In case of the aircraft guns, their purpose is a matter of key relevance. Whether it’s about effective elimination of the target, armour penetration or about destruction of the equipment or neutralization of the infantry or suppressing the enemy, firepower or rate of fire is the main factor to be considered here. In case of the helicopters we have 30 mm cannons on one side of the spectrum, with rates of fire of several hundred rounds per minute, and multi-barrel 7.62 mm machine guns on the other side, offering rates of fire of several thousand rounds per minute.
Large calibre cannons are primarily used in pods and as main armament of the turrets of support/attack helicopters, as these allow for effective neutralization of armour. Machine guns, as they are lightweight and offer a high rate of fire, are used primarily by the gunners working onboard multi-role, transport and support helicopters.
.50 caliber machine guns have become a kind of compromise, offering rates of fire of 700 to 800 rounds per minute with rounds powerful enough to act against most of the threats. This type of weaponry is commonly used as the armament of vehicles and attack helicopters. In case of the combat aircraft the .50-cal. machine guns turned out to be insufficient in the 1950s when F-86 Sabre jets received 20 mm cannons replacing the .50-cal. machine guns. Since then the calibre in question has been becoming increasingly more popular. A myriad of 20 mm rounds is used by numerous NATO combat aircraft.
Six-barrel M61 Vulcan cannon is the most popular weapon of this type, being the armament of numerous MRCA (F-16 included), along with the lighter 3-barrel M197 gun used in case of helicopters. This very cannon is the armament of AH-1Z Viper and A129 Mangusta helicopters. The gun utilizes the 20×102 mm rounds.
Light Support Weapon
The French military was in need of a light an effective 20 mm cannon shooting a NATO-compliant round. This is how a very light, low recoil Nexter 20M621 gun was born, using the 20×102 mm round. The gun is available in land, naval and air variants - both manually as well as remotely operated ones. The system is supplied to the French military and to 25 other states. The group in question has been recently joined by Poland. The variant installed on a vehicular platform, designated P20, has been acquired by JW GROM special forces unit of the Polish military, from the Works 11 company that distributes of the aforesaid system in Poland.
Another important feature is the fact that a broad range of rounds can be used with this gun, including fragmentation or armour-piercing rounds that offer penetration performance sufficient to effectively act against most of the BTR/BMP-class platforms. The main reason for which weapons as such have not fully replaced the 12.7 mm machine guns stems from the ammunition weight and dimensions. 20×102 mm M50 round weighs 0.25 kg, while 12.7×99 mm round weighs around 0.12 kg.
Nexter M621 is a simple design that remains easy to employ. The weapon is gas-operated and fires, in most of the modes, from an open bolt which facilitates cooling. The weapon also has the so called Sniper Shot function - a single shot with a closed bolt which greatly enhances its precision and accuracy. The manufacturer emphasizes the unique character of this function. The weapon comes in many variants, three of which are destined for being mounted on a helicopter.
Nexter SH20 is the designation of an extendable door-mounted gun station fitted with the M261 cannon with 240 rounds. It is a module that can be used by the side gunner or it can also be mounted on the rear ramp.
The system design solution allows for free use of the door when it is not in use, thus it does not limit the loading and unloading capacity. It is also still possible to close the door completely. Despite these abilities, only 10 seconds are required to deploy the gun and use it. SH20 module weighs 165 kilograms without the ammunition. Fully loaded, with 240 20×102 mm rounds, the system weighs 248 kilograms.
SH20 systems became a standard armament of the French H225M Caracal helicopters of the French Ed'h 1/67 Pyrénées air force squadron and of the EOS 3 Squadron of the 4th Special Forces Helicopter Regiment. These units support the operations of the French Special Forces. They frequently deploy abroad. 20 mm guns have replaced the FN M2M .50-cal. machine guns.
Precision Shooting System
M621 may also be integrated with the avionics with the use of a THL20 stabilized turret module. It is a lightweight solution weighing just 164 kilograms, without the ammunition. 300 to 850 20x102 mm rounds can be stored alongside, depending on the platform. Thanks to its being low-weight, compact and thanks to its low-recoil the cannon may be installed on helicopters that are relatively light. Alternatively it may also be fitted onto multi-role helicopters not really limiting the capabilities that they originally offer. Due to its simplicity it is a weapon that can easily be installed on a helicopter within the framework of overhauls or upgrades.
THL20 is a system that, thanks to integration with the optoelectronic systems of the helicopter, makes it possible to use the advantages offered by the 20 mm gun, including accuracy and Sniper Shot functionality. The turret may be controlled manually or via a helmet-mounted sight. The latter solution has been applied in case of the Indian HAL LCH (Light Combat Helicopter) or HAL ALH (Advanced Light Helicopter) helicopters.
In Europe THL20 turret has been integrated onto the Romanian IAR330L SOCAT platform (Romanian: Sistem Optronic de Cercetare si Anti-Tanc - Optronic Reconnaissance and Anti-Tank System). It has also been fitted with optoelectronic sensors and guided missiles. The helicopter is a Romanian anti-tank, license-manufactured derivative of the French AS330 Puma helicopter.
Gun Pod - A Universal Tool
M621 20 mm cannon is used most commonly in the form of a NC621 gun pod. It is destined for being used by helicopters and light combat aircraft. It has also been certified for use with several types of helicopters and combat aircraft. The types certified include almost all of the French Airbus Helicopters platforms, but also the Sikorsky Black Hawk, Bell JetRanger/Kiowa Warrior or Pilatus PC7/PC9 turboprop fixed-wing platforms.
The pod accommodates 180 rounds alongside the gun and can work with a myriad of targeting systems. It could also be integrated on other aircraft, Polish Armed Forces’ helicopters included.
Introduction of the M621 into the GROM Unit’s inventory paves the way towards broader employment of this system in Poland. Apart from the vehicles used by the special forces, the very same type of armament could be employed onboard the helicopters used by the 7th Special Operations Squadron (7. EDS) based in Powidz and helicopters used by other airborne units.
THL20 turrets may also be an interesting proposal when it comes to Mi-24 attack helicopter or W-3WA support helicopter upgrades. In both cases the 20 mm gun would replace the .50-cal. solution, much less effective, especially against armour. Meanwhile, NC621 pods with a 20 mm gun could replace the Post-Soviet UPK-23-250 pods with a 23 mm cannon.
Article written on the basis of information provided by Works 11 Sp. z o. o.