The History of Mounting a Gun to an Aircraft During World War I
by
Nolan
After the first instance of powered flight by Orville and Wilbur Wright in 1903 military commanders soon saw the benefit they could gain if they armed planes[1]. One of the first obstacles was being able to shoot while still controlling the plane. There were already planes that had two people in the plane, an observer and a pilot. The observer’s job was to look for key objects on the battlefield and help larger guns behind the front line aim while flying high above. Some planes like the German Albatross (Figure 1) underwent modifications so that the observer was in control of a gun to ensure that the pilot would not have to worry about flying and shooting at the same time. Although the weaponry eventually settled on machine guns, smaller arms were more common during the early parts of the war.
[Image pending permission for use]
Figure 1: An artist interpretation of a German Albatross in flight with the two person crew.[2]
Firing Small Arms
Even before the war started, planes were being armed with various weapons. In 1912 Lieutenant Jacob Fickerl experimented with shooting from a Wright flyer with machine guns (Figure 2).[3] In Fickerl’s case he sat next to the pilot not behind him as many later planes would have. This method would unbalance the plane and make it harder to fly. Eventually, the design evolved into having the observer or shooter behind the pilot. One example is the Bleriot monoplane where a swiss Karabiner 11, an infantry rifle, was tested in the air from the plane[4]. Early aviators and fighter pilots did not only use and experiment with rifles during and before the war but often brought up other more exotic weapons. There were several occasions where the aviators would use pistols, shotguns and eventually machine guns.[5] The British even developed incendiary rounds and chain shot for the shotguns to enhance their ability to destroy a plane[6].
[Image pending permission for use]
Figure 2: Lieutenant Jacob Fickerl experimenting with firing from a plane.
Pilot-Held Machine Guns
In 1912, the early attempts of using non-automatic guns started to become pointless. Shooting from a moving platform to another moving platform and attempting to successfully hit it with a non-automatic gun was extremely difficult to accomplish. Improvements were made to allow the addition of machine guns to the plane. The increased rate of fire greatly helped incapacitate other planes[7]. When planes did not have a turret mounting for the machine gun, the recoil from the gun made it challenging to shoot effectively and accurately. The British invented a turret in 1914 called the British Scarff which was widely used among bombers and British planes with turrets (Figure 3)[8]. The stability offered by the turret helped shooters precisely aim and fire the gun.
[Image pending permission for use]
Figure 3: The British Scarff turret with a Lewis gun attached.
Observer Controlled Gun
Throughout the war, weapons were fired without engaging the propeller arc (the area where the propeller spins). This resulted in the need to have another person to shoot the weapon. The observer in many planes was reassigned as a shooter controlling a weapon of sorts whether it be a machine gun or shotgun. In the British Air Service the commanders would bring their own guns from home so the type could vary widely from shotguns and pistols to machine guns. The additional person in the back of the plane was a significant increase in weight. The two-seater Bristol F.2 was 1934 pounds (lb) when empty compared to the single seater Spad S XIII which was 1245 lb when empty[9] [10]. This gave rise to planes with observers or seperate shooters being slower and less maneuverable. During Bloody April, or the Battle of Arras, a largely unsuccessful battle for the British, several examples of different types of these planes were seen by both the British and the Germans. German and British examples are, respectively, Albatros D.III and the F.E.2b.
Single Seater Planes
Engineers in France, England and Germany came up with single-seat fighters to create more maneuverable planes. Examples of the single-seat fighters include , respectively, the SPAD S.XII, the Bristol M.1 and the Fokker Dr.I. An issue with this is the pilot is the only one to fire the gun with no assistance from another person. This means that the pilot needs to be in control of their own gun as seen on the Martinsyde G.100, a British bomber[11]. One other solution was to change the entire design of the plane and make it into a pusher propeller plane as seen on the French Voisin LA (Figure 4)[12]. A pusher-propeller plane means the engine is behind the pilot. When in a dog fight, a pusher propeller planes engine is vulnerable to direct fire from the pursuer.
[Image pending permission for use]
Figure 4: A Voisin push propeller biplane.
