as it was explained in the craft's description. In addition,
  “[...] its use as a military and a passenger aircraft employs all of the characteristics of modern aircraft - speed, excellent climbing characteristics, comfortable, light handling, maneuverability, gliding potential, good visibility, and extraordinary safety with significant elasticity of the shock-absorbing parts. From the standpoint of aerodynamics and stability, the design is a fortunate combination of all the current aviation construction and light metal expertise. As a result, the overall value of this type (but also of its parts) is a leader among current aircraft. ”
  The advertising and technical department of LZ did not exaggerate here. The Zeppelin-Jaray C-aircraft did indeed show extraordinary technical parameters for 1917, such as an altitude ceiling of 8,000 meters and a top speed of 210 kilometers per hour. The aircraft owed its speed to Jaray's aerodynamics research, which flowed into its design. On August 18th 1917, 30 workers began building the Zeppelin (Ja) C.I. However, the first two pre-serial construction fuselages in the hangar were made of wood. This two-seater biplane with a wingspan of 12 meters and a fuselage length of 6.9 meters was powered buy a 260 HP Maybach Mb IVa engine.
  The fuselage, referred to internally as "Aircraft 1", was covered in wood veneer. Only Aircraft 2 was given fabric coverings over openings on the sides and top of the fuselage. In addition to the lower weight, these openings could be used as maintenance access for the fuselage. This was surely also changed on Aircraft 1 later. Since these two aircraft were primarily used for LZ's testing purposes, various cooling systems, exhaust collectors, and propellers were tested out on them. In addition, clear Cellon was tested on the upper wing to increase the pilot's upward visibility. Since these pre-serial aircraft carried no official designation, they cannot be tracked.
  The wing and tail constructions, spars, ribs, and rudders of the prototypes were already made of duraluminum, which was produced at the ZWL in Reutin, and covered with fabric as was the usual case at the time. On October 17th, 1917, in a record time of two months, the Zeppelin (Ja) C.I took off for its maiden flight in Lowental. The company pilot Hausmann was satisfied with the fight characteristics, and with an operating weight of 1,500 kg (empty weight 1,000 kg) the C.I reached a top speed of 210 kilometers per hour. In the following days, Hausmann made several more test flights, focusing on the maneuverability of the aircraft as well as dives and spins.
  At the same time the wooden aircraft were being constructed in the hangars of the LZ, Dornier's engineers in Lindau began to work on transferring Jaray's plans to build a metal fuselage. The all-metal aircraft was designated C.II.
  The LZ hangar in Friedrichshafen was not able to begin serial construction - it could only be done in collaboration with the ZWL in Lindau. Colsman therefore assigned additional workers from Luftschiffbau to ZWL.
  On December 8th, 1917, Luftschiffbau Zeppelin GmbH received a binding order for six test C-aircraft, three each of ZWL C.I and Zeppelin C.II, from IdFlieg's flight master:
  “Subject: Delivery of test aircraft.
  With the approval of the war ministry dated November 23rd, 1917, I issue the company with the order of the delivery of 3 - three - pieces test C-aircraft for 160 HP Mercedes engines and 3 - three - pieces test C-aircraft for 260 HP Maybach engines.
  With complete accessories for aircraft and power plants, as well as installation of MGs.
  The aircraft will carry the military designations C 15800 through 15805/17.
  The installation of F.T. (??) - or photography equipment, the installation of the MG, the delivery of shell feeding equipment is included in the price. ”
  On December 14th, 1917, LZ answered with the following letter:
  “We confirm with thanks the receipt of the order to deliver 3 test C-aircraft with 260 HP Maybach engines. The confirmation of the 3 test C-aircraft with 160 HP Mercedes engines will follow from our Zeppelin Factory in Lindau. For the three test aircraft with 260 HP Maybach engines, we have noted the military designations of 15803/17, 15804/17 and 15805/17. We will assume delivery dates for the light metal aircraft of early, mid-, and end-February 1918.”
  The partial assembly of the Zepp. (Ja) C.II military numbers 15803 through 15805/17 made of aluminum took place in Lindau Reutin. According to the description, the "fuselage was made of a duraluminum lattice. In the engine area as a rotation paraboloid towards the rear in a square cross-section with lightly curved side walls.
  The wings, top 12 meters, bottom 11.6 meters (divided by the fuselage) were made of two duraluminum spars each, with riveted ribs, also of duraluminum. The elevator and the rudder as well as the tail skid were also of duraluminum.”
  The construction description says that the engine was a Maybach Mb IVa engine, with LZ cooling system and Jaray propeller (LZ-Pi 61/62). The C.II (Ja) had a special starter that allowed the engine to start without external help. In anticipation of its use as a civilian aircraft as well, the surveillance seat as well as the MG mount could be replaced with a comfortable passenger seat.
  All of the parts for Dornier's first serially produced aircraft were completed in Lindau-Reutin by March 1918. The assembly and fabric covering took place in Friedrichshafen at LZ. Less than five months after the prototype's first flight, on March 10th, 1918, the aircraft was flown in Lowental. On March 11th, 1918, IdFlieg approved and accepted it. An order for 20 combat-ready trial aircraft, with the military designations of C.5500 through 5519/18 followed. These aircraft were completed by the end of November at ZWL and LZ. Internally, the C.II airplanes were sequentially numbered (C.II/1 through C.II/20). But none of these made it to combat. C.II/2 was used as a test aircraft in Adlershof, and C.II/4 burst into flames upon landing at the Lilienthal airfield in Berlin.
  In 1920, LZ purchased back the remaining aircraft from the German Army Peace Commission of the Weimar Republic. Through a mediator, 20 Zeppelin (Ja) C.II were sold to the Swiss Air Force, where they remained in service until October 1927. That means that at least three more Zeppelin (Ja) C.II were built before the construction ban as dictated by the Treaty of Versailles was instituted.
  Three airplanes of Paul Jaray's final design, the Zeppelin C.IV, were also built: Military designations 12255 through 12257/18. The last remaining aircraft of this type, with the internal company number 01, was destroyed in a fire as a result of welding work in a hangar at the aviation museum at Le Bourget near Paris on May 17th, 1990.


