A.Weyl Fokker: The Creative Years (Putnam)

THE FOKKER-KREUTZER BIPLANES, 1915-16

   While the Fokker monoplanes were making the name of Fokker world-famous, the firm’s financial position was improving out of all recognition. Military orders had brought profits; credits were now easily obtained against government guarantees; financiers approached Fokker with attractive offers. Ample funds became available to Fokker and all other German aircraft manufacturers for the expansion of production facilities and the purchase of equipment and materials.
   Fokker was able to repay the loans made to him by his father, his uncle, and the Cremers, and did so without delay. He also repaid Hans Haller, his first financial helper at Johannisthal. In consequence of these settlements the Fokker Aviatik G.m.b.H, was dissolved on January 13, 1915, by decision of the shareholders. This body had been merely a holding firm for the shares of the foreign partners of the Fokker Aeroplanbau G.m.b.H., as a legal means of giving the Fokker Works the status of a German-owned enterprise: the military authorities were not normally permitted to place orders with foreign-owned firms. Now a holding company was no longer needed; moreover, Fokker intended to adopt German nationality if such a course were suggested to him.
   When the dissolution of the Fokker Aviatik G.m.b.H. was announced, it was widely assumed in Allied countries that the Fokker works at Schwerin had either gone bankrupt or had closed because of Fokker’s return to Holland. The British journal Flight praised young Fokker’s high patriotic sense, but the only change was that Fokker was now the sole owner of his firm. Hans Haller was retained as business manager for the time being, but in December 1915 he relinquished his executive position and severed all connexions with Fokker. The Fokker Aeroplanbau now changed its name to Fokker Flugzeugwerke G.m.b.H. with “technician” A. H. G. Fokker as sole director.
   The works at Schwerin grew substantially. But whereas all other German aircraft firms invested at least a part of their profits and government-backed credits in new equipment, enlarged workshops, comprehensive material-testing laboratories, up-to-date drawing offices and so on, Fokker was a stingy as ever. He resisted all suggestions that better working facilities should be provided: every addition or expansion had to be makeshift and dirt cheap. His ignorance of engineering production was partly to blame for this parsimony; it certainly could not be attributed to lack of funds. The main reason was his firm resolve to invest as little as possible in anything that could not immediately be converted into cash. Fokker always had an eye to the possible need for making a quick getaway from Germany: he has recorded how he bought up foreign currency and valuables with a view to leaving nothing of value behind him.
   As a result of this policy the Fokker works were never anything better than a shoddy collection of shacks and sheds, while Fokker’s profits grew and were stored away for his own benefit. It is strange that the German authorities apparently thought nothing of the marked contrast between the Fokker works and those of comparable German firms.
   The staff, too, increased; and more instructors and works pilots were engaged. Among the latter were Alexander von Bismarck, unfit for active service on account of poor eyesight, and M. Scherff, airman hero of the Balkan war. Kuntner and Ditzuleit volunteered for active service. The former became an Austrian pilot and was soon decorated for gallantry, but died in a crash in 1916. Ditzuleit survived an exciting career as a naval pilot of fighters and seaplanes. He did much to promote Fokker aircraft in the Navy. However, when he wanted to rejoin the firm immediately after the armistice, Fokker’s business manager Hotter claimed never to have heard of him. Haller tried to rectify the injustice thus done to one of Fokker’s oldest associates, but failed. Fokker himself had probably forgotten that his first mechanic ever existed.
   It has already been noted that work on the seven Fokker M.7 two-seat biplanes ordered by the Admiralty before the outbreak of war had been suspended in face of IdFlieg pressure for the M.8 monoplane. Development of the M.7 was resumed late in 1914, by which time the Admiralty had more than tripled their original order. The prototype was ready in January 1915; as usual, Fokker tried it first. After three days of test flying he declared himself satisfied with it and pronounced it safe and serviceable. De Waal and Weidner found it pleasant to handle and with better load-carrying ability than the M.8 monoplanes. To permit the completion of the stipulated sand-loading tests on the prototype, it was arranged that military acceptance trials were to be deferred until the first production aircraft began to come out in February.
   The M.7 was a sesquiplane. The great overhang of the upper mainplane was emphasized by the inward inclination of the interplane struts; the extensions were braced from above by cables from inverted-vee king-posts; they warped to provide lateral control, the warp-return cables running over king-posts.
   The fuselage, engine installation and undercarriage resembled those of the M.8. In the M.7 the cockpits were separated, and the observer had more room; the pilot occupied the rear seat, as in the later biplane type M.10. Dual control was provided. The upper wing was made in one piece, the lower in two panels attached to fittings welded to the lower longerons. The upper wing was connected to the fuselage by two inverted- V struts of steel tubing braced fore-and-aft and diagonally by steel cables. This structure was not very rigid, which may have contributed to the wing flutter mentioned below.
   Judged against the standards of its day, the M.7’s performance was creditable. A total load of 230 kg. (506 lb.), including fuel for 1 1/2 hours, could be carried. With this load the M.7 climbed to 800 m. (2,600 ft.) in six minutes and to 2,000 m. (7,560 ft.) in 22 minutes.
   The prototype underwent the prescribed sand-loading test at Schwerin early in February 1915. With engine removed, the aircraft was slung inverted from the roof of the hangar, the fuselage being supported by trestles. A uniform load of sand was then distributed carefully over the wings. No account was taken of the stress relief provided by the taut wing covering of doped fabric. A photograph of this sand-loading test was published in Flugsport. The military officials were satisfied that the machine was safe enough for operational service; but in fact it was not.
   During February, von Bismarck made an acceptance flight with one of the first production M.7s, accompanied by Sergeant Opel. While making steep turns at low altitude, von Bismarck felt severe wing flutter, the control column rocking in his hands. The amplitude of the torsional flexing in the extensions of the upper wing grew; von Bismarck tried to reach the ground quickly in a steep spiral glide, but the wing failed and the M.7 crashed. Von Bismarck and Opel were seriously injured.
   About this accident von Bismarck says: “I crashed on this biplane because of wing failure close to the ground, following a steepish spiral glide from about 200 metres. The strain was too much for the wing structure. This aircraft had warping of the extensions of the upper wing, similar to the Morane-Saulnier. The upper pylons had, however, been made too low; this gave a rather shallow wing bracing. The irregular and high stress during the glide induced flutter in the wing extensions. The oscillations suddenly increased noticeably, until the wing failed. Scherff must have suffered the same fate, although in his biplane the height of the bracing pylons had been doubled as in all subsequent biplanes. It was lucky for me that the wing failed at a very low altitude, otherwise we would most certainly not have survived.”
