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This changed in 1915 based on what was happening in the war and the development of air warfare, in which the French and British air forces were clearly gaining the upper hand. In early 1915 the French introduced the Nieuport biplane, the first fighter aircraft armed with a machine gun in a fixed mount on the upper wing which could fire over the propeller disc. Even though this installation did not allow the pilot to truly aim the entire aircraft intuitively, it came as a rude awakening to the German air forces. From then on, observation aircraft were not only subjected to ground fire but also to direct engagement by enemy fighter aircraft. There were technical limitations, however: the machine gun was loaded with 47-round ammunition drums which, with a rate of fire of 300 to 400 rounds per minute, did not permit lengthy engagements. When the drum was empty, the pilot had to swing down the machine gun to load a fresh drum, an almost impossible task in flight.

The next development step was the Morane-Saulnier parasol monoplane, whose machine gun was rigidly mounted on the engine cowling. The weapon fired through the propeller disc, but it was not synchronized. Instead, the propeller blades were armoured with steel plates at the level of the machine gun to prevent machine gun bullets from piercing them. This solution was far from ideal, however, as an incalculable number of machine gun bullets were lost. There was also the considerable danger that bullets ricocheting off the propeller blades might strike the pilot or damage important parts of the aircraft. Third, despite the armour, the propeller itself was in danger of being damaged. Nevertheless, with this method the Allies gained air superiority at the front in 1915. An increasing number of German aircraft, armed with just rifles or pistols and thus defenceless, fell victim to their fighters, making it almost impossible for the Oberste Heeres-Leitung to carry out tactical aerial reconnaissance in enemy airspace. On April 19, 1915, however, the well-known French fighter-pilot Roland Garros, who had already achieved five victories, was shot down over Courtrai while flying a Morane-Saulnier thus equipped. Garros was forced to crash-land on the German side of the lines and his aircraft was immediately sent to Berlin. There, on March 11, 1915, Major i.G. Thomsen, the newly-appointed Chief of Field Air Forces, handed the aircraft with a Parabellum machine gun and a sufficient supply of ammunition to Fokker. Born in Batavia in the Dutch East Indies in 1890, Antony Herman Gerard Fokker was given the task of examining and if possible copying the French device. Fokker was an engineer and owned the AHG Fokker Aeroplanbau GmbH established in Berlin-Johannisthal in 1912, which in 1913 moved to Schwerin and was renamed Fokker Aeroplanbau GmbH. The experiment quickly revealed that the German Type S ammunition—unlike the French `balle-D’ bullet made entirely of copper in the French Lebel calibre of 8 mm—did not simply bounce off the propeller blades, instead destroying them despite their steel plates.

Building on Schneider’s patent, in the summer of 1915 Fokker and engineer Heinrich Lübbe, who had been working for him since 1913, developed an interrupter mechanism which drew on the engine’s camshaft and which thus synchronized an operating machine gun with an aero-engine so that the burst was interrupted by an approaching propeller blade. As the propeller of an aircraft turned at about 1,200 rpm at full speed, this meant that a roughly ten-centimetre-wide propeller blade passed in front of the muzzle of the machine gun 2,400 times per minute. A machine gun firing at 500 to 700 rounds per minute had to be synchronized with this very fast-moving propeller blade, another challenge being that machine gun bullets travelled much faster than the propeller turned.

Fokker therefore developed an interrupter mechanism which interrupted the burst of fire as soon as the leading edge of a propeller blade neared the muzzle of the machine gun. In this way the pilot could continue squeezing the trigger and concentrate fully on controlling the aircraft and intuitive aiming. A synchronization system later developed by the British worked exactly the opposite: each passing propeller blade allowed the machine gun to fire. This solution entailed the risk that the machine gun might fire a shot too soon and this might subsequently strike the propeller.

The first system developed by Fokker and Lübbe was the pushrod control system, in which engine position was transmitted to the machine gun by a system of levers and engine-driven pushrods. The pushrod control system, very few of which have survived to the present day, can be recognized by the transmitting rods positioned under the machine gun’s cooling jacket. It was soon replaced by the central control system, in which the engine position was transmitted to the machine gun directly, either by the crankshaft or camshaft by means of a small drive and shaft similar to a tachometer shaft. The pushrod control system quickly proved to be susceptible to wear and sensitive to bending and deformation. Both synchronization systems worked with the Parabellum as well as the LMG 08 and 08/15 machine guns. The Fokker synchronization systems—especially the central system—were thus more reliable and easier for the pilot to use.

