Friedrichshafen FF 33 (1916)

Marine-Fliegerabteilung: 470 manufactured 1915-1917. In service until 1929

The Friedrichshafen FF.33 family was the backbone of German naval aviation during most of World War One. Of the numerous seaplanes Friedrichshafen provided to the German Navy, half were from the FF.33 model. It came after a gradual development, from the 1913 experiments to the 1914 FF 19 and more powerful FF 29 which cemented the appreciation of Friedrichsafen model by the general staff of the Kaiserliches Marine.

FF 33j 1918

Not only they made 1/3 of the total numbers of German seaplanes fielded in WWI, they were instrumental in many occasions, and they soldiered for 6 other countries long in the interwar as well. Reliable, rugged, stable and with a long range, it perfectly filled all requirements of the Imperial german Navy until 1918. From its origin with Zeppelin in 1912 to its demise in 1921, the company secured its name in the history of naval aviation.

FF 33j 1918

About Flugzeugbau Friedrichshafen GmbH

The company was founded on June 17, 1912 in Friedrichshafen, Lake Constance, by Theodor Kober (capital 372,000 Marks, equiv. 2,300,000 EUR today) and was supported by Ferdinand Graf von Zeppelin which invested a lot. Kober also installed his first workshop and factory in a Zeppelin hangar in Manzell. By the summer of 1916, the Warnemünde shipyard became a branch of Flugzeugbau Friedrichshafen nand its hall was partly rented from July 1914. In March 1917 production of floats alone was set up in the former spinning mill in Weingarten (100–120 employees). From 1913, Karl Gehlen was its chief of design office.

By laye 1918, FF had 3,240 employees at Manzell and the Friedrichshafen plants. After the war aircraft construction stopped and from November 1920, Dinos automobile works started at the Warnemünde shipyard. On May 15, 1921, Maschinen- und Schiffbau GmbH was created in Manzell with Gründer & Cie. KG and by May, Luftschiffbau Zeppelin took over its shares while Dornier works took over the Manzell site. In 1925, Maschinen- und Schiffbau GmbH and FF were liquidated.

Friedrichshafen initially produced Curtiss-drived Curtiss "hydroplanes" designed by chief engineer Karl Gehlen. The latter also designed large bombers and other landplane but Friedrichshafen became quickly a specialist in naval aircraft, providing all Kaiserlisches marine's naval air bases over the North Sea and Baltic. In fact, in WWI, 908 of 2,150 seaplanes delivered to the Imperial Navy were from Friedrichshafen alone. Not all were seaplanes. The twin-engine G.III bomber (600 manufactured) was also a stunning success of the company.

The list of seaplanes produced by Friedrichshafen is the following. Production models are in black:
1912: Friedrichshafen FF 1 curtiss-derived prototype seaplane
1913: Friedrichshafen FF 17 seaplane (1 made)
1914: Friedrichshafen FF 19 seaplane (16 made)
1914: Friedrichshafen FF 21 flying boat (1 made)
1914: Friedrichshafen FF 27 seaplane (1 made)
1914/15: Friedrichshafen FF 29 seaplane (44 made)
1915: Friedrichshafen FF 31 sea fighter (2 made)
1915: Friedrichshafen FF 33 sea fighter/utility (c470 made)
1916: Friedrichshafen FF 24 sea reconnaissance aircraft (1 prototype made)
1916: Friedrichshafen FF 35 torpedo aircraft (1 test 2-engine pusher made)
1916: Friedrichshafen FF 40 sea fighter (1 made)
1916: Friedrichshafen FF 41 sea fighter (9 made 1916-17)
1916: Friedrichshafen FF 43 sea fighter (1 made)
1917: Friedrichshafen FF 39 naval combat aircraft (14 made)
1917: Friedrichshafen FF 44 naval combat aircraft (1 made)
1917: Friedrichshafen FF 48 naval combat aircraft (3 made)
1917: Friedrichshafen FF 49 naval combat aircraft (260 made)
1918: Friedrichshafen FF 53 torpedo aircraft (3 made)
1918: Friedrichshafen FF 59 naval combat aircraft (22 made)
1918: Friedrichshafen FF 60 large naval aircraft (1 triplan 4 engines made)
1918: Friedrichshafen FF 63 naval combat aircraft (1 monoplane made)
1918: Friedrichshafen FF 64 (3 made)
1919: Friedrichshafen FF 71 (6 transport made)

