Staaken L

  The German Navy had an increasing need for a long-range, high-endurance seaplane despite the crash of the R.M.L.1. This military requirement was driven by the increasing success of the British America/Felixstowe flying boats against the German airships. Additional advantages of large seaplanes over airships included being faster and more heavily armed, cheaper, and could use smaller hangars, required fewer support personnel, and had faster response time. The primary task was to be low-altitude reconnaissance for mine-spotting, antisubmarine warfare, and shipping control; the low planned cruising altitude of 500 m demanded greater reliability than any other aircraft type.
  Only two companies, Zeppelin-Staaken and Zeppelin-Lindau, delivered R-seaplanes to the German Navy. A report of 26 December 1916 by Oblt.z.S Mans, who had just visited Zeppelin-Lindau to inspect the all-metal Dornier R-type flying boat prototype then under construction, noted that Staaken was planning to propose a new R-type seaplane. This proposal was the Staaken L. The German Navy ordered an example of this aircraft on February 15, 1917, and assigned it the Marine Number 1432. This aircraft was delivered on November 14, 1917.
  The Staaken L, designed as a floatplane derivative of the R.VI, was built as a landplane, most likely to facilitate flight-testing at the factory and its delivery flight to Potsdam where the floats were fitted. During taxi trials there a number of modifications were made; a central fin was added to improve stability, standard two-bladed pusher propellers replaced the four-bladed pusher propellers, and the floats were reinforced.
  Apart from being a floatplane, the Staaken L was very similar to the R.VI. The wing area was increased and the ailerons were enlarged and balanced. The all-duralumin floats were highly compartmentalized to retain buoyancy in case of damage. The float struts were made of steel. The Navy classed the Staaken L as a bomber, and the lack of cross-bracing between the float struts indicates that carriage of torpedoes was considered a possibility.
  The fuel tanks were the 245 liter type used in the R.VI, but instead of the 8 or 10 used in the R.VI, 14 were installed in the Staaken L. Additional fuel was carried in two 150 liter tanks in each nacelle and a 155 liter gravity tank as used in the R.VI. The fuel load enabled a 10-hour endurance at cruise speed compared to the 7-hour endurance standard for the R.VI - which did not have the heavy floats of the L. During evaluation flights it was determined that the endurance of the Staaken L could be extended by cruising on only three engines once the Staaken L had burned enough fuel to reduce its weight to a certain point. This procedure is used by some modern patrol planes for the same reason.
  Once the Staaken L was completed it was assigned to the SVK (Seeflugzeug-Versuchs-Kommando - Seaplane Testing Command). A special wooden hangar for the Staaken L was built for the aircraft on piles over the water.
  On June 3, 1918 the Staaken L crashed over Warnemunde killing the crew, reportedly after engine failure. The Staaken L was not as stable on the water as the Dornier all-metal R-flying boats; at a 7° heel the tips of the lower wings would touch the water whereas the Dornier R-flying boat accepted a 14° heel before its wingtips would touch the water. However, the Staaken L was based on a proven design and was far easier to produce than the metal Dornier flying boats.