Fokker demonstrated the operation of his control system—in this case the pushrod control system—to the Commander of Field Air Forces on May 19 and 20, 1915 at Training Camp Döberitz. On May 30 Leutnant Otto Parschau flew an E1 converted to carry the Fokker synchronizer. Fokker subsequently equipped five aircraft for military trials. Leutnant Kurt Wintgens of the Bavarian Feld-Flieger-Abteilung 6b scored the first victory achieved with this synchronizer on July 1, 1915. The next airmen whose aircraft received such a synchronizer were Leutnant Oswald Boelcke and Leutnant Max Immelmann. Within the next six months these synchronizers helped the German Fliegertruppe establish comprehensive air superiority, which the British and French fliers could initially do little to counter. Whereas in the beginning only Parabellum machine gun were synchronized, during 1915 and 1916 synchronized Luft-MG 08 and later Luft-MG 08/15 machine guns also saw action.

Another synchronization system was developed by Werkmeister Hedtke of the Albatros-Werke and used in the Albatros-Werke’s D.I, D.II and D.III fighter aircraft from the end of 1916 until July 1917. Further improved in the summer of 1917, this synchronization system, also called the Semmler synchronizer, was installed in Albatros D.III, D.IV and D.V aircraft until the end of the war. As of March 1918, however, on the initiative of the Inspektion der Fliegertruppen the Albatros-Werke cut back on production of its own aircraft and instead produced Fokker D.VII biplane fighters under license. Accordingly the Hedtke or Semmler synchronizer played little role from that date and Albatros installed Fokker’s central synchronizer in license-built aircraft. As a result, the Albatros synchronizers are very rarely seen today.

A special version, the LMG 08 (Luft-MG 08), which differed from the standard MG 08, was developed in 1914. The cooling jacket was provided with slots, in order to convert the machine gun from liquid to air cooling. Like the machine guns used in aircraft, it was expected that their use in airships would involve relatively short bursts. Even though the airships flew relatively slowly, the resulting airflow together with the very low temperatures common at high altitude would be sufficient to cool the machine gun. As the machine guns were supposed to fire from flexible mounts and not from the classic machine gun sledge, the trunnions on the jacket needed to mount it on the sledge could be omitted. The holes for mounting the optical sight on the left rear of the receiver were deleted—because of its relatively narrow field of view the ZF 12 was rather ill-suited for use in the air. Instead a shorter sliding sight was placed on the rear of the weapon.

The ejection tube, which could lead to stoppages in conjunction with the brass catcher on the sledge, was also left off the LMG 08, as it was on the LMG 08/15. Nevertheless, therewere some early Luft-MG 08s, and 08/15s which still had ejection tubes. As well, the LMG 08, unlike the MG 08, had a new 08/15 S recoil booster, which leads to the conclusion that Model 16 locks were probably also installed in this machine gun to increase rate of fire. The LMG 08 thus received a number of significant design features of the MG 08/15. The LMG 08 was built exclusively by the Gewehrfabrik Spandau, not by DWM or other state-owned gun factories. When, from the end of 1915, the Parabellum machine gun was synchronized to fire through the propeller disc of an aircraft, Fokker developed a corresponding synchronization system for the LMG 08, which thus also became available for use in fighters. This machine gun’s crank handle was also modified and was fitted with a longer, perforated lever-arm—called the Segenhebel (charging and clearing lever)—which was coupled with special cams and enabled the pilot to operate the machine gun while wearing gloves and charge it—in case of a stoppage, for example. The pilot could chamber a round and cock the gun with a single movement toward him. Over time this lever was further developed and was also used on the LMG 08/15.

This lever was manufactured by firms such as the Carl Lindström AG electrische Antriebe of Berlin and delivered to the Gewehrfabrik Spandau. Other manufacturers included the Fokker-Flugzeug-Werke. Lindström (26/6/1869–29/12/1932) was a Swedish mechanic and industrialist, whose company actually specialized in the manufacture of gramophones, phonographs and cinematographs and which in 1917 helped found the Universal Film AG (Ufa). As the charging levers made by Lindström bore the manufacturer’s stamp “C. Lindström”, the corrupted and actually incorrect term “Klingstrom Device” has embedded itself in the American literature.