Development

With the FF 49 later, the Friedrichshafen FF 31 was the greatest success of the company, with some 470 made in 1915-1917. This was a generalist naval combat aircraft that proceeded from the successful FF 19 and FF 29 in 1914. The formula was borrowed from Curtiss originally through the prewar FF 1 and a serie of projects until the more successful FF 17, later improved as the serial FF 19, first production model of the company for the Kaiserliches Marine.

Friedrichshafen FF 19

Friedrichshafen FF 19, the first success of the company. First flight was in May 1914 and 16 were produced from April to November 1914. This 860 kg model had a wing surface of 48,00 m², powered by a Mercedes D II 105 hp (77 kW), capable of 95 km/h and 500 m+ altitude. In the course of 1913 indeed, in response to an order issued by Kaiser Wilhelm II on May 3, to set up a naval aviation department, the Kaiserliches Marine envisioned to acquire the British Avro 503 floatplane for seaworthiness tests, under the naval registration D–12 during the 1913 autumn maneuvers.

There was a lack of domestic alternatives at the time indeed, but still, three German companies produced models for comarative tests, derived from existing land-based aircraft. The Avro 503 performed much better than the prototypes from Albatros and AGO. Not going to purchase more Avro, in 1914 the naval command ordered AGO GmbH to develop a similar model. But this copy powered by an Oberursel rotary engine, fitted with an outdated AGO lattice fuselage was not able to convince the naval staff during a presentation held in Kiel-Holtenau in January 1914. So they turned to Albatros, ordering five aircraft as well as the same to Friedrichshafen in February, which was recommended.

Delivery of the two competing models started at the end of April 1914. The Albatros design failed to meet requirements, but the five FF 19s started tests from May completed rigorous tests from May 7 to June 18 without any issues and perfectly meeting requirements. They entered service immediately service, numbered 25 to 29. One more was ordered for rigidity tests on May 2, showing their wing only broke at 7.02 times the load. The FF 19 was marked as the primary reconnaissance floatplane of the Gderman Imperial Navy, first official model meeting all its requirements.

Its top speed was average but it was very stable and without vices, had an excellent seaworthiness, a four hours plus flight time, all the necessary seafaring equipment with signaling devices and a two-man crew, one used as navigator and spotter. More important, it was rugged enough to be deployed from any ship. This successful design resulted in a follow-up order for ten more delivered by November 1914 (numbered 76 to 85). The FF 19 was the first German seaplane also used for wireless radio experiments, and succeeded by the even better FF 29 fitted with a more powerful engine.

Friedrichshafen FF 29

The Friedrichshafen FF 29 was essentially a FF 19 with more power. It first flew in November 1914 but was studied from mid-1914. Like its predecessor, this braced, three-stem biplane with a square fuselage cross-section and a slightly curved fuselage top had flat-bottom floats, arranged parallel to each other. The new engine fitted was a Mercedes D II (129 PS (95 kW)). It was also wider, with a wing area of 57,50 m² to compensate the engine's extra weight, and faster, capable of 95 km/h at low altitude, but could carry bombs, up to 1.4 tons useful payload, for offensive missions.

The Imperial Navy command placed another order with FF GmbH for eleven more units of the DD 19. However in the meantilme the company had been working on an improvement with a new engine. Proposed as an alternative upgrade it was accepted and on paper, by August 15, 1914, the Navy expanded its order to 20 units of this improved version. The adaptation of the Mercedes D II engine. Designer Theodor Kober, at the head of the design team, increased the wingspan and wing area to compensate for the aded weight and ensure autonomy and stability were preserved.