Staaken R.XIV

  The next Staaken giant design to be built was designated the Staaken R.XIV; the R.VIII and R.IX designations were used for projects that were not built and the R.X through R.XIII are not known. The R.XIV followed the basic R.VI configuration but the rear nacelle engines were the 350 hp Austro-Daimler V-12. The first R.XIV, R.43/17, flew in March 1918. The nose contours were different than the R.VI because the cockpit was redesigned with an open cockpit to give a better view for the pilots.
  The R.43 was built without reduction gears for the propellers to gain performance data to compare with the geared propellers of other R-planes. On April 12, during a flight for its acceptance program, a connecting rod broke in one of its rear V-12 engines. The Austro-Daimler engines were not ready for operational service and the next day they were replaced by 300 hp Basse & Selve BuS.IVa engines. The next flight was scheduled for May 10. However, the Basse & Selve engines were also new designs that were not fully de-bugged and were prone to failure. They in turn were replaced by the proven 245 hp Maybach Mb.IVa engines. However, this required a highly visible modification; a fifth Maybach engine had to be installed in the nose to compensate for their lower power because the R.XIV was substantially heavier than the R.VI which used four of these engines.
  Installing the fifth engine in the R.43 took two months; the modified R.43 was ready for acceptance in July. The R.44, which had been built originally with four Basse & Selve engines, did not fly with those engines and was modified with the five Maybach engines. It was delivered in August and the R.45, which was built with the five Maybach engines, was delivered in July. The nacelle tractor propellers for these aircraft did not have reduction gears.
  Balanced ailerons were added to the R.XIV design in an attempt to reduce control forces; the balance was kept within the wing outline. Upper wing gun positions were fitted outboard of the engine nacelle centerlines. The nacelles themselves were slimmer than those of the R.VI, mounted higher, and the struts were rearranged. Large spinners were fitted to the tractor propellers.
  The R.XIV carried parachutes for all crewmembers; these were carried in external fuselage compartments with lines running to each crewman's station. Six machine guns were carried; one in each upper wing position and two guns in the dorsal and ventral positions. The increased armament reflected the greater Allied use of night-fighters.
  The R.45 had its pilots' cockpit moved aft of the wing trailing edge for a better view of the main wheels when landing. Tests were made with wingroot panels open for a better view during landing, but these were covered before R.45 left for the front on August 9, 1918.
  During a bombing raid together with R.31, R.45 received a wireless message that it was not to return to its base at Morville, then the home base of Rfa 500, because enemy aircraft over the field meant the landing lights could not be turned on. However, the aircraft commander decided that the low fuel state of R.45 meant that it had to land at Morville. The radio operator notified the field of the decision and requested ground personnel signal with flashlights. The first two landing attempts were not successful; on the third attempt signal flares were fired to better illuminate the field. R.45 landed but missed the runway and hit obstructions that stopped the aircraft. The following morning the obstructions were found to be a water wagon and large ladder on the left and construction material and the roof of a house on the right. Had the R.45 not hit the obstructions, it would have run into a barracks where 60 men were sleeping. R.45 is not thought to have been repaired in time for more missions.
  R.43 was one of two R-planes shot down during a bombing mission. On the night of 10/11 August 1918 R.43 was assigned a target not far behind the lines; lit up by searchlights it was attacked by four Sopwith Camels from 151 Squadron, RAF, a specialized night fighter unit that had recently been transferred to France from Home Defence in Britain. R.43 was attacked by four aircraft and shot down by Capt. A.B. Yuille, who got in close under the tail of R.43. R.43 was totally destroyed when a bomb exploded when it hit the ground and all nine crewmen were killed.
  The R.XIV, powered by five engines, was not a significant advance over the four-engine R.VI. The fifth engine gave the R.XIV greater reliability in case of engine failure. However, the installation of the nose engine again made the aircraft more likely to catch fire in the event of a crash-landing, and its vibrations affected the more delicate instruments. The smaller diameter and higher RPM of the ungeared propellers also reduced their aerodynamic efficiency. The R.XIV was also heavier than the R.VI for several reasons; it had another engine, its structure was built heavier and stronger for the 350 hp V-12s expected to be used, and various other changes had been made that increased weight.


Staaken R.XIVa

  The Staaken R.XIVa was an improved model of the R.XIV, although it was delivered later than the Staaken R.XV The R.XIVa was intended to offer better climb and ceiling than the R.XIV while carrying a greater bombload, so it was given reduction gearing on all engines to improve propeller efficiency. The weight of the R.XIVa was reduced by lightening the structure, removal of the wing machine gun positions, and removal of the bomb bay fairings. A small reduction of the fuselage and engine nacelle cross sectional area contributed to a slight speed increase. The elevators were balanced, a first for a Staaken design.
  Idflieg ordered four R.XIVa aircraft, serial numbers R.69 to R.72, from Staaken; these were the last R-planes built by Staaken during the war. The first aircraft, R.69, was built so quickly that not all the modifications could be included. Despite the rushed construction, R.69 was only delivered on Oct. 19, 1918, and did not have time to see operational service. R.70 and R.71 incorporated the modifications and were completed post-war; it is not known if R.72 was completed.
  All three aircraft were used to transport money into the Ukraine after the war. R.69 was seized by the IAACC (Inter-Allied Aircraft Control Commission) after landing at Aspern near Vienna on a return flight from the Ukraine. On September 19, 1919 R.70 was seized by Romania when it has to make a forced landing in Bessarabia. R.71 crashed of unknown causes during the summer of 1919.
  Schutte-Lanz was given a contract for three R.XIVa aircraft, R.84-R.86, but these were not completed before the Armistice.


