High explosive incendiary

In warfare, High-explosive incendiary (HEI) is a type of ammunition specially designed to pierce armor, fragment, and ignite readily combustible materials.

High Explosive Incendiary shells (HEIS) are designed to penetrate the armor of the target using high explosive properties, and then fragment and flare up, causing a fire either inside or outside of the target.HEI shells have been in use with numerous countries since the invention of the modern howitzer.

They work off the principle of a HEAT round, but are filled with flammable liquids to cause a secondary fire, which either detonates any combustible material such as ammunition or fuel and also injures crew, or simply causes large fires which must be dealt with. The incendiary capability also quickly depletes oxygen in small contained areas such as within a tank or shipboard compartment, causing suffocation of the crew.

HEI ammunition is fused either mechanically or chemically. The armor piercing ability can vary widely, allowing for more focused fragmentation or larger scatter. The incendiary capability also quickly depletes oxygen in small contained areas, such as within a tank or shipboard compartment.

History

HEI ammunition was originally developed for use in large-caliber cannon, howitzer and naval artillery. Currently, HEI rounds are most commonly made in medium-caliber sizes of 20 mm, 25 mm, and 30 mm. They are fired from various platforms, including aircraft, anti-aircraft cannons, and anti-missile systems, as well as common battlefield howitzers, though the latter has gone through a recent decline in use.

HEI ammunition has also been used on the battlefield against tanks and other armoured vehicles, but this has become impractical due to the invention of modern armour systems such as Chobham and explosive reactive armour, which can absorb most high-explosive rounds currently used.

Recently, APIS (armour piercing incendiary shells) have been used; these penetrate the target using the kinetic properties of the round before the incendiary round goes off, smothering the crew in flames and detonating combustible materials, generally destroying the target.

Employment

The shells were first employed in naval batteries, but soon found their way to land-based howiters as well. They caused fires, which on ships can be difficult to extinguish in the tight spaces. Also, fired at tanks and soft targets, they can cause fires that completely engulf the vehicle, killing anyone inside.

Occasionally HEIS were used against tanks and other hightly armoured vehicles, but, since the invention of modern battle armour, such as Chobham, and Explosive Reactive Armour, these shells have become less and less practical for anti-tank work, and more useful for destroying “soft” targets such as airbases, trenches, or bunkers, in which they can create fires of over 1000 degrees Celsius. Incendiary shells are no longer in use by many countries, due to bans on the use of phosphorus weapons.

Armor-piercing shot and shell penetrate the target using kinetic energy before the incendiary charge ignites, smothering the crew in flames, detonating ammunition, and destroying the target.

ee also

* HEIAP High Explosive Incendiary/Armor Piercing Ammunition

References

External links

* [http://www.dtic.mil/ndia/2001gun/Tasson1.pdf Live fire experiment of mechanically fuzed HEI rounds]
* [http://www.fas.org/man/dod-101/sys/land/pgu-13.htm Example of US military 30 mm HEI round]
* [http://history.amedd.army.mil/booksdocs/wwii/actvssurgconvol2/chapter4figure140.jpgFragmentation pattern of a German Round]