The first FF 29 prototype flew for the first time in November 1914. The first FF 29s were handed over to the Navy in December. In the meantime, the order was increased to 47 units, of which seven (second series) received an Argus engine for comparative tests and a third series the D II. Some were designated FF 29a when manufactured at the Imperial Shipyard in Wilhelmshaven, equipped with the weaker, older D-I engines rated for 105 hp in take-off power and a modified tail and specific floats. The order for three was later cancelled making for a total of 44 FF 29s and FF 29as by September 1915. Numbers indicates however only 30 reliably identified. These were used from naval air stations along the North and Baltic Seas or were deployed as on-board aircraft notably from the seaplane tenders SMS Answald or the Glyndwr in WWI. The company in 1915 work on their successor, the FF 33, which is the current subect of the post.

Towards the FF.33

FF 33 "Wölfchen" (Little Wolf) aboard SMS Wolf (1916).

The FF 33 was easily the most produced seaplane of Friedrichshafen in this war, counting for almost 1/3 of all seaplane models fielded by the Kaiseliches Marine. It was ordered in several batches for a grand total of 315 planes between, 180 FF 33E and 135 of the later FF 33L. Not only they were used until 1918, but they were also fielded by Bulgaria, Finland, the Netherlands, Poland, and Sweden long after the war. However production numbers are conflicting, and some sources went up to 427 FF.33 over a total of 854 seaplanes provided by Friedrichshafen to the German Navy so roughgly half. In any case, this model was a backbone of Gerrman naval observation, rugged and reliable, with a long range and easy to fly.

FF 33:
This was still a repeat of the FF 29, a two-bay floatplane which general layout and architecture was not changed a lot. The initial production version powered by a Mercedes D.II engine, with six built, which first flew in December 1914. In this first model (6 built), the FF 33, the observer sat in front of the pilot.

FF 33b:
This was changed from the FF 33b variant onwards (early 1915, 5 made) in that the pilot sat at the front and the observer could operate a flexible mounted machine gun at the back for defence, which was new. Also it was powered by 119 kW (160 hp) Maybach inline piston engine, five built.

FF 33e:
This variant was unarmed, but fitted with radio equipment. In some cases it had a dual control installed and the to be used as a training aircraft. Many were retofitted later this way. This became the early, main production reconnaissance variant, powered by a new and more powerful Benz Bz.III inline engine. It also had longer twin floats for better seaworthiness, and the under tail central float removed. The radio transmitter was of course a game changer, but the lack of armament was an issue. It was also called the 1st serie, with about 180 built. Of course, the General Naval staff liked this variant due to the immediate feedback, but the lack of protection was an issue.

FF.33f:
This semi-experimental Scout/Fighter version in late 1915 was based on FF.33e but with reduced span wings, reduced length and fitted with a machine-gun on a pivoted mount. Only 5 were built. It was generally smaller in size and was delivered with two-stem wings. No Radio.

FF.33h:
FF.33f but with aerodynamic refinements (early 1916). It had a duplication of wing-bay bracing cables as safeguard, if the observer had to fire his machine-gun forward through the wings. 50 built. No radio.

FF.33j:
FF.33e but with aerodynamic refinements and provision of a radio transmitter and receiver. So the Navy at last had the best of both worlds: An observer capable of defending the aircraft or operate the radio however the pilot was still not armed himelf, and many complained of this in reports. Production: 60. Note:

FF.33l:
In September 1916, the last variant was delivered a the FF 33l, basis for the future Friedrichshafen FF 49. This Main production scout/fighter version had further aerodynamic improvements and a fixed machine gun for the pilot, with about 130 built. This forward-firing fixed machine gun was added, operated by the pilot, which could also manage to solve jammings. It went with a synchronized gear to fire through the propeller. It was recoignisable by its engine fairing and aerodynamic nose, faster and with greater range than the previous models. Because of this fixed forward MG it was called a "scout-fighter". The last order was passed in February 1917. 40 were of the class C2MG and 85 of the class CHFT. The latter had the forward firing MG for the pilot.

FF.33s:
The FF.33s was a dual-control trainer version. 32 were made: 2 prototypes (numbered 789 and 790) in 1916 and 30 in 1917 (numbered 3001 to 3030).