Standing Firing Position
Throughout the war a frequently used method was to fire over the propeller by placing the gun on the top wing. As most planes in WWI were biplanes, placing the machine gun on the top wing would prevent bullets from hitting the propeller. This method would vary from plane to plane with some being easier to fire than others. One of the more extreme examples was the Deperdussin monoplane where the pilot would stand up on their seat to fire the gun (Figure 5)[13]. This was a single-seat plane so while he was shooting, the plane would not be controlled by anybody. There were other versions of this technology where the pilot would not have to stand but simply lift his arms above his head, still not controlling the plane, and then shoot. The gun was placed on a curved rail so that it could be brought down to almost eye level where the pilot would reload the gun and then slide it back up. To reload this gun was much easier than the previous take on this technology, where the pilot had to completely stand up. One example of a plane that used the sliding-gun method is the Royal Aircraft Factory S.E.5[14]. After the Battle of Arras the S.E.5 was brought into service. While the battle was a failure for the British, the new S.E.5 was more effective than the overworked planes in the Jastas, the equivalent of a squadron for the Germans.
[Image pending permission for use]
Figure 5: The Deperdussin monoplane with the standing gun mounting.
Hispano-Suiza Engine
One French design came out in 1917 which fired a 37-mm gun from the Hispano-Suiza engine. This engine was very common among French planes and even the famous French fighter pilot, Roland Garros, used it.[15] Before this gun came out, almost all machine guns shot 33-caliber bullets[16]. This new single-fire gun shot from the boss cap of the propeller and the ammunition would be loaded in one at a time by the pilot. The larger round helped to penetrate armored targets that simply were impossible to penetrate with a machine gun[17]. The gun saw limited deployment only being applied on the SPAD S.XII. The plane's cockpit that was built with the variation on the Hispano engine with the cannon were somewhat different. Instead of having a stick in between the pilots legs the guns bolt handle would be there to reload the gun (Figure 6). The stick that used to be between the pilots legs had been replaced by two sticks on each side of him[18]. Like the other technologies this led to pilot to have no control over his plane while he was reloading his gun. In battle the pilot would carry 12 rounds of ammunition to be loaded in one at a time.
[Image pending permission for use]
Figure 6: The guns bolt handle where the pilot would insert one round into the gun.
Deflector Gear
The optimal method of firing from a plane would be to fire through the propeller arc, while not having to stand up or momentarily lose control over the plane. In that scenario the pilot has a direct line of vision to whatever he is pursuing or shooting at, whether it be another plane or a machine gun post on the ground. Nations did not want to risk shooting through the propeller arc because of the risk of destroying your own propeller. He achieved this by using deflectors on his propeller. This method would deflect any bullets that happened to hit the propeller with steel wedges (Figure 7).[19] This technique unnerved pilots as they were essentially shooting their own plane in order to shoot down the enemy's plane. From a technical perspective it also decreased the effective rate of fire by 25%[20]. According to some sources Roland Garros was also the first to shoot down another plane earlier that month over Belgium[21].
[Image pending permission for use]
Figure 7: The deflector gear with the steel wedges on the propeller blades.
Interrupter Gear
The first effective method of shooting and destroying the enemy's plane was the interrupter gear (Figure 8)[22]. The pilot did not need another person to shoot for him. He did not need to stand on his chair to shoot, nor did he need to lose control over his plane to shoot or shoot his one propeller. With the interrupter gear, the gun would negatively fire when a blade was in front of it, meaning that whenever the interrupter gear was not activated the gun would fire. This made sure that the propeller blade would not be destroyed in the act of firing and that the effective rate of fire was not reduced so dramatically. The interrupter, first designed by Fokker, consisted of several cam pushrods and ovals. Each propeller would have one bulge in a circle. This would result in the cam operated actuator wheel to move up and down as the propellers move past the barrel of the gun. This would then be connected to a pushrod linkage which is a metal rod that's only job is to bridge the distance from the gun to behind the boss cap, the cap that houses the place where each blade meets. The third part of the interrupter is the connection with the trigger sear. This is activated whenever one of the bulges in the circle activates the actuator wheel. When the trigger sear is activated it stops the gun from firing by disengaging the trigger. The return spring simply pushes the actuator wheel back onto the oval shaped disk behind the boss cap. Later advancements were made to change the delicate mechanical apparatus to a more sophisticated and rugged pneumatic system. The system completed the same task but without all of the spindly cam rods. During the Fokker Scourge, from 1915 to 1916 a period of time when the German military gained overwhelming air superiority, the Fokker E.I came out with the first interrupter gear. The new innovation made firing from the plane much easier than before as the guns had a direct line of sight parallel to that of the pilot.