   On his recovery, von Bismarck found that his services were no longer required by Fokker. He joined the Halberstadt Aircraft Works as a test pilot. He was destined always to suffer from the injuries he sustained in the M.7 crash.
   Blame for the accident was laid upon the unfavourable angles of bracing and warp-return cables provided by the king-posts above the upper wing. The height of these pylons was therefore increased on all M.7s.
   But this did not cure the trouble. On April 17, 1915, Scherff took off in the second of the Austrian M.7s on an acceptance test; his passenger Hoengen was a foreman mechanic. Scherff handled the aircraft with caution, for he was not certain that the structure was as safe as Fokker had claimed it to be. After completing the prescribed one hour’s flight at 2,000 m. he came down in a shallow glide. At low altitude the upper wing extensions began to flutter violently. This time a warping cable broke before the wing itself failed. Scherff managed to steer the almost uncontrollable aircraft to shallow water near the shore of the Ostorf Lake, where it finally crashed. Scherff was thrown out into the water; he suffered serious internal injuries and nearly drowned. Hoengen seemed less badly hurt, but died a year later.
   Scherff spent well over a year in the Schwerin hospital gravely ill; more than once his life was in danger. In all this time Fokker never paid him a visit. Indeed, he dismissed Scherff a few days after the accident. Later, he even forbade him to enter the factory or aerodrome.
   After a partial recovery, Scherff was able to work for other aircraft firms as a test and acceptance pilot. He always had a high reputation for his reliability, skill and integrity in his dangerous profession.
   Scherff’s accident was ascribed to defective material. Fokker maintained that design changes were not called for, but the authorities thought differently: all M.7s were grounded until the structure was reinforced. An investigation by Adlershof experts revealed that the wing-attachment bolts of the production M.7s were less well secured than those of the prototype. Although this could not have been the direct cause of the two wing failures Fokker was bluntly warned to pay more attention to his standards of production. The warning had no lasting effect, however.
   A strengthened version of the M.7 was proof-loaded at Schwerin, and the ban on the type was lifted on April 24, 1915. The empty weight was now 394 kg. (870 lb.), or 30-5% of the total. Loaded, the aircraft weighed 676 kg. (1,490 lb.), a figure much larger than the original estimate. The rate of climb of the strengthened M.7 was consequently poor.
   The Fokker M.7, or Fok. B, equipped both landplane coastal defence squadrons of the German Navy for a time; these units were at Kiel and Wilhelmshaven.
   Some M.7s were used for training purposes at Johannisthal, and a few went into the Fokker school and gave good service. One of the Fokker school machines crashed: the pupil, Lt. Gloege, was killed instantly; the instructor, Franz Krebe, was injured. This crash, like von Bismarck’s and Scherff’s, occurred during a gliding turn.
   Three M.7s had been ordered by the Army Flying Corps. Perhaps because of the type’s reputation they never went into service, although they were accepted and paid for. They may have been transferred to the Fokker school. The IdFlieg suggested that a more substantial biplane, fitted with wireless telegraphy for artillery spotting, should be developed. The result of this suggestion was the M.10. On the whole, the M.7 had been a failure.
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   The M.10 was a development of the M.7, which it closely resembled; but its wing structure was more substantial and it was improved in some details. Like its predecessor it was an unarmed two-seat artillery spotter, in which the pilot occupied the rear seat.
   The M.10 prototype retained the not very rigid cabane structure of the M.7. This aircraft was Factory No. 169. It was later modified to have the 100-h.p. Mercedes engine in place of the standard 80-h.p. or 100-h.p. rotary. The Mercedes-powered version was soon abandoned as being too heavy.
   The production M.10s had two additional struts to the forward cabane struts; these were standardized. The wing-warping levers were moved farther aft, leaving more room in the observer’s cockpit, where a wireless transmitter was installed.
   Most production M.10s had the 100-h.p. Oberursel U.l engine. However, those used as trainers and some of those supplied to Austria had the 80-h.p. Oberursel, which was more easily obtained from existing stocks or from obsolete aeroplanes.
   The M.10 was produced in two forms. The original single-bay form of the design was named M.10E (“E” signifying einstielig, or single-bay). It differed from the earlier M.7 in having its lower wing slightly farther aft, greater wing chord, and heightened upper-wing king-posts.
   First of the type to be accepted by the Army Flying Corps was Factory No. 171, which was taken over at Schwerin on June 7, 1915. Modifications were demanded, however, and the acceptance did not become effective until the following month. This M.10E and its immediate successors had the 80-h.p. Oberursel. The type was also delivered to Austria.
   The military load of the M.10 affected its climbing performance adversely, so new, two-bay wings were designed. The first machine to have them was Factory No. 199. This version of the design was designated M.10Z, the “Z” signifying zweistielig, or two-bay.
The prototype was accepted for the Army Flying Corps at Schwerin on November 17, 1915, and was sent to Adlershof for further trials during December. The wings of the M.10Z were of equal span, and the entire wing cell warped to provide lateral control, whereas on the M.10E only the upper-wing extensions warped. The new arrangement was more practical and safer, because the danger of torsional flutter was much reduced.
   A small batch of M.10Z biplanes, known in the Service as Fok.B.II, gave good service on some sectors of the Eastern Front. The type was also supplied to the Navy and Austria. Various M.10 biplanes were still flying on training duties until late in 1917.
   During the first half of 1915 the Fokker works had developed and constructed no fewer than six different aircraft types: the M.7, M.9, M.10, M.14, M.15 and W.3. These included monoplanes, biplanes and floatplanes, and development embraced several variants and trial engine installations. One cannot but admire Fokker’s energy in undertaking so many projects: even in those days of uncomplicated aeroplanes and simple equipment his output would have been a remarkable achievement for a much larger aircraft works.
   For all this work Fokker had only a couple of draughtsmen and no trained designer. Admittedly, the “design work” for prototypes, and modifications, were done on the job by the try-and-fit method. No stressing was attempted. All the prototypes were built within the busy production organization; there was no separate experimental shop. Fokker thought this was the way to carry on development: he paid no heed to Dr. Lissauer’s advice to separate production from development.