Around 470 FF 33s in grand total were built and the numbers are not disputed today, as if lot of documentation disappeared in 1919 (plans in particular), production records were preserved. See the German wikipedia source for a complete table of numbers and types. The DD 33L had the factory code C2MG. There was also an attempt to provide the army with a decent late war reconnaissance model, the Friedrichshafen C.I, a landplane version of the FF.33l with a wheeled landing gear, of which a single one was ever built.

Design of the FF 33

Design Drawing

General design

The Friedrichshafen FF.33 seaplane was a two-seater patrol aircraft of mixed construction. It was powered by a liquid-cooled inline engine forward with a two-bladed fixed pitch wooden propeller. In the fuselage behind it was the pilot's seat (depending on versions it could be the observer's seat) and observer's seat, both covered with a small windshield. In latter variants, H and L, the rear position was both the observer and gunner's position with the ring-mounted machine gun. The pilot had a set of controls and basic on-board instruments. The second post for the observer comprises maps and goggles. Communication wit the pilot was complicated the best of times. The was also a classic large-surface tail at the rear with compensated rudder.

The fuselage was composed of a metal skinned engine section, followed by the gravity fiel tank and a wooden hull, to be precise, a wooden truss structure covered with plywood. The tail was was framed in wood and covered with fabric. The wings were two-spar, with a wooden structure covered with doped fabric. They were stiffened by three pairs of vertical, profiled struts and steel rods at their core on the early version and on the late FF.33L, only two struts either side due to shorter wings. There were ailerons only on the upper wing.

Two wooden floats were attacked by N type struts. They were flat-bottom with two steps and divided into several bulkheads in case of performation to maintain buoyancy. The struts structure applied both to the inner underwings main frames and fuselage belly structure, all reinforced by steel beams covered with wooden profiles to reduce drag.

Armament

The basic early FF.33, 33b, 33e was unarmed but latter versions, from the FF.33f onwards had a pintle mounted machine gun. The FF33h was the first to integrate a pilot's fixed forward machine gun. It seems the FF 33J was unarmed but the 33L had both the forward LMG and aft defensive LMG. In both case, these were 7.92 mm (0.312 in) Parabellum MG14, caracterized by a weight of 9.5 kgs, rate of fire of 600-700 rpm (250 rds fabric belt), air-cooled with a perforated outer sleeve. Thus their combined with with ammunition was around 12 kgs. To this, the FF 33 could also carry eight man-handled 12 kgs bombs for limited air support.

⚙ specifications
Length:	10.27 m (33 ft 8 in)
Height:	3.73 m (12 ft 3 in)
Upper wingspan:	16.8 m (55 ft 1 in)
Lower wingspan:	15.15 m (49 ft 8 in)
Wing area:	52.7 m2 (567 sq ft)
Empty weight:	984 kg (2,169 lb) to 1,010 kg (2,230 lb)
Gross weight:	1,635 kg (3,605 lb) to 1,675 kg (3,693 lb)
Powerplant:	1× Benz Bz.III 6-cy. wc in-line piston engine, 110 kW (150 hp)
Maximum speed:	119–128 km/h (74–80 mph, 64–69 kn)
Cruise speed:	110 km/h (68 mph, 59 kn)
Range:	600 km (370 mi, 320 nmi) to 700 km (430 mi)
Endurance:	4-5 hours
Time to altitude:	500 m (1,600 ft) in 16 to 28 minutes
Crew	2: Pilot, Observer/Gunner
Armament	2x 7.92 mm (0.312 in) Parabellum MG14, 8× 12 kg (26 lb) bombs

Succession: FF 39, 49, 59.

The success of the FF 33 did not prevented the company to try to improve its model, and generated a serie of improved model, still with "9" as generic seaplane code for the company and incremental series. Productions were limited though, with only the FF 49 seeing some decent production (260) in 1918. The 59 series remained aerodynamic prototypes in 1918, seeing for the c variant a limited order of 20 in production in the last weeks of the war. Meanwhile Friedrichhafen worked on larger models, notably torpedo bombers, also seeing a limited production.
FF.39
Refined version of the FF.33e, 149 kW (200 hp) Benz Bz.IV engine: 14 built.

FF.49c
Further improved FF.39 with strengthened structures and better balanced controls, radio, observer MG: 260 built.