[Image pending permission for use]
Figure 8: The interrupter gear invented by Anthony Fokker.
Synchronization Gear
The final method seen in WWI was with the synchronization gear. Several sources confuse the interrupter and synchronization gear as one and the same.[23] As explained above the interrupter gear negatively fires the gun when the blade is in front of the barrel of the gun. Synchronization on the other hand positively fires the gun when there is no blade in front of the barrel[24]. Although the difference is small, it improved the use and effectiveness of the gun. The mechanism is very similar except that instead of having each of the bulges where the blades are, they are in between where there is no blade (Figure 9). And instead of blocking the gun when the actuator wheel is on it insead blocks the gun from firing when the actuator wheel is not actuated. For each bulge received by the actuator wheel only one shot is fired effectively turning the machine gun into a semi-automatic gun. Another note is that the rate of fire depends greatly on the engines rotation speed. If the engine is spinning very slowly, as if the plane is on a patrol, than when the pilot fires the rate of fire would be slower. If the pilot is engaged in a dogfight and is on full throttle the engine would subsequently be spinning much faster and so the rate of fire would also be faster. One of the reasons that the interrupter was less effective than the synchronization gear is because the rate of fire on the interrupter gear is so high that not many machine guns could handle it and so pilots had to be careful when shooting the gun. Both Verdun and the March 1918 offensive saw this technology. The Fokker Dr.1 triplane, made famous by Manfred von Richthofen, the Red Baron, used synchronization gear to claim his last 19 confirmed kills during the offensive before he was shot down[25].
[Image pending permission for use]
Figure 9: The differences between synchronization (top) and interrupter gear (above)[26].
Only a few years after the Wright brothers invented the airplane in 1903 different air forces and militaries were experimenting with weapon systems on planes. When WWI broke out it led to a war of back and forth competition to be the most technologically advanced country and military. The main competitors were France and Germany. The beginning consisted of technologies that were tried and most of the time failed. The ones that did not, however, helped develop more sophisticated and technologies. Eventually both countries developed interrupter and synchronization gear which was the most effective technology of WWI in terms of firing from a plane[27].
Sources
Footnotes
[1] Phoebus, Warplanes of World War I (London, England: BPC Publishing Ltd., 1973), 7.
[2] “Albatros” first-world-war.com, http://www.first-world-war.com/albatros.htm (accessed January 11 2018).
[3]Anthony G. Williams, and Dr. Emmanuel Gustin, Flying Guns World War I, (Ramsbury: Airlife publishing, 2003), 42.
[4] Ibid., 45.
[5] Ibid., 44.
[6] Ibid.
[7] Ibid., 47.
[8] Ibid., 31.
[9] Phoebus, Warplanes of World War I, 141
[10] Ibid., 158.
[11] Williams, and Gustin, Flying Guns World War I, 55.
[12] Phoebus, Warplanes of World War I, 37.
[13] Williams, and Gustin, Flying Guns World War I, 46.
[14] Ibid., 59.
[15] Interview with Harry Cawood, Docent at the National Air and Space Museum. January 6 2018.
[16] Ibid.
[17] Ibid.
[18] Ibid.
[19] Williams and Gustin, Flying Guns World War I, 32.
[20] Ibid., 33.
[21] Dan Hampton, Lords of the Sky (New York, NY: Harper-Collins Publisher, 2014), 8.
[22] Richthofen's War, Mission Briefing Manual.
[23] “Synchronization gear” Wikipideia, https://en.wikipedia.org/wiki/Synchronization_gear (accessed January, 15, 2017).
[24] Williams and Gustin, Flying Guns World War I, 33.
[25] Interview with Harry Cawood, Docent at the National Air and Space Museum. January 6 2018.
[26] Ibid.
[27] Ibid.