Because the components of the LMG 08 were identical to those of the MG 08, with the above-described exceptions, the LMG 08 was built in small numbers at Spandau alongside the MG 08. Whether production ended in 1916 when production of the LMG 08/15 began or continued into 1917 or even longer remains unanswered, however it is likely that at most 1,000 examples of the LMG 08 were produced. Because of synchronization, the LMG 08’s rate of fire was reduced to about 300 to 400 rounds per minute. In general, composite belts for about 1,000 rounds were carried on combat sorties.

Luft-MG 08 Specification

Manufacturer: Gewehrfabrik Spandau

Operating principle: Recoil loader, Maxim system

Calibre: 8 mm x 57 IS (S cartridge)

Rate of fire: 450 to 500 rounds per minute (reduced to 300 to 400 rounds per minute by synchronization)

Ammunition feed: Fabric belt with 250 rounds, as on MG 08

Overall length: 1,010 mm (without round counter)

Barrel length: 720 mm (without recoil booster), right hand twist with 4 grooves

Weight (air cooling): 19 kg

Sight: Open sight with small ring sight

The LMG 08/15 became available at the beginning of 1916, the first light machine gun with a Maxim system comparable to the MG 08, and it immediately attracted the attention of the Fliegertruppe. The air-cooled version of the 08/15 with slotted jacket and no bipod still weighed about 14 kg. As aircraft were being equipped with ever more powerful engines and were thus able to carry increasing loads, 14 kg (with slotted cooling jacket and no coolant) was an acceptable weight class, especially as it presented the opportunity to equip the Fliegertruppe and also airship crews with a standard machine gun system like that of the army. This was surely a considerable advantage for the training of machine gunners and armorer-artificers. The Type 16 lock became available at the same time, increasing the gun’s firing rate to 600 rounds per minute—here too the difference compared to the Parabellum was less. Synchronization reduced the firing rate somewhat, however.

The LMG 08/15, the “Luft-MG 08/15”, entered production in May 1916. Compared to the “normal” 08/15, the sighting system of the LMG 08/15 was changed. A small ring sight was mounted on the front of the weapon, while the rear sight remained unchanged. The ring sight had a reticle made of wire, and the outer ring served as a lead mark for the pilot when engaging targets flying from one side to the other. The LMG 08/15’s cooling jacket was also slotted for air cooling and was manufactured without the steam valve and bayonet clip for the bipod. The shoulder stock and pistol grip were left off and the back side of the receiver was prepared for the installation of a special sight and a round counter. These two items were not installed on every LMG, however. Often there was just a leather pad on the rear end of the machine gun. The LMG 08 was also fitted with a charging and clearing lever on the right side of the receiver.

Luft-MG 08/15 Specification

Manufacturer: Gewehrfabrik Spandau

Operating principle: Recoil loader, Maxim system

Calibre: 8 mm x 57 IS

Rate of fire: 600 rounds per minute (reduced to approx. 500 rounds per minute by synchronization)

Ammunition feed: Fabric belt with 250 rounds, as on MG 08

Overall length: 1,010 mm (without stock and round counter)

Barrel length: 720 mm (without recoil booster), right hand twist with 4 grooves

Weight (air cooling): 14 kg

Sight: Open sight with small ring sight

The LMG 08/15 was also produced exclusively by the Gewehrfabrik Spandau. Unlike the MG 08/15, the LMG 08/15 received its own serial number range, and thus the extent of production can be roughly estimated: the highest known serial number is 23,450—one can thus assume a maximum of 24,000 LMG 08/15 machine guns produced by the end of the war. An analysis of serial numbers carried out by American collectors revealed that of these approximately 2,500 were produced in 1916, about 10,000 in 1917 and 11,500 in 1918. Thus, the DWM produced the Parabellum machine gun as armament for the Fliegertruppe and the Gewehrfabrik Spandau the LMG 08/15. The Parabellum machine gun was used primarily in flexible mounts in multi-seat aircraft. It was simpler to handle and could be pivoted more quickly on account of its light weight. The gun’s optical sight with yellow filter also made it possible to acquire targets more quickly and engage them effectively in unfavourable light conditions, such as backlight, for example. Later versions of the Parabellum machine gun had a clearly smaller cooling jacket, which reduced drag and made it easier to swing the gun around during flight. The LMG 08/15 was as a rule installed in single-seat fighter aircraft with a synchronizer.