FF.49b:
Naval Bomber variant of the FF.49c with crew positions reversed, provision to carry a light bombload: 15 built.

FF.59a:
Developmental prototype of the FF.39 with new tail.

FF.59b:
Development prototype, same as above and different tail.

FF.59:c
Same as above, modified tail, wing interplane struts moved outwards, no inner-bay bracing wires to avoid drag.

Career of the FF.33

The Kaiserliche Marine operated the FF 33 inside dedicated reconnaissance squadron stationed at its main navalr air stations dependent of its large ports, naval yards and arsenals on the north sea coast or Baltic coast. Every naval yard had its local air defence, with AA batteries but also naval fighters and a small detachment of FF 33L which could act as fighters. They provided the Navy invaluable insight during operations leading to Jutland and afterwards, albeit naval activity was more reduced. U-Boats however could communicate with these seaplanes while underway to be kept updated, when possible. The range of these onboard transmitters was limited.

The FF.33L was fairly agile for its size and the later variants with a fixed MG could be used for escort or offensive use. However as fighters, they were penalized by the drag caused by their wingspan, floats, and never possessed the manoeuvrability or speed of the late Hansa-Brandenburg W.12. However they were far more robust and could operate in high sea states unlike the the W.12. The most often changed element was the vertical tail surfaces, new tail design eliminating the fin and featuring an alongated, triangular shape which helped stability.

Some were also stationed in Belgium, notably at Zeebruge, allowing them to go further at sea. The Zeebrügge seaplane base indeed allowed pilots to venture as far as 350 km in the L variant (700 km or 430 mi at cruise speed in transit A to B). From Zeebruge they could reach as far north as Edinburgh, or the Irish sea west, where U-Boats liked to venture. They could also fly over Britanny down south and all along the Channel. From Bremerhaven they could reach also the British coast and stay for long above the Dogger bank, c200 km away.

The FF 33 was not limited to the European Threater. They also flew in the Baltic as far as the Russian coast. In addition, four FF.33Es and four FF.33Ls were stationed since 1916 at the German Naval Air Station Peynerdjik, near Varna, on the Black Sea. They were transferred in June 1918 to the Bulgarian Navy but scrapped in 1920 in accordance with the Peace Treaty.

Some models gained fame as well, such as the case of "little wolf". It was essentially a flying blockade runner. Its success was a huge morale booster at a time when German civilians were starving and German industry was very short in vital raw materials. It was so popular as to generate an Exhibition in Munich. Wolfchen flew missions over an empty sea to formed colonies in Africa to get back with valuable materials. To spare weight, it was stripped, only kept the pilot (Alex Stein), and still could carry almost 500 kg. This was of course symbolic. Cargo subs such as the Deutschland could carry 700t during her only trip in March 1917 to the still neutral US and brought back notably 230t of rubber in its ballasts or free floating spaces.

Other nations adopted the model:
-The Finnish Air Force in late WWI for example: Recently independent, the Finns purchased two FF.33Es from Germany in February 1918, they arroved on 20 April 1918 to Vaasa and in the summer of 1918 under the German designation numbers 1999 and 1998 changed as FAF numbers F16 and F24 and later S58/18 and S73/18. Another FF.33E was purchased from in Estonia on 26 November 1918 and they remained in service until 1923.
-The Royal Netherlands Navy received several FF 33 also in 1918 as they fled there, integrated into its aviation for a about a year before being scrapped by treaty.
-The Polish Navy operated three captured models, the FF.33E, FF.33H, FF.33L in 1920–1922 against the Russians, decommissioned probably due to the lack of spares.

The Swedish Case:
At last the Swedish Navy operated the type as well as its air force. The Swedish Naval aviation was not favourably treated by the parliament initially but by April 1918 five FF 33 E and five FF 33 L were bought from Germany, delivered without armaments as Sweden was neutral, arriving at Stockholm in September. After only a month in service, one 33 L crashed, another in 1921 during the fire at Galärvarvet, the ancient wooden shipyard in central Stockholm. Others were damaged or totally destroyed, incuding 63 aircraft engines. Two new FF33Ls were locally built at Galärvarvet and three copies of the FF 33E. They were active until... 1929.