Camouflage Painting of the Zeppelin (Ja) C.I / C.II

  The Zeppelin Jaray prototype aircraft C.I and C.II received the usual airship fabric covering delivered by the company's own subsidiary Ballonhullengesellschaft mbH ("Balloon covering association") in Berlin Tempelhof.
  For aerodynamic reasons, or for a smooth surface, the fabric had a protective covering of Cellon or stretching lacquer. It was mixed with iron oxide (1.5%) and aluminum powder (3%):
  “[...] For the textile covering, one used varnished linen, which was sewn onto the ribs with a special technique. "
  After the first two coats, it was smoothed by what was then called "glass paper", now known as sanding paper.
  The duraluminum parts of the C.II, such as the engine cover, struts, and shafts, remained unpainted. The national emblems and other markings were applied according to the construction and delivery regulations of the army. Only the C.II series aircraft, which had the military designations 5500 through 5519/18, received the three-color camouflage coverings from the Ballonhullengesellschaft mbH.



Specifications of Zeppelin-Lindau Aircraft

Type Length, m Span, m Height, m Chord, m Propeller Manufact. Armament
(guns) Weight, kg Motor Crew
C.I 7.60 10.50 2.84 LZ-Jaray 1 fixed, 1 flex 696 Daimler D III 2
C.II 7.92 12.00 3.58 1.80 LZ-Jaray 1 fixed, 1 flex 1,000 Maybach Mb IVa 2



Military Numbers of Dornier-ZWL Aircraft
Military Designation Manufact. Type Class Engine Notes
15800-15802/17 ZWL (Do) C.I DIIIa
15803-15805/17 Zepp. C.II Mb IVa
5500-5519/18 C.II Mb IVa 20 aircraft sold to Switzerland
12255-12257/18 Zepp C.IV Last aircraft, burned in Paris 5/17/1990

M.Dusing German Aviation Industry in WWI. Volume 2 (A Centennial Perspective on Great War Airplanes 85)

Zeppelin-Werke Lindau GmbH (ZWL), (Do)

Aircraft Development:

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  Luftschiffbau Zeppelin GmbH, a part of the Zeppelin Gesellschaft, also received the request. There, it had long been recognized that the time of the great war airships was over and the company was intensively engaged in aircraft construction. The Lindau plant saw the development of the fast C-airplane as a great opportunity to establish itself in aircraft construction. One of the best and most experienced engineers of the Zeppelin Gesellschaft - Paul Jaray - was appointed to head the project.
  Coming from airship construction, where he had been responsible for the aerodynamic design of all Zeppelins, Paul Jaray was now given the task of developing such an aircraft in the shortest possible time.
  To achieve a higher speed, there were several ways:
   1. as powerful an engine as possible,
   2. the lowest possible empty mass,
   3. a good aerodynamic design and thus low drag,
   4. as small dimensions as possible.
  Paul Jaray knew the Maybach Mb VIa engines used in airship construction very well. In contrast to the BMW BMW.IIIa and Daimler D.IIIa or Oberursel UR.IIa usually used, which ranged in output from 150 to 175 hp, the Maybach Mb.IVa produced 240 hp. It was a water-cooled standing six-cylinder in-line engine with a displacement of 23.1 liters, a compression ratio of 6.08:1, an output of 240 hp (176.5 kW) at 1,800 rpm and an average consumption of 67 liters/hour. The engine was very reliable. Its only disadvantage was the high weight of 400 kg. If the Maybach was to be used, weight had to be saved elsewhere, because the empty mass of the aircraft was not to exceed one ton. This meant, however, that a metal construction or a mixed construction of metal and wood, which Jaray had in mind, was out of the question. The new airplane had to be made entirely of wood and canvas to meet the one-ton requirement. Only the engine had to be partially clad in light metal because of heat generation. By August 1917, the design was completed and submitted for review to the Idflieg (Inspectorate of Air Forces) Commanding General of the Air Forces (Kogenluft). In order not to lose any time, the Zeppelin Company decided to start building two machines immediately, without an official order from the Idflieg.
  The C.I was a two-seat biplane with normal tailplane and fixed slip-spur landing gear of wooden construction. The fuselage with an oval cross-section consisted of wooden frames and longitudinal chords and was wrapped with plywood. This construction method made the fuselage very robust and allowed for an aerodynamically favorable design. The forward fuselage accommodated the large Maybach engine, which protruded significantly above the fuselage contour. To reduce frontal drag, it was carefully clad in light metal sheeting. A sheet steel firewall separated the engine area from the rest of the fuselage. Since the radiator was centered under the upper wing, an appropriate connecting pipe had to be used between the engine and the radiator, which contained the supply and exhaust lines made of copper tubing. The engine directly drove a fixed two-bladed wooden propeller model Heine. Directly behind the fire bulkhead was the fuel tank with a volume of 220 liters.
  The two crew members were accommodated in two separate round-cut fuselage sections, one behind the other. The pilot's cockpit had no wind protection of any kind. The pilot sat low in the fuselage, able to look straight across the long fuselage structure, with the protruding voluminous engine cowling and the connecting tube from the engine to the radiator further limiting visibility. The observer sat on a turntable, so he could operate his various devices, such as camera, later FT-device, as well as in case of attack by enemy aircraft, the swiveling 7.92 mm Spandau machine gun. The ammunition supply for this was 500 rounds. Light bombs were also to be carried, with three mounts for 10 kg bombs attached to each side of the fuselage at the level of the observer's seat.
  By means of two N-struts made of aerodynamically shaped steel tube, it was firmly connected to the corresponding fuselage frames. In addition, there was a bracing to the fuselage. Two further V-posts, one on each side, also made of steel tubing, went from the fuselage at 45 degrees to the wing and were connected there to the longitudinal spars. Directly above the fuselage on the underside of the upper wing was the radiator, designed as a finned radiator. The upper and lower wings were connected on each side by a V-stem of formed steel tubing and were also cross-braced with steel cables running from the bottom of the fuselage to the V-stem connections. The tailplane resembled a rounded triangle and was also a fabric-covered wooden structure, with both spars passing through the rear of the fuselage and also forming a solid box with the spars. This connection was so strong that it could be cantilevered, which was unusual at the time.
  In September 1917, the first machine was completed in Lindau and could be tested. The aircraft generally showed good flight characteristics, only a few minor modifications were necessary, for example the aircraft was slightly top-heavy, caused by the heavy Maybach Mb IVa. This was remedied by slightly lengthening the tail of the fuselage. One complaint was the very poor visibility for the pilot, which was sought to be improved by a higher seating position. By early 1918, the second machine was also completed and had flown by mid-February. Both machines were transferred to Adlershof for the C-type competition, where they were thoroughly tested and found to be good by the frontline pilots acting as test pilots, prompting a series order from Idflieg for 200 units to Luftschiffbau Zeppelin GmbH Friedrichshafen. However, some modifications were required, as well as the substitution of various wartime bottleneck materials and equipment. The most important changes were that the ailerons, elevators and rudders were now made of fabric-covered metal structures, since the wooden frames could not withstand the stresses. The fuel tank was also moved under the pilot's seat and designed to be jettisonable for emergencies to reduce the risk of fire. The design was given the designation C.II and series production began in June 1918.
  Difficulties were encountered in supplying the Maybach engines needed for various models, including the Zeppelin-Staaken giant aircraft, as production did not keep up. By the time the armistice negotiations began on November 8, 1918, only 19 examples of the Zeppelin C.II had been completed.
  By order of the Allied Control Commission, these were to be scrapped. In a night and fog operation, however, the Swiss Air Force acquired all 19 machines, where they were then successfully used as reconnaissance aircraft until 1928.
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P.Grosz, G.Haddow, P.Shiemer Austro-Hungarian Army Aircraft of World War One (Flying Machines)

Dornier Cl.II

  On 27 August 1918, the LFT recommended the purchase of two Zeppelin C.II(Ja) reconnaissance biplanes, powered by 230 hp Hiero engines, for evaluation. The War Ministry approved the purchase in October. Designed by Ingenieur Paul Jaray, the Zeppelin C.II(Ja) was constructed of duraluminum and covered with fabric. Twenty had been ordered by the German Fliegertruppe. But after having visited the Zeppelin factory in September 1918, the LFT command changed its mind and replaced the Zeppelin C.II(Ja) by the Dornier Cl.II, which was regarded as a more modern design due to its all-metal, stressed-skin construction. At the cessation of hostilities, the contract for the purchase of two Dornier Cl.II biplanes was annulled. To prepare for all-metal aircraft manufacture in Austria, the Zeppelin Werke established a subsidiary in mid 191(?), in Horbranz near Bregenz, known as the Zeppelin Werke Oesterreich GmbH. No production was undertaken.