[Image pending permission for use]
Figure 1: An artist interpretation of a German Albatross in flight with the two person crew.[2]
Firing Small Arms
Even before the war started, planes were being armed with various weapons. In 1912 Lieutenant Jacob Fickerl experimented with shooting from a Wright flyer with machine guns (Figure 2).[3] In Fickerl’s case he sat next to the pilot not behind him as many later planes would have. This method would unbalance the plane and make it harder to fly. Eventually, the design evolved into having the observer or shooter behind the pilot. One example is the Bleriot monoplane where a swiss Karabiner 11, an infantry rifle, was tested in the air from the plane[4]. Early aviators and fighter pilots did not only use and experiment with rifles during and before the war but often brought up other more exotic weapons. There were several occasions where the aviators would use pistols, shotguns and eventually machine guns.[5] The British even developed incendiary rounds and chain shot for the shotguns to enhance their ability to destroy a plane[6].
[Image pending permission for use]
Figure 2: Lieutenant Jacob Fickerl experimenting with firing from a plane.
Pilot-Held Machine Guns
In 1912, the early attempts of using non-automatic guns started to become pointless. Shooting from a moving platform to another moving platform and attempting to successfully hit it with a non-automatic gun was extremely difficult to accomplish. Improvements were made to allow the addition of machine guns to the plane. The increased rate of fire greatly helped incapacitate other planes[7]. When planes did not have a turret mounting for the machine gun, the recoil from the gun made it challenging to shoot effectively and accurately. The British invented a turret in 1914 called the British Scarff which was widely used among bombers and British planes with turrets (Figure 3)[8]. The stability offered by the turret helped shooters precisely aim and fire the gun.
[Image pending permission for use]
Figure 3: The British Scarff turret with a Lewis gun attached.
Observer Controlled Gun
Throughout the war, weapons were fired without engaging the propeller arc (the area where the propeller spins). This resulted in the need to have another person to shoot the weapon. The observer in many planes was reassigned as a shooter controlling a weapon of sorts whether it be a machine gun or shotgun. In the British Air Service the commanders would bring their own guns from home so the type could vary widely from shotguns and pistols to machine guns. The additional person in the back of the plane was a significant increase in weight. The two-seater Bristol F.2 was 1934 pounds (lb) when empty compared to the single seater Spad S XIII which was 1245 lb when empty[9] [10]. This gave rise to planes with observers or seperate shooters being slower and less maneuverable. During Bloody April, or the Battle of Arras, a largely unsuccessful battle for the British, several examples of different types of these planes were seen by both the British and the Germans. German and British examples are, respectively, Albatros D.III and the F.E.2b.
Single Seater Planes
Engineers in France, England and Germany came up with single-seat fighters to create more maneuverable planes. Examples of the single-seat fighters include , respectively, the SPAD S.XII, the Bristol M.1 and the Fokker Dr.I. An issue with this is the pilot is the only one to fire the gun with no assistance from another person. This means that the pilot needs to be in control of their own gun as seen on the Martinsyde G.100, a British bomber[11]. One other solution was to change the entire design of the plane and make it into a pusher propeller plane as seen on the French Voisin LA (Figure 4)[12]. A pusher-propeller plane means the engine is behind the pilot. When in a dog fight, a pusher propeller planes engine is vulnerable to direct fire from the pursuer.
[Image pending permission for use]
Figure 4: A Voisin push propeller biplane.
Standing Firing Position
Throughout the war a frequently used method was to fire over the propeller by placing the gun on the top wing. As most planes in WWI were biplanes, placing the machine gun on the top wing would prevent bullets from hitting the propeller. This method would vary from plane to plane with some being easier to fire than others. One of the more extreme examples was the Deperdussin monoplane where the pilot would stand up on their seat to fire the gun (Figure 5)[13]. This was a single-seat plane so while he was shooting, the plane would not be controlled by anybody. There were other versions of this technology where the pilot would not have to stand but simply lift his arms above his head, still not controlling the plane, and then shoot. The gun was placed on a curved rail so that it could be brought down to almost eye level where the pilot would reload the gun and then slide it back up. To reload this gun was much easier than the previous take on this technology, where the pilot had to completely stand up. One example of a plane that used the sliding-gun method is the Royal Aircraft Factory S.E.5[14]. After the Battle of Arras the S.E.5 was brought into service. While the battle was a failure for the British, the new S.E.5 was more effective than the overworked planes in the Jastas, the equivalent of a squadron for the Germans.
