Editing Synchronization gear (section)

==== The Fokker ''Stangensteuerung'' gear ====
[[File:Fok E I's U-0 & Stangensteuerung.jpg|thumb|right|Detail of early Fokker Eindecker – cowl is removed, showing Fokker's original ''Stangensteuerung'' gear connected directly to the oil pump drive at the rear of the engine]]
{{Multiple image
|direction=vertical
|image1 = Toggle Trigger Enabler on Propeller Aircraft with Machine Guns.gif
  |caption1 = The pilot first pushes a trigger enabler, which enables the cam follower.
|image2 = Toggle Trigger Lever on Propeller Aircraft with Machine Guns.gif
  |caption2 = The pilot can then push the trigger lever to fire the machine gun while staying synchronized with the propeller.
|footer = Different parts of the gear are color-coded as follows:
{{legend|#0FDACE|Trigger enabler}}
{{legend|#BD00FF|Trigger lever}}
{{legend|#269EE1|Gun trigger}}
{{legend|#EB4040|Coupling piece}}
{{legend|#34B641|Push rod}}
{{legend|#AC97AB|Cam follower}}
{{legend|#808563|Cam & shaft (shown in both front view and lateral view)}}
}}

Whatever its ultimate source, the initial version of the Fokker synchronization gear (see illustration) very closely followed, not Schneider's patent, as claimed by Schneider and others,<ref group="Note">In 1916 LVG and Schneider [[lawsuit|sued]] Fokker for [[patent infringement]]{{snd}}and though the courts repeatedly found in Schneider's favour, Fokker refused to pay any royalties, all the way to the time of the Third Reich in 1933.</ref> but ''Saulnier's''. Like the Saulnier patent, Fokker's gear was designed to actively fire the gun rather than interrupt it, and, like the later Vickers-Challenger gear developed for the RFC, it followed Saulnier in taking its primary mechanical drive from the oil pump of a rotary engine.  The "transmission" between the motor and the gun was by a version of Saulnier's reciprocating push-rod.<ref name=Woodman7>Woodman 1989, p. 183.</ref> The main difference was that instead of the push rod passing directly from the engine to the gun itself, which would have required a tunnel through the firewall and fuel tank (as shown in the Saulnier patent drawings), it was driven by a shaft joining the oil pump to a small cam at the top of the fuselage. This eventually proved unsatisfactory, as the oil pump's mechanical drive spindle was insufficiently robust to take the extra load.<ref name=Woodman7 />

Before the failings of the first form of the gear had become clear, Fokker's team had adapted the new system to the new [[Parabellum MG14]] machine gun, and fitted it to a [[Fokker M.5K]], a type which was at the time serving in small numbers with the ''Fliegertruppen ''as the A.III. This aircraft, [[Otto Parschau#The Green Machine (A.16/15)|bearing IdFlieg serial number ''A.16/15'']] became the direct forerunner to the five M.5K/MG pre-production prototypes built, and was effectively the prototype of the [[Fokker E.I]] – the first production single-seat fighter aircraft armed with a synchronized machine gun.<ref name=Grosz2>Grosz 2002, p. 9.</ref>

This prototype was demonstrated to IdFlieg by Fokker in person on 19–20 May 1915 at the [[Dallgow-Döberitz|Döberitz]] proving ground near Berlin. ''Leutnant'' [[Otto Parschau]] was test flying this aircraft by 30 May 1915. The five production prototypes (factory designated '''M.5K/MG '''and serialed E.1/15 – E.5/15<ref name=Grosz2>Grosz 2002, p. 9.</ref>) were undergoing military trials shortly thereafter. These were all armed with the Parabellum gun, synchronized with the first version of the Fokker gear. This prototype gear had such a short life that a redesign was necessary, producing the second, more familiar, production form of the gear.

The gear used in the production [[Fokker Eindecker fighters|Eindecker]] fighters replaced the oil pump's mechanical driveshaft-based system with a large cam wheel, almost a light flywheel, driven directly from the [[Rotary engine|spinning rotary engine's crankcase]]. The push rod now took its reciprocating motion directly from a "follower" on this cam wheel. At the same time the machine gun used was also changed{{snd}}an [[MG 08#Aircraft versions|lMG 08]] machine gun, the so-called "Spandau", replacing the Parabellum used with the prototype gear. At this time the Parabellum was still in very short supply, and all available examples were required as observers' guns, the lighter and handier weapon being far superior in this role.

The first victory using a synchronized gun-equipped fighter is now believed to have occurred on 1 July 1915 when ''Leutnant'' [[Kurt Wintgens]] of ''Feldflieger Abteilung 6b'', flying the Parabellum-armed Fokker M.5K/MG aircraft "E.5/15", forced down a French [[Morane-Saulnier Type L]] east of [[Lunéville]].<ref name=VanWyngarden12>VanWyngarden 2006, p. 12.</ref>

Exclusive possession of a working gun synchronizer enabled a period of German air superiority on the [[Western Front (World War I)|Western Front]] known as the [[Fokker Scourge]].  The German high command was protective of the synchronizer system, instructing pilots not to venture over enemy territory in case they were forced down and the secret revealed, but the basic principles involved were already common knowledge,<ref name=Courtney2>Courtney 1972, p. 82.</ref><ref group="Note">Courtney rather pungently remarks that "...&nbsp;there was no particular secret to protect".</ref> and by the middle of 1916 several Allied synchronizers were already available in quantity.

[[File:Forward placed synchronised gun.jpg|thumb|left|''Stangensteuerung'' synchronized machine gun mounted well forward on Albatros C.III]]

By this time, the Fokker ''Stangensteuerung'' gear, which had worked reasonably well for synchronizing a single gun, firing at a modest cyclic rate through a two-bladed propeller driven by a rotary engine, was becoming obsolete.

''Stangensteuerung'' gears for "stationary", ''i.e.'',  in-line engines, worked from a small cam immediately behind the propeller (see illustration). This produced a basic dilemma: A short, fairly robust push rod meant that the machine gun had to be mounted well forward, putting the breech of the gun out of the pilot's reach for clearing jams. If the gun was mounted in the ideal position, within easy reach of the pilot, a much longer push rod was required, which tended to bend and break.

The other problem was that the ''Stangensteuerung'' never worked well with more than one gun. [[Fokker E.IV#Design and development|Two (or even three) guns]], mounted side by side ''and firing simultaneously'', would have produced a wide spread of fire that would have been impossible to match with the "safe zone" between the whirling propeller blades. Fokker's initial answer to this was the fitting of extra "followers" to the ''Stangensteuerung's'' large cam wheel, to (theoretically) produce the "ripple" salvo necessary to ensure that the guns were aimed at the same point on the propeller disc. This proved a disastrously unstable arrangement in the case of three guns, and was rather less than satisfactory, even for two.<ref name=Grosz1>Grosz 1996, p. 1.</ref> Most of the early Fokker and Halberstadt biplane fighters were limited to a single gun for this reason.<ref group="Note">At least as much as the more commonly cited effect on performance of the weight of an extra gun.</ref>

In fact, the builders of the new Albatros twin-gunned stationary-engine fighters of late 1916 had to introduce their own synchronization gear, known as the ''Hedtke gear'' or ''Hedtkesteuerung'', and it was evident that Fokker were going to have to come up with something radically new.<ref name=Woodman7 />