Why do pilots shoot guns without dangling the rotor blades?

How could a machine gun mounted on the nose of a World War I propeller plane be able to release bullets steadily without destroying the rotor that was rotating very fast ahead? In this article we will learn about the history of an interesting invention called synchronization gear (temporarily called "synchronous trigger") and this device will explain the above question.

The circumstances of the fighter

The story is that when World War I broke out, the planes were still only considered a means of reconnaissance, gathering information and tracking the activities of the enemy forces. Pilots at the time began to think about dropping bombs from above or attaching guns to planes to attack enemy aircraft, though this action was still unapproved and even criticized. Most experiments on the first generation of fighter jets were carried out by French and German engineers, but their efforts were not appreciated by military organizations because they believed the value of the aircraft. There are not many weapons and the difficulties faced when integrating guns that can shoot forward on aircraft using tractor propeller engines .

Picture 1 of Why do pilots shoot guns without dangling the rotor blades?
One of the first reconnaissance aircraft - the British Avro 504.

However, the thinking of fighters has begun to change since the war broke out in Europe. Reconnaissance planes are used for both purposes of collecting information and countering enemy exploration. Therefore, the first generation of fighters was born as the fighter reconnaissance aircraft. Most of them are 2-seat aircraft with 1 pilot and 1 observer to collect information. In the early days, observers were equipped with simply a revolver, a rifle or even a hand grenade to attack enemy aircraft. The accuracy and effective range of these weapons are generally poor and it is nearly impossible to shoot down a target moving in three dimensions like an airplane.

So they started thinking about bringing machine guns - the most important weapons at ground clashes on planes. That said, it was difficult to do because pilots and designers quickly concluded that the most effective location for mounting machine guns was right in front of the cockpit. This position allows the pilot to fire while being able to aim by pointing the aircraft at the target. Not only does it support more accurate aiming, this installation position also makes pilots reloading bullets or removing stuck bullets more easily. Unfortunately, the location of the gun in front of the cockpit is considered impossible on all aircraft powered by propellers because the rapid fire of machine guns can damage or completely destroy the propellers.

Picture 2 of Why do pilots shoot guns without dangling the rotor blades?
A Nieuport 11 with a machine gun mounted on the upper deck.

To avoid this problem, machine guns were usually mounted on the upper wings of biplane planes and guns were tilted forward at an angle, avoiding firing directly at the propellers. Although this design solves the problem of engine obstruction, it is difficult for pilots to both fly, aim and shoot targets. In addition, reloading ammunition for the gun is also a challenge because the pilot is forced to stand on a chair to do this while operating the aircraft.

Picture 3 of Why do pilots shoot guns without dangling the rotor blades?
French Voisin III aircraft.

As a result, it was still not feasible to mount a machine gun on the upper wing, while fighter aircraft relied heavily on observers and gunner in air battles. These aircraft are still fitted with one or two machine guns mounted on a rotating base behind the cockpit. Observers will stand and operate the gun, the body is tied by safety belts to ensure they do not fall out during the acrobatic plane, changing direction while fighting. The first case of the plane was shot down by machine gun in October 1914 when the gunner on a French double-decker Voisin III aircraft used the Hotchkiss machine gun to shoot down Aviatik CI's reconnaissance aircraft. Virtue.

Picture 4 of Why do pilots shoot guns without dangling the rotor blades?
The FE 2d aircraft model uses a propulsion engine, the gunner operates a gun in the open cockpit.

The British, meanwhile, still thought that a gun mounted at the nose of the aircraft was still the optimal answer but could not find a solution to avoid the rotor of the engine blocking the projectile. The Royal Air Force tested the design of the aircraft using a propeller propeller - the propeller was placed behind the cockpit or tail of the aircraft to propel the aircraft forward so that the pilot could fly. operating a gun mounted at the nose of the aircraft. However, this solution is not really good because the design of the rear propeller engine does not allow the aircraft to maneuver as flexibly as the drag rotor motor.

The first solution

Picture 5 of Why do pilots shoot guns without dangling the rotor blades?

The French instead sought a different approach. Renowned pilot Roland Garros proposed to aircraft designer Raymond Saulnier to find a solution to fire the 8-inch Hotchkiss machine gun through the rotor disc of the engine. The idea they developed was to attach armor plates and triangular shields that deflected bullets to the rotor. These shields have a nose toward the cockpit and its function is that when the bullet from the machine gun hits the propeller, it will spread the bullet out, not back toward the cockpit. Garros tested this armored propeller-mounted propeller on a Morane-Saulnier Type L fighter in April 1915 and shortly after takeoff, Garros shot down two Albatros reconnaissance aircraft. Virtue.Garros is considered a hero, but his design significantly reduces the performance of the rotor motor. In a massive bombardment, Garros's plane was rifle bullets into the fuel tank and caught fire. He was arrested and designed armored propellers, bullet shields and machine gun mounting structures fell into German hands.