J.Herris Fokker Aircraft of WWI. Vol.1: Spinne - M.10 & Watercraft (A Centennial Perspective on Great War Airplanes 51)

Fokker M.7 (B.I)
  
  The M.7 was Fokker's first successful biplane design. Fokker's earlier designs had been monoplanes, but given the primitive structural technology of the time, the biplane configuration generally offered a better combination of strength with light weight, a mix that was very important considering the modest engine power available from contemporary aero-engines.
  Power was from an 80 hp Oberursel U.0, and there were two cockpits for the crew. The M.7 was designed for the German Navy, which ordered seven aircraft. However, the Army was pressuring Fokker for a development of the M.6, which became the M.8, and because the Army bought 20 times the number of airplanes the Navy did, the M.8 monoplane was produced before the M.7.
  The fuselage of the M.7 and M.8 were nearly the same, both being about 40% wider than that of the M.6, giving the crew more room to work. The wings were a sesquiplane design with the upper wing much longer than the lower. Construction details followed the M.5 (steel tube frames for the fuselage and tail surfaces, wooden wings, all fabric covered) except for the configuration.
  The enforced delay of the M.7 meant that the prototype was not completed until January 1916. Performance was good for the time but flight experience demonstrated that the upper wing and bracing structure needed to be strengthened. The added weight reduced performance. Regardless, the Navy bought 21 examples for coastal defense flights that were designated Fokker B. The Army bought three but these were not used at the front and almost certainly were used as trainers.
  The Austro-Hungarians bought 15 aircraft. These first served at the front as unarmed reconnaissance aircraft but after a time were reassigned to training service due to their modest performance.