Staaken R.XV

  The Staaken R.XV was almost identical to the R.XIV; it looked nearly the same and had the same engine configuration, five 245 hp Maybach Mb.IVa engines. The differences are not documented but were probably focused on weight reduction to improve performance because the shape of the nose was slightly refined.
  The R.46/17, the first of three R.XV aircraft completed, was ready for its maiden flight on July 25, 1918 and was delivered in August. Both the R.47/17 and R.48/17 were accepted on September 1, 1918. At least two of the aircraft were in time to see service over the Western Front. Postwar, R.47 was shipped to Japan as spoils of victory, and the IAACC found R.48 in the factory in 1919.

Staaken R.XVI

  The Staaken R.XVI was similar in appearance to the original, four-engine configuration of the R.XIV with squared-off nose. The key difference was installation of powerful new V-12 engines in the pusher position.
  In May 1917, Idflieg ordered 20 new Benz Bz.VI V-12 engines designed to produce 530 hp. The increased power was intended to improve R-plane performance and increase bombload. When in early 1918 the first engines became available, they were delivered to Aviatik for the R.XVI. Aviatik had already built several R.VI aircraft under license so had the qualifications, and Staaken was already committed to development of all-metal aircraft.
  Three of these aircraft, R.49/17 to R.51/17, were ordered from Aviatik as the R.XVI(Av). They were nearly identical to the last series of R.VI aircraft built by Aviatik that had the squared-off nose. The engine nacelle was refined and somewhat enlarged to accommodate the large V-12 engines installed as pushers. The 300 hp Basse & Selve BuS.IVa engine was installed as the tractor engine with a large spinner. However, as in the R.XIV, the Basse & Selve engines had to be replaced due to their poor reliability. The replacement engine was the reliable 220 hp Benz Bz.IV.
  Radiators were mounted on the same struts that supported the engine nacelles, with the V-12 engines receiving two radiators. Oil radiators were located at the bottom of each nacelle. Wing area was slightly increased over the earlier aircraft by eliminating the indentations in the trailing edge of the wing for propeller clearance.
  Bench testing of the Benz Bz.VI V-12 engine and associated reduction gears was progressing by May 1918; delivery of the R.49 was expected in June. By September the R.49 had made a number of satisfactory flights and there were no problems with the engines. In October R.49 was performing its acceptance flights. During these flights, a heavy landing collapsed the landing gear and the lower wings were badly damaged. R.49 was probably not rebuilt.
  R.50 was not completed until early 1919, and was converted into a civil aircraft during construction. The upper wing gun mounts, ladders, and bomb-bay fairing were omitted, which were not necessary for a passenger aircraft and saved weight. The aircraft had 'Aviatik' painted under the lower wings.
  The third aircraft of the batch, R.51, was three-quarters complete in January 1919 but was never finished. The R.XVI was the most powerful aircraft built and flown in Germany during WWI.