Stork sync

Garros's design was commissioned by a Dutch aircraft manufacturer, Anthony Fokker, who worked at a German factory to make similar things. Fokker was unimpressed by Garros's bullet-shield design, but they suggested that he turn an idea into something later called a "synchronous trigger" or "synchronization gear".. The objective of the synchronous mechanism was to align the trigger with the engine so that the gun did not release the bullets when the rotor was about to turn to cover the bullet path. Fokker was not the first to study this idea, but in fact, Swiss engineer Franz Schneider was granted a patent for a similar synchronization mechanism in 1913. In addition, the designer Raymond Saulnier also built and tested the trigger in April 1914, but no design was complete enough to be used in combat.

Picture 6 of Why do pilots shoot guns without dangling the rotor blades?

Fokker was more persistent and within a few days of acquiring Garros' valuable technologies, he succeeded in creating a usable synchronization system. This device was used to link the German Parabellum IMG 14 machine gun to the engine of the 1-seat 1-wing Fokker A.III aircraft. Fokker had originally wanted to turn Eindecker single-decker planes into fighter planes but could not equip an effective machine gun on this aircraft. Therefore, Germany still uses Eindecker aircraft as a reconnaissance or unarmed communication. His new invention of synchronization mechanism will allow this aircraft design to fulfill its full potential.

Fokker named the invention Zentralsteuerung (central control) and the heart of the whole system was a camwheel mounted and rotated with the rotating shaft of the engine rotor. First the gun is mounted in front of the cockpit and loaded, then the pilot pulls a handle to open the trigger. This handle will lower a lever leading down to the cam follower. This orange pie has a completely non-rounded design that has a protrusion. Each time the cam wheel rotates in the rotation of the propeller, the convex part will push the guide arm upwards causing the connecting rod with the trigger to be pushed backwards, activating the gun just like when we used a finger to squeeze the trigger. The protruding part on the camwheel is designed and installed in such a position that the trigger is only activated when the engine rotor does not block the projectile path in rotating motion.

After successful ground-based testing and proof of effectiveness on an Eindecker aircraft, the German Air Force Inspection Board ordered a series of Fokker EI aircraft with synchronized trigger systems and This aircraft began to be delivered to the western line. By the first half of 1916, Germany dominated the skies of Western Europe with EI, E.II and E.III fighters fitted with machine guns. French or British planes were shot down repeatedly, so France was forced to cancel daytime bombing missions, and the UK lost an average of 2 planes a day.

Picture 7 of Why do pilots shoot guns without dangling the rotor blades?
Fokker on the Eindecker plane.

Although the synchronous trigger technology of Fokker was strictly protected by Germany, in the end, the Fokker E fell into the hands of allied troops and countries began developing different versions of the trigger. A series of British and French fighter jets equipped with synchronized machine guns and trigger were introduced. Although their performance was not high due to the slow rate of fire at low flight speeds and the connection between guns and engines was often broken, the Allies at least caught up with Germany.

Picture 8 of Why do pilots shoot guns without dangling the rotor blades?
The invention of George Constantinescu.

In March 1917, Romanian inventor George Constantinescu developed a synchronous trigger system of the same name or CC trigger and the improvement on this system was that it used a liquid tube to create thrust on the trigger. Constantinescu's invention was more reliable and gave a higher rate of fire, close to conventional machine guns. This design was used as a standard on British warplanes until World War 2 broke out.

Stork synchronization is still an important component of fighter design and is applied to many other aircraft. A major technological improvement later came with the development of the turret mounted on bombers. These gun turrets are designed to rotate and elevate with a wide angle of fire to both attack and protect the aircraft against small fighters. To avoid accidentally firing bullets at the aircraft as the gunner rotated the turret, engineers developed an electrical system that uses solenoid to disable the gun at certain locations in the gun. firing range. When the gun is put into a prohibited position, electricity is cut off and the trigger is disabled.

Picture 9 of Why do pilots shoot guns without dangling the rotor blades?
The P-40 Warhawk during the early part of World War II.

In the early stages of World War II, the fighter still used the trigger in sync with the gun behind the propeller engine. However, when the machine gun began to get bigger and stronger, mounting it right in front of the cockpit was impossible. In addition, improvements in aiming capabilities allow guns to be launched far away from the pilot without compromising accuracy. At this point, people return to the original design of attaching a gun to the outside, on the wings where there is more space, stiffer and more durable. The guns were moved away from the propellers and again set at an angle toward convergence according to a predetermined point in front of the nose of the aircraft. Such wing-mounted guns became standard equipment on most fighter planes during World War 2, although some German and Russian aircraft still use the old-style cockpit gun design next to the mounted gun. wing.

Picture 10 of Why do pilots shoot guns without dangling the rotor blades?
Yakovlev Yak-9.

The last synchronous trigger mechanism aircraft were the Lavochkin La-11 and Yakovlev Yak-9 used by North Korean troops during the Korean War. This system gradually disappeared with the appearance of fighter jet engines. Machine guns were still mounted in front or in the wings and were considered an important equipment until the introduction of air-to-air missiles.

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