Fokker M.7 (B.l) Specifications
Engine: 80 hp Oberursel U.0
Wing: Span Upper 11.7m
Span Lower 7.2 m
Wing Area 26.0 m2
General: Length 8.00 m
Height 2.95 m
Empty Weight 380 kg
Loaded Weight. 679 kg
Maximum Speed: 130 km/h
Climb: 1000m 8 min
2000m 15.5 min


Fokker M.10 (B.I & B.II)

  The M.10 was a development of the M.7 biplane. The Army needed a two-seater with wireless capability for artillery cooperation, and the wing warping controls were moved aft to give the observer more room for the wireless. The wings were strengthened to carry the extra weight of the wireless. Originally an 80 hp Oberursel U.0 was fitted but the extra weight of the wireless and strengthened wings meant more power was needed for adequate performance and the 80 hp engine was replaced with a 100 hp engine. At first a water-cooled 100 hp Mercedes was tried but the extra weight of the engine and cooling system absorbed the additional power, so it was replaced with a 100 hp Oberursel U.I rotary.
  Two versions of the M.10 were built. First was the M.10E (E for einstielig = single-bay). This was normally fitted with the 80 hp Oberursel U.0, with which they were seriously under-powered. Nevertheless, the Army bought the M.10E and used it at the front. The Austro-Hungarian Army also bought 23 airplanes and used them at the front. Later both Armies used them for training after they were retired from the front. The military designation was B.I, which was the same designation as the M.7 aircraft bought by the military.
  The second version of the M10 was the M.10Z (Z for zweistielig = two-bay); this had redesigned two-bay wings and most were powered by the 100 hp Oberursel U.I rotary. The M.10Z was designated the Fokker B.II in service and was used at the front by the German Army and Navy and the Austro-Hungarian Army. After being retired from the front the surviving examples were used for training.

Fokker M.10 (B.I) Specifications
Engine: 80 hp Oberursel U.0
Wing: Span Upper 11.3 m
Span Lower 7.77 m
Chord (U & L) 1.6 m
Wing Area 28.0 m2
General: Length 7.50 m
Height 2.50 m
Empty Weight 409 kg
Loaded Weight 712 kg
Maximum Speed: 130 km/h
Climb: 2000m 25 min


Fokker B.I in Austro-Hungarian Service
Type Series Numbers Order Date
M.7 03.01,02,04-12 20 Sep. 1914
M.5L 03.03 29 Jan.1915
M.10 03.13-24 17 Oct. 1914
M.7 03.25-28 6 May 1915
M.10 03.29-40 29 Jan. 1915
Notes:
  1. Last two orders were less engines.
  2. The M.7 aircraft 03.25-03.28 ordered in May 1915 were rebuilt, not new, aircraft.
  3. Source: Austro-Hungarian Army Aircraft of World War One by Peter M. Grosz, et. al.

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

Fokker M 7
   With a sesquiplane (1 1/2-wing) layout, the remainder of the machine was virtually M 5, with necessary lengthening of the fuselage to accommodate the two crew members, the pilot sitting in front. Production was from January 1915, and twenty machines were built, some being used by the German Naval shore stations. Engine, 80 h.p. Oberursel U O.

Fokker M 10 E
   A similar machine to the earlier M 7, but with modification to the undercarriage and centre-section struts. The "E" suffix to the factory designation indicated Einstielig - or single-bay - to differentiate from the two-bay M 10 Z which also existed. A few aircraft of this type were supplied to Austro-Hungarians, who designated it B I. Engine, 80 h.p. Oberursel U O.

Fokker M 10 Z
   Differed from M 10 E in being two-bay aircraft - Z suffix indicating Zweistielig - also the more powerful 100 h.p. Oberursel U I engine was installed. A small number of the type was supplied to Austro-Hungarian air force, who designated it B II.

E.Hauke, W.Schroeder, B.Totschinger Die Flugzeuge der k.u.k. Luftfahrtruppe und Seeflieger 1914-1918

01. — 010. Flugzeuge ausländischer Produktion (Самолеты иностранного производства)
03.01 — 03.02 Fokker B.I (Type M 7) Ob/Gn 80
03.04 — 03.12 Fokker B.I (Type M 7) Ob/Gn 80
03.13 — 03.24 Fokker B.I (Type M 10) Ob/Gn 80
03.25 — 03.28 Fokker B.I (Type M 7) Ob/Gn 80
03.29 — 03.40 Fokker B.I (Type M 10) Ob/Gn 80