Staaken 8301 & 8303

  Staaken's R-floatplane family did not stop with the Staaken L; it had been successful enough that the Navy ordered additional aircraft. In December 1917 the Navy ordered two developments of the Staaken L, given Marine Numbers 8301 and 8302. The next month the Navy ordered two slightly improved aircraft, Marine Numbers 8303 and 8304. These four aircraft were improved developments of the Staaken L with modifications based on the lessons learned from evaluating that aircraft.
  These aircraft were very similar to the Staaken L, with the most visible difference being the fuselage was raised above the lower wing. Raising the fuselage and tail higher above the water improved the sea keeping. The forward gun ring was raised level with the top of the fuselage, giving the aircraft a rectangular nose profile.
  Windows of Cellon were installed around the nose giving a wide field of view. The nose also had the bomb releases for ten 10 kg bombs stored in two containers along each side of the nose. An anchor winch was installed there for a small anchor hung externally on the nose. A mast antenna enabled the radio to transmit while the aircraft was on the surface and was collapsible for flight.
  Other improvements to the 8301/8303 over the Staaken L were derived from the modifications introduced by the newer Staaken landplanes. The wing and control surfaces resembled the R.XIV and the tail had balanced elevators. Becker 2 cm cannon were planned for the rear gun positions. The five-man crew, less then that for the R.VI, reduced the weight to enable the larger fuel load to be carried. Twelve 300-liter fuel tanks gave an endurance of 9-10 hours at cruising speed on all four engines.
  In the summer of 1918 the 8301 made its maiden flight as a landplane. The wheeled landing gear resembled that of the standard Staaken R-planes except that the raised fuselage meant the nose landing gear had to be longer. All-duralumin floats were then fitted; these were longer than those on the Staaken L and divided into 12 compartments to minimize flooding in case of damage.
  The 8301 and 8302 were based at Warnemunde for evaluation until the Armistice.
  The 8303 and 8304 were completed but not delivered; postwar they were found at the Staaken seaplane hangar at Wildpark near Potsdam by the IAACC. The most visible difference between the 8301/8302 and the 8303/8304 is the later aircraft had slightly swept wings. Postwar, the 8301 and perhaps the 8303 and 8304 were used on regular weekend passenger flights between Berlin and Swinemunde.
  These Staaken floatplanes are the largest, though not the heaviest, floatplanes ever built.

Staaken E.4/20

  The all-metal Staaken E.4/20, a result of the desire to build advanced R-planes for daylight bombing missions, was a complete departure from the earlier Staaken designs. Built after the Armistice, it was built as a transport instead of a bomber for the postwar era.
  Construction of the Staaken E.4/20 started in May 1919 with the intention of starting passenger service between Friedrichshafen and Berlin. The aircraft was completed on a relaxed schedule on September 30, 1920.
  The Staaken E.4/20 was a high-wing cantilever monoplane with four 245 hp Maybach Mb.IVa engines buried in the leading edge of the thick wing. The engines had frontal, car-type radiators and a conventional tail assembly was fitted. The fixed main landing gear had two wheels on each side with a small tail skid. The configuration was very modern and set the style for later passenger airplanes. The structure was all-metal semi-monocoque throughout. This advanced construction was subsequently used for high-performance aircraft to the present day.
  The width of the massive wing spar was 1/3 of the chord of the wing and was 1.5 m deep at the wing roots. The leading edge was made of 4 mm thick duraluminium and was attached to the wing spar, as was the trailing edge. The rest of the wing was covered with fabric. The wing spar had oval openings to enable a mechanic to access the engines in flight. Supplementary bracing cables were added to the wing for safety; however, all the normal flight loads could be handled without them. Fuel was carried in two large tanks placed in the leading edge between the engines and four fuel tanks located in the trailing edge structure.
  The pilot's open cockpit was located on the upper fuselage just forward of the wing leading edge. Later the nose was cut down and a fully-enclosed cabin with cellon windows was added. The passenger door was in the nose and 12-18 passengers could be carried. A large mail compartment was installed together with toilet, wash-room, and luggage space.
  During construction the Staaken E.4/20 was inspected by the IAACC, who permitted Staaken to complete it. The IAACC felt they could not determine the military potential until the aircraft was completed and test flown.
  Test pilot Carl Kuring performed a number of very successful test flights as soon as the aircraft was completed. During one flight the aircraft was clocked at 225 km/h, an unprecedented speed for the time for an aircraft of its size. This was a speed that could be achieved by only the fastest contemporary fighters and reconnaissance planes. Staaken had achieved its goal of R-plane performance enabling daylight bombing missions - albeit if the aircraft had been completed as a bomber instead of a passenger plane. Although a design goal was to be able to maintain flight on two engines, the E.4/20 could not do that. It needed fully-feathering propellers to reduce the drag of wind-milling propellers, a technology that was not available at the time. Further test flights were prohibited by the IAACC, which was now convinced the E.4/20 had military potential. The IAACC obstinately prohibited selling or giving away this aircraft, forcing its scrapping on November 21, 1922. The opinion of the company was the IAACC did this to financially damage the Zeppelin-Staaken company to drive it out of business. Unfortunately, this historic aircraft, the forerunner of later large transport and military aircraft, was not preserved for posterity.