[Image pending permission for use]
Figure 5: The Deperdussin monoplane with the standing gun mounting.
Hispano-Suiza Engine
One French design came out in 1917 which fired a 37-mm gun from the Hispano-Suiza engine. This engine was very common among French planes and even the famous French fighter pilot, Roland Garros, used it.[15] Before this gun came out, almost all machine guns shot 33-caliber bullets[16]. This new single-fire gun shot from the boss cap of the propeller and the ammunition would be loaded in one at a time by the pilot. The larger round helped to penetrate armored targets that simply were impossible to penetrate with a machine gun[17]. The gun saw limited deployment only being applied on the SPAD S.XII. The plane's cockpit that was built with the variation on the Hispano engine with the cannon were somewhat different. Instead of having a stick in between the pilots legs the guns bolt handle would be there to reload the gun (Figure 6). The stick that used to be between the pilots legs had been replaced by two sticks on each side of him[18]. Like the other technologies this led to pilot to have no control over his plane while he was reloading his gun. In battle the pilot would carry 12 rounds of ammunition to be loaded in one at a time.
[Image pending permission for use]
Figure 6: The guns bolt handle where the pilot would insert one round into the gun.
Deflector Gear
The optimal method of firing from a plane would be to fire through the propeller arc, while not having to stand up or momentarily lose control over the plane. In that scenario the pilot has a direct line of vision to whatever he is pursuing or shooting at, whether it be another plane or a machine gun post on the ground. Nations did not want to risk shooting through the propeller arc because of the risk of destroying your own propeller. He achieved this by using deflectors on his propeller. This method would deflect any bullets that happened to hit the propeller with steel wedges (Figure 7).[19] This technique unnerved pilots as they were essentially shooting their own plane in order to shoot down the enemy's plane. From a technical perspective it also decreased the effective rate of fire by 25%[20]. According to some sources Roland Garros was also the first to shoot down another plane earlier that month over Belgium[21].
[Image pending permission for use]
Figure 7: The deflector gear with the steel wedges on the propeller blades.
Interrupter Gear
The first effective method of shooting and destroying the enemy's plane was the interrupter gear (Figure 8)[22]. The pilot did not need another person to shoot for him. He did not need to stand on his chair to shoot, nor did he need to lose control over his plane to shoot or shoot his one propeller. With the interrupter gear, the gun would negatively fire when a blade was in front of it, meaning that whenever the interrupter gear was not activated the gun would fire. This made sure that the propeller blade would not be destroyed in the act of firing and that the effective rate of fire was not reduced so dramatically. The interrupter, first designed by Fokker, consisted of several cam pushrods and ovals. Each propeller would have one bulge in a circle. This would result in the cam operated actuator wheel to move up and down as the propellers move past the barrel of the gun. This would then be connected to a pushrod linkage which is a metal rod that's only job is to bridge the distance from the gun to behind the boss cap, the cap that houses the place where each blade meets. The third part of the interrupter is the connection with the trigger sear. This is activated whenever one of the bulges in the circle activates the actuator wheel. When the trigger sear is activated it stops the gun from firing by disengaging the trigger. The return spring simply pushes the actuator wheel back onto the oval shaped disk behind the boss cap. Later advancements were made to change the delicate mechanical apparatus to a more sophisticated and rugged pneumatic system. The system completed the same task but without all of the spindly cam rods. During the Fokker Scourge, from 1915 to 1916 a period of time when the German military gained overwhelming air superiority, the Fokker E.I came out with the first interrupter gear. The new innovation made firing from the plane much easier than before as the guns had a direct line of sight parallel to that of the pilot.
[Image pending permission for use]
Figure 8: The interrupter gear invented by Anthony Fokker.
Synchronization Gear
The final method seen in WWI was with the synchronization gear. Several sources confuse the interrupter and synchronization gear as one and the same.[23] As explained above the interrupter gear negatively fires the gun when the blade is in front of the barrel of the gun. Synchronization on the other hand positively fires the gun when there is no blade in front of the barrel[24]. Although the difference is small, it improved the use and effectiveness of the gun. The mechanism is very similar except that instead of having each of the bulges where the blades are, they are in between where there is no blade (Figure 9). And instead of blocking the gun when the actuator wheel is on it insead blocks the gun from firing when the actuator wheel is not actuated. For each bulge received by the actuator wheel only one shot is fired effectively turning the machine gun into a semi-automatic gun. Another note is that the rate of fire depends greatly on the engines rotation speed. If the engine is spinning very slowly, as if the plane is on a patrol, than when the pilot fires the rate of fire would be slower. If the pilot is engaged in a dogfight and is on full throttle the engine would subsequently be spinning much faster and so the rate of fire would also be faster. One of the reasons that the interrupter was less effective than the synchronization gear is because the rate of fire on the interrupter gear is so high that not many machine guns could handle it and so pilots had to be careful when shooting the gun. Both Verdun and the March 1918 offensive saw this technology. The Fokker Dr.1 triplane, made famous by Manfred von Richthofen, the Red Baron, used synchronization gear to claim his last 19 confirmed kills during the offensive before he was shot down[25].
[Image pending permission for use]
Figure 9: The differences between synchronization (top) and interrupter gear (above)[26].
Only a few years after the Wright brothers invented the airplane in 1903 different air forces and militaries were experimenting with weapon systems on planes. When WWI broke out it led to a war of back and forth competition to be the most technologically advanced country and military. The main competitors were France and Germany. The beginning consisted of technologies that were tried and most of the time failed. The ones that did not, however, helped develop more sophisticated and technologies. Eventually both countries developed interrupter and synchronization gear which was the most effective technology of WWI in terms of firing from a plane[27].
Sources
- “Albatros” first-world-war.com, http://www.first-world-war.com/albatros.htm (accessed January 11, 2018).
- Dan Hampton, Lords of the Sky (New York, NY: Harper-Collins Publisher, 2014), 8.
- Interview with Harry Cawood, Docent at the National Air and Space Museum. January 6, 2018.
- Phoebus. Warplanes of World War I. London, England: BPC Publishing Ltd., 1973
- Randall C. Reed. Mission Briefing Manual In Richthofen's War Board Game.The Avalon Hill Game Co, 1972.
- “Synchronization gear” Wikipedia, https://en.wikipedia.org/wiki/Synchronization_gear (accessed January, 15, 2017).
- Williams, Anthony G, and Dr. Emmanuel Gustin. Flying Guns World War I. Ramsbury: Airlife publishing, 2003
Footnotes
[1] Phoebus, Warplanes of World War I (London, England: BPC Publishing Ltd., 1973), 7.
[2] “Albatros” first-world-war.com, http://www.first-world-war.com/albatros.htm (accessed January 11 2018).
[3]Anthony G. Williams, and Dr. Emmanuel Gustin, Flying Guns World War I, (Ramsbury: Airlife publishing, 2003), 42.
[4] Ibid., 45.
[5] Ibid., 44.
[6] Ibid.
[7] Ibid., 47.
[8] Ibid., 31.
[9] Phoebus, Warplanes of World War I, 141
[10] Ibid., 158.
[11] Williams, and Gustin, Flying Guns World War I, 55.
[12] Phoebus, Warplanes of World War I, 37.
[13] Williams, and Gustin, Flying Guns World War I, 46.
[14] Ibid., 59.
[15] Interview with Harry Cawood, Docent at the National Air and Space Museum. January 6 2018.
[16] Ibid.
[17] Ibid.
[18] Ibid.
[19] Williams and Gustin, Flying Guns World War I, 32.
[20] Ibid., 33.
[21] Dan Hampton, Lords of the Sky (New York, NY: Harper-Collins Publisher, 2014), 8.
[22] Richthofen's War, Mission Briefing Manual.
[23] “Synchronization gear” Wikipideia, https://en.wikipedia.org/wiki/Synchronization_gear (accessed January, 15, 2017).
[24] Williams and Gustin, Flying Guns World War I, 33.
[25] Interview with Harry Cawood, Docent at the National Air and Space Museum. January 6 2018.
[26] Ibid.
[